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* [PATCH v4 00/29] Add support for Clang LTO
@ 2020-09-29 21:46 Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 01/29] RAS/CEC: Fix cec_init() prototype Sami Tolvanen
                   ` (30 more replies)
  0 siblings, 31 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

This patch series adds support for building x86_64 and arm64 kernels
with Clang's Link Time Optimization (LTO).

In addition to performance, the primary motivation for LTO is
to allow Clang's Control-Flow Integrity (CFI) to be used in the
kernel. Google has shipped millions of Pixel devices running three
major kernel versions with LTO+CFI since 2018.

Most of the patches are build system changes for handling LLVM
bitcode, which Clang produces with LTO instead of ELF object files,
postponing ELF processing until a later stage, and ensuring initcall
ordering.

Again, patches 1-3 are not directly related to LTO, but are needed
to compile LTO kernels with ToT Clang, so I'm including them in the
series for your convenience:

 - Patch 1 ("RAS/CEC: Fix cec_init() prototype") fixes an initcall
   type mismatch which breaks allmodconfig with LTO. This patch is
   in linux-next.
   
 - Patch 2 ("x86/asm: Replace __force_order with memory clobber")
   fixes x86 builds with LLVM's integrated assembler, which we use
   with LTO for inline assembly. This patch hasn't been picked up
   by maintainers yet.

 - Patch 3 ("kbuild: preprocess module linker script") is from
   Masahiro's kbuild tree and makes the LTO linker script changes
   much cleaner.

Furthermore, patches 4-8 include Peter's patch for generating
__mcount_loc with objtool, and build system changes to enable it on
x86. With these patches, we no longer need to annotate functions
that have non-call references to __fentry__ with LTO, which makes
supporting dynamic ftrace much simpler.

Patch 9 disables recordmcount for arm64 when patchable function
entry is used (enabled by default if the compiler supports the
feature), which removes thousands of unnecessary recordmcount
invocations from a defconfig build.

Note that you can also pull this series from

  https://github.com/samitolvanen/linux.git lto-v4


---
Changes in v4:

  - Fixed a typo in Makefile.lib to correctly pass --no-fp to objtool.

  - Moved ftrace configs related to generating __mcount_loc to Kconfig,
    so they are available also in Makefile.modfinal.

  - Dropped two prerequisite patches that were merged to Linus' tree.

Changes in v3:

  - Added a separate patch to remove the unused DISABLE_LTO treewide,
    as filtering out CC_FLAGS_LTO instead is preferred.

  - Updated the Kconfig help to explain why LTO is behind a choice
    and disabled by default.

  - Dropped CC_FLAGS_LTO_CLANG, compiler-specific LTO flags are now
    appended directly to CC_FLAGS_LTO.

  - Updated $(AR) flags as KBUILD_ARFLAGS was removed earlier.

  - Fixed ThinLTO cache handling for external module builds.

  - Rebased on top of Masahiro's patch for preprocessing modules.lds,
    and moved the contents of module-lto.lds to modules.lds.S.

  - Moved objtool_args to Makefile.lib to avoid duplication of the
    command line parameters in Makefile.modfinal.

  - Clarified in the commit message for the initcall ordering patch
    that the initcall order remains the same as without LTO.

  - Changed link-vmlinux.sh to use jobserver-exec to control the
    number of jobs started by generate_initcall_ordering.pl.

  - Dropped the x86/relocs patch to whitelist L4_PAGE_OFFSET as it's
    no longer needed with ToT kernel.

  - Disabled LTO for arch/x86/power/cpu.c to work around a Clang bug
    with stack protector attributes.

Changes in v2:

  - Fixed -Wmissing-prototypes warnings with W=1.

  - Dropped cc-option from -fsplit-lto-unit and added .thinlto-cache
    scrubbing to make distclean.

  - Added a comment about Clang >=11 being required.

  - Added a patch to disable LTO for the arm64 KVM nVHE code.

  - Disabled objtool's noinstr validation with LTO unless enabled.

  - Included Peter's proposed objtool mcount patch in the series
    and replaced recordmcount with the objtool pass to avoid
    whitelisting relocations that are not calls.

  - Updated several commit messages with better explanations.


Arvind Sankar (1):
  x86/asm: Replace __force_order with memory clobber

Luca Stefani (1):
  RAS/CEC: Fix cec_init() prototype

Masahiro Yamada (1):
  kbuild: preprocess module linker script

Peter Zijlstra (1):
  objtool: Add a pass for generating __mcount_loc

Sami Tolvanen (25):
  objtool: Don't autodetect vmlinux.o
  tracing: move function tracer options to Kconfig
  tracing: add support for objtool mcount
  x86, build: use objtool mcount
  arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS
  treewide: remove DISABLE_LTO
  kbuild: add support for Clang LTO
  kbuild: lto: fix module versioning
  kbuild: lto: postpone objtool
  kbuild: lto: limit inlining
  kbuild: lto: merge module sections
  kbuild: lto: remove duplicate dependencies from .mod files
  init: lto: ensure initcall ordering
  init: lto: fix PREL32 relocations
  PCI: Fix PREL32 relocations for LTO
  modpost: lto: strip .lto from module names
  scripts/mod: disable LTO for empty.c
  efi/libstub: disable LTO
  drivers/misc/lkdtm: disable LTO for rodata.o
  arm64: vdso: disable LTO
  KVM: arm64: disable LTO for the nVHE directory
  arm64: allow LTO_CLANG and THINLTO to be selected
  x86, vdso: disable LTO only for vDSO
  x86, cpu: disable LTO for cpu.c
  x86, build: allow LTO_CLANG and THINLTO to be selected

 .gitignore                                    |   1 +
 Makefile                                      |  68 +++--
 arch/Kconfig                                  |  68 +++++
 arch/arm/Makefile                             |   4 -
 .../module.lds => include/asm/module.lds.h}   |   2 +
 arch/arm64/Kconfig                            |   4 +
 arch/arm64/Makefile                           |   4 -
 .../module.lds => include/asm/module.lds.h}   |   2 +
 arch/arm64/kernel/vdso/Makefile               |   4 +-
 arch/arm64/kvm/hyp/nvhe/Makefile              |   4 +-
 arch/ia64/Makefile                            |   1 -
 .../{module.lds => include/asm/module.lds.h}  |   0
 arch/m68k/Makefile                            |   1 -
 .../module.lds => include/asm/module.lds.h}   |   0
 arch/powerpc/Makefile                         |   1 -
 .../module.lds => include/asm/module.lds.h}   |   0
 arch/riscv/Makefile                           |   3 -
 .../module.lds => include/asm/module.lds.h}   |   3 +-
 arch/sparc/vdso/Makefile                      |   2 -
 arch/um/include/asm/Kbuild                    |   1 +
 arch/x86/Kconfig                              |   3 +
 arch/x86/Makefile                             |   5 +
 arch/x86/boot/compressed/pgtable_64.c         |   9 -
 arch/x86/entry/vdso/Makefile                  |   5 +-
 arch/x86/include/asm/special_insns.h          |  28 +-
 arch/x86/kernel/cpu/common.c                  |   4 +-
 arch/x86/power/Makefile                       |   4 +
 drivers/firmware/efi/libstub/Makefile         |   2 +
 drivers/misc/lkdtm/Makefile                   |   1 +
 drivers/ras/cec.c                             |   9 +-
 include/asm-generic/Kbuild                    |   1 +
 include/asm-generic/module.lds.h              |  10 +
 include/asm-generic/vmlinux.lds.h             |  11 +-
 include/linux/init.h                          |  79 ++++-
 include/linux/pci.h                           |  19 +-
 kernel/Makefile                               |   3 -
 kernel/trace/Kconfig                          |  29 ++
 scripts/.gitignore                            |   1 +
 scripts/Makefile                              |   3 +
 scripts/Makefile.build                        |  69 +++--
 scripts/Makefile.lib                          |  17 +-
 scripts/Makefile.modfinal                     |  29 +-
 scripts/Makefile.modpost                      |  22 +-
 scripts/generate_initcall_order.pl            | 270 ++++++++++++++++++
 scripts/link-vmlinux.sh                       |  95 +++++-
 scripts/mod/Makefile                          |   1 +
 scripts/mod/modpost.c                         |  16 +-
 scripts/mod/modpost.h                         |   9 +
 scripts/mod/sumversion.c                      |   6 +-
 scripts/{module-common.lds => module.lds.S}   |  31 ++
 scripts/package/builddeb                      |   2 +-
 tools/objtool/builtin-check.c                 |  13 +-
 tools/objtool/builtin.h                       |   2 +-
 tools/objtool/check.c                         |  83 ++++++
 tools/objtool/check.h                         |   1 +
 tools/objtool/objtool.h                       |   1 +
 56 files changed, 906 insertions(+), 160 deletions(-)
 rename arch/arm/{kernel/module.lds => include/asm/module.lds.h} (72%)
 rename arch/arm64/{kernel/module.lds => include/asm/module.lds.h} (76%)
 rename arch/ia64/{module.lds => include/asm/module.lds.h} (100%)
 rename arch/m68k/{kernel/module.lds => include/asm/module.lds.h} (100%)
 rename arch/powerpc/{kernel/module.lds => include/asm/module.lds.h} (100%)
 rename arch/riscv/{kernel/module.lds => include/asm/module.lds.h} (84%)
 create mode 100644 include/asm-generic/module.lds.h
 create mode 100755 scripts/generate_initcall_order.pl
 rename scripts/{module-common.lds => module.lds.S} (59%)


base-commit: ccc1d052eff9f3cfe59d201263903fe1d46c79a5
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 01/29] RAS/CEC: Fix cec_init() prototype
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 02/29] x86/asm: Replace __force_order with memory clobber Sami Tolvanen
                   ` (29 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Luca Stefani, Sami Tolvanen

From: Luca Stefani <luca.stefani.ge1@gmail.com>

late_initcall() expects a function that returns an integer. Update the
function signature to match.

 [ bp: Massage commit message into proper sentences. ]

Fixes: 9554bfe403nd ("x86/mce: Convert the CEC to use the MCE notifier")
Signed-off-by: Luca Stefani <luca.stefani.ge1@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lkml.kernel.org/r/20200805095708.83939-1-luca.stefani.ge1@gmail.com
---
 drivers/ras/cec.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 569d9ad2c594..6939aa5b3dc7 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -553,20 +553,20 @@ static struct notifier_block cec_nb = {
 	.priority	= MCE_PRIO_CEC,
 };
 
-static void __init cec_init(void)
+static int __init cec_init(void)
 {
 	if (ce_arr.disabled)
-		return;
+		return -ENODEV;
 
 	ce_arr.array = (void *)get_zeroed_page(GFP_KERNEL);
 	if (!ce_arr.array) {
 		pr_err("Error allocating CE array page!\n");
-		return;
+		return -ENOMEM;
 	}
 
 	if (create_debugfs_nodes()) {
 		free_page((unsigned long)ce_arr.array);
-		return;
+		return -ENOMEM;
 	}
 
 	INIT_DELAYED_WORK(&cec_work, cec_work_fn);
@@ -575,6 +575,7 @@ static void __init cec_init(void)
 	mce_register_decode_chain(&cec_nb);
 
 	pr_info("Correctable Errors collector initialized.\n");
+	return 0;
 }
 late_initcall(cec_init);
 
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 02/29] x86/asm: Replace __force_order with memory clobber
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 01/29] RAS/CEC: Fix cec_init() prototype Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 03/29] kbuild: preprocess module linker script Sami Tolvanen
                   ` (28 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Arvind Sankar

From: Arvind Sankar <nivedita@alum.mit.edu>

The CRn accessor functions use __force_order as a dummy operand to
prevent the compiler from reordering CRn reads/writes with respect to
each other.

The fact that the asm is volatile should be enough to prevent this:
volatile asm statements should be executed in program order. However GCC
4.9.x and 5.x have a bug that might result in reordering. This was fixed
in 8.1, 7.3 and 6.5. Versions prior to these, including 5.x and 4.9.x,
may reorder volatile asm statements with respect to each other.

There are some issues with __force_order as implemented:
- It is used only as an input operand for the write functions, and hence
  doesn't do anything additional to prevent reordering writes.
- It allows memory accesses to be cached/reordered across write
  functions, but CRn writes affect the semantics of memory accesses, so
  this could be dangerous.
- __force_order is not actually defined in the kernel proper, but the
  LLVM toolchain can in some cases require a definition: LLVM (as well
  as GCC 4.9) requires it for PIE code, which is why the compressed
  kernel has a definition, but also the clang integrated assembler may
  consider the address of __force_order to be significant, resulting in
  a reference that requires a definition.

Fix this by:
- Using a memory clobber for the write functions to additionally prevent
  caching/reordering memory accesses across CRn writes.
- Using a dummy input operand with an arbitrary constant address for the
  read functions, instead of a global variable. This will prevent reads
  from being reordered across writes, while allowing memory loads to be
  cached/reordered across CRn reads, which should be safe.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82602
Link: https://lore.kernel.org/lkml/20200527135329.1172644-1-arnd@arndb.de/
---
 arch/x86/boot/compressed/pgtable_64.c |  9 ---------
 arch/x86/include/asm/special_insns.h  | 28 ++++++++++++++-------------
 arch/x86/kernel/cpu/common.c          |  4 ++--
 3 files changed, 17 insertions(+), 24 deletions(-)

diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
index c8862696a47b..7d0394f4ebf9 100644
--- a/arch/x86/boot/compressed/pgtable_64.c
+++ b/arch/x86/boot/compressed/pgtable_64.c
@@ -5,15 +5,6 @@
 #include "pgtable.h"
 #include "../string.h"
 
-/*
- * __force_order is used by special_insns.h asm code to force instruction
- * serialization.
- *
- * It is not referenced from the code, but GCC < 5 with -fPIE would fail
- * due to an undefined symbol. Define it to make these ancient GCCs work.
- */
-unsigned long __force_order;
-
 #define BIOS_START_MIN		0x20000U	/* 128K, less than this is insane */
 #define BIOS_START_MAX		0x9f000U	/* 640K, absolute maximum */
 
diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
index 59a3e13204c3..d6e3bb9363d2 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -11,45 +11,47 @@
 #include <linux/jump_label.h>
 
 /*
- * Volatile isn't enough to prevent the compiler from reordering the
- * read/write functions for the control registers and messing everything up.
- * A memory clobber would solve the problem, but would prevent reordering of
- * all loads stores around it, which can hurt performance. Solution is to
- * use a variable and mimic reads and writes to it to enforce serialization
+ * The compiler should not reorder volatile asm statements with respect to each
+ * other: they should execute in program order. However GCC 4.9.x and 5.x have
+ * a bug (which was fixed in 8.1, 7.3 and 6.5) where they might reorder
+ * volatile asm. The write functions are not affected since they have memory
+ * clobbers preventing reordering. To prevent reads from being reordered with
+ * respect to writes, use a dummy memory operand.
  */
-extern unsigned long __force_order;
+
+#define __FORCE_ORDER "m"(*(unsigned int *)0x1000UL)
 
 void native_write_cr0(unsigned long val);
 
 static inline unsigned long native_read_cr0(void)
 {
 	unsigned long val;
-	asm volatile("mov %%cr0,%0\n\t" : "=r" (val), "=m" (__force_order));
+	asm volatile("mov %%cr0,%0\n\t" : "=r" (val) : __FORCE_ORDER);
 	return val;
 }
 
 static __always_inline unsigned long native_read_cr2(void)
 {
 	unsigned long val;
-	asm volatile("mov %%cr2,%0\n\t" : "=r" (val), "=m" (__force_order));
+	asm volatile("mov %%cr2,%0\n\t" : "=r" (val) : __FORCE_ORDER);
 	return val;
 }
 
 static __always_inline void native_write_cr2(unsigned long val)
 {
-	asm volatile("mov %0,%%cr2": : "r" (val), "m" (__force_order));
+	asm volatile("mov %0,%%cr2": : "r" (val) : "memory");
 }
 
 static inline unsigned long __native_read_cr3(void)
 {
 	unsigned long val;
-	asm volatile("mov %%cr3,%0\n\t" : "=r" (val), "=m" (__force_order));
+	asm volatile("mov %%cr3,%0\n\t" : "=r" (val) : __FORCE_ORDER);
 	return val;
 }
 
 static inline void native_write_cr3(unsigned long val)
 {
-	asm volatile("mov %0,%%cr3": : "r" (val), "m" (__force_order));
+	asm volatile("mov %0,%%cr3": : "r" (val) : "memory");
 }
 
 static inline unsigned long native_read_cr4(void)
@@ -64,10 +66,10 @@ static inline unsigned long native_read_cr4(void)
 	asm volatile("1: mov %%cr4, %0\n"
 		     "2:\n"
 		     _ASM_EXTABLE(1b, 2b)
-		     : "=r" (val), "=m" (__force_order) : "0" (0));
+		     : "=r" (val) : "0" (0), __FORCE_ORDER);
 #else
 	/* CR4 always exists on x86_64. */
-	asm volatile("mov %%cr4,%0\n\t" : "=r" (val), "=m" (__force_order));
+	asm volatile("mov %%cr4,%0\n\t" : "=r" (val) : __FORCE_ORDER);
 #endif
 	return val;
 }
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index c5d6f17d9b9d..178499f90366 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -359,7 +359,7 @@ void native_write_cr0(unsigned long val)
 	unsigned long bits_missing = 0;
 
 set_register:
-	asm volatile("mov %0,%%cr0": "+r" (val), "+m" (__force_order));
+	asm volatile("mov %0,%%cr0": "+r" (val) : : "memory");
 
 	if (static_branch_likely(&cr_pinning)) {
 		if (unlikely((val & X86_CR0_WP) != X86_CR0_WP)) {
@@ -378,7 +378,7 @@ void native_write_cr4(unsigned long val)
 	unsigned long bits_changed = 0;
 
 set_register:
-	asm volatile("mov %0,%%cr4": "+r" (val), "+m" (cr4_pinned_bits));
+	asm volatile("mov %0,%%cr4": "+r" (val) : : "memory");
 
 	if (static_branch_likely(&cr_pinning)) {
 		if (unlikely((val & cr4_pinned_mask) != cr4_pinned_bits)) {
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 03/29] kbuild: preprocess module linker script
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 01/29] RAS/CEC: Fix cec_init() prototype Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 02/29] x86/asm: Replace __force_order with memory clobber Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
                   ` (27 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86

From: Masahiro Yamada <masahiroy@kernel.org>

There was a request to preprocess the module linker script like we
do for the vmlinux one. (https://lkml.org/lkml/2020/8/21/512)

The difference between vmlinux.lds and module.lds is that the latter
is needed for external module builds, thus must be cleaned up by
'make mrproper' instead of 'make clean'. Also, it must be created
by 'make modules_prepare'.

You cannot put it in arch/$(SRCARCH)/kernel/, which is cleaned up by
'make clean'. I moved arch/$(SRCARCH)/kernel/module.lds to
arch/$(SRCARCH)/include/asm/module.lds.h, which is included from
scripts/module.lds.S.

scripts/module.lds is fine because 'make clean' keeps all the
build artifacts under scripts/.

You can add arch-specific sections in <asm/module.lds.h>.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Jessica Yu <jeyu@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
---
 Makefile                                               | 10 ++++++----
 arch/arm/Makefile                                      |  4 ----
 .../{kernel/module.lds => include/asm/module.lds.h}    |  2 ++
 arch/arm64/Makefile                                    |  4 ----
 .../{kernel/module.lds => include/asm/module.lds.h}    |  2 ++
 arch/ia64/Makefile                                     |  1 -
 arch/ia64/{module.lds => include/asm/module.lds.h}     |  0
 arch/m68k/Makefile                                     |  1 -
 .../{kernel/module.lds => include/asm/module.lds.h}    |  0
 arch/powerpc/Makefile                                  |  1 -
 .../{kernel/module.lds => include/asm/module.lds.h}    |  0
 arch/riscv/Makefile                                    |  3 ---
 .../{kernel/module.lds => include/asm/module.lds.h}    |  3 ++-
 arch/um/include/asm/Kbuild                             |  1 +
 include/asm-generic/Kbuild                             |  1 +
 include/asm-generic/module.lds.h                       | 10 ++++++++++
 scripts/.gitignore                                     |  1 +
 scripts/Makefile                                       |  3 +++
 scripts/Makefile.modfinal                              |  5 ++---
 scripts/{module-common.lds => module.lds.S}            |  3 +++
 scripts/package/builddeb                               |  2 +-
 21 files changed, 34 insertions(+), 23 deletions(-)
 rename arch/arm/{kernel/module.lds => include/asm/module.lds.h} (72%)
 rename arch/arm64/{kernel/module.lds => include/asm/module.lds.h} (76%)
 rename arch/ia64/{module.lds => include/asm/module.lds.h} (100%)
 rename arch/m68k/{kernel/module.lds => include/asm/module.lds.h} (100%)
 rename arch/powerpc/{kernel/module.lds => include/asm/module.lds.h} (100%)
 rename arch/riscv/{kernel/module.lds => include/asm/module.lds.h} (84%)
 create mode 100644 include/asm-generic/module.lds.h
 rename scripts/{module-common.lds => module.lds.S} (93%)

diff --git a/Makefile b/Makefile
index 992d24467ca0..476f19ccac17 100644
--- a/Makefile
+++ b/Makefile
@@ -505,7 +505,6 @@ KBUILD_CFLAGS_KERNEL :=
 KBUILD_AFLAGS_MODULE  := -DMODULE
 KBUILD_CFLAGS_MODULE  := -DMODULE
 KBUILD_LDFLAGS_MODULE :=
-export KBUILD_LDS_MODULE := $(srctree)/scripts/module-common.lds
 KBUILD_LDFLAGS :=
 CLANG_FLAGS :=
 
@@ -1384,7 +1383,7 @@ endif
 # using awk while concatenating to the final file.
 
 PHONY += modules
-modules: $(if $(KBUILD_BUILTIN),vmlinux) modules_check
+modules: $(if $(KBUILD_BUILTIN),vmlinux) modules_check modules_prepare
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 
 PHONY += modules_check
@@ -1401,6 +1400,7 @@ targets += modules.order
 # Target to prepare building external modules
 PHONY += modules_prepare
 modules_prepare: prepare
+	$(Q)$(MAKE) $(build)=scripts scripts/module.lds
 
 # Target to install modules
 PHONY += modules_install
@@ -1722,7 +1722,9 @@ help:
 	@echo  '  clean           - remove generated files in module directory only'
 	@echo  ''
 
-PHONY += prepare
+# no-op for external module builds
+PHONY += prepare modules_prepare
+
 endif # KBUILD_EXTMOD
 
 # Single targets
@@ -1755,7 +1757,7 @@ MODORDER := .modules.tmp
 endif
 
 PHONY += single_modpost
-single_modpost: $(single-no-ko)
+single_modpost: $(single-no-ko) modules_prepare
 	$(Q){ $(foreach m, $(single-ko), echo $(extmod-prefix)$m;) } > $(MODORDER)
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 4e877354515f..a0cb15de9677 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -16,10 +16,6 @@ LDFLAGS_vmlinux	+= --be8
 KBUILD_LDFLAGS_MODULE	+= --be8
 endif
 
-ifeq ($(CONFIG_ARM_MODULE_PLTS),y)
-KBUILD_LDS_MODULE	+= $(srctree)/arch/arm/kernel/module.lds
-endif
-
 GZFLAGS		:=-9
 #KBUILD_CFLAGS	+=-pipe
 
diff --git a/arch/arm/kernel/module.lds b/arch/arm/include/asm/module.lds.h
similarity index 72%
rename from arch/arm/kernel/module.lds
rename to arch/arm/include/asm/module.lds.h
index 79cb6af565e5..0e7cb4e314b4 100644
--- a/arch/arm/kernel/module.lds
+++ b/arch/arm/include/asm/module.lds.h
@@ -1,5 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#ifdef CONFIG_ARM_MODULE_PLTS
 SECTIONS {
 	.plt : { BYTE(0) }
 	.init.plt : { BYTE(0) }
 }
+#endif
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 130569f90c54..4e8bb73359c8 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -120,10 +120,6 @@ endif
 
 CHECKFLAGS	+= -D__aarch64__
 
-ifeq ($(CONFIG_ARM64_MODULE_PLTS),y)
-KBUILD_LDS_MODULE	+= $(srctree)/arch/arm64/kernel/module.lds
-endif
-
 ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_REGS),y)
   KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
   CC_FLAGS_FTRACE := -fpatchable-function-entry=2
diff --git a/arch/arm64/kernel/module.lds b/arch/arm64/include/asm/module.lds.h
similarity index 76%
rename from arch/arm64/kernel/module.lds
rename to arch/arm64/include/asm/module.lds.h
index 22e36a21c113..691f15af788e 100644
--- a/arch/arm64/kernel/module.lds
+++ b/arch/arm64/include/asm/module.lds.h
@@ -1,5 +1,7 @@
+#ifdef CONFIG_ARM64_MODULE_PLTS
 SECTIONS {
 	.plt (NOLOAD) : { BYTE(0) }
 	.init.plt (NOLOAD) : { BYTE(0) }
 	.text.ftrace_trampoline (NOLOAD) : { BYTE(0) }
 }
+#endif
diff --git a/arch/ia64/Makefile b/arch/ia64/Makefile
index 2876a7df1b0a..703b1c4f6d12 100644
--- a/arch/ia64/Makefile
+++ b/arch/ia64/Makefile
@@ -20,7 +20,6 @@ CHECKFLAGS	+= -D__ia64=1 -D__ia64__=1 -D_LP64 -D__LP64__
 
 OBJCOPYFLAGS	:= --strip-all
 LDFLAGS_vmlinux	:= -static
-KBUILD_LDS_MODULE += $(srctree)/arch/ia64/module.lds
 KBUILD_AFLAGS_KERNEL := -mconstant-gp
 EXTRA		:=
 
diff --git a/arch/ia64/module.lds b/arch/ia64/include/asm/module.lds.h
similarity index 100%
rename from arch/ia64/module.lds
rename to arch/ia64/include/asm/module.lds.h
diff --git a/arch/m68k/Makefile b/arch/m68k/Makefile
index 4438ffb4bbe1..ea14f2046fb4 100644
--- a/arch/m68k/Makefile
+++ b/arch/m68k/Makefile
@@ -75,7 +75,6 @@ KBUILD_CPPFLAGS += -D__uClinux__
 endif
 
 KBUILD_LDFLAGS := -m m68kelf
-KBUILD_LDS_MODULE += $(srctree)/arch/m68k/kernel/module.lds
 
 ifdef CONFIG_SUN3
 LDFLAGS_vmlinux = -N
diff --git a/arch/m68k/kernel/module.lds b/arch/m68k/include/asm/module.lds.h
similarity index 100%
rename from arch/m68k/kernel/module.lds
rename to arch/m68k/include/asm/module.lds.h
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 3e8da9cf2eb9..8935658fcd06 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -65,7 +65,6 @@ UTS_MACHINE := $(subst $(space),,$(machine-y))
 ifdef CONFIG_PPC32
 KBUILD_LDFLAGS_MODULE += arch/powerpc/lib/crtsavres.o
 else
-KBUILD_LDS_MODULE += $(srctree)/arch/powerpc/kernel/module.lds
 ifeq ($(call ld-ifversion, -ge, 225000000, y),y)
 # Have the linker provide sfpr if possible.
 # There is a corresponding test in arch/powerpc/lib/Makefile
diff --git a/arch/powerpc/kernel/module.lds b/arch/powerpc/include/asm/module.lds.h
similarity index 100%
rename from arch/powerpc/kernel/module.lds
rename to arch/powerpc/include/asm/module.lds.h
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index fb6e37db836d..8edaa8bd86d6 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -53,9 +53,6 @@ endif
 ifeq ($(CONFIG_CMODEL_MEDANY),y)
 	KBUILD_CFLAGS += -mcmodel=medany
 endif
-ifeq ($(CONFIG_MODULE_SECTIONS),y)
-	KBUILD_LDS_MODULE += $(srctree)/arch/riscv/kernel/module.lds
-endif
 ifeq ($(CONFIG_PERF_EVENTS),y)
         KBUILD_CFLAGS += -fno-omit-frame-pointer
 endif
diff --git a/arch/riscv/kernel/module.lds b/arch/riscv/include/asm/module.lds.h
similarity index 84%
rename from arch/riscv/kernel/module.lds
rename to arch/riscv/include/asm/module.lds.h
index 295ecfb341a2..4254ff2ff049 100644
--- a/arch/riscv/kernel/module.lds
+++ b/arch/riscv/include/asm/module.lds.h
@@ -1,8 +1,9 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /* Copyright (C) 2017 Andes Technology Corporation */
-
+#ifdef CONFIG_MODULE_SECTIONS
 SECTIONS {
 	.plt (NOLOAD) : { BYTE(0) }
 	.got (NOLOAD) : { BYTE(0) }
 	.got.plt (NOLOAD) : { BYTE(0) }
 }
+#endif
diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild
index 8d435f8a6dec..1c63b260ecc4 100644
--- a/arch/um/include/asm/Kbuild
+++ b/arch/um/include/asm/Kbuild
@@ -16,6 +16,7 @@ generic-y += kdebug.h
 generic-y += mcs_spinlock.h
 generic-y += mm-arch-hooks.h
 generic-y += mmiowb.h
+generic-y += module.lds.h
 generic-y += param.h
 generic-y += pci.h
 generic-y += percpu.h
diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild
index 74b0612601dd..7cd4e627e00e 100644
--- a/include/asm-generic/Kbuild
+++ b/include/asm-generic/Kbuild
@@ -40,6 +40,7 @@ mandatory-y += mmiowb.h
 mandatory-y += mmu.h
 mandatory-y += mmu_context.h
 mandatory-y += module.h
+mandatory-y += module.lds.h
 mandatory-y += msi.h
 mandatory-y += pci.h
 mandatory-y += percpu.h
diff --git a/include/asm-generic/module.lds.h b/include/asm-generic/module.lds.h
new file mode 100644
index 000000000000..f210d5c1b78b
--- /dev/null
+++ b/include/asm-generic/module.lds.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_GENERIC_MODULE_LDS_H
+#define __ASM_GENERIC_MODULE_LDS_H
+
+/*
+ * <asm/module.lds.h> can specify arch-specific sections for linking modules.
+ * Empty for the asm-generic header.
+ */
+
+#endif /* __ASM_GENERIC_MODULE_LDS_H */
diff --git a/scripts/.gitignore b/scripts/.gitignore
index 0d1c8e217cd7..a6c11316c969 100644
--- a/scripts/.gitignore
+++ b/scripts/.gitignore
@@ -8,3 +8,4 @@ asn1_compiler
 extract-cert
 sign-file
 insert-sys-cert
+/module.lds
diff --git a/scripts/Makefile b/scripts/Makefile
index bc018e4b733e..b5418ec587fb 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -29,6 +29,9 @@ endif
 # The following programs are only built on demand
 hostprogs += unifdef
 
+# The module linker script is preprocessed on demand
+targets += module.lds
+
 subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
 subdir-$(CONFIG_MODVERSIONS) += genksyms
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 411c1e600e7d..ae01baf96f4e 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -33,11 +33,10 @@ quiet_cmd_ld_ko_o = LD [M]  $@
       cmd_ld_ko_o =                                                     \
 	$(LD) -r $(KBUILD_LDFLAGS)					\
 		$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE)		\
-		$(addprefix -T , $(KBUILD_LDS_MODULE))			\
-		-o $@ $(filter %.o, $^);				\
+		-T scripts/module.lds -o $@ $(filter %.o, $^);		\
 	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
 
-$(modules): %.ko: %.o %.mod.o $(KBUILD_LDS_MODULE) FORCE
+$(modules): %.ko: %.o %.mod.o scripts/module.lds FORCE
 	+$(call if_changed,ld_ko_o)
 
 targets += $(modules) $(modules:.ko=.mod.o)
diff --git a/scripts/module-common.lds b/scripts/module.lds.S
similarity index 93%
rename from scripts/module-common.lds
rename to scripts/module.lds.S
index d61b9e8678e8..69b9b71a6a47 100644
--- a/scripts/module-common.lds
+++ b/scripts/module.lds.S
@@ -24,3 +24,6 @@ SECTIONS {
 
 	__jump_table		0 : ALIGN(8) { KEEP(*(__jump_table)) }
 }
+
+/* bring in arch-specific sections */
+#include <asm/module.lds.h>
diff --git a/scripts/package/builddeb b/scripts/package/builddeb
index 6df3c9f8b2da..44f212e37935 100755
--- a/scripts/package/builddeb
+++ b/scripts/package/builddeb
@@ -55,7 +55,7 @@ deploy_kernel_headers () {
 		cd $srctree
 		find . arch/$SRCARCH -maxdepth 1 -name Makefile\*
 		find include scripts -type f -o -type l
-		find arch/$SRCARCH -name module.lds -o -name Kbuild.platforms -o -name Platform
+		find arch/$SRCARCH -name Kbuild.platforms -o -name Platform
 		find $(find arch/$SRCARCH -name include -o -name scripts -type d) -type f
 	) > debian/hdrsrcfiles
 
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (2 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 03/29] kbuild: preprocess module linker script Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-10-01 13:17   ` Miroslav Benes
  2020-09-29 21:46 ` [PATCH v4 05/29] objtool: Don't autodetect vmlinux.o Sami Tolvanen
                   ` (26 subsequent siblings)
  30 siblings, 1 reply; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

From: Peter Zijlstra <peterz@infradead.org>

Add the --mcount option for generating __mcount_loc sections
needed for dynamic ftrace. Using this pass requires the kernel to
be compiled with -mfentry and CC_USING_NOP_MCOUNT to be defined
in Makefile.

Link: https://lore.kernel.org/lkml/20200625200235.GQ4781@hirez.programming.kicks-ass.net/
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
[Sami: rebased to mainline, dropped config changes, fixed to actually use
       --mcount, and wrote a commit message.]
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 tools/objtool/builtin-check.c |  3 +-
 tools/objtool/builtin.h       |  2 +-
 tools/objtool/check.c         | 83 +++++++++++++++++++++++++++++++++++
 tools/objtool/check.h         |  1 +
 tools/objtool/objtool.h       |  1 +
 5 files changed, 88 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 7a44174967b5..71595cf4946d 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -18,7 +18,7 @@
 #include "builtin.h"
 #include "objtool.h"
 
-bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux;
+bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount;
 
 static const char * const check_usage[] = {
 	"objtool check [<options>] file.o",
@@ -35,6 +35,7 @@ const struct option check_options[] = {
 	OPT_BOOLEAN('s', "stats", &stats, "print statistics"),
 	OPT_BOOLEAN('d', "duplicate", &validate_dup, "duplicate validation for vmlinux.o"),
 	OPT_BOOLEAN('l', "vmlinux", &vmlinux, "vmlinux.o validation"),
+	OPT_BOOLEAN('M', "mcount", &mcount, "generate __mcount_loc"),
 	OPT_END(),
 };
 
diff --git a/tools/objtool/builtin.h b/tools/objtool/builtin.h
index 85c979caa367..94565a72b701 100644
--- a/tools/objtool/builtin.h
+++ b/tools/objtool/builtin.h
@@ -8,7 +8,7 @@
 #include <subcmd/parse-options.h>
 
 extern const struct option check_options[];
-extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux;
+extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount;
 
 extern int cmd_check(int argc, const char **argv);
 extern int cmd_orc(int argc, const char **argv);
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 90a66891441a..ff0cd4d27d40 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -433,6 +433,65 @@ static int add_dead_ends(struct objtool_file *file)
 	return 0;
 }
 
+static int create_mcount_loc_sections(struct objtool_file *file)
+{
+	struct section *sec, *reloc_sec;
+	struct reloc *reloc;
+	unsigned long *loc;
+	struct instruction *insn;
+	int idx;
+
+	sec = find_section_by_name(file->elf, "__mcount_loc");
+	if (sec) {
+		INIT_LIST_HEAD(&file->mcount_loc_list);
+		WARN("file already has __mcount_loc section, skipping");
+		return 0;
+	}
+
+	if (list_empty(&file->mcount_loc_list))
+		return 0;
+
+	idx = 0;
+	list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node)
+		idx++;
+
+	sec = elf_create_section(file->elf, "__mcount_loc", sizeof(unsigned long), idx);
+	if (!sec)
+		return -1;
+
+	reloc_sec = elf_create_reloc_section(file->elf, sec, SHT_RELA);
+	if (!reloc_sec)
+		return -1;
+
+	idx = 0;
+	list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node) {
+
+		loc = (unsigned long *)sec->data->d_buf + idx;
+		memset(loc, 0, sizeof(unsigned long));
+
+		reloc = malloc(sizeof(*reloc));
+		if (!reloc) {
+			perror("malloc");
+			return -1;
+		}
+		memset(reloc, 0, sizeof(*reloc));
+
+		reloc->sym = insn->sec->sym;
+		reloc->addend = insn->offset;
+		reloc->type = R_X86_64_64;
+		reloc->offset = idx * sizeof(unsigned long);
+		reloc->sec = reloc_sec;
+		elf_add_reloc(file->elf, reloc);
+
+		idx++;
+	}
+
+	if (elf_rebuild_reloc_section(file->elf, reloc_sec))
+		return -1;
+
+	return 0;
+}
+
 /*
  * Warnings shouldn't be reported for ignored functions.
  */
@@ -784,6 +843,22 @@ static int add_call_destinations(struct objtool_file *file)
 			insn->type = INSN_NOP;
 		}
 
+		if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) {
+			if (reloc) {
+				reloc->type = R_NONE;
+				elf_write_reloc(file->elf, reloc);
+			}
+
+			elf_write_insn(file->elf, insn->sec,
+				       insn->offset, insn->len,
+				       arch_nop_insn(insn->len));
+
+			insn->type = INSN_NOP;
+
+			list_add_tail(&insn->mcount_loc_node,
+				      &file->mcount_loc_list);
+		}
+
 		/*
 		 * Whatever stack impact regular CALLs have, should be undone
 		 * by the RETURN of the called function.
@@ -2791,6 +2866,7 @@ int check(const char *_objname, bool orc)
 
 	INIT_LIST_HEAD(&file.insn_list);
 	hash_init(file.insn_hash);
+	INIT_LIST_HEAD(&file.mcount_loc_list);
 	file.c_file = !vmlinux && find_section_by_name(file.elf, ".comment");
 	file.ignore_unreachables = no_unreachable;
 	file.hints = false;
@@ -2838,6 +2914,13 @@ int check(const char *_objname, bool orc)
 		warnings += ret;
 	}
 
+	if (mcount) {
+		ret = create_mcount_loc_sections(&file);
+		if (ret < 0)
+			goto out;
+		warnings += ret;
+	}
+
 	if (orc) {
 		ret = create_orc(&file);
 		if (ret < 0)
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index 061aa96e15d3..b62afd3d970b 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -22,6 +22,7 @@ struct insn_state {
 struct instruction {
 	struct list_head list;
 	struct hlist_node hash;
+	struct list_head mcount_loc_node;
 	struct section *sec;
 	unsigned long offset;
 	unsigned int len;
diff --git a/tools/objtool/objtool.h b/tools/objtool/objtool.h
index 528028a66816..427806079540 100644
--- a/tools/objtool/objtool.h
+++ b/tools/objtool/objtool.h
@@ -16,6 +16,7 @@ struct objtool_file {
 	struct elf *elf;
 	struct list_head insn_list;
 	DECLARE_HASHTABLE(insn_hash, 20);
+	struct list_head mcount_loc_list;
 	bool ignore_unreachables, c_file, hints, rodata;
 };
 
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 05/29] objtool: Don't autodetect vmlinux.o
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (3 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 06/29] tracing: move function tracer options to Kconfig Sami Tolvanen
                   ` (25 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With LTO, we run objtool on vmlinux.o, but don't want noinstr
validation. This change requires --vmlinux to be passed to objtool
explicitly.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 scripts/link-vmlinux.sh       |  2 +-
 tools/objtool/builtin-check.c | 10 +---------
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index e6e2d9e5ff48..372c3719f94c 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -64,7 +64,7 @@ objtool_link()
 	local objtoolopt;
 
 	if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
-		objtoolopt="check"
+		objtoolopt="check --vmlinux"
 		if [ -z "${CONFIG_FRAME_POINTER}" ]; then
 			objtoolopt="${objtoolopt} --no-fp"
 		fi
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 71595cf4946d..eaa06eb18690 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -41,18 +41,10 @@ const struct option check_options[] = {
 
 int cmd_check(int argc, const char **argv)
 {
-	const char *objname, *s;
-
 	argc = parse_options(argc, argv, check_options, check_usage, 0);
 
 	if (argc != 1)
 		usage_with_options(check_usage, check_options);
 
-	objname = argv[0];
-
-	s = strstr(objname, "vmlinux.o");
-	if (s && !s[9])
-		vmlinux = true;
-
-	return check(objname, false);
+	return check(argv[0], false);
 }
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 06/29] tracing: move function tracer options to Kconfig
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (4 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 05/29] objtool: Don't autodetect vmlinux.o Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-30  0:12   ` Steven Rostedt
  2020-09-29 21:46 ` [PATCH v4 07/29] tracing: add support for objtool mcount Sami Tolvanen
                   ` (24 subsequent siblings)
  30 siblings, 1 reply; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

Move function tracer options to Kconfig to make it easier to add
new methods for generating __mcount_loc, and to make the options
available also when building kernel modules.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 Makefile               | 20 ++++++++------------
 kernel/trace/Kconfig   | 16 ++++++++++++++++
 scripts/Makefile.build |  6 ++----
 3 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/Makefile b/Makefile
index 476f19ccac17..77e4f0a9495e 100644
--- a/Makefile
+++ b/Makefile
@@ -841,12 +841,8 @@ KBUILD_CFLAGS += $(DEBUG_CFLAGS)
 export DEBUG_CFLAGS
 
 ifdef CONFIG_FUNCTION_TRACER
-ifdef CONFIG_FTRACE_MCOUNT_RECORD
-  # gcc 5 supports generating the mcount tables directly
-  ifeq ($(call cc-option-yn,-mrecord-mcount),y)
-    CC_FLAGS_FTRACE	+= -mrecord-mcount
-    export CC_USING_RECORD_MCOUNT := 1
-  endif
+ifdef CONFIG_FTRACE_MCOUNT_USE_CC
+  CC_FLAGS_FTRACE	+= -mrecord-mcount
   ifdef CONFIG_HAVE_NOP_MCOUNT
     ifeq ($(call cc-option-yn, -mnop-mcount),y)
       CC_FLAGS_FTRACE	+= -mnop-mcount
@@ -854,6 +850,12 @@ ifdef CONFIG_FTRACE_MCOUNT_RECORD
     endif
   endif
 endif
+ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
+  ifdef CONFIG_HAVE_C_RECORDMCOUNT
+    BUILD_C_RECORDMCOUNT := y
+    export BUILD_C_RECORDMCOUNT
+  endif
+endif
 ifdef CONFIG_HAVE_FENTRY
   ifeq ($(call cc-option-yn, -mfentry),y)
     CC_FLAGS_FTRACE	+= -mfentry
@@ -863,12 +865,6 @@ endif
 export CC_FLAGS_FTRACE
 KBUILD_CFLAGS	+= $(CC_FLAGS_FTRACE) $(CC_FLAGS_USING)
 KBUILD_AFLAGS	+= $(CC_FLAGS_USING)
-ifdef CONFIG_DYNAMIC_FTRACE
-	ifdef CONFIG_HAVE_C_RECORDMCOUNT
-		BUILD_C_RECORDMCOUNT := y
-		export BUILD_C_RECORDMCOUNT
-	endif
-endif
 endif
 
 # We trigger additional mismatches with less inlining
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index a4020c0b4508..927ad004888a 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -595,6 +595,22 @@ config FTRACE_MCOUNT_RECORD
 	depends on DYNAMIC_FTRACE
 	depends on HAVE_FTRACE_MCOUNT_RECORD
 
+config FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
+	bool
+	depends on FTRACE_MCOUNT_RECORD
+
+config FTRACE_MCOUNT_USE_CC
+	def_bool y
+	depends on $(cc-option,-mrecord-mcount)
+	depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
+	depends on FTRACE_MCOUNT_RECORD
+
+config FTRACE_MCOUNT_USE_RECORDMCOUNT
+	def_bool y
+	depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
+	depends on !FTRACE_MCOUNT_USE_CC
+	depends on FTRACE_MCOUNT_RECORD
+
 config TRACING_MAP
 	bool
 	depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index a467b9323442..a4634aae1506 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -178,8 +178,7 @@ cmd_modversions_c =								\
 	fi
 endif
 
-ifdef CONFIG_FTRACE_MCOUNT_RECORD
-ifndef CC_USING_RECORD_MCOUNT
+ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 # compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
 ifdef BUILD_C_RECORDMCOUNT
 ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
@@ -206,8 +205,7 @@ recordmcount_source := $(srctree)/scripts/recordmcount.pl
 endif # BUILD_C_RECORDMCOUNT
 cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)),	\
 	$(sub_cmd_record_mcount))
-endif # CC_USING_RECORD_MCOUNT
-endif # CONFIG_FTRACE_MCOUNT_RECORD
+endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 
 ifdef CONFIG_STACK_VALIDATION
 ifneq ($(SKIP_STACK_VALIDATION),1)
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 07/29] tracing: add support for objtool mcount
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (5 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 06/29] tracing: move function tracer options to Kconfig Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 08/29] x86, build: use " Sami Tolvanen
                   ` (23 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

This change adds build support for using objtool to generate
__mcount_loc sections.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 Makefile             | 12 ++++++++++--
 kernel/trace/Kconfig | 13 +++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 77e4f0a9495e..9717005e41c4 100644
--- a/Makefile
+++ b/Makefile
@@ -850,6 +850,9 @@ ifdef CONFIG_FTRACE_MCOUNT_USE_CC
     endif
   endif
 endif
+ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
+  CC_FLAGS_USING	+= -DCC_USING_NOP_MCOUNT
+endif
 ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
   ifdef CONFIG_HAVE_C_RECORDMCOUNT
     BUILD_C_RECORDMCOUNT := y
@@ -1209,11 +1212,16 @@ uapi-asm-generic:
 PHONY += prepare-objtool prepare-resolve_btfids
 prepare-objtool: $(objtool_target)
 ifeq ($(SKIP_STACK_VALIDATION),1)
+objtool-lib-prompt := "please install libelf-dev, libelf-devel or elfutils-libelf-devel"
+ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
+	@echo "error: Cannot generate __mcount_loc for CONFIG_DYNAMIC_FTRACE=y, $(objtool-lib-prompt)" >&2
+	@false
+endif
 ifdef CONFIG_UNWINDER_ORC
-	@echo "error: Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
+	@echo "error: Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, $(objtool-lib-prompt)" >&2
 	@false
 else
-	@echo "warning: Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
+	@echo "warning: Cannot use CONFIG_STACK_VALIDATION=y, $(objtool-lib-prompt)" >&2
 endif
 endif
 
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 927ad004888a..89263210ab26 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -51,6 +51,11 @@ config HAVE_NOP_MCOUNT
 	help
 	  Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
 
+config HAVE_OBJTOOL_MCOUNT
+	bool
+	help
+	  Arch supports objtool --mcount
+
 config HAVE_C_RECORDMCOUNT
 	bool
 	help
@@ -605,10 +610,18 @@ config FTRACE_MCOUNT_USE_CC
 	depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
 	depends on FTRACE_MCOUNT_RECORD
 
+config FTRACE_MCOUNT_USE_OBJTOOL
+	def_bool y
+	depends on HAVE_OBJTOOL_MCOUNT
+	depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
+	depends on !FTRACE_MCOUNT_USE_CC
+	depends on FTRACE_MCOUNT_RECORD
+
 config FTRACE_MCOUNT_USE_RECORDMCOUNT
 	def_bool y
 	depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
 	depends on !FTRACE_MCOUNT_USE_CC
+	depends on !FTRACE_MCOUNT_USE_OBJTOOL
 	depends on FTRACE_MCOUNT_RECORD
 
 config TRACING_MAP
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 08/29] x86, build: use objtool mcount
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (6 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 07/29] tracing: add support for objtool mcount Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 09/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
                   ` (22 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

Select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION is selected to use
objtool to generate __mcount_loc sections for dynamic ftrace with
Clang and gcc <5 (later versions of gcc use -mrecord-mcount).

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7101ac64bb20..6de2e5c0bdba 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -163,6 +163,7 @@ config X86
 	select HAVE_CMPXCHG_LOCAL
 	select HAVE_CONTEXT_TRACKING		if X86_64
 	select HAVE_C_RECORDMCOUNT
+	select HAVE_OBJTOOL_MCOUNT		if STACK_VALIDATION
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_DYNAMIC_FTRACE
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 09/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (7 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 08/29] x86, build: use " Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-30  9:58   ` Mark Rutland
  2020-09-29 21:46 ` [PATCH v4 10/29] treewide: remove DISABLE_LTO Sami Tolvanen
                   ` (21 subsequent siblings)
  30 siblings, 1 reply; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

Select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY to disable
recordmcount when DYNAMIC_FTRACE_WITH_REGS is selected.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/arm64/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d232837cbee..ad522b021f35 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -155,6 +155,8 @@ config ARM64
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS \
 		if $(cc-option,-fpatchable-function-entry=2)
+	select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \
+		if DYNAMIC_FTRACE_WITH_REGS
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS
 	select HAVE_FAST_GUP
 	select HAVE_FTRACE_MCOUNT_RECORD
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 10/29] treewide: remove DISABLE_LTO
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (8 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 09/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-30 20:45   ` Kees Cook
  2020-09-29 21:46 ` [PATCH v4 11/29] kbuild: add support for Clang LTO Sami Tolvanen
                   ` (20 subsequent siblings)
  30 siblings, 1 reply; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

This change removes all instances of DISABLE_LTO from
Makefiles, as they are currently unused, and the preferred
method of disabling LTO is to filter out the flags instead.

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/arm64/kernel/vdso/Makefile | 1 -
 arch/sparc/vdso/Makefile        | 2 --
 arch/x86/entry/vdso/Makefile    | 2 --
 kernel/Makefile                 | 3 ---
 scripts/Makefile.build          | 2 +-
 5 files changed, 1 insertion(+), 9 deletions(-)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 45d5cfe46429..e836e300440f 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -31,7 +31,6 @@ ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18
 ccflags-y += -DDISABLE_BRANCH_PROFILING
 
 CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) $(GCC_PLUGINS_CFLAGS)
-KBUILD_CFLAGS			+= $(DISABLE_LTO)
 KASAN_SANITIZE			:= n
 UBSAN_SANITIZE			:= n
 OBJECT_FILES_NON_STANDARD	:= y
diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile
index f44355e46f31..476c4b315505 100644
--- a/arch/sparc/vdso/Makefile
+++ b/arch/sparc/vdso/Makefile
@@ -3,8 +3,6 @@
 # Building vDSO images for sparc.
 #
 
-KBUILD_CFLAGS += $(DISABLE_LTO)
-
 VDSO64-$(CONFIG_SPARC64)	:= y
 VDSOCOMPAT-$(CONFIG_COMPAT)	:= y
 
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 215376d975a2..ecc27018ae13 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -9,8 +9,6 @@ ARCH_REL_TYPE_ABS := R_X86_64_JUMP_SLOT|R_X86_64_GLOB_DAT|R_X86_64_RELATIVE|
 ARCH_REL_TYPE_ABS += R_386_GLOB_DAT|R_386_JMP_SLOT|R_386_RELATIVE
 include $(srctree)/lib/vdso/Makefile
 
-KBUILD_CFLAGS += $(DISABLE_LTO)
-
 # Sanitizer runtimes are unavailable and cannot be linked here.
 KASAN_SANITIZE			:= n
 UBSAN_SANITIZE			:= n
diff --git a/kernel/Makefile b/kernel/Makefile
index 9a20016d4900..347254f07dab 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -38,9 +38,6 @@ KASAN_SANITIZE_kcov.o := n
 KCSAN_SANITIZE_kcov.o := n
 CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector
 
-# cond_syscall is currently not LTO compatible
-CFLAGS_sys_ni.o = $(DISABLE_LTO)
-
 obj-y += sched/
 obj-y += locking/
 obj-y += power/
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index a4634aae1506..2175ddb1ee0c 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -111,7 +111,7 @@ endif
 # ---------------------------------------------------------------------------
 
 quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
-      cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) $(DISABLE_LTO) -fverbose-asm -S -o $@ $<
+      cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) -fverbose-asm -S -o $@ $<
 
 $(obj)/%.s: $(src)/%.c FORCE
 	$(call if_changed_dep,cc_s_c)
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 11/29] kbuild: add support for Clang LTO
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (9 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 10/29] treewide: remove DISABLE_LTO Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 12/29] kbuild: lto: fix module versioning Sami Tolvanen
                   ` (19 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:

  https://llvm.org/docs/LinkTimeOptimization.html

The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:

  - compiling with Clang,
  - compiling inline assembly with Clang's integrated assembler,
  - and linking with LLD.

While using full LTO results in the best runtime performance, the
compilation is not scalable in time or memory. CONFIG_THINLTO
enables ThinLTO, which allows parallel optimization and faster
incremental builds. ThinLTO is used by default if the architecture
also selects ARCH_SUPPORTS_THINLTO:

  https://clang.llvm.org/docs/ThinLTO.html

To enable LTO, LLVM tools must be used to handle bitcode files. The
easiest way is to pass the LLVM=1 option to make:

  $ make LLVM=1 defconfig
  $ scripts/config -e LTO_CLANG
  $ make LLVM=1

Alternatively, at least the following LLVM tools must be used:

  CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm

To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.

Note that support for DYNAMIC_FTRACE and MODVERSIONS are added in
follow-up patches.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 Makefile                          | 20 ++++++++-
 arch/Kconfig                      | 69 +++++++++++++++++++++++++++++++
 include/asm-generic/vmlinux.lds.h | 11 +++--
 scripts/Makefile.build            |  9 +++-
 scripts/Makefile.modfinal         |  9 +++-
 scripts/Makefile.modpost          | 18 +++++++-
 scripts/link-vmlinux.sh           | 32 ++++++++++----
 7 files changed, 150 insertions(+), 18 deletions(-)

diff --git a/Makefile b/Makefile
index 9717005e41c4..8e2eaf6452ba 100644
--- a/Makefile
+++ b/Makefile
@@ -886,6 +886,21 @@ KBUILD_CFLAGS	+= $(CC_FLAGS_SCS)
 export CC_FLAGS_SCS
 endif
 
+ifdef CONFIG_LTO_CLANG
+ifdef CONFIG_THINLTO
+CC_FLAGS_LTO	+= -flto=thin -fsplit-lto-unit
+KBUILD_LDFLAGS	+= --thinlto-cache-dir=$(extmod-prefix).thinlto-cache
+else
+CC_FLAGS_LTO	+= -flto
+endif
+CC_FLAGS_LTO	+= -fvisibility=default
+endif
+
+ifdef CONFIG_LTO
+KBUILD_CFLAGS	+= $(CC_FLAGS_LTO)
+export CC_FLAGS_LTO
+endif
+
 ifdef CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_32B
 KBUILD_CFLAGS += -falign-functions=32
 endif
@@ -1477,7 +1492,7 @@ MRPROPER_FILES += include/config include/generated          \
 		  *.spec
 
 # Directories & files removed with 'make distclean'
-DISTCLEAN_FILES += tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS
+DISTCLEAN_FILES += tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS .thinlto-cache
 
 # clean - Delete most, but leave enough to build external modules
 #
@@ -1714,7 +1729,8 @@ _emodinst_post: _emodinst_
 	$(call cmd,depmod)
 
 clean-dirs := $(KBUILD_EXTMOD)
-clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps
+clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \
+		   $(KBUILD_EXTMOD)/.thinlto-cache
 
 PHONY += help
 help:
diff --git a/arch/Kconfig b/arch/Kconfig
index af14a567b493..0742ec643d79 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -552,6 +552,75 @@ config SHADOW_CALL_STACK
 	  reading and writing arbitrary memory may be able to locate them
 	  and hijack control flow by modifying the stacks.
 
+config LTO
+	bool
+
+config ARCH_SUPPORTS_LTO_CLANG
+	bool
+	help
+	  An architecture should select this option if it supports:
+	  - compiling with Clang,
+	  - compiling inline assembly with Clang's integrated assembler,
+	  - and linking with LLD.
+
+config ARCH_SUPPORTS_THINLTO
+	bool
+	help
+	  An architecture should select this option if it supports Clang's
+	  ThinLTO.
+
+config THINLTO
+	bool "Clang ThinLTO"
+	depends on LTO_CLANG && ARCH_SUPPORTS_THINLTO
+	default y
+	help
+	  This option enables Clang's ThinLTO, which allows for parallel
+	  optimization and faster incremental compiles. More information
+	  can be found from Clang's documentation:
+
+	    https://clang.llvm.org/docs/ThinLTO.html
+
+choice
+	prompt "Link Time Optimization (LTO)"
+	default LTO_NONE
+	help
+	  This option enables Link Time Optimization (LTO), which allows the
+	  compiler to optimize binaries globally.
+
+	  If unsure, select LTO_NONE. Note that LTO is very resource-intensive
+	  so it's disabled by default.
+
+config LTO_NONE
+	bool "None"
+
+config LTO_CLANG
+	bool "Clang's Link Time Optimization (EXPERIMENTAL)"
+	# Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
+	depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD
+	depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
+	depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
+	depends on ARCH_SUPPORTS_LTO_CLANG
+	depends on !FTRACE_MCOUNT_RECORD
+	depends on !KASAN
+	depends on !GCOV_KERNEL
+	depends on !MODVERSIONS
+	select LTO
+	help
+          This option enables Clang's Link Time Optimization (LTO), which
+          allows the compiler to optimize the kernel globally. If you enable
+          this option, the compiler generates LLVM bitcode instead of ELF
+          object files, and the actual compilation from bitcode happens at
+          the LTO link step, which may take several minutes depending on the
+          kernel configuration. More information can be found from LLVM's
+          documentation:
+
+	    https://llvm.org/docs/LinkTimeOptimization.html
+
+	  To select this option, you also need to use LLVM tools to handle
+	  the bitcode by passing LLVM=1 to make.
+
+endchoice
+
 config HAVE_ARCH_WITHIN_STACK_FRAMES
 	bool
 	help
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 5430febd34be..c1f0d58272bd 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -89,15 +89,18 @@
  * .data. We don't want to pull in .data..other sections, which Linux
  * has defined. Same for text and bss.
  *
+ * With LTO_CLANG, the linker also splits sections by default, so we need
+ * these macros to combine the sections during the final link.
+ *
  * RODATA_MAIN is not used because existing code already defines .rodata.x
  * sections to be brought in with rodata.
  */
-#ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
+#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG)
 #define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
-#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX*
+#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral*
 #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
-#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]*
-#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]*
+#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L*
+#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral*
 #define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]*
 #else
 #define TEXT_MAIN .text
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 2175ddb1ee0c..ed74b2f986f7 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -111,7 +111,7 @@ endif
 # ---------------------------------------------------------------------------
 
 quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
-      cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) -fverbose-asm -S -o $@ $<
+      cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS) $(CC_FLAGS_LTO), $(c_flags)) -fverbose-asm -S -o $@ $<
 
 $(obj)/%.s: $(src)/%.c FORCE
 	$(call if_changed_dep,cc_s_c)
@@ -425,8 +425,15 @@ $(obj)/lib.a: $(lib-y) FORCE
 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
 # module is turned into a multi object module, $^ will contain header file
 # dependencies recorded in the .*.cmd file.
+ifdef CONFIG_LTO_CLANG
+quiet_cmd_link_multi-m = AR [M]  $@
+cmd_link_multi-m =						\
+	rm -f $@; 						\
+	$(AR) cDPrsT $@ $(filter %.o,$^)
+else
 quiet_cmd_link_multi-m = LD [M]  $@
       cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
+endif
 
 $(multi-used-m): FORCE
 	$(call if_changed,link_multi-m)
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index ae01baf96f4e..2cb9a1d88434 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -6,6 +6,7 @@
 PHONY := __modfinal
 __modfinal:
 
+include $(objtree)/include/config/auto.conf
 include $(srctree)/scripts/Kbuild.include
 
 # for c_flags
@@ -29,6 +30,12 @@ quiet_cmd_cc_o_c = CC [M]  $@
 
 ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
 
+ifdef CONFIG_LTO_CLANG
+# With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to
+# avoid a second slow LTO link
+prelink-ext := .lto
+endif
+
 quiet_cmd_ld_ko_o = LD [M]  $@
       cmd_ld_ko_o =                                                     \
 	$(LD) -r $(KBUILD_LDFLAGS)					\
@@ -36,7 +43,7 @@ quiet_cmd_ld_ko_o = LD [M]  $@
 		-T scripts/module.lds -o $@ $(filter %.o, $^);		\
 	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
 
-$(modules): %.ko: %.o %.mod.o scripts/module.lds FORCE
+$(modules): %.ko: %$(prelink-ext).o %.mod.o scripts/module.lds FORCE
 	+$(call if_changed,ld_ko_o)
 
 targets += $(modules) $(modules:.ko=.mod.o)
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index f54b6ac37ac2..66e0c256403c 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -102,12 +102,26 @@ $(input-symdump):
 	@echo >&2 'WARNING: Symbol version dump "$@" is missing.'
 	@echo >&2 '         Modules may not have dependencies or modversions.'
 
+ifdef CONFIG_LTO_CLANG
+# With CONFIG_LTO_CLANG, .o files might be LLVM bitcode, so we need to run
+# LTO to compile them into native code before running modpost
+prelink-ext = .lto
+
+quiet_cmd_cc_lto_link_modules = LTO [M] $@
+cmd_cc_lto_link_modules = $(LD) $(ld_flags) -r -o $@ --whole-archive $^
+
+%.lto.o: %.o
+	$(call if_changed,cc_lto_link_modules)
+endif
+
+modules := $(sort $(shell cat $(MODORDER)))
+
 # Read out modules.order to pass in modpost.
 # Otherwise, allmodconfig would fail with "Argument list too long".
 quiet_cmd_modpost = MODPOST $@
-      cmd_modpost = sed 's/ko$$/o/' $< | $(MODPOST) -T -
+      cmd_modpost = sed 's/\.ko$$/$(prelink-ext)\.o/' $< | $(MODPOST) -T -
 
-$(output-symdump): $(MODORDER) $(input-symdump) FORCE
+$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(prelink-ext).o) FORCE
 	$(call if_changed,modpost)
 
 targets += $(output-symdump)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 372c3719f94c..ebb9f912aab6 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -56,6 +56,14 @@ modpost_link()
 		${KBUILD_VMLINUX_LIBS}				\
 		--end-group"
 
+	if [ -n "${CONFIG_LTO_CLANG}" ]; then
+		# This might take a while, so indicate that we're doing
+		# an LTO link
+		info LTO ${1}
+	else
+		info LD ${1}
+	fi
+
 	${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${objects}
 }
 
@@ -103,13 +111,22 @@ vmlinux_link()
 	fi
 
 	if [ "${SRCARCH}" != "um" ]; then
-		objects="--whole-archive			\
-			${KBUILD_VMLINUX_OBJS}			\
-			--no-whole-archive			\
-			--start-group				\
-			${KBUILD_VMLINUX_LIBS}			\
-			--end-group				\
-			${@}"
+		if [ -n "${CONFIG_LTO_CLANG}" ]; then
+			# Use vmlinux.o instead of performing the slow LTO
+			# link again.
+			objects="--whole-archive		\
+				vmlinux.o 			\
+				--no-whole-archive		\
+				${@}"
+		else
+			objects="--whole-archive		\
+				${KBUILD_VMLINUX_OBJS}		\
+				--no-whole-archive		\
+				--start-group			\
+				${KBUILD_VMLINUX_LIBS}		\
+				--end-group			\
+				${@}"
+		fi
 
 		${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}	\
 			${strip_debug#-Wl,}			\
@@ -274,7 +291,6 @@ fi;
 ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1
 
 #link vmlinux.o
-info LD vmlinux.o
 modpost_link vmlinux.o
 objtool_link vmlinux.o
 
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 12/29] kbuild: lto: fix module versioning
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (10 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 11/29] kbuild: add support for Clang LTO Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 13/29] kbuild: lto: postpone objtool Sami Tolvanen
                   ` (18 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With CONFIG_MODVERSIONS, version information is linked into each
compilation unit that exports symbols. With LTO, we cannot use this
method as all C code is compiled into LLVM bitcode instead. This
change collects symbol versions into .symversions files and merges
them in link-vmlinux.sh where they are all linked into vmlinux.o at
the same time.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 .gitignore               |  1 +
 Makefile                 |  3 ++-
 arch/Kconfig             |  1 -
 scripts/Makefile.build   | 33 +++++++++++++++++++++++++++++++--
 scripts/Makefile.modpost |  6 +++++-
 scripts/link-vmlinux.sh  | 25 ++++++++++++++++++++++++-
 6 files changed, 63 insertions(+), 6 deletions(-)

diff --git a/.gitignore b/.gitignore
index 162bd2b67bdf..06e76dc39ffe 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,6 +41,7 @@
 *.so.dbg
 *.su
 *.symtypes
+*.symversions
 *.tab.[ch]
 *.tar
 *.xz
diff --git a/Makefile b/Makefile
index 8e2eaf6452ba..23cdb475c445 100644
--- a/Makefile
+++ b/Makefile
@@ -1827,7 +1827,8 @@ clean: $(clean-dirs)
 		-o -name '.tmp_*.o.*' \
 		-o -name '*.c.[012]*.*' \
 		-o -name '*.ll' \
-		-o -name '*.gcno' \) -type f -print | xargs rm -f
+		-o -name '*.gcno' \
+		-o -name '*.*.symversions' \) -type f -print | xargs rm -f
 
 # Generate tags for editors
 # ---------------------------------------------------------------------------
diff --git a/arch/Kconfig b/arch/Kconfig
index 0742ec643d79..520e900efc75 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -603,7 +603,6 @@ config LTO_CLANG
 	depends on !FTRACE_MCOUNT_RECORD
 	depends on !KASAN
 	depends on !GCOV_KERNEL
-	depends on !MODVERSIONS
 	select LTO
 	help
           This option enables Clang's Link Time Optimization (LTO), which
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index ed74b2f986f7..eae2f5386a03 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -166,6 +166,15 @@ ifdef CONFIG_MODVERSIONS
 #   the actual value of the checksum generated by genksyms
 # o remove .tmp_<file>.o to <file>.o
 
+ifdef CONFIG_LTO_CLANG
+# Generate .o.symversions files for each .o with exported symbols, and link these
+# to the kernel and/or modules at the end.
+cmd_modversions_c =								\
+	if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then			\
+		$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
+		    > $@.symversions;						\
+	fi;
+else
 cmd_modversions_c =								\
 	if $(OBJDUMP) -h $@ | grep -q __ksymtab; then				\
 		$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
@@ -177,6 +186,7 @@ cmd_modversions_c =								\
 		rm -f $(@D)/.tmp_$(@F:.o=.ver);					\
 	fi
 endif
+endif
 
 ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 # compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
@@ -390,6 +400,18 @@ $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
 $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
 $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 
+# combine symversions for later processing
+quiet_cmd_update_lto_symversions = SYMVER  $@
+ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
+      cmd_update_lto_symversions =					\
+	rm -f $@.symversions						\
+	$(foreach n, $(filter-out FORCE,$^),				\
+		$(if $(wildcard $(n).symversions),			\
+			; cat $(n).symversions >> $@.symversions))
+else
+      cmd_update_lto_symversions = echo >/dev/null
+endif
+
 #
 # Rule to compile a set of .o files into one .a file (without symbol table)
 #
@@ -397,8 +419,11 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 quiet_cmd_ar_builtin = AR      $@
       cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
 
+quiet_cmd_ar_and_symver = AR      $@
+      cmd_ar_and_symver = $(cmd_update_lto_symversions); $(cmd_ar_builtin)
+
 $(obj)/built-in.a: $(real-obj-y) FORCE
-	$(call if_changed,ar_builtin)
+	$(call if_changed,ar_and_symver)
 
 #
 # Rule to create modules.order file
@@ -418,8 +443,11 @@ $(obj)/modules.order: $(obj-m) FORCE
 #
 # Rule to compile a set of .o files into one .a file (with symbol table)
 #
+quiet_cmd_ar_lib = AR      $@
+      cmd_ar_lib = $(cmd_update_lto_symversions); $(cmd_ar)
+
 $(obj)/lib.a: $(lib-y) FORCE
-	$(call if_changed,ar)
+	$(call if_changed,ar_lib)
 
 # NOTE:
 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
@@ -428,6 +456,7 @@ $(obj)/lib.a: $(lib-y) FORCE
 ifdef CONFIG_LTO_CLANG
 quiet_cmd_link_multi-m = AR [M]  $@
 cmd_link_multi-m =						\
+	$(cmd_update_lto_symversions);				\
 	rm -f $@; 						\
 	$(AR) cDPrsT $@ $(filter %.o,$^)
 else
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 66e0c256403c..753725b88683 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -108,7 +108,11 @@ ifdef CONFIG_LTO_CLANG
 prelink-ext = .lto
 
 quiet_cmd_cc_lto_link_modules = LTO [M] $@
-cmd_cc_lto_link_modules = $(LD) $(ld_flags) -r -o $@ --whole-archive $^
+cmd_cc_lto_link_modules =						\
+	$(LD) $(ld_flags) -r -o $@					\
+		$(shell [ -s $(@:.lto.o=.o.symversions) ] &&		\
+			echo -T $(@:.lto.o=.o.symversions))		\
+		--whole-archive $^
 
 %.lto.o: %.o
 	$(call if_changed,cc_lto_link_modules)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index ebb9f912aab6..3e99a19b9195 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -43,11 +43,28 @@ info()
 	fi
 }
 
+# If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
+# .tmp_symversions.lds
+gen_symversions()
+{
+	info GEN .tmp_symversions.lds
+	rm -f .tmp_symversions.lds
+
+	for a in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
+		for o in $(${AR} t $a 2>/dev/null); do
+			if [ -f ${o}.symversions ]; then
+				cat ${o}.symversions >> .tmp_symversions.lds
+			fi
+		done
+	done
+}
+
 # Link of vmlinux.o used for section mismatch analysis
 # ${1} output file
 modpost_link()
 {
 	local objects
+	local lds=""
 
 	objects="--whole-archive				\
 		${KBUILD_VMLINUX_OBJS}				\
@@ -57,6 +74,11 @@ modpost_link()
 		--end-group"
 
 	if [ -n "${CONFIG_LTO_CLANG}" ]; then
+		if [ -n "${CONFIG_MODVERSIONS}" ]; then
+			gen_symversions
+			lds="${lds} -T .tmp_symversions.lds"
+		fi
+
 		# This might take a while, so indicate that we're doing
 		# an LTO link
 		info LTO ${1}
@@ -64,7 +86,7 @@ modpost_link()
 		info LD ${1}
 	fi
 
-	${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${objects}
+	${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${lds} ${objects}
 }
 
 objtool_link()
@@ -242,6 +264,7 @@ cleanup()
 {
 	rm -f .btf.*
 	rm -f .tmp_System.map
+	rm -f .tmp_symversions.lds
 	rm -f .tmp_vmlinux*
 	rm -f System.map
 	rm -f vmlinux
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 13/29] kbuild: lto: postpone objtool
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (11 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 12/29] kbuild: lto: fix module versioning Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 14/29] kbuild: lto: limit inlining Sami Tolvanen
                   ` (17 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With LTO, LLVM bitcode won't be compiled into native code until
modpost_link, or modfinal for modules. This change postpones calls
to objtool until after these steps, and moves objtool_args to
Makefile.lib, so the arguments can be reused in Makefile.modfinal.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/Kconfig              |  2 +-
 scripts/Makefile.build    | 19 ++-----------------
 scripts/Makefile.lib      | 11 +++++++++++
 scripts/Makefile.modfinal | 19 ++++++++++++++++---
 scripts/link-vmlinux.sh   | 23 ++++++++++++++++++++++-
 5 files changed, 52 insertions(+), 22 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 520e900efc75..db57ea19649b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -600,7 +600,7 @@ config LTO_CLANG
 	depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
 	depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
 	depends on ARCH_SUPPORTS_LTO_CLANG
-	depends on !FTRACE_MCOUNT_RECORD
+	depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
 	depends on !KASAN
 	depends on !GCOV_KERNEL
 	select LTO
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index eae2f5386a03..ab0ddf4884fd 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -218,27 +218,11 @@ cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)),
 endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 
 ifdef CONFIG_STACK_VALIDATION
+ifndef CONFIG_LTO_CLANG
 ifneq ($(SKIP_STACK_VALIDATION),1)
 
 __objtool_obj := $(objtree)/tools/objtool/objtool
 
-objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
-
-objtool_args += $(if $(part-of-module), --module,)
-
-ifndef CONFIG_FRAME_POINTER
-objtool_args += --no-fp
-endif
-ifdef CONFIG_GCOV_KERNEL
-objtool_args += --no-unreachable
-endif
-ifdef CONFIG_RETPOLINE
-  objtool_args += --retpoline
-endif
-ifdef CONFIG_X86_SMAP
-  objtool_args += --uaccess
-endif
-
 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
@@ -250,6 +234,7 @@ objtool_obj = $(if $(patsubst y%,, \
 	$(__objtool_obj))
 
 endif # SKIP_STACK_VALIDATION
+endif # CONFIG_LTO_CLANG
 endif # CONFIG_STACK_VALIDATION
 
 # Rebuild all objects when objtool changes, or is enabled/disabled.
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 3d599716940c..ecb97c9f5feb 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -216,6 +216,17 @@ dtc_cpp_flags  = -Wp,-MMD,$(depfile).pre.tmp -nostdinc                    \
 		 $(addprefix -I,$(DTC_INCLUDE))                          \
 		 -undef -D__DTS__
 
+# Objtool arguments are also needed for modfinal with LTO, so we define
+# then here to avoid duplication.
+objtool_args =								\
+	$(if $(CONFIG_UNWINDER_ORC),orc generate,check)			\
+	$(if $(part-of-module), --module,)				\
+	$(if $(CONFIG_FRAME_POINTER),, --no-fp)				\
+	$(if $(CONFIG_GCOV_KERNEL), --no-unreachable,)			\
+	$(if $(CONFIG_RETPOLINE), --retpoline,)				\
+	$(if $(CONFIG_X86_SMAP), --uaccess,)				\
+	$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount,)
+
 # Useful for describing the dependency of composite objects
 # Usage:
 #   $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add)
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 2cb9a1d88434..1bd2953b11c4 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -9,7 +9,7 @@ __modfinal:
 include $(objtree)/include/config/auto.conf
 include $(srctree)/scripts/Kbuild.include
 
-# for c_flags
+# for c_flags and objtool_args
 include $(srctree)/scripts/Makefile.lib
 
 # find all modules listed in modules.order
@@ -34,10 +34,23 @@ ifdef CONFIG_LTO_CLANG
 # With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to
 # avoid a second slow LTO link
 prelink-ext := .lto
-endif
+
+# ELF processing was skipped earlier because we didn't have native code,
+# so let's now process the prelinked binary before we link the module.
+
+ifdef CONFIG_STACK_VALIDATION
+ifneq ($(SKIP_STACK_VALIDATION),1)
+cmd_ld_ko_o +=								\
+	$(objtree)/tools/objtool/objtool $(objtool_args)		\
+		$(@:.ko=$(prelink-ext).o);
+
+endif # SKIP_STACK_VALIDATION
+endif # CONFIG_STACK_VALIDATION
+
+endif # CONFIG_LTO_CLANG
 
 quiet_cmd_ld_ko_o = LD [M]  $@
-      cmd_ld_ko_o =                                                     \
+      cmd_ld_ko_o +=							\
 	$(LD) -r $(KBUILD_LDFLAGS)					\
 		$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE)		\
 		-T scripts/module.lds -o $@ $(filter %.o, $^);		\
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 3e99a19b9195..96cf5a5d19df 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -93,8 +93,29 @@ objtool_link()
 {
 	local objtoolopt;
 
+	if [ "${CONFIG_LTO_CLANG} ${CONFIG_STACK_VALIDATION}" = "y y" ]; then
+		# Don't perform vmlinux validation unless explicitly requested,
+		# but run objtool on vmlinux.o now that we have an object file.
+		if [ -n "${CONFIG_UNWINDER_ORC}" ]; then
+			objtoolopt="orc generate"
+		else
+			objtoolopt="check"
+		fi
+
+		if [ -n ${CONFIG_FTRACE_MCOUNT_USE_OBJTOOL} ]; then
+			objtoolopt="${objtoolopt} --mcount"
+		fi
+	fi
+
 	if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
-		objtoolopt="check --vmlinux"
+		if [ -z "${objtoolopt}" ]; then
+			objtoolopt="check --vmlinux"
+		else
+			objtoolopt="${objtoolopt} --vmlinux"
+		fi
+	fi
+
+	if [ -n "${objtoolopt}" ]; then
 		if [ -z "${CONFIG_FRAME_POINTER}" ]; then
 			objtoolopt="${objtoolopt} --no-fp"
 		fi
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 14/29] kbuild: lto: limit inlining
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (12 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 13/29] kbuild: lto: postpone objtool Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 15/29] kbuild: lto: merge module sections Sami Tolvanen
                   ` (16 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

This change limits function inlining across translation unit boundaries
in order to reduce the binary size with LTO. The -import-instr-limit
flag defines a size limit, as the number of LLVM IR instructions, for
importing functions from other TUs, defaulting to 100.

Based on testing with arm64 defconfig, we found that a limit of 5 is a
reasonable compromise between performance and binary size, reducing the
size of a stripped vmlinux by 11%.

Suggested-by: George Burgess IV <gbiv@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Makefile b/Makefile
index 23cdb475c445..d6510ee99ffc 100644
--- a/Makefile
+++ b/Makefile
@@ -894,6 +894,9 @@ else
 CC_FLAGS_LTO	+= -flto
 endif
 CC_FLAGS_LTO	+= -fvisibility=default
+
+# Limit inlining across translation units to reduce binary size
+KBUILD_LDFLAGS += -mllvm -import-instr-limit=5
 endif
 
 ifdef CONFIG_LTO
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 15/29] kbuild: lto: merge module sections
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (13 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 14/29] kbuild: lto: limit inlining Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 16/29] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
                   ` (15 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

LLD always splits sections with LTO, which increases module sizes. This
change adds linker script rules to merge the split sections in the final
module.

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 scripts/module.lds.S | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/scripts/module.lds.S b/scripts/module.lds.S
index 69b9b71a6a47..037120173a22 100644
--- a/scripts/module.lds.S
+++ b/scripts/module.lds.S
@@ -25,5 +25,33 @@ SECTIONS {
 	__jump_table		0 : ALIGN(8) { KEEP(*(__jump_table)) }
 }
 
+#ifdef CONFIG_LTO_CLANG
+/*
+ * With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and
+ * -ffunction-sections, which increases the size of the final module.
+ * Merge the split sections in the final binary.
+ */
+SECTIONS {
+	__patchable_function_entries : { *(__patchable_function_entries) }
+
+	.bss : {
+		*(.bss .bss.[0-9a-zA-Z_]*)
+		*(.bss..L*)
+	}
+
+	.data : {
+		*(.data .data.[0-9a-zA-Z_]*)
+		*(.data..L*)
+	}
+
+	.rodata : {
+		*(.rodata .rodata.[0-9a-zA-Z_]*)
+		*(.rodata..L*)
+	}
+
+	.text : { *(.text .text.[0-9a-zA-Z_]*) }
+}
+#endif
+
 /* bring in arch-specific sections */
 #include <asm/module.lds.h>
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 16/29] kbuild: lto: remove duplicate dependencies from .mod files
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (14 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 15/29] kbuild: lto: merge module sections Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 17/29] init: lto: ensure initcall ordering Sami Tolvanen
                   ` (14 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With LTO, llvm-nm prints out symbols for each archive member
separately, which results in a lot of duplicate dependencies in the
.mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module
consists of several compilation units, the output can exceed the
default xargs command size limit and split the dependency list to
multiple lines, which results in used symbols getting trimmed.

This change removes duplicate dependencies, which will reduce the
probability of this happening and makes .mod files smaller and
easier to read.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 scripts/Makefile.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index ab0ddf4884fd..96d6c9e18901 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -266,7 +266,7 @@ endef
 
 # List module undefined symbols (or empty line if not enabled)
 ifdef CONFIG_TRIM_UNUSED_KSYMS
-cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | xargs echo
+cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | sort -u | xargs echo
 else
 cmd_undef_syms = echo
 endif
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 17/29] init: lto: ensure initcall ordering
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (15 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 16/29] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 18/29] init: lto: fix PREL32 relocations Sami Tolvanen
                   ` (13 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With LTO, the compiler doesn't necessarily obey the link order for
initcalls, and initcall variables need globally unique names to avoid
collisions at link time.

This change exports __KBUILD_MODNAME and adds the initcall_id() macro,
which uses it together with __COUNTER__ and __LINE__ to help ensure
these variables have unique names, and moves each variable to its own
section when LTO is enabled, so the correct order can be specified using
a linker script.

The generate_initcall_ordering.pl script uses nm to find initcalls from
the object files passed to the linker, and generates a linker script
that specifies the same order for initcalls that we would have without
LTO. With LTO enabled, the script is called in link-vmlinux.sh through
jobserver-exec to limit the number of jobs spawned.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 include/linux/init.h               |  52 +++++-
 scripts/Makefile.lib               |   6 +-
 scripts/generate_initcall_order.pl | 270 +++++++++++++++++++++++++++++
 scripts/link-vmlinux.sh            |  15 ++
 4 files changed, 334 insertions(+), 9 deletions(-)
 create mode 100755 scripts/generate_initcall_order.pl

diff --git a/include/linux/init.h b/include/linux/init.h
index 212fc9e2f691..af638cd6dd52 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -184,19 +184,57 @@ extern bool initcall_debug;
  * as KEEP() in the linker script.
  */
 
+/* Format: <modname>__<counter>_<line>_<fn> */
+#define __initcall_id(fn)					\
+	__PASTE(__KBUILD_MODNAME,				\
+	__PASTE(__,						\
+	__PASTE(__COUNTER__,					\
+	__PASTE(_,						\
+	__PASTE(__LINE__,					\
+	__PASTE(_, fn))))))
+
+/* Format: __<prefix>__<iid><id> */
+#define __initcall_name(prefix, __iid, id)			\
+	__PASTE(__,						\
+	__PASTE(prefix,						\
+	__PASTE(__,						\
+	__PASTE(__iid, id))))
+
+#ifdef CONFIG_LTO_CLANG
+/*
+ * With LTO, the compiler doesn't necessarily obey link order for
+ * initcalls. In order to preserve the correct order, we add each
+ * variable into its own section and generate a linker script (in
+ * scripts/link-vmlinux.sh) to specify the order of the sections.
+ */
+#define __initcall_section(__sec, __iid)			\
+	#__sec ".init.." #__iid
+#else
+#define __initcall_section(__sec, __iid)			\
+	#__sec ".init"
+#endif
+
 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define ___define_initcall(fn, id, __sec)			\
+#define ____define_initcall(fn, __name, __sec)			\
 	__ADDRESSABLE(fn)					\
-	asm(".section	\"" #__sec ".init\", \"a\"	\n"	\
-	"__initcall_" #fn #id ":			\n"	\
+	asm(".section	\"" __sec "\", \"a\"		\n"	\
+	    __stringify(__name) ":			\n"	\
 	    ".long	" #fn " - .			\n"	\
 	    ".previous					\n");
 #else
-#define ___define_initcall(fn, id, __sec) \
-	static initcall_t __initcall_##fn##id __used \
-		__attribute__((__section__(#__sec ".init"))) = fn;
+#define ____define_initcall(fn, __name, __sec)			\
+	static initcall_t __name __used 			\
+		__attribute__((__section__(__sec))) = fn;
 #endif
 
+#define __unique_initcall(fn, id, __sec, __iid)			\
+	____define_initcall(fn,					\
+		__initcall_name(initcall, __iid, id),		\
+		__initcall_section(__sec, __iid))
+
+#define ___define_initcall(fn, id, __sec)			\
+	__unique_initcall(fn, id, __sec, __initcall_id(fn))
+
 #define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
 
 /*
@@ -236,7 +274,7 @@ extern bool initcall_debug;
 #define __exitcall(fn)						\
 	static exitcall_t __exitcall_##fn __exit_call = fn
 
-#define console_initcall(fn)	___define_initcall(fn,, .con_initcall)
+#define console_initcall(fn)	___define_initcall(fn, con, .con_initcall)
 
 struct obs_kernel_param {
 	const char *str;
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index ecb97c9f5feb..1142de6a4161 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -117,9 +117,11 @@ target-stem = $(basename $(patsubst $(obj)/%,%,$@))
 # These flags are needed for modversions and compiling, so we define them here
 # $(modname_flags) defines KBUILD_MODNAME as the name of the module it will
 # end up in (or would, if it gets compiled in)
-name-fix = $(call stringify,$(subst $(comma),_,$(subst -,_,$1)))
+name-fix-token = $(subst $(comma),_,$(subst -,_,$1))
+name-fix = $(call stringify,$(call name-fix-token,$1))
 basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
-modname_flags  = -DKBUILD_MODNAME=$(call name-fix,$(modname))
+modname_flags  = -DKBUILD_MODNAME=$(call name-fix,$(modname)) \
+		 -D__KBUILD_MODNAME=kmod_$(call name-fix-token,$(modname))
 modfile_flags  = -DKBUILD_MODFILE=$(call stringify,$(modfile))
 
 _c_flags       = $(filter-out $(CFLAGS_REMOVE_$(target-stem).o), \
diff --git a/scripts/generate_initcall_order.pl b/scripts/generate_initcall_order.pl
new file mode 100755
index 000000000000..1a88d3f1b913
--- /dev/null
+++ b/scripts/generate_initcall_order.pl
@@ -0,0 +1,270 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+#
+# Generates a linker script that specifies the correct initcall order.
+#
+# Copyright (C) 2019 Google LLC
+
+use strict;
+use warnings;
+use IO::Handle;
+use IO::Select;
+use POSIX ":sys_wait_h";
+
+my $nm = $ENV{'NM'} || die "$0: ERROR: NM not set?";
+my $objtree = $ENV{'objtree'} || '.';
+
+## currently active child processes
+my $jobs = {};		# child process pid -> file handle
+## results from child processes
+my $results = {};	# object index -> [ { level, secname }, ... ]
+
+## reads _NPROCESSORS_ONLN to determine the maximum number of processes to
+## start
+sub get_online_processors {
+	open(my $fh, "getconf _NPROCESSORS_ONLN 2>/dev/null |")
+		or die "$0: ERROR: failed to execute getconf: $!";
+	my $procs = <$fh>;
+	close($fh);
+
+	if (!($procs =~ /^\d+$/)) {
+		return 1;
+	}
+
+	return int($procs);
+}
+
+## writes results to the parent process
+## format: <file index> <initcall level> <base initcall section name>
+sub write_results {
+	my ($index, $initcalls) = @_;
+
+	# sort by the counter value to ensure the order of initcalls within
+	# each object file is correct
+	foreach my $counter (sort { $a <=> $b } keys(%{$initcalls})) {
+		my $level = $initcalls->{$counter}->{'level'};
+
+		# section name for the initcall function
+		my $secname = $initcalls->{$counter}->{'module'} . '__' .
+			      $counter . '_' .
+			      $initcalls->{$counter}->{'line'} . '_' .
+			      $initcalls->{$counter}->{'function'};
+
+		print "$index $level $secname\n";
+	}
+}
+
+## reads a result line from a child process and adds it to the $results array
+sub read_results{
+	my ($fh) = @_;
+
+	# each child prints out a full line w/ autoflush and exits after the
+	# last line, so even if buffered I/O blocks here, it shouldn't block
+	# very long
+	my $data = <$fh>;
+
+	if (!defined($data)) {
+		return 0;
+	}
+
+	chomp($data);
+
+	my ($index, $level, $secname) = $data =~
+		/^(\d+)\ ([^\ ]+)\ (.*)$/;
+
+	if (!defined($index) ||
+		!defined($level) ||
+		!defined($secname)) {
+		die "$0: ERROR: child process returned invalid data: $data\n";
+	}
+
+	$index = int($index);
+
+	if (!exists($results->{$index})) {
+		$results->{$index} = [];
+	}
+
+	push (@{$results->{$index}}, {
+		'level'   => $level,
+		'secname' => $secname
+	});
+
+	return 1;
+}
+
+## finds initcalls from an object file or all object files in an archive, and
+## writes results back to the parent process
+sub find_initcalls {
+	my ($index, $file) = @_;
+
+	die "$0: ERROR: file $file doesn't exist?" if (! -f $file);
+
+	open(my $fh, "\"$nm\" --defined-only \"$file\" 2>/dev/null |")
+		or die "$0: ERROR: failed to execute \"$nm\": $!";
+
+	my $initcalls = {};
+
+	while (<$fh>) {
+		chomp;
+
+		# check for the start of a new object file (if processing an
+		# archive)
+		my ($path)= $_ =~ /^(.+)\:$/;
+
+		if (defined($path)) {
+			write_results($index, $initcalls);
+			$initcalls = {};
+			next;
+		}
+
+		# look for an initcall
+		my ($module, $counter, $line, $symbol) = $_ =~
+			/[a-z]\s+__initcall__(\S*)__(\d+)_(\d+)_(.*)$/;
+
+		if (!defined($module)) {
+			$module = ''
+		}
+
+		if (!defined($counter) ||
+			!defined($line) ||
+			!defined($symbol)) {
+			next;
+		}
+
+		# parse initcall level
+		my ($function, $level) = $symbol =~
+			/^(.*)((early|rootfs|con|[0-9])s?)$/;
+
+		die "$0: ERROR: invalid initcall name $symbol in $file($path)"
+			if (!defined($function) || !defined($level));
+
+		$initcalls->{$counter} = {
+			'module'   => $module,
+			'line'     => $line,
+			'function' => $function,
+			'level'    => $level,
+		};
+	}
+
+	close($fh);
+	write_results($index, $initcalls);
+}
+
+## waits for any child process to complete, reads the results, and adds them to
+## the $results array for later processing
+sub wait_for_results {
+	my ($select) = @_;
+
+	my $pid = 0;
+	do {
+		# unblock children that may have a full write buffer
+		foreach my $fh ($select->can_read(0)) {
+			read_results($fh);
+		}
+
+		# check for children that have exited, read the remaining data
+		# from them, and clean up
+		$pid = waitpid(-1, WNOHANG);
+		if ($pid > 0) {
+			if (!exists($jobs->{$pid})) {
+				next;
+			}
+
+			my $fh = $jobs->{$pid};
+			$select->remove($fh);
+
+			while (read_results($fh)) {
+				# until eof
+			}
+
+			close($fh);
+			delete($jobs->{$pid});
+		}
+	} while ($pid > 0);
+}
+
+## forks a child to process each file passed in the command line and collects
+## the results
+sub process_files {
+	my $index = 0;
+	my $njobs = $ENV{'PARALLELISM'} || get_online_processors();
+	my $select = IO::Select->new();
+
+	while (my $file = shift(@ARGV)) {
+		# fork a child process and read it's stdout
+		my $pid = open(my $fh, '-|');
+
+		if (!defined($pid)) {
+			die "$0: ERROR: failed to fork: $!";
+		} elsif ($pid) {
+			# save the child process pid and the file handle
+			$select->add($fh);
+			$jobs->{$pid} = $fh;
+		} else {
+			# in the child process
+			STDOUT->autoflush(1);
+			find_initcalls($index, "$objtree/$file");
+			exit;
+		}
+
+		$index++;
+
+		# limit the number of children to $njobs
+		if (scalar(keys(%{$jobs})) >= $njobs) {
+			wait_for_results($select);
+		}
+	}
+
+	# wait for the remaining children to complete
+	while (scalar(keys(%{$jobs})) > 0) {
+		wait_for_results($select);
+	}
+}
+
+sub generate_initcall_lds() {
+	process_files();
+
+	my $sections = {};	# level -> [ secname, ...]
+
+	# sort results to retain link order and split to sections per
+	# initcall level
+	foreach my $index (sort { $a <=> $b } keys(%{$results})) {
+		foreach my $result (@{$results->{$index}}) {
+			my $level = $result->{'level'};
+
+			if (!exists($sections->{$level})) {
+				$sections->{$level} = [];
+			}
+
+			push(@{$sections->{$level}}, $result->{'secname'});
+		}
+	}
+
+	die "$0: ERROR: no initcalls?" if (!keys(%{$sections}));
+
+	# print out a linker script that defines the order of initcalls for
+	# each level
+	print "SECTIONS {\n";
+
+	foreach my $level (sort(keys(%{$sections}))) {
+		my $section;
+
+		if ($level eq 'con') {
+			$section = '.con_initcall.init';
+		} else {
+			$section = ".initcall${level}.init";
+		}
+
+		print "\t${section} : {\n";
+
+		foreach my $secname (@{$sections->{$level}}) {
+			print "\t\t*(${section}..${secname}) ;\n";
+		}
+
+		print "\t}\n";
+	}
+
+	print "}\n";
+}
+
+generate_initcall_lds();
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 96cf5a5d19df..28b6bb36b6bf 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -43,6 +43,17 @@ info()
 	fi
 }
 
+# Generate a linker script to ensure correct ordering of initcalls.
+gen_initcalls()
+{
+	info GEN .tmp_initcalls.lds
+
+	${PYTHON} ${srctree}/scripts/jobserver-exec		\
+	${PERL} ${srctree}/scripts/generate_initcall_order.pl	\
+		${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}	\
+		> .tmp_initcalls.lds
+}
+
 # If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
 # .tmp_symversions.lds
 gen_symversions()
@@ -74,6 +85,9 @@ modpost_link()
 		--end-group"
 
 	if [ -n "${CONFIG_LTO_CLANG}" ]; then
+		gen_initcalls
+		lds="-T .tmp_initcalls.lds"
+
 		if [ -n "${CONFIG_MODVERSIONS}" ]; then
 			gen_symversions
 			lds="${lds} -T .tmp_symversions.lds"
@@ -285,6 +299,7 @@ cleanup()
 {
 	rm -f .btf.*
 	rm -f .tmp_System.map
+	rm -f .tmp_initcalls.lds
 	rm -f .tmp_symversions.lds
 	rm -f .tmp_vmlinux*
 	rm -f System.map
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 18/29] init: lto: fix PREL32 relocations
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (16 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 17/29] init: lto: ensure initcall ordering Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 19/29] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
                   ` (12 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With LTO, the compiler can rename static functions to avoid global
naming collisions. As initcall functions are typically static,
renaming can break references to them in inline assembly. This
change adds a global stub with a stable name for each initcall to
fix the issue when PREL32 relocations are used.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 include/linux/init.h | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/include/linux/init.h b/include/linux/init.h
index af638cd6dd52..cea63f7e7705 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -209,26 +209,49 @@ extern bool initcall_debug;
  */
 #define __initcall_section(__sec, __iid)			\
 	#__sec ".init.." #__iid
+
+/*
+ * With LTO, the compiler can rename static functions to avoid
+ * global naming collisions. We use a global stub function for
+ * initcalls to create a stable symbol name whose address can be
+ * taken in inline assembly when PREL32 relocations are used.
+ */
+#define __initcall_stub(fn, __iid, id)				\
+	__initcall_name(initstub, __iid, id)
+
+#define __define_initcall_stub(__stub, fn)			\
+	int __init __stub(void);				\
+	int __init __stub(void)					\
+	{ 							\
+		return fn();					\
+	}							\
+	__ADDRESSABLE(__stub)
 #else
 #define __initcall_section(__sec, __iid)			\
 	#__sec ".init"
+
+#define __initcall_stub(fn, __iid, id)	fn
+
+#define __define_initcall_stub(__stub, fn)			\
+	__ADDRESSABLE(fn)
 #endif
 
 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define ____define_initcall(fn, __name, __sec)			\
-	__ADDRESSABLE(fn)					\
+#define ____define_initcall(fn, __stub, __name, __sec)		\
+	__define_initcall_stub(__stub, fn)			\
 	asm(".section	\"" __sec "\", \"a\"		\n"	\
 	    __stringify(__name) ":			\n"	\
-	    ".long	" #fn " - .			\n"	\
+	    ".long	" __stringify(__stub) " - .	\n"	\
 	    ".previous					\n");
 #else
-#define ____define_initcall(fn, __name, __sec)			\
+#define ____define_initcall(fn, __unused, __name, __sec)	\
 	static initcall_t __name __used 			\
 		__attribute__((__section__(__sec))) = fn;
 #endif
 
 #define __unique_initcall(fn, id, __sec, __iid)			\
 	____define_initcall(fn,					\
+		__initcall_stub(fn, __iid, id),			\
 		__initcall_name(initcall, __iid, id),		\
 		__initcall_section(__sec, __iid))
 
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 19/29] PCI: Fix PREL32 relocations for LTO
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (17 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 18/29] init: lto: fix PREL32 relocations Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 20/29] modpost: lto: strip .lto from module names Sami Tolvanen
                   ` (11 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With Clang's Link Time Optimization (LTO), the compiler can rename
static functions to avoid global naming collisions. As PCI fixup
functions are typically static, renaming can break references
to them in inline assembly. This change adds a global stub to
DECLARE_PCI_FIXUP_SECTION to fix the issue when PREL32 relocations
are used.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 include/linux/pci.h | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 835530605c0d..4e64421981c7 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1909,19 +1909,28 @@ enum pci_fixup_pass {
 };
 
 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class,	\
-				    class_shift, hook)			\
-	__ADDRESSABLE(hook)						\
+#define ___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class,	\
+				    class_shift, hook, stub)		\
+	void stub(struct pci_dev *dev);					\
+	void stub(struct pci_dev *dev)					\
+	{ 								\
+		hook(dev); 						\
+	}								\
 	asm(".section "	#sec ", \"a\"				\n"	\
 	    ".balign	16					\n"	\
 	    ".short "	#vendor ", " #device "			\n"	\
 	    ".long "	#class ", " #class_shift "		\n"	\
-	    ".long "	#hook " - .				\n"	\
+	    ".long "	#stub " - .				\n"	\
 	    ".previous						\n");
+
+#define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class,	\
+				  class_shift, hook, stub)		\
+	___DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class,	\
+				  class_shift, hook, stub)
 #define DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class,	\
 				  class_shift, hook)			\
 	__DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class,	\
-				  class_shift, hook)
+				  class_shift, hook, __UNIQUE_ID(hook))
 #else
 /* Anonymous variables would be nice... */
 #define DECLARE_PCI_FIXUP_SECTION(section, name, vendor, device, class,	\
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 20/29] modpost: lto: strip .lto from module names
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (18 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 19/29] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 21/29] scripts/mod: disable LTO for empty.c Sami Tolvanen
                   ` (10 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With LTO, everything is compiled into LLVM bitcode, so we have to link
each module into native code before modpost. Kbuild uses the .lto.o
suffix for these files, which also ends up in module information. This
change strips the unnecessary .lto suffix from the module name.

Suggested-by: Bill Wendling <morbo@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 scripts/mod/modpost.c    | 16 +++++++---------
 scripts/mod/modpost.h    |  9 +++++++++
 scripts/mod/sumversion.c |  6 +++++-
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 69341b36f271..5a329df55cc3 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -17,7 +17,6 @@
 #include <ctype.h>
 #include <string.h>
 #include <limits.h>
-#include <stdbool.h>
 #include <errno.h>
 #include "modpost.h"
 #include "../../include/linux/license.h"
@@ -80,14 +79,6 @@ modpost_log(enum loglevel loglevel, const char *fmt, ...)
 		exit(1);
 }
 
-static inline bool strends(const char *str, const char *postfix)
-{
-	if (strlen(str) < strlen(postfix))
-		return false;
-
-	return strcmp(str + strlen(str) - strlen(postfix), postfix) == 0;
-}
-
 void *do_nofail(void *ptr, const char *expr)
 {
 	if (!ptr)
@@ -1984,6 +1975,10 @@ static char *remove_dot(char *s)
 		size_t m = strspn(s + n + 1, "0123456789");
 		if (m && (s[n + m] == '.' || s[n + m] == 0))
 			s[n] = 0;
+
+		/* strip trailing .lto */
+		if (strends(s, ".lto"))
+			s[strlen(s) - 4] = '\0';
 	}
 	return s;
 }
@@ -2007,6 +2002,9 @@ static void read_symbols(const char *modname)
 		/* strip trailing .o */
 		tmp = NOFAIL(strdup(modname));
 		tmp[strlen(tmp) - 2] = '\0';
+		/* strip trailing .lto */
+		if (strends(tmp, ".lto"))
+			tmp[strlen(tmp) - 4] = '\0';
 		mod = new_module(tmp);
 		free(tmp);
 	}
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 3aa052722233..fab30d201f9e 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -2,6 +2,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <stdbool.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -180,6 +181,14 @@ static inline unsigned int get_secindex(const struct elf_info *info,
 	return info->symtab_shndx_start[sym - info->symtab_start];
 }
 
+static inline bool strends(const char *str, const char *postfix)
+{
+	if (strlen(str) < strlen(postfix))
+		return false;
+
+	return strcmp(str + strlen(str) - strlen(postfix), postfix) == 0;
+}
+
 /* file2alias.c */
 extern unsigned int cross_build;
 void handle_moddevtable(struct module *mod, struct elf_info *info,
diff --git a/scripts/mod/sumversion.c b/scripts/mod/sumversion.c
index d587f40f1117..760e6baa7eda 100644
--- a/scripts/mod/sumversion.c
+++ b/scripts/mod/sumversion.c
@@ -391,10 +391,14 @@ void get_src_version(const char *modname, char sum[], unsigned sumlen)
 	struct md4_ctx md;
 	char *fname;
 	char filelist[PATH_MAX + 1];
+	int postfix_len = 1;
+
+	if (strends(modname, ".lto.o"))
+		postfix_len = 5;
 
 	/* objects for a module are listed in the first line of *.mod file. */
 	snprintf(filelist, sizeof(filelist), "%.*smod",
-		 (int)strlen(modname) - 1, modname);
+		 (int)strlen(modname) - postfix_len, modname);
 
 	buf = read_text_file(filelist);
 
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 21/29] scripts/mod: disable LTO for empty.c
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (19 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 20/29] modpost: lto: strip .lto from module names Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 22/29] efi/libstub: disable LTO Sami Tolvanen
                   ` (9 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With CONFIG_LTO_CLANG, clang generates LLVM IR instead of ELF object
files. As empty.o is used for probing target properties, disable LTO
for it to produce an object file instead.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 scripts/mod/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
index 78071681d924..c9e38ad937fd 100644
--- a/scripts/mod/Makefile
+++ b/scripts/mod/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 OBJECT_FILES_NON_STANDARD := y
+CFLAGS_REMOVE_empty.o += $(CC_FLAGS_LTO)
 
 hostprogs-always-y	+= modpost mk_elfconfig
 always-y		+= empty.o
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 22/29] efi/libstub: disable LTO
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (20 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 21/29] scripts/mod: disable LTO for empty.c Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 23/29] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
                   ` (8 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

With CONFIG_LTO_CLANG, we produce LLVM bitcode instead of ELF object
files. Since LTO is not really needed here and the Makefile assumes we
produce an object file, disable LTO for libstub.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 drivers/firmware/efi/libstub/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 296b18fbd7a2..0ea5aa52c7fa 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -35,6 +35,8 @@ KBUILD_CFLAGS			:= $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \
 
 # remove SCS flags from all objects in this directory
 KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
+# disable LTO
+KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
 
 GCOV_PROFILE			:= n
 # Sanitizer runtimes are unavailable and cannot be linked here.
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 23/29] drivers/misc/lkdtm: disable LTO for rodata.o
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (21 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 22/29] efi/libstub: disable LTO Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 24/29] arm64: vdso: disable LTO Sami Tolvanen
                   ` (7 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

Disable LTO for rodata.o to allow objcopy to be used to
manipulate sections.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
---
 drivers/misc/lkdtm/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile
index c70b3822013f..dd4c936d4d73 100644
--- a/drivers/misc/lkdtm/Makefile
+++ b/drivers/misc/lkdtm/Makefile
@@ -13,6 +13,7 @@ lkdtm-$(CONFIG_LKDTM)		+= cfi.o
 
 KASAN_SANITIZE_stackleak.o	:= n
 KCOV_INSTRUMENT_rodata.o	:= n
+CFLAGS_REMOVE_rodata.o		+= $(CC_FLAGS_LTO)
 
 OBJCOPYFLAGS :=
 OBJCOPYFLAGS_rodata_objcopy.o	:= \
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 24/29] arm64: vdso: disable LTO
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (22 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 23/29] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 25/29] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen
                   ` (6 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

Disable LTO for the vDSO by filtering out CC_FLAGS_LTO, as there's no
point in using link-time optimization for the small about of C code.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/kernel/vdso/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index e836e300440f..aa47070a3ccf 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -30,7 +30,8 @@ ldflags-y := -shared -nostdlib -soname=linux-vdso.so.1 --hash-style=sysv	\
 ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18
 ccflags-y += -DDISABLE_BRANCH_PROFILING
 
-CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) $(GCC_PLUGINS_CFLAGS)
+CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) $(GCC_PLUGINS_CFLAGS) \
+				$(CC_FLAGS_LTO)
 KASAN_SANITIZE			:= n
 UBSAN_SANITIZE			:= n
 OBJECT_FILES_NON_STANDARD	:= y
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 25/29] KVM: arm64: disable LTO for the nVHE directory
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (23 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 24/29] arm64: vdso: disable LTO Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 26/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
                   ` (5 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

We use objcopy to manipulate ELF binaries for the nVHE code,
which fails with LTO as the compiler produces LLVM bitcode
instead. Disable LTO for this code to allow objcopy to be used.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/kvm/hyp/nvhe/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index aef76487edc2..c903c8f31280 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -45,9 +45,9 @@ quiet_cmd_hypcopy = HYPCOPY $@
 		   --rename-section=.text=.hyp.text			\
 		   $< $@
 
-# Remove ftrace and Shadow Call Stack CFLAGS.
+# Remove ftrace, LTO, and Shadow Call Stack CFLAGS.
 # This is equivalent to the 'notrace' and '__noscs' annotations.
-KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
+KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_LTO) $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
 
 # KVM nVHE code is run at a different exception code with a different map, so
 # compiler instrumentation that inserts callbacks or checks into the code may
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 26/29] arm64: allow LTO_CLANG and THINLTO to be selected
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (24 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 25/29] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 27/29] x86, vdso: disable LTO only for vDSO Sami Tolvanen
                   ` (4 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

Allow CONFIG_LTO_CLANG and CONFIG_THINLTO to be enabled.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ad522b021f35..7016d193864f 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -72,6 +72,8 @@ config ARM64
 	select ARCH_USE_SYM_ANNOTATIONS
 	select ARCH_SUPPORTS_MEMORY_FAILURE
 	select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
+	select ARCH_SUPPORTS_LTO_CLANG
+	select ARCH_SUPPORTS_THINLTO
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && (GCC_VERSION >= 50000 || CC_IS_CLANG)
 	select ARCH_SUPPORTS_NUMA_BALANCING
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 27/29] x86, vdso: disable LTO only for vDSO
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (25 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 26/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 28/29] x86, cpu: disable LTO for cpu.c Sami Tolvanen
                   ` (3 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

Disable LTO for the vDSO. Note that while we could use Clang's LTO
for the 64-bit vDSO, it won't add noticeable benefit for the small
amount of C code.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/entry/vdso/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index ecc27018ae13..9b742f21d2db 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -90,7 +90,7 @@ ifneq ($(RETPOLINE_VDSO_CFLAGS),)
 endif
 endif
 
-$(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
+$(vobjs): KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
 
 #
 # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
@@ -148,6 +148,7 @@ KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 := $(filter-out $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS_32))
+KBUILD_CFLAGS_32 := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
 KBUILD_CFLAGS_32 += -fno-stack-protector
 KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 28/29] x86, cpu: disable LTO for cpu.c
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (26 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 27/29] x86, vdso: disable LTO only for vDSO Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-29 21:46 ` [PATCH v4 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
                   ` (2 subsequent siblings)
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

Clang incorrectly inlines functions with differing stack protector
attributes, which breaks __restore_processor_state() that relies on
stack protector being disabled. This change disables LTO for cpu.c
to work aroung the bug.

Link: https://bugs.llvm.org/show_bug.cgi?id=47479
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/x86/power/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/power/Makefile b/arch/x86/power/Makefile
index 6907b523e856..5f711a441623 100644
--- a/arch/x86/power/Makefile
+++ b/arch/x86/power/Makefile
@@ -5,5 +5,9 @@ OBJECT_FILES_NON_STANDARD_hibernate_asm_$(BITS).o := y
 # itself be stack-protected
 CFLAGS_cpu.o	:= -fno-stack-protector
 
+# Clang may incorrectly inline functions with stack protector enabled into
+# __restore_processor_state(): https://bugs.llvm.org/show_bug.cgi?id=47479
+CFLAGS_REMOVE_cpu.o := $(CC_FLAGS_LTO)
+
 obj-$(CONFIG_PM_SLEEP)		+= cpu.o
 obj-$(CONFIG_HIBERNATION)	+= hibernate_$(BITS).o hibernate_asm_$(BITS).o hibernate.o
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* [PATCH v4 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (27 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 28/29] x86, cpu: disable LTO for cpu.c Sami Tolvanen
@ 2020-09-29 21:46 ` Sami Tolvanen
  2020-09-30 21:10 ` [PATCH v4 00/29] Add support for Clang LTO Kees Cook
  2020-09-30 21:58 ` Nick Desaulniers
  30 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-29 21:46 UTC (permalink / raw)
  To: Masahiro Yamada, Will Deacon, Steven Rostedt
  Cc: Peter Zijlstra, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, Sami Tolvanen

Pass code model and stack alignment to the linker as these are
not stored in LLVM bitcode, and allow both CONFIG_LTO_CLANG and
CONFIG_THINLTO to be selected.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/Kconfig  | 2 ++
 arch/x86/Makefile | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6de2e5c0bdba..0a49008c2363 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -92,6 +92,8 @@ config X86
 	select ARCH_SUPPORTS_ACPI
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_NUMA_BALANCING	if X86_64
+	select ARCH_SUPPORTS_LTO_CLANG		if X86_64
+	select ARCH_SUPPORTS_THINLTO		if X86_64
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 4346ffb2e39f..49e3b8674eb5 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -173,6 +173,11 @@ ifeq ($(ACCUMULATE_OUTGOING_ARGS), 1)
 	KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args,)
 endif
 
+ifdef CONFIG_LTO_CLANG
+KBUILD_LDFLAGS	+= -plugin-opt=-code-model=kernel \
+		   -plugin-opt=-stack-alignment=$(if $(CONFIG_X86_32),4,8)
+endif
+
 # Workaround for a gcc prelease that unfortunately was shipped in a suse release
 KBUILD_CFLAGS += -Wno-sign-compare
 #
-- 
2.28.0.709.gb0816b6eb0-goog


^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 06/29] tracing: move function tracer options to Kconfig
  2020-09-29 21:46 ` [PATCH v4 06/29] tracing: move function tracer options to Kconfig Sami Tolvanen
@ 2020-09-30  0:12   ` Steven Rostedt
  2020-09-30 16:05     ` Sami Tolvanen
  0 siblings, 1 reply; 42+ messages in thread
From: Steven Rostedt @ 2020-09-30  0:12 UTC (permalink / raw)
  To: Sami Tolvanen
  Cc: Masahiro Yamada, Will Deacon, Peter Zijlstra, Greg Kroah-Hartman,
	Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-built-linux,
	kernel-hardening, linux-arch, linux-arm-kernel, linux-kbuild,
	linux-kernel, linux-pci, x86

On Tue, 29 Sep 2020 14:46:08 -0700
Sami Tolvanen <samitolvanen@google.com> wrote:

> +++ b/kernel/trace/Kconfig
> @@ -595,6 +595,22 @@ config FTRACE_MCOUNT_RECORD
>  	depends on DYNAMIC_FTRACE
>  	depends on HAVE_FTRACE_MCOUNT_RECORD
>  
> +config FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
> +	bool
> +	depends on FTRACE_MCOUNT_RECORD
> +
> +config FTRACE_MCOUNT_USE_CC
> +	def_bool y
> +	depends on $(cc-option,-mrecord-mcount)

Does the above get executed at every build? Or does a make *config need
to be done? If someone were to pass a .config to someone else that had
a compiler that didn't support this, would it be changed if the person
just did a make?

-- Steve


> +	depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
> +	depends on FTRACE_MCOUNT_RECORD
> +
> +config FTRACE_MCOUNT_USE_RECORDMCOUNT
> +	def_bool y
> +	depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
> +	depends on !FTRACE_MCOUNT_USE_CC
> +	depends on FTRACE_MCOUNT_RECORD
> +
>  config TRACING_MAP
>  	bool
>  	depends on ARCH_HAVE_NMI_SAFE_CMPXCHG

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 09/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS
  2020-09-29 21:46 ` [PATCH v4 09/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
@ 2020-09-30  9:58   ` Mark Rutland
  2020-09-30 17:10     ` Sami Tolvanen
  0 siblings, 1 reply; 42+ messages in thread
From: Mark Rutland @ 2020-09-30  9:58 UTC (permalink / raw)
  To: Sami Tolvanen
  Cc: Masahiro Yamada, Will Deacon, Steven Rostedt, Peter Zijlstra,
	Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86

Hi Sami,

On Tue, Sep 29, 2020 at 02:46:11PM -0700, Sami Tolvanen wrote:
> Select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY to disable
> recordmcount when DYNAMIC_FTRACE_WITH_REGS is selected.

Could you please add an explanation as to /why/ this is necessary in the
commit message? I couldn't figure this out form the commit message
alone, and reading the cover letter also didn't help.

If the minimum required GCC version supports patchable-function-entry
I'd be happy to make that a requirement for dynamic ftrace on arm64, as
then we'd only need to support one mechanism, and can get rid of some
redundant code. We already default to it when present anyhow.

> 
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> ---
>  arch/arm64/Kconfig | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 6d232837cbee..ad522b021f35 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -155,6 +155,8 @@ config ARM64
>  	select HAVE_DYNAMIC_FTRACE
>  	select HAVE_DYNAMIC_FTRACE_WITH_REGS \
>  		if $(cc-option,-fpatchable-function-entry=2)
> +	select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \
> +		if DYNAMIC_FTRACE_WITH_REGS

This doesn't look quite right to me. Presumably we shouldn't allow
DYNAMIC_FTRACE_WITH_REGS to be selected if HAVE_DYNAMIC_FTRACE_WITH_REGS
isn't.

Thanks,
Mark.

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 06/29] tracing: move function tracer options to Kconfig
  2020-09-30  0:12   ` Steven Rostedt
@ 2020-09-30 16:05     ` Sami Tolvanen
  0 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-30 16:05 UTC (permalink / raw)
  To: Steven Rostedt
  Cc: Masahiro Yamada, Will Deacon, Peter Zijlstra, Greg Kroah-Hartman,
	Paul E. McKenney, Kees Cook, Nick Desaulniers, clang-built-linux,
	Kernel Hardening, linux-arch, linux-arm-kernel, linux-kbuild,
	LKML, linux-pci, X86 ML

On Tue, Sep 29, 2020 at 5:13 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Tue, 29 Sep 2020 14:46:08 -0700
> Sami Tolvanen <samitolvanen@google.com> wrote:
>
> > +++ b/kernel/trace/Kconfig
> > @@ -595,6 +595,22 @@ config FTRACE_MCOUNT_RECORD
> >       depends on DYNAMIC_FTRACE
> >       depends on HAVE_FTRACE_MCOUNT_RECORD
> >
> > +config FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
> > +     bool
> > +     depends on FTRACE_MCOUNT_RECORD
> > +
> > +config FTRACE_MCOUNT_USE_CC
> > +     def_bool y
> > +     depends on $(cc-option,-mrecord-mcount)
>
> Does the above get executed at every build? Or does a make *config need
> to be done? If someone were to pass a .config to someone else that had
> a compiler that didn't support this, would it be changed if the person
> just did a make?

Yes, it's updated if you copy a .config and just run make. For
example, here's what happens when I create a config with gcc and then
build it with Clang:

$ make defconfig
...
$ ./scripts/config -e FUNCTION_TRACER -e DYNAMIC_FTRACE
$ make olddefconfig
...
$ grep MCOUNT_USE .config
CONFIG_FTRACE_MCOUNT_USE_CC=y
$ make CC=clang
scripts/kconfig/conf  --syncconfig Kconfig
...
^C
$ grep MCOUNT_USE .config
CONFIG_FTRACE_MCOUNT_USE_OBJTOOL=y

Sami

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 09/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS
  2020-09-30  9:58   ` Mark Rutland
@ 2020-09-30 17:10     ` Sami Tolvanen
  0 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-30 17:10 UTC (permalink / raw)
  To: Mark Rutland
  Cc: Masahiro Yamada, Will Deacon, Steven Rostedt, Peter Zijlstra,
	Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, Kernel Hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, LKML, linux-pci,
	X86 ML

Hi Mark,

On Wed, Sep 30, 2020 at 2:59 AM Mark Rutland <mark.rutland@arm.com> wrote:
>
> Hi Sami,
>
> On Tue, Sep 29, 2020 at 02:46:11PM -0700, Sami Tolvanen wrote:
> > Select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY to disable
> > recordmcount when DYNAMIC_FTRACE_WITH_REGS is selected.
>
> Could you please add an explanation as to /why/ this is necessary in the
> commit message? I couldn't figure this out form the commit message
> alone, and reading the cover letter also didn't help.

Sorry about that, I'll add a better explanation in the next version.

Note that without LTO, this change is not strictly necessary as
there's no harm in running recordmcount even if it's not needed. It
might slow down the build slightly, but I suspect a few thousand
invocations of the program won't take that long. However, with LTO we
need to disable recordmcount because it doesn't understand LLVM
bitcode.

> If the minimum required GCC version supports patchable-function-entry
> I'd be happy to make that a requirement for dynamic ftrace on arm64, as
> then we'd only need to support one mechanism, and can get rid of some
> redundant code. We already default to it when present anyhow.

That would be great, but Documentation/process/changes.rst suggests
the minimum gcc version is 4.9, and according to Godbolt we would need
gcc >= 8 for -fpatchable-function-entry:

  https://godbolt.org/z/jdzcMW

> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index 6d232837cbee..ad522b021f35 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -155,6 +155,8 @@ config ARM64
> >       select HAVE_DYNAMIC_FTRACE
> >       select HAVE_DYNAMIC_FTRACE_WITH_REGS \
> >               if $(cc-option,-fpatchable-function-entry=2)
> > +     select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \
> > +             if DYNAMIC_FTRACE_WITH_REGS
>
> This doesn't look quite right to me. Presumably we shouldn't allow
> DYNAMIC_FTRACE_WITH_REGS to be selected if HAVE_DYNAMIC_FTRACE_WITH_REGS
> isn't.

This won't allow DYNAMIC_FTRACE_WITH_REGS to be selected without
HAVE_DYNAMIC_FTRACE_WITH_REGS. Testing with a compiler that does
support -fpatchable-function-entry, I get the following, as expected:

$ grep -E '(DYNAMIC_FTRACE|MCOUNT_USE)' .config
CONFIG_HAVE_DYNAMIC_FTRACE=y
CONFIG_HAVE_DYNAMIC_FTRACE_WITH_REGS=y
CONFIG_DYNAMIC_FTRACE=y
CONFIG_DYNAMIC_FTRACE_WITH_REGS=y
CONFIG_FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY=y

And if the compiler doesn't support -fpatchable-function-entry, we
would end up with the following:

$ grep -E '(DYNAMIC_FTRACE|MCOUNT_USE)' .config
CONFIG_HAVE_DYNAMIC_FTRACE=y
CONFIG_DYNAMIC_FTRACE=y
CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT=y

Sami

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 10/29] treewide: remove DISABLE_LTO
  2020-09-29 21:46 ` [PATCH v4 10/29] treewide: remove DISABLE_LTO Sami Tolvanen
@ 2020-09-30 20:45   ` Kees Cook
  0 siblings, 0 replies; 42+ messages in thread
From: Kees Cook @ 2020-09-30 20:45 UTC (permalink / raw)
  To: Sami Tolvanen
  Cc: Masahiro Yamada, Will Deacon, Steven Rostedt, Peter Zijlstra,
	Greg Kroah-Hartman, Paul E. McKenney, Nick Desaulniers,
	clang-built-linux, kernel-hardening, linux-arch,
	linux-arm-kernel, linux-kbuild, linux-kernel, linux-pci, x86

On Tue, Sep 29, 2020 at 02:46:12PM -0700, Sami Tolvanen wrote:
> This change removes all instances of DISABLE_LTO from
> Makefiles, as they are currently unused, and the preferred
> method of disabling LTO is to filter out the flags instead.
> 
> Suggested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

Thanks! I think this makes things cleaner in the later patches. :)

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 00/29] Add support for Clang LTO
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (28 preceding siblings ...)
  2020-09-29 21:46 ` [PATCH v4 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
@ 2020-09-30 21:10 ` Kees Cook
  2020-09-30 21:58 ` Nick Desaulniers
  30 siblings, 0 replies; 42+ messages in thread
From: Kees Cook @ 2020-09-30 21:10 UTC (permalink / raw)
  To: Peter Zijlstra, Steven Rostedt
  Cc: Sami Tolvanen, Masahiro Yamada, Will Deacon, Greg Kroah-Hartman,
	Paul E. McKenney, Nick Desaulniers, clang-built-linux,
	kernel-hardening, linux-arch, linux-arm-kernel, linux-kbuild,
	linux-kernel, linux-pci, x86

On Tue, Sep 29, 2020 at 02:46:02PM -0700, Sami Tolvanen wrote:
> Furthermore, patches 4-8 include Peter's patch for generating
> __mcount_loc with objtool, and build system changes to enable it on
> x86. With these patches, we no longer need to annotate functions
> that have non-call references to __fentry__ with LTO, which makes
> supporting dynamic ftrace much simpler.

Peter, can you take patches 4-8 into -tip? I think it'd make sense
to keep them together. Steven, it sounds like you're okay with the
changes (i.e. Sami showed the one concern you had was already handled)?
Getting these into v5.10 would be really really nice.

I'd really like to get the tree-spanning prerequisites nailed down
for this series. It's been difficult to coordinate given the multiple
maintainers. :)

Specifically these patches:

Peter Zijlstra (1):
  objtool: Add a pass for generating __mcount_loc

Sami Tolvanen (4):
  objtool: Don't autodetect vmlinux.o
  tracing: move function tracer options to Kconfig
  tracing: add support for objtool mcount
  x86, build: use objtool mcount

https://lore.kernel.org/lkml/20200929214631.3516445-5-samitolvanen@google.com/
https://lore.kernel.org/lkml/20200929214631.3516445-6-samitolvanen@google.com/
https://lore.kernel.org/lkml/20200929214631.3516445-7-samitolvanen@google.com/
https://lore.kernel.org/lkml/20200929214631.3516445-8-samitolvanen@google.com/
https://lore.kernel.org/lkml/20200929214631.3516445-9-samitolvanen@google.com/

Thanks!

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 00/29] Add support for Clang LTO
  2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (29 preceding siblings ...)
  2020-09-30 21:10 ` [PATCH v4 00/29] Add support for Clang LTO Kees Cook
@ 2020-09-30 21:58 ` Nick Desaulniers
  2020-09-30 22:12   ` Sami Tolvanen
  30 siblings, 1 reply; 42+ messages in thread
From: Nick Desaulniers @ 2020-09-30 21:58 UTC (permalink / raw)
  To: Sami Tolvanen
  Cc: Masahiro Yamada, Will Deacon, Steven Rostedt, Peter Zijlstra,
	Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	clang-built-linux, Kernel Hardening, linux-arch, Linux ARM,
	Linux Kbuild mailing list, LKML, linux-pci,
	maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)

On Tue, Sep 29, 2020 at 2:46 PM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> This patch series adds support for building x86_64 and arm64 kernels
> with Clang's Link Time Optimization (LTO).
>
> In addition to performance, the primary motivation for LTO is
> to allow Clang's Control-Flow Integrity (CFI) to be used in the
> kernel. Google has shipped millions of Pixel devices running three
> major kernel versions with LTO+CFI since 2018.
>
> Most of the patches are build system changes for handling LLVM
> bitcode, which Clang produces with LTO instead of ELF object files,
> postponing ELF processing until a later stage, and ensuring initcall
> ordering.

Sami, thanks for continuing to drive the series. I encourage you to
keep resending with fixes accumulated or dropped on a weekly cadence.

The series worked well for me on arm64, but for x86_64 on mainline I
saw a stream of new objtool warnings:

testing your LTO series; x86_64 defconfig + CONFIG_THINLTO:
``` LTO vmlinux.o OBJTOOL vmlinux.o vmlinux.o: warning: objtool:
wakeup_long64()+0x61: indirect jump found in RETPOLINE build
vmlinux.o: warning: objtool: .text+0x308a: indirect jump found in
RETPOLINE build vmlinux.o: warning: objtool: .text+0x30c5: indirect
jump found in RETPOLINE build vmlinux.o: warning: objtool:
copy_user_enhanced_fast_string() falls through to next function
copy_user_generic_unrolled() vmlinux.o: warning: objtool:
__memcpy_mcsafe() falls through to next function mcsafe_handle_tail()
vmlinux.o: warning: objtool: memset() falls through to next function
memset_erms() vmlinux.o: warning: objtool: __memcpy() falls through to
next function memcpy_erms() vmlinux.o: warning: objtool:
__x86_indirect_thunk_rax() falls through to next function
__x86_retpoline_rax() vmlinux.o: warning: objtool:
__x86_indirect_thunk_rbx() falls through to next function
__x86_retpoline_rbx() vmlinux.o: warning: objtool:
__x86_indirect_thunk_rcx() falls through to next function
__x86_retpoline_rcx() vmlinux.o: warning: objtool:
__x86_indirect_thunk_rdx() falls through to next function
__x86_retpoline_rdx() vmlinux.o: warning: objtool:
__x86_indirect_thunk_rsi() falls through to next function
__x86_retpoline_rsi() vmlinux.o: warning: objtool:
__x86_indirect_thunk_rdi() falls through to next function
__x86_retpoline_rdi() vmlinux.o: warning: objtool:
__x86_indirect_thunk_rbp() falls through to next function
__x86_retpoline_rbp() vmlinux.o: warning: objtool:
__x86_indirect_thunk_r8() falls through to next function
__x86_retpoline_r8() vmlinux.o: warning: objtool:
__x86_indirect_thunk_r9() falls through to next function
__x86_retpoline_r9() vmlinux.o: warning: objtool:
__x86_indirect_thunk_r10() falls through to next function
__x86_retpoline_r10() vmlinux.o: warning: objtool:
__x86_indirect_thunk_r11() falls through to next function
__x86_retpoline_r11() vmlinux.o: warning: objtool:
__x86_indirect_thunk_r12() falls through to next function
__x86_retpoline_r12() vmlinux.o: warning: objtool:
__x86_indirect_thunk_r13() falls through to next function
__x86_retpoline_r13() vmlinux.o: warning: objtool:
__x86_indirect_thunk_r14() falls through to next function
__x86_retpoline_r14() vmlinux.o: warning: objtool:
__x86_indirect_thunk_r15() falls through to next function
__x86_retpoline_r15() ```

I think those should be resolved before I provide any kind of tested
by tag.  My other piece of feedback was that I like the default
ThinLTO, but I think the help text in the Kconfig which is visible
during menuconfig could be improved by informing the user the
tradeoffs.  For example, if CONFIG_THINLTO is disabled, it should be
noted that full LTO will be used instead.  Also, that full LTO may
produce slightly better optimized binaries than ThinLTO, at the cost
of not utilizing multiple cores when linking and thus significantly
slower to link.

Maybe explaining that setting it to "n" implies a full LTO build,
which will be much slower to link but possibly slightly faster would
be good?  It's not visible unless LTO_CLANG and ARCH_SUPPORTS_THINLTO
is enabled, so I don't think you need to explain that THINLTO without
those is *not* full LTO.  I'll leave the precise wording to you. WDYT?

Also, when I look at your treewide DISABLE_LTO patch, I think "does
that need to be a part of this series, or is it a cleanup that can
stand on its own?"  I think it may be the latter?  Maybe it would help
shed one more patch than to have to carry it to just send it?  Or did
I miss something as to why it should remain a part of this series?
-- 
Thanks,
~Nick Desaulniers

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 00/29] Add support for Clang LTO
  2020-09-30 21:58 ` Nick Desaulniers
@ 2020-09-30 22:12   ` Sami Tolvanen
  0 siblings, 0 replies; 42+ messages in thread
From: Sami Tolvanen @ 2020-09-30 22:12 UTC (permalink / raw)
  To: Nick Desaulniers, Peter Zijlstra
  Cc: Masahiro Yamada, Will Deacon, Steven Rostedt, Greg Kroah-Hartman,
	Paul E. McKenney, Kees Cook, clang-built-linux, Kernel Hardening,
	linux-arch, Linux ARM, Linux Kbuild mailing list, LKML,
	linux-pci, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)

On Wed, Sep 30, 2020 at 2:58 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Tue, Sep 29, 2020 at 2:46 PM Sami Tolvanen <samitolvanen@google.com> wrote:
> >
> > This patch series adds support for building x86_64 and arm64 kernels
> > with Clang's Link Time Optimization (LTO).
> >
> > In addition to performance, the primary motivation for LTO is
> > to allow Clang's Control-Flow Integrity (CFI) to be used in the
> > kernel. Google has shipped millions of Pixel devices running three
> > major kernel versions with LTO+CFI since 2018.
> >
> > Most of the patches are build system changes for handling LLVM
> > bitcode, which Clang produces with LTO instead of ELF object files,
> > postponing ELF processing until a later stage, and ensuring initcall
> > ordering.
>
> Sami, thanks for continuing to drive the series. I encourage you to
> keep resending with fixes accumulated or dropped on a weekly cadence.
>
> The series worked well for me on arm64, but for x86_64 on mainline I
> saw a stream of new objtool warnings:
[...]

Objtool normally won't print out these warnings when run on vmlinux.o,
but we can't pass --vmlinux to objtool as that also implies noinstr
validation right now. I think we'd have to split that from --vmlinux
to avoid these. I can include a patch to add a --noinstr flag in v5.
Peter, any thoughts about this?

> I think those should be resolved before I provide any kind of tested
> by tag.  My other piece of feedback was that I like the default
> ThinLTO, but I think the help text in the Kconfig which is visible
> during menuconfig could be improved by informing the user the
> tradeoffs.  For example, if CONFIG_THINLTO is disabled, it should be
> noted that full LTO will be used instead.  Also, that full LTO may
> produce slightly better optimized binaries than ThinLTO, at the cost
> of not utilizing multiple cores when linking and thus significantly
> slower to link.
>
> Maybe explaining that setting it to "n" implies a full LTO build,
> which will be much slower to link but possibly slightly faster would
> be good?  It's not visible unless LTO_CLANG and ARCH_SUPPORTS_THINLTO
> is enabled, so I don't think you need to explain that THINLTO without
> those is *not* full LTO.  I'll leave the precise wording to you. WDYT?

Sure, sounds good. I'll update the help text in the next version.

> Also, when I look at your treewide DISABLE_LTO patch, I think "does
> that need to be a part of this series, or is it a cleanup that can
> stand on its own?"  I think it may be the latter?  Maybe it would help
> shed one more patch than to have to carry it to just send it?  Or did
> I miss something as to why it should remain a part of this series?

I suppose it could be stand-alone, but as these patches are also
disabling LTO by filtering out flags in some of the same files,
removing the unused DISABLE_LTO flags first would reduce confusion.
But I'm fine with sending it separately too if that's preferred.

Sami

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc
  2020-09-29 21:46 ` [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
@ 2020-10-01 13:17   ` Miroslav Benes
  2020-10-01 13:36     ` Peter Zijlstra
  0 siblings, 1 reply; 42+ messages in thread
From: Miroslav Benes @ 2020-10-01 13:17 UTC (permalink / raw)
  To: Sami Tolvanen
  Cc: Masahiro Yamada, Will Deacon, Steven Rostedt, Peter Zijlstra,
	Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, jthierry, jpoimboe

Hi Sami,

On Tue, 29 Sep 2020, Sami Tolvanen wrote:

> From: Peter Zijlstra <peterz@infradead.org>
> 
> Add the --mcount option for generating __mcount_loc sections
> needed for dynamic ftrace. Using this pass requires the kernel to
> be compiled with -mfentry and CC_USING_NOP_MCOUNT to be defined
> in Makefile.
> 
> Link: https://lore.kernel.org/lkml/20200625200235.GQ4781@hirez.programming.kicks-ass.net/
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> [Sami: rebased to mainline, dropped config changes, fixed to actually use
>        --mcount, and wrote a commit message.]
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>

I am sorry to reply on v4. Should have been sooner.

Julien has been sending patches to make objtool's check functionality 
arch-agnostic as much as possible. So it seems to me that the patch should 
be based on the effort

I also wonder about making 'mcount' command separate from 'check'. Similar 
to what is 'orc' now. But that could be done later.

See tip-tree/objtool/core for both.

Thanks
Miroslav

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc
  2020-10-01 13:17   ` Miroslav Benes
@ 2020-10-01 13:36     ` Peter Zijlstra
  2020-10-02 14:13       ` Josh Poimboeuf
  0 siblings, 1 reply; 42+ messages in thread
From: Peter Zijlstra @ 2020-10-01 13:36 UTC (permalink / raw)
  To: Miroslav Benes
  Cc: Sami Tolvanen, Masahiro Yamada, Will Deacon, Steven Rostedt,
	Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, jthierry, jpoimboe

On Thu, Oct 01, 2020 at 03:17:07PM +0200, Miroslav Benes wrote:

> I also wonder about making 'mcount' command separate from 'check'. Similar 
> to what is 'orc' now. But that could be done later.

I'm not convinced more commands make sense. That only begets us the
problem of having to run multiple commands.

^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc
  2020-10-01 13:36     ` Peter Zijlstra
@ 2020-10-02 14:13       ` Josh Poimboeuf
  2020-10-05  7:10         ` Miroslav Benes
  0 siblings, 1 reply; 42+ messages in thread
From: Josh Poimboeuf @ 2020-10-02 14:13 UTC (permalink / raw)
  To: Peter Zijlstra
  Cc: Miroslav Benes, Sami Tolvanen, Masahiro Yamada, Will Deacon,
	Steven Rostedt, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, jthierry

On Thu, Oct 01, 2020 at 03:36:12PM +0200, Peter Zijlstra wrote:
> On Thu, Oct 01, 2020 at 03:17:07PM +0200, Miroslav Benes wrote:
> 
> > I also wonder about making 'mcount' command separate from 'check'. Similar 
> > to what is 'orc' now. But that could be done later.
> 
> I'm not convinced more commands make sense. That only begets us the
> problem of having to run multiple commands.

Agreed, it gets hairy when we need to combine things.  I think "orc" as
a separate subcommand was a mistake.

We should change to something like

  objtool run [--check] [--orc] [--mcount]
  objtool dump [--orc] [--mcount]

-- 
Josh


^ permalink raw reply	[flat|nested] 42+ messages in thread

* Re: [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc
  2020-10-02 14:13       ` Josh Poimboeuf
@ 2020-10-05  7:10         ` Miroslav Benes
  0 siblings, 0 replies; 42+ messages in thread
From: Miroslav Benes @ 2020-10-05  7:10 UTC (permalink / raw)
  To: Josh Poimboeuf
  Cc: Peter Zijlstra, Sami Tolvanen, Masahiro Yamada, Will Deacon,
	Steven Rostedt, Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, clang-built-linux, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86, jthierry

On Fri, 2 Oct 2020, Josh Poimboeuf wrote:

> On Thu, Oct 01, 2020 at 03:36:12PM +0200, Peter Zijlstra wrote:
> > On Thu, Oct 01, 2020 at 03:17:07PM +0200, Miroslav Benes wrote:
> > 
> > > I also wonder about making 'mcount' command separate from 'check'. Similar 
> > > to what is 'orc' now. But that could be done later.
> > 
> > I'm not convinced more commands make sense. That only begets us the
> > problem of having to run multiple commands.
> 
> Agreed, it gets hairy when we need to combine things.  I think "orc" as
> a separate subcommand was a mistake.
> 
> We should change to something like
> 
>   objtool run [--check] [--orc] [--mcount]
>   objtool dump [--orc] [--mcount]

Yes, that makes sense.

Miroslav

^ permalink raw reply	[flat|nested] 42+ messages in thread

end of thread, back to index

Thread overview: 42+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-09-29 21:46 [PATCH v4 00/29] Add support for Clang LTO Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 01/29] RAS/CEC: Fix cec_init() prototype Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 02/29] x86/asm: Replace __force_order with memory clobber Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 03/29] kbuild: preprocess module linker script Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
2020-10-01 13:17   ` Miroslav Benes
2020-10-01 13:36     ` Peter Zijlstra
2020-10-02 14:13       ` Josh Poimboeuf
2020-10-05  7:10         ` Miroslav Benes
2020-09-29 21:46 ` [PATCH v4 05/29] objtool: Don't autodetect vmlinux.o Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 06/29] tracing: move function tracer options to Kconfig Sami Tolvanen
2020-09-30  0:12   ` Steven Rostedt
2020-09-30 16:05     ` Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 07/29] tracing: add support for objtool mcount Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 08/29] x86, build: use " Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 09/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
2020-09-30  9:58   ` Mark Rutland
2020-09-30 17:10     ` Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 10/29] treewide: remove DISABLE_LTO Sami Tolvanen
2020-09-30 20:45   ` Kees Cook
2020-09-29 21:46 ` [PATCH v4 11/29] kbuild: add support for Clang LTO Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 12/29] kbuild: lto: fix module versioning Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 13/29] kbuild: lto: postpone objtool Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 14/29] kbuild: lto: limit inlining Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 15/29] kbuild: lto: merge module sections Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 16/29] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 17/29] init: lto: ensure initcall ordering Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 18/29] init: lto: fix PREL32 relocations Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 19/29] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 20/29] modpost: lto: strip .lto from module names Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 21/29] scripts/mod: disable LTO for empty.c Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 22/29] efi/libstub: disable LTO Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 23/29] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 24/29] arm64: vdso: disable LTO Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 25/29] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 26/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 27/29] x86, vdso: disable LTO only for vDSO Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 28/29] x86, cpu: disable LTO for cpu.c Sami Tolvanen
2020-09-29 21:46 ` [PATCH v4 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-09-30 21:10 ` [PATCH v4 00/29] Add support for Clang LTO Kees Cook
2020-09-30 21:58 ` Nick Desaulniers
2020-09-30 22:12   ` Sami Tolvanen

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