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* [PATCH v5 00/29] Add support for Clang LTO
@ 2020-10-09 16:13 Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 01/29] kbuild: preprocess module linker script Sami Tolvanen
                   ` (30 more replies)
  0 siblings, 31 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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.

Note that this version is based on tip/master to reduce the number
of prerequisite patches, and to make it easier to manage changes to
objtool. Patch 1 is from Masahiro's kbuild tree, and while it's not
directly related to LTO, it makes the module linker script changes
cleaner.

Furthermore, patches 2-6 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 greatly
simplifies supporting dynamic ftrace.

You can also pull this series from

  https://github.com/samitolvanen/linux.git lto-v5

---
Changes in v5:

  - Rebased on top of tip/master.

  - Changed the command line for objtool to use --vmlinux --duplicate
    to disable warnings about retpoline thunks and to fix .orc_unwind
    generation for vmlinux.o.

  - Added --noinstr flag to objtool, so we can use --vmlinux without
    also enabling noinstr validation.

  - Disabled objtool's unreachable instruction warnings with LTO to
    disable false positives for the int3 padding in vmlinux.o.

  - Added ANNOTATE_RETPOLINE_SAFE annotations to the indirect jumps
    in x86 assembly code to fix objtool warnings with retpoline.

  - Fixed modpost warnings about missing version information with
    CONFIG_MODVERSIONS.

  - Included Makefile.lib into Makefile.modpost for ld_flags. Thanks
    to Sedat for pointing this out.

  - Updated the help text for ThinLTO to better explain the trade-offs.

  - Updated commit messages with better explanations.

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.


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

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

Sami Tolvanen (27):
  objtool: Don't autodetect vmlinux.o
  tracing: move function tracer options to Kconfig
  tracing: add support for objtool mcount
  x86, build: use objtool mcount
  treewide: remove DISABLE_LTO
  kbuild: add support for Clang LTO
  kbuild: lto: fix module versioning
  objtool: Split noinstr validation from --vmlinux
  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: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS
  arm64: allow LTO_CLANG and THINLTO to be selected
  x86/asm: annotate indirect jumps
  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                                  |  74 +++++
 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/entry/vdso/Makefile                  |   5 +-
 arch/x86/kernel/acpi/wakeup_64.S              |   2 +
 arch/x86/platform/pvh/head.S                  |   2 +
 arch/x86/power/Makefile                       |   4 +
 arch/x86/power/hibernate_asm_64.S             |   3 +
 drivers/firmware/efi/libstub/Makefile         |   2 +
 drivers/misc/lkdtm/Makefile                   |   1 +
 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                      |  25 +-
 scripts/generate_initcall_order.pl            | 270 ++++++++++++++++++
 scripts/link-vmlinux.sh                       |  98 ++++++-
 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                 |  10 +-
 tools/objtool/check.c                         |  84 +++++-
 tools/objtool/include/objtool/builtin.h       |   2 +-
 tools/objtool/include/objtool/check.h         |   1 +
 tools/objtool/include/objtool/objtool.h       |   1 +
 tools/objtool/objtool.c                       |   1 +
 56 files changed, 903 insertions(+), 131 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: 80396d76da65fc8b82581c0260c25a6aa0a495a3
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 01/29] kbuild: preprocess module linker script
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 02/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
                   ` (29 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Jessica Yu <jeyu@kernel.org>
---
 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 f84d7e4ca0be..a913a6829754 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 e589da3c8949..9c4d19ae7d61 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -20,10 +20,6 @@ endif
 # linker. All sections should be explicitly named in the linker script.
 LDFLAGS_vmlinux += $(call ld-option, --orphan-handling=warn)
 
-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 aff994473eb2..32d7e07b0acf 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -127,10 +127,6 @@ 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
 
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 02/29] objtool: Add a pass for generating __mcount_loc
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 01/29] kbuild: preprocess module linker script Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 03/29] objtool: Don't autodetect vmlinux.o Sami Tolvanen
                   ` (28 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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, 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/check.c                   | 82 +++++++++++++++++++++++++
 tools/objtool/include/objtool/builtin.h |  2 +-
 tools/objtool/include/objtool/check.h   |  1 +
 tools/objtool/include/objtool/objtool.h |  1 +
 tools/objtool/objtool.c                 |  1 +
 6 files changed, 88 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index f47951e19c9d..6518c1a6ad1e 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -18,7 +18,7 @@
 #include <objtool/builtin.h>
 #include <objtool/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/check.c b/tools/objtool/check.c
index 32e6a0db6768..61dcd80feec5 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -524,6 +524,65 @@ static int create_static_call_sections(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", 0, 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.
  */
@@ -950,6 +1009,22 @@ 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.
@@ -2921,6 +2996,13 @@ int check(struct objtool_file *file)
 		goto out;
 	warnings += ret;
 
+	if (mcount) {
+		ret = create_mcount_loc_sections(file);
+		if (ret < 0)
+			goto out;
+		warnings += ret;
+	}
+
 out:
 	if (ret < 0) {
 		/*
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index 85c979caa367..94565a72b701 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/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/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index bba10968eac0..f04415852c29 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -23,6 +23,7 @@ struct instruction {
 	struct list_head list;
 	struct hlist_node hash;
 	struct list_head static_call_node;
+	struct list_head mcount_loc_node;
 	struct section *sec;
 	unsigned long offset;
 	unsigned int len;
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index 32f4cd1da9fa..3c899e0ab861 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -19,6 +19,7 @@ struct objtool_file {
 	struct list_head insn_list;
 	DECLARE_HASHTABLE(insn_hash, 20);
 	struct list_head static_call_list;
+	struct list_head mcount_loc_list;
 	bool ignore_unreachables, c_file, hints, rodata;
 };
 
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index e848feb0a5fc..7b97ce499405 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -62,6 +62,7 @@ struct objtool_file *objtool_open_read(const char *_objname)
 	INIT_LIST_HEAD(&file.insn_list);
 	hash_init(file.insn_hash);
 	INIT_LIST_HEAD(&file.static_call_list);
+	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;
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 03/29] objtool: Don't autodetect vmlinux.o
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 01/29] kbuild: preprocess module linker script Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 02/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 04/29] tracing: move function tracer options to Kconfig Sami Tolvanen
                   ` (27 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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 | 6 +-----
 2 files changed, 2 insertions(+), 6 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 6518c1a6ad1e..ff4d7f5c0e80 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -41,7 +41,7 @@ const struct option check_options[] = {
 
 int cmd_check(int argc, const char **argv)
 {
-	const char *objname, *s;
+	const char *objname;
 	struct objtool_file *file;
 	int ret;
 
@@ -52,10 +52,6 @@ int cmd_check(int argc, const char **argv)
 
 	objname = argv[0];
 
-	s = strstr(objname, "vmlinux.o");
-	if (s && !s[9])
-		vmlinux = true;
-
 	file = objtool_open_read(objname);
 	if (!file)
 		return 1;
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 04/29] tracing: move function tracer options to Kconfig
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (2 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 03/29] objtool: Don't autodetect vmlinux.o Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 05/29] tracing: add support for objtool mcount Sami Tolvanen
                   ` (26 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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.

Note that FTRACE_MCOUNT_USE_* options are updated on rebuild and
therefore, work even if the .config was generated in a different
environment.

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 a913a6829754..434da9fcbf3c 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)
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 05/29] tracing: add support for objtool mcount
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (3 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 04/29] tracing: move function tracer options to Kconfig Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 06/29] x86, build: use " Sami Tolvanen
                   ` (25 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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 434da9fcbf3c..fb2cf557d3ca 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 06/29] x86, build: use objtool mcount
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (4 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 05/29] tracing: add support for objtool mcount Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 07/29] treewide: remove DISABLE_LTO Sami Tolvanen
                   ` (24 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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 5e832fd520b5..6d67646153bc 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 07/29] treewide: remove DISABLE_LTO
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (5 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 06/29] x86, build: use " Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 08/29] kbuild: add support for Clang LTO Sami Tolvanen
                   ` (23 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 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 16ec9262ce9d..2561abc91961 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)
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 08/29] kbuild: add support for Clang LTO
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (6 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 07/29] treewide: remove DISABLE_LTO Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 09/29] kbuild: lto: fix module versioning Sami Tolvanen
                   ` (22 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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                      | 75 +++++++++++++++++++++++++++++++
 include/asm-generic/vmlinux.lds.h | 11 +++--
 scripts/Makefile.build            |  9 +++-
 scripts/Makefile.modfinal         |  9 +++-
 scripts/Makefile.modpost          | 21 ++++++++-
 scripts/link-vmlinux.sh           | 32 +++++++++----
 7 files changed, 159 insertions(+), 18 deletions(-)

diff --git a/Makefile b/Makefile
index fb2cf557d3ca..a3baf8388163 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 76ec3395b843..4ac5dda6d873 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -558,6 +558,81 @@ 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
+
+	  If you say N here, the compiler will use full LTO, which may
+	  produce faster code, but building the kernel will be significantly
+	  slower as the linker won't efficiently utilize multiple threads.
+
+	  If unsure, say Y.
+
+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 e1843976754a..77e5bd069dd4 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -90,15 +90,18 @@
  * .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..9ff8bfdb574d 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -43,6 +43,9 @@ __modpost:
 include include/config/auto.conf
 include scripts/Kbuild.include
 
+# for ld_flags
+include scripts/Makefile.lib
+
 MODPOST = scripts/mod/modpost								\
 	$(if $(CONFIG_MODVERSIONS),-m)							\
 	$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a)					\
@@ -102,12 +105,26 @@ $(input-symdump):
 	@echo >&2 'WARNING: Symbol version dump "$@" 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
 
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 09/29] kbuild: lto: fix module versioning
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (7 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 08/29] kbuild: add support for Clang LTO Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 10/29] objtool: Split noinstr validation from --vmlinux Sami Tolvanen
                   ` (21 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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  | 23 ++++++++++++++++++++++-
 6 files changed, 61 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 a3baf8388163..6d31a78d79ce 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 4ac5dda6d873..caeb6feb517e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -615,7 +615,6 @@ 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 9ff8bfdb574d..066beffca09a 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -111,7 +111,11 @@ 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..1a48ef525f46 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -43,11 +43,26 @@ 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 o in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
+		if [ -f ${o}.symversions ]; then
+			cat ${o}.symversions >> .tmp_symversions.lds
+		fi
+	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 +72,11 @@ 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 +84,7 @@ 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 +262,7 @@ 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 10/29] objtool: Split noinstr validation from --vmlinux
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (8 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 09/29] kbuild: lto: fix module versioning Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 11/29] kbuild: lto: postpone objtool Sami Tolvanen
                   ` (20 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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 a --noinstr flag to objtool to allow us to specify
that we're processing vmlinux.o without also enabling noinstr
validation. This is needed to avoid false positives with LTO when we
run objtool on vmlinux.o without CONFIG_DEBUG_ENTRY.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 scripts/link-vmlinux.sh                 | 2 +-
 tools/objtool/builtin-check.c           | 3 ++-
 tools/objtool/check.c                   | 2 +-
 tools/objtool/include/objtool/builtin.h | 2 +-
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 1a48ef525f46..5ace1dc43993 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -92,7 +92,7 @@ objtool_link()
 	local objtoolopt;
 
 	if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
-		objtoolopt="check --vmlinux"
+		objtoolopt="check --vmlinux --noinstr"
 		if [ -z "${CONFIG_FRAME_POINTER}" ]; then
 			objtoolopt="${objtoolopt} --no-fp"
 		fi
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index ff4d7f5c0e80..c3a85d8f6c5c 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -18,7 +18,7 @@
 #include <objtool/builtin.h>
 #include <objtool/objtool.h>
 
-bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount;
+bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount, noinstr;
 
 static const char * const check_usage[] = {
 	"objtool check [<options>] file.o",
@@ -34,6 +34,7 @@ const struct option check_options[] = {
 	OPT_BOOLEAN('a', "uaccess", &uaccess, "enable uaccess checking"),
 	OPT_BOOLEAN('s', "stats", &stats, "print statistics"),
 	OPT_BOOLEAN('d', "duplicate", &validate_dup, "duplicate validation for vmlinux.o"),
+	OPT_BOOLEAN('n', "noinstr", &noinstr, "noinstr 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/check.c b/tools/objtool/check.c
index 61dcd80feec5..0c05d58608b0 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -245,7 +245,7 @@ static void init_insn_state(struct insn_state *state, struct section *sec)
 	 * not correctly determine insn->call_dest->sec (external symbols do
 	 * not have a section).
 	 */
-	if (vmlinux && sec)
+	if (vmlinux && noinstr && sec)
 		state->noinstr = sec->noinstr;
 }
 
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index 94565a72b701..2502bb27de17 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/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, mcount;
+extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount, noinstr;
 
 extern int cmd_check(int argc, const char **argv);
 extern int cmd_orc(int argc, const char **argv);
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 11/29] kbuild: lto: postpone objtool
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (9 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 10/29] objtool: Split noinstr validation from --vmlinux Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 12/29] kbuild: lto: limit inlining Sami Tolvanen
                   ` (19 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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.

As we didn't have objects to process earlier, we use --duplicate
when processing vmlinux.o. This change also disables unreachable
instruction warnings with LTO to avoid warnings about the int3
padding between functions.

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   | 28 +++++++++++++++++++++++++---
 5 files changed, 55 insertions(+), 24 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index caeb6feb517e..74cbd6e3b116 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -612,7 +612,7 @@ 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 5ace1dc43993..7f4d19271180 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -89,14 +89,36 @@ modpost_link()
 
 objtool_link()
 {
+	local objtoolcmd;
 	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
+			objtoolcmd="orc generate"
+		fi
+
+		objtoolopt="${objtoolopt} --duplicate"
+
+		if [ -n "${CONFIG_FTRACE_MCOUNT_USE_OBJTOOL}" ]; then
+			objtoolopt="${objtoolopt} --mcount"
+		fi
+	fi
+
 	if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
-		objtoolopt="check --vmlinux --noinstr"
+		objtoolopt="${objtoolopt} --noinstr"
+	fi
+
+	if [ -n "${objtoolopt}" ]; then
+		if [ -z "${objtoolcmd}" ]; then
+			objtoolcmd="check"
+		fi
+		objtoolopt="${objtoolopt} --vmlinux"
 		if [ -z "${CONFIG_FRAME_POINTER}" ]; then
 			objtoolopt="${objtoolopt} --no-fp"
 		fi
-		if [ -n "${CONFIG_GCOV_KERNEL}" ]; then
+		if [ -n "${CONFIG_GCOV_KERNEL}" ] || [ -n "${CONFIG_LTO_CLANG}" ]; then
 			objtoolopt="${objtoolopt} --no-unreachable"
 		fi
 		if [ -n "${CONFIG_RETPOLINE}" ]; then
@@ -106,7 +128,7 @@ objtool_link()
 			objtoolopt="${objtoolopt} --uaccess"
 		fi
 		info OBJTOOL ${1}
-		tools/objtool/objtool ${objtoolopt} ${1}
+		tools/objtool/objtool ${objtoolcmd} ${objtoolopt} ${1}
 	fi
 }
 
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 12/29] kbuild: lto: limit inlining
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (10 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 11/29] kbuild: lto: postpone objtool Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 13/29] kbuild: lto: merge module sections Sami Tolvanen
                   ` (18 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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 6d31a78d79ce..3fe2dca17261 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 13/29] kbuild: lto: merge module sections
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (11 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 12/29] kbuild: lto: limit inlining Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 14/29] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
                   ` (17 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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>
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 14/29] kbuild: lto: remove duplicate dependencies from .mod files
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (12 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 13/29] kbuild: lto: merge module sections Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 15/29] init: lto: ensure initcall ordering Sami Tolvanen
                   ` (16 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 15/29] init: lto: ensure initcall ordering
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (13 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 14/29] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 16/29] init: lto: fix PREL32 relocations Sami Tolvanen
                   ` (15 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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 7f4d19271180..cd649dc21c04 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()
@@ -72,6 +83,9 @@ 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"
@@ -284,6 +298,7 @@ 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 16/29] init: lto: fix PREL32 relocations
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (14 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 15/29] init: lto: ensure initcall ordering Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 17/29] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
                   ` (14 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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))
 
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 17/29] PCI: Fix PREL32 relocations for LTO
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (15 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 16/29] init: lto: fix PREL32 relocations Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 18/29] modpost: lto: strip .lto from module names Sami Tolvanen
                   ` (13 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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,	\
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 18/29] modpost: lto: strip .lto from module names
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (16 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 17/29] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 19/29] scripts/mod: disable LTO for empty.c Sami Tolvanen
                   ` (12 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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);
 
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 19/29] scripts/mod: disable LTO for empty.c
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (17 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 18/29] modpost: lto: strip .lto from module names Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 20/29] efi/libstub: disable LTO Sami Tolvanen
                   ` (11 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 20/29] efi/libstub: disable LTO
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (18 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 19/29] scripts/mod: disable LTO for empty.c Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 21/29] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
                   ` (10 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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 0c911e391d75..e927876f3a05 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -36,6 +36,8 @@ 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.
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 21/29] drivers/misc/lkdtm: disable LTO for rodata.o
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (19 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 20/29] efi/libstub: disable LTO Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 22/29] arm64: vdso: disable LTO Sami Tolvanen
                   ` (9 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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	:= \
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 22/29] arm64: vdso: disable LTO
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (20 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 21/29] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 23/29] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen
                   ` (8 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 23/29] KVM: arm64: disable LTO for the nVHE directory
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (21 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 22/29] arm64: vdso: disable LTO Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 24/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
                   ` (7 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 24/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (22 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 23/29] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
                   ` (6 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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

DYNAMIC_FTRACE_WITH_REGS uses -fpatchable-function-entry, which makes
running recordmcount unnecessary as there are no mcount calls in object
files, and __mcount_loc doesn't need to be generated.

While there's normally no harm in running recordmcount even when it's
not strictly needed, this won't work with LTO as we have LLVM bitcode
instead of ELF objects.

This change selects FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY, which
disables recordmcount when patchable function entries are used instead.

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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (23 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 24/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-12  8:31   ` Will Deacon
  2020-10-09 16:13 ` [PATCH v5 26/29] x86/asm: annotate indirect jumps Sami Tolvanen
                   ` (5 subsequent siblings)
  30 siblings, 1 reply; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 26/29] x86/asm: annotate indirect jumps
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (24 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 27/29] x86, vdso: disable LTO only for vDSO Sami Tolvanen
                   ` (4 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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

Running objtool --vmlinux --duplicate on vmlinux.o produces a few
warnings about indirect jumps with retpoline:

  vmlinux.o: warning: objtool: wakeup_long64()+0x61: indirect jump
  found in RETPOLINE build
  ...

This change adds ANNOTATE_RETPOLINE_SAFE annotations to the jumps
in assembly code to stop the warnings.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/x86/kernel/acpi/wakeup_64.S  | 2 ++
 arch/x86/platform/pvh/head.S      | 2 ++
 arch/x86/power/hibernate_asm_64.S | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
index c8daa92f38dc..041e79c4e195 100644
--- a/arch/x86/kernel/acpi/wakeup_64.S
+++ b/arch/x86/kernel/acpi/wakeup_64.S
@@ -7,6 +7,7 @@
 #include <asm/msr.h>
 #include <asm/asm-offsets.h>
 #include <asm/frame.h>
+#include <asm/nospec-branch.h>
 
 # Copyright 2003 Pavel Machek <pavel@suse.cz
 
@@ -39,6 +40,7 @@ SYM_FUNC_START(wakeup_long64)
 	movq	saved_rbp, %rbp
 
 	movq	saved_rip, %rax
+	ANNOTATE_RETPOLINE_SAFE
 	jmp	*%rax
 SYM_FUNC_END(wakeup_long64)
 
diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index 43b4d864817e..640b79cc64b8 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -15,6 +15,7 @@
 #include <asm/asm.h>
 #include <asm/boot.h>
 #include <asm/processor-flags.h>
+#include <asm/nospec-branch.h>
 #include <asm/msr.h>
 #include <xen/interface/elfnote.h>
 
@@ -105,6 +106,7 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
 	/* startup_64 expects boot_params in %rsi. */
 	mov $_pa(pvh_bootparams), %rsi
 	mov $_pa(startup_64), %rax
+	ANNOTATE_RETPOLINE_SAFE
 	jmp *%rax
 
 #else /* CONFIG_X86_64 */
diff --git a/arch/x86/power/hibernate_asm_64.S b/arch/x86/power/hibernate_asm_64.S
index 7918b8415f13..715509d94fa3 100644
--- a/arch/x86/power/hibernate_asm_64.S
+++ b/arch/x86/power/hibernate_asm_64.S
@@ -21,6 +21,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/processor-flags.h>
 #include <asm/frame.h>
+#include <asm/nospec-branch.h>
 
 SYM_FUNC_START(swsusp_arch_suspend)
 	movq	$saved_context, %rax
@@ -66,6 +67,7 @@ SYM_CODE_START(restore_image)
 
 	/* jump to relocated restore code */
 	movq	relocated_restore_code(%rip), %rcx
+	ANNOTATE_RETPOLINE_SAFE
 	jmpq	*%rcx
 SYM_CODE_END(restore_image)
 
@@ -97,6 +99,7 @@ SYM_CODE_START(core_restore_code)
 
 .Ldone:
 	/* jump to the restore_registers address from the image header */
+	ANNOTATE_RETPOLINE_SAFE
 	jmpq	*%r8
 SYM_CODE_END(core_restore_code)
 
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 27/29] x86, vdso: disable LTO only for vDSO
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (25 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 26/29] x86/asm: annotate indirect jumps Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 28/29] x86, cpu: disable LTO for cpu.c Sami Tolvanen
                   ` (3 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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)
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 28/29] x86, cpu: disable LTO for cpu.c
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (26 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 27/29] x86, vdso: disable LTO only for vDSO Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:13 ` [PATCH v5 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
                   ` (2 subsequent siblings)
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* [PATCH v5 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (27 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 28/29] x86, cpu: disable LTO for cpu.c Sami Tolvanen
@ 2020-10-09 16:13 ` Sami Tolvanen
  2020-10-09 16:30 ` [PATCH v5 00/29] Add support for Clang LTO Sedat Dilek
       [not found] ` <20201009153512.1546446a@gandalf.local.home>
  30 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 16:13 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 6d67646153bc..c579d7000b67 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 154259f18b8b..774a7debb27c 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
 #
-- 
2.28.0.1011.ga647a8990f-goog


^ permalink raw reply	[flat|nested] 39+ messages in thread

* Re: [PATCH v5 00/29] Add support for Clang LTO
  2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
                   ` (28 preceding siblings ...)
  2020-10-09 16:13 ` [PATCH v5 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
@ 2020-10-09 16:30 ` Sedat Dilek
  2020-10-09 20:50   ` Sami Tolvanen
       [not found] ` <20201009153512.1546446a@gandalf.local.home>
  30 siblings, 1 reply; 39+ messages in thread
From: Sedat Dilek @ 2020-10-09 16:30 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 ML, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86

On Fri, Oct 9, 2020 at 6:13 PM 'Sami Tolvanen' via Clang Built Linux
<clang-built-linux@googlegroups.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.
>
> Note that this version is based on tip/master to reduce the number
> of prerequisite patches, and to make it easier to manage changes to
> objtool. Patch 1 is from Masahiro's kbuild tree, and while it's not
> directly related to LTO, it makes the module linker script changes
> cleaner.
>
> Furthermore, patches 2-6 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 greatly
> simplifies supporting dynamic ftrace.
>
> You can also pull this series from
>
>   https://github.com/samitolvanen/linux.git lto-v5
>
> ---
> Changes in v5:
>
>   - Rebased on top of tip/master.
>

What are the plans to get this into mainline?
Linux v5.10 :-) too early - needs more review/testing?

Will clang-cfi be based on this, too?

>   - Changed the command line for objtool to use --vmlinux --duplicate
>     to disable warnings about retpoline thunks and to fix .orc_unwind
>     generation for vmlinux.o.
>
>   - Added --noinstr flag to objtool, so we can use --vmlinux without
>     also enabling noinstr validation.
>
>   - Disabled objtool's unreachable instruction warnings with LTO to
>     disable false positives for the int3 padding in vmlinux.o.
>
>   - Added ANNOTATE_RETPOLINE_SAFE annotations to the indirect jumps
>     in x86 assembly code to fix objtool warnings with retpoline.
>
>   - Fixed modpost warnings about missing version information with
>     CONFIG_MODVERSIONS.
>
>   - Included Makefile.lib into Makefile.modpost for ld_flags. Thanks
>     to Sedat for pointing this out.
>

That was a long way to detect this as I had very big Debian Linux
debug packages generated with CONFIG_DEBUG_INFO_COMPRESSED=y.

Thanks for v5 of clang-lto.

- Sedat -

[1] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-705754002

>   - Updated the help text for ThinLTO to better explain the trade-offs.
>
>   - Updated commit messages with better explanations.
>
> 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.
>
>
> Masahiro Yamada (1):
>   kbuild: preprocess module linker script
>
> Peter Zijlstra (1):
>   objtool: Add a pass for generating __mcount_loc
>
> Sami Tolvanen (27):
>   objtool: Don't autodetect vmlinux.o
>   tracing: move function tracer options to Kconfig
>   tracing: add support for objtool mcount
>   x86, build: use objtool mcount
>   treewide: remove DISABLE_LTO
>   kbuild: add support for Clang LTO
>   kbuild: lto: fix module versioning
>   objtool: Split noinstr validation from --vmlinux
>   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: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS
>   arm64: allow LTO_CLANG and THINLTO to be selected
>   x86/asm: annotate indirect jumps
>   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                                  |  74 +++++
>  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/entry/vdso/Makefile                  |   5 +-
>  arch/x86/kernel/acpi/wakeup_64.S              |   2 +
>  arch/x86/platform/pvh/head.S                  |   2 +
>  arch/x86/power/Makefile                       |   4 +
>  arch/x86/power/hibernate_asm_64.S             |   3 +
>  drivers/firmware/efi/libstub/Makefile         |   2 +
>  drivers/misc/lkdtm/Makefile                   |   1 +
>  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                      |  25 +-
>  scripts/generate_initcall_order.pl            | 270 ++++++++++++++++++
>  scripts/link-vmlinux.sh                       |  98 ++++++-
>  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                 |  10 +-
>  tools/objtool/check.c                         |  84 +++++-
>  tools/objtool/include/objtool/builtin.h       |   2 +-
>  tools/objtool/include/objtool/check.h         |   1 +
>  tools/objtool/include/objtool/objtool.h       |   1 +
>  tools/objtool/objtool.c                       |   1 +
>  56 files changed, 903 insertions(+), 131 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: 80396d76da65fc8b82581c0260c25a6aa0a495a3
> --
> 2.28.0.1011.ga647a8990f-goog
>
> --
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^ permalink raw reply	[flat|nested] 39+ messages in thread

* Re: [PATCH v5 00/29] Add support for Clang LTO
  2020-10-09 16:30 ` [PATCH v5 00/29] Add support for Clang LTO Sedat Dilek
@ 2020-10-09 20:50   ` Sami Tolvanen
  0 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 20:50 UTC (permalink / raw)
  To: Sedat Dilek
  Cc: Masahiro Yamada, Will Deacon, Steven Rostedt, Peter Zijlstra,
	Greg Kroah-Hartman, Paul E. McKenney, Kees Cook,
	Nick Desaulniers, Clang-Built-Linux ML, kernel-hardening,
	linux-arch, linux-arm-kernel, linux-kbuild, linux-kernel,
	linux-pci, x86

On Fri, Oct 09, 2020 at 06:30:24PM +0200, Sedat Dilek wrote:
> Will clang-cfi be based on this, too?

At least until the prerequisite patches are merged into mainline. In the
meanwhile, I have a CFI tree based on this series here:

  https://github.com/samitolvanen/linux/tree/tip/clang-lto

Sami

^ permalink raw reply	[flat|nested] 39+ messages in thread

* Re: [PATCH v5 00/29] Add support for Clang LTO
       [not found] ` <20201009153512.1546446a@gandalf.local.home>
@ 2020-10-09 21:05   ` Sami Tolvanen
  2020-10-09 23:38     ` Steven Rostedt
  0 siblings, 1 reply; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-09 21:05 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,
	linux-kernel, linux-pci, x86

On Fri, Oct 09, 2020 at 03:35:12PM -0400, Steven Rostedt wrote:
> On Fri,  9 Oct 2020 09:13:09 -0700
> 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.
> > 
> > Note that this version is based on tip/master to reduce the number
> > of prerequisite patches, and to make it easier to manage changes to
> > objtool. Patch 1 is from Masahiro's kbuild tree, and while it's not
> > directly related to LTO, it makes the module linker script changes
> > cleaner.
> > 
> 
> I went to test this, but it appears that the latest tip/master fails to
> build for me. This error is on tip/master, before I even applied a single
> patch.
> 
> (config attached)

Ah yes, X86_DECODER_SELFTEST seems to be broken in tip/master. If you
prefer, I have these patches on top of mainline here:

  https://github.com/samitolvanen/linux/tree/clang-lto

Testing your config with LTO on this tree, it does build and boot for
me, although I saw a couple of new objtool warnings, and with LLVM=1,
one warning from llvm-objdump.

Sami

^ permalink raw reply	[flat|nested] 39+ messages in thread

* Re: [PATCH v5 00/29] Add support for Clang LTO
  2020-10-09 21:05   ` Sami Tolvanen
@ 2020-10-09 23:38     ` Steven Rostedt
  2020-10-10  0:00       ` Sami Tolvanen
  0 siblings, 1 reply; 39+ messages in thread
From: Steven Rostedt @ 2020-10-09 23:38 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 Fri, 9 Oct 2020 14:05:48 -0700
Sami Tolvanen <samitolvanen@google.com> wrote:

> Ah yes, X86_DECODER_SELFTEST seems to be broken in tip/master. If you
> prefer, I have these patches on top of mainline here:
> 
>   https://github.com/samitolvanen/linux/tree/clang-lto
> 
> Testing your config with LTO on this tree, it does build and boot for
> me, although I saw a couple of new objtool warnings, and with LLVM=1,
> one warning from llvm-objdump.

Thanks, I disabled X86_DECODER_SELFTEST and it now builds.

I forced the objdump mcount logic with the below patch, which produces:

CONFIG_FTRACE_MCOUNT_RECORD=y
CONFIG_FTRACE_MCOUNT_USE_OBJTOOL=y

But I don't see the __mcount_loc sections being created.

I applied patches 1 - 6.

-- Steve

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 89263210ab26..3042619e21b7 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -606,7 +606,7 @@ config FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
 
 config FTRACE_MCOUNT_USE_CC
 	def_bool y
-	depends on $(cc-option,-mrecord-mcount)
+	depends on $(cc-option,-mrecord-mcount1)
 	depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
 	depends on FTRACE_MCOUNT_RECORD
 

^ permalink raw reply	[flat|nested] 39+ messages in thread

* Re: [PATCH v5 00/29] Add support for Clang LTO
  2020-10-09 23:38     ` Steven Rostedt
@ 2020-10-10  0:00       ` Sami Tolvanen
  0 siblings, 0 replies; 39+ messages in thread
From: Sami Tolvanen @ 2020-10-10  0:00 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 Fri, Oct 9, 2020 at 4:38 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Fri, 9 Oct 2020 14:05:48 -0700
> Sami Tolvanen <samitolvanen@google.com> wrote:
>
> > Ah yes, X86_DECODER_SELFTEST seems to be broken in tip/master. If you
> > prefer, I have these patches on top of mainline here:
> >
> >   https://github.com/samitolvanen/linux/tree/clang-lto
> >
> > Testing your config with LTO on this tree, it does build and boot for
> > me, although I saw a couple of new objtool warnings, and with LLVM=1,
> > one warning from llvm-objdump.
>
> Thanks, I disabled X86_DECODER_SELFTEST and it now builds.
>
> I forced the objdump mcount logic with the below patch, which produces:
>
> CONFIG_FTRACE_MCOUNT_RECORD=y
> CONFIG_FTRACE_MCOUNT_USE_OBJTOOL=y
>
> But I don't see the __mcount_loc sections being created.
>
> I applied patches 1 - 6.

Patch 6 is missing the part where we actually pass --mcount to
objtool, it's in patch 11 ("kbuild: lto: postpone objtool"). I'll fix
this in v6. In the meanwhile, please apply patches 1-11 to test the
objtool change. Do you have any thoughts about the approach otherwise?

Sami

^ permalink raw reply	[flat|nested] 39+ messages in thread

* Re: [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected
  2020-10-09 16:13 ` [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
@ 2020-10-12  8:31   ` Will Deacon
  2020-10-12 20:44     ` Kees Cook
  0 siblings, 1 reply; 39+ messages in thread
From: Will Deacon @ 2020-10-12  8:31 UTC (permalink / raw)
  To: Sami Tolvanen
  Cc: Masahiro Yamada, 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

On Fri, Oct 09, 2020 at 09:13:34AM -0700, Sami Tolvanen wrote:
> 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

Please don't enable this for arm64 until we have the dependency stuff sorted
out. I posted patches [1] for this before, but I think they should be part
of this series as they don't make sense on their own.

Will

[1] https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=rwonce/read-barrier-depends

^ permalink raw reply	[flat|nested] 39+ messages in thread

* Re: [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected
  2020-10-12  8:31   ` Will Deacon
@ 2020-10-12 20:44     ` Kees Cook
  2020-10-12 20:51       ` Will Deacon
  0 siblings, 1 reply; 39+ messages in thread
From: Kees Cook @ 2020-10-12 20:44 UTC (permalink / raw)
  To: Will Deacon
  Cc: Sami Tolvanen, Masahiro Yamada, 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 Mon, Oct 12, 2020 at 09:31:16AM +0100, Will Deacon wrote:
> On Fri, Oct 09, 2020 at 09:13:34AM -0700, Sami Tolvanen wrote:
> > 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
> 
> Please don't enable this for arm64 until we have the dependency stuff sorted
> out. I posted patches [1] for this before, but I think they should be part
> of this series as they don't make sense on their own.

Oh, hm. We've been trying to trim down this series, since it's already
quite large. Why can't [1] land first? It would make this easier to deal
with, IMO.

> [1] https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=rwonce/read-barrier-depends

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 39+ messages in thread

* Re: [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected
  2020-10-12 20:44     ` Kees Cook
@ 2020-10-12 20:51       ` Will Deacon
  2020-10-12 21:02         ` Kees Cook
  0 siblings, 1 reply; 39+ messages in thread
From: Will Deacon @ 2020-10-12 20:51 UTC (permalink / raw)
  To: Kees Cook
  Cc: Sami Tolvanen, Masahiro Yamada, 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 Mon, Oct 12, 2020 at 01:44:56PM -0700, Kees Cook wrote:
> On Mon, Oct 12, 2020 at 09:31:16AM +0100, Will Deacon wrote:
> > On Fri, Oct 09, 2020 at 09:13:34AM -0700, Sami Tolvanen wrote:
> > > 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
> > 
> > Please don't enable this for arm64 until we have the dependency stuff sorted
> > out. I posted patches [1] for this before, but I think they should be part
> > of this series as they don't make sense on their own.
> 
> Oh, hm. We've been trying to trim down this series, since it's already
> quite large. Why can't [1] land first? It would make this easier to deal
> with, IMO.

I'm happy to handle [1] along with the LTO Kconfig change when the time
comes, if that helps. I just don't want to merge dead code!

Will

> > [1] https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=rwonce/read-barrier-depends

^ permalink raw reply	[flat|nested] 39+ messages in thread

* Re: [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected
  2020-10-12 20:51       ` Will Deacon
@ 2020-10-12 21:02         ` Kees Cook
  0 siblings, 0 replies; 39+ messages in thread
From: Kees Cook @ 2020-10-12 21:02 UTC (permalink / raw)
  To: Will Deacon
  Cc: Sami Tolvanen, Masahiro Yamada, 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 Mon, Oct 12, 2020 at 09:51:09PM +0100, Will Deacon wrote:
> On Mon, Oct 12, 2020 at 01:44:56PM -0700, Kees Cook wrote:
> > On Mon, Oct 12, 2020 at 09:31:16AM +0100, Will Deacon wrote:
> > > On Fri, Oct 09, 2020 at 09:13:34AM -0700, Sami Tolvanen wrote:
> > > > 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
> > > 
> > > Please don't enable this for arm64 until we have the dependency stuff sorted
> > > out. I posted patches [1] for this before, but I think they should be part
> > > of this series as they don't make sense on their own.
> > 
> > Oh, hm. We've been trying to trim down this series, since it's already
> > quite large. Why can't [1] land first? It would make this easier to deal
> > with, IMO.
> 
> I'm happy to handle [1] along with the LTO Kconfig change when the time
> comes, if that helps. I just don't want to merge dead code!

Okay, understood. Thanks!

> 
> Will
> 
> > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=rwonce/read-barrier-depends

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 39+ messages in thread

end of thread, back to index

Thread overview: 39+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 01/29] kbuild: preprocess module linker script Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 02/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 03/29] objtool: Don't autodetect vmlinux.o Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 04/29] tracing: move function tracer options to Kconfig Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 05/29] tracing: add support for objtool mcount Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 06/29] x86, build: use " Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 07/29] treewide: remove DISABLE_LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 08/29] kbuild: add support for Clang LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 09/29] kbuild: lto: fix module versioning Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 10/29] objtool: Split noinstr validation from --vmlinux Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 11/29] kbuild: lto: postpone objtool Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 12/29] kbuild: lto: limit inlining Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 13/29] kbuild: lto: merge module sections Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 14/29] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 15/29] init: lto: ensure initcall ordering Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 16/29] init: lto: fix PREL32 relocations Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 17/29] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 18/29] modpost: lto: strip .lto from module names Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 19/29] scripts/mod: disable LTO for empty.c Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 20/29] efi/libstub: disable LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 21/29] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 22/29] arm64: vdso: disable LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 23/29] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 24/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-10-12  8:31   ` Will Deacon
2020-10-12 20:44     ` Kees Cook
2020-10-12 20:51       ` Will Deacon
2020-10-12 21:02         ` Kees Cook
2020-10-09 16:13 ` [PATCH v5 26/29] x86/asm: annotate indirect jumps Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 27/29] x86, vdso: disable LTO only for vDSO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 28/29] x86, cpu: disable LTO for cpu.c Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-10-09 16:30 ` [PATCH v5 00/29] Add support for Clang LTO Sedat Dilek
2020-10-09 20:50   ` Sami Tolvanen
     [not found] ` <20201009153512.1546446a@gandalf.local.home>
2020-10-09 21:05   ` Sami Tolvanen
2020-10-09 23:38     ` Steven Rostedt
2020-10-10  0:00       ` Sami Tolvanen

Linux-PCI Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-pci/0 linux-pci/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-pci linux-pci/ https://lore.kernel.org/linux-pci \
		linux-pci@vger.kernel.org
	public-inbox-index linux-pci

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-pci


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git