From: Kees Cook <keescook@chromium.org> To: Will Deacon <will@kernel.org> Cc: Kees Cook <keescook@chromium.org>, Catalin Marinas <catalin.marinas@arm.com>, Mark Rutland <mark.rutland@arm.com>, Ard Biesheuvel <ardb@kernel.org>, Peter Collingbourne <pcc@google.com>, James Morse <james.morse@arm.com>, Borislav Petkov <bp@suse.de>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Russell King <linux@armlinux.org.uk>, Masahiro Yamada <masahiroy@kernel.org>, Arvind Sankar <nivedita@alum.mit.edu>, Nick Desaulniers <ndesaulniers@google.com>, Nathan Chancellor <natechancellor@gmail.com>, Arnd Bergmann <arnd@arndb.de>, x86@kernel.org, clang-built-linux@googlegroups.com, linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 9/9] arm64/build: Warn on orphan section placement Date: Tue, 23 Jun 2020 18:49:40 -0700 [thread overview] Message-ID: <20200624014940.1204448-10-keescook@chromium.org> (raw) In-Reply-To: <20200624014940.1204448-1-keescook@chromium.org> We don't want to depend on the linker's orphan section placement heuristics as these can vary between linkers, and may change between versions. All sections need to be explicitly named in the linker script. Avoid .eh_frame* by making sure both -fno-asychronous-unwind-tables and -fno-unwind-tables are present in both CFLAGS and AFLAGS. Remove one last instance of .eh_frame by removing the needless Call Frame Information annotations from arch/arm64/kernel/smccc-call.S. Add .plt, .data.rel.ro, .igot.*, and .iplt to discards as they are not actually used. While .got.plt is also not used, it must be included otherwise ld.bfd will fail to link with the error: aarch64-linux-gnu-ld: discarded output section: `.got.plt' However, as it'd be better to validate that it stays effectively empty, add an assert. Explicitly include debug sections when they're present. Fix a case of needless quotes in __section(), which Clang doesn't like. Finally, enable orphan section warnings. Thanks to Ard Biesheuvel for many hints on correct ways to handle mysterious sections. :) Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/arm64/Makefile | 9 ++++++++- arch/arm64/kernel/smccc-call.S | 2 -- arch/arm64/kernel/vmlinux.lds.S | 11 ++++++++++- arch/arm64/mm/mmu.c | 2 +- 4 files changed, 19 insertions(+), 5 deletions(-) diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index a0d94d063fa8..fb3aa2d7de4d 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -29,6 +29,10 @@ LDFLAGS_vmlinux += --fix-cortex-a53-843419 endif endif +# We never want expected sections to be placed heuristically by the +# linker. All sections should be explicitly named in the linker script. +LDFLAGS_vmlinux += --orphan-handling=warn + ifeq ($(CONFIG_ARM64_USE_LSE_ATOMICS), y) ifneq ($(CONFIG_ARM64_LSE_ATOMICS), y) $(warning LSE atomics not supported by binutils) @@ -47,13 +51,16 @@ endif KBUILD_CFLAGS += -mgeneral-regs-only \ $(compat_vdso) $(cc_has_k_constraint) -KBUILD_CFLAGS += -fno-asynchronous-unwind-tables KBUILD_CFLAGS += $(call cc-disable-warning, psabi) KBUILD_AFLAGS += $(compat_vdso) KBUILD_CFLAGS += $(call cc-option,-mabi=lp64) KBUILD_AFLAGS += $(call cc-option,-mabi=lp64) +# Avoid generating .eh_frame* sections. +KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables +KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables + ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) prepare: stack_protector_prepare stack_protector_prepare: prepare0 diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S index 1f93809528a4..d62447964ed9 100644 --- a/arch/arm64/kernel/smccc-call.S +++ b/arch/arm64/kernel/smccc-call.S @@ -9,7 +9,6 @@ #include <asm/assembler.h> .macro SMCCC instr - .cfi_startproc \instr #0 ldr x4, [sp] stp x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS] @@ -21,7 +20,6 @@ b.ne 1f str x6, [x4, ARM_SMCCC_QUIRK_STATE_OFFS] 1: ret - .cfi_endproc .endm /* diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 5427f502c3a6..f6c781768f83 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -94,7 +94,8 @@ SECTIONS /DISCARD/ : { *(.interp .dynamic) *(.dynsym .dynstr .hash .gnu.hash) - *(.eh_frame) + *(.plt) *(.data.rel.ro) + *(.igot.*) *(.iplt) } . = KIMAGE_VADDR + TEXT_OFFSET; @@ -244,8 +245,16 @@ SECTIONS _end = .; STABS_DEBUG + DWARF_DEBUG HEAD_SYMBOLS + + /* + * Make sure that the .got.plt is either completely empty or it + * contains only the lazy dispatch entries. + */ + .got.plt (INFO) : { *(.got.plt) } + ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, ".got.plt not empty") } #include "image-vars.h" diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 1df25f26571d..dce024ea6084 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -42,7 +42,7 @@ u64 idmap_t0sz = TCR_T0SZ(VA_BITS); u64 idmap_ptrs_per_pgd = PTRS_PER_PGD; -u64 __section(".mmuoff.data.write") vabits_actual; +u64 __section(.mmuoff.data.write) vabits_actual; EXPORT_SYMBOL(vabits_actual); u64 kimage_voffset __ro_after_init; -- 2.25.1
WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org> To: Will Deacon <will@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com>, linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>, Catalin Marinas <catalin.marinas@arm.com>, Masahiro Yamada <masahiroy@kernel.org>, x86@kernel.org, Nick Desaulniers <ndesaulniers@google.com>, Russell King <linux@armlinux.org.uk>, linux-kernel@vger.kernel.org, Nathan Chancellor <natechancellor@gmail.com>, clang-built-linux@googlegroups.com, Arvind Sankar <nivedita@alum.mit.edu>, Ingo Molnar <mingo@redhat.com>, James Morse <james.morse@arm.com>, Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@suse.de>, Peter Collingbourne <pcc@google.com>, Ard Biesheuvel <ardb@kernel.org>, linux-arm-kernel@lists.infradead.org Subject: [PATCH v3 9/9] arm64/build: Warn on orphan section placement Date: Tue, 23 Jun 2020 18:49:40 -0700 [thread overview] Message-ID: <20200624014940.1204448-10-keescook@chromium.org> (raw) In-Reply-To: <20200624014940.1204448-1-keescook@chromium.org> We don't want to depend on the linker's orphan section placement heuristics as these can vary between linkers, and may change between versions. All sections need to be explicitly named in the linker script. Avoid .eh_frame* by making sure both -fno-asychronous-unwind-tables and -fno-unwind-tables are present in both CFLAGS and AFLAGS. Remove one last instance of .eh_frame by removing the needless Call Frame Information annotations from arch/arm64/kernel/smccc-call.S. Add .plt, .data.rel.ro, .igot.*, and .iplt to discards as they are not actually used. While .got.plt is also not used, it must be included otherwise ld.bfd will fail to link with the error: aarch64-linux-gnu-ld: discarded output section: `.got.plt' However, as it'd be better to validate that it stays effectively empty, add an assert. Explicitly include debug sections when they're present. Fix a case of needless quotes in __section(), which Clang doesn't like. Finally, enable orphan section warnings. Thanks to Ard Biesheuvel for many hints on correct ways to handle mysterious sections. :) Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/arm64/Makefile | 9 ++++++++- arch/arm64/kernel/smccc-call.S | 2 -- arch/arm64/kernel/vmlinux.lds.S | 11 ++++++++++- arch/arm64/mm/mmu.c | 2 +- 4 files changed, 19 insertions(+), 5 deletions(-) diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index a0d94d063fa8..fb3aa2d7de4d 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -29,6 +29,10 @@ LDFLAGS_vmlinux += --fix-cortex-a53-843419 endif endif +# We never want expected sections to be placed heuristically by the +# linker. All sections should be explicitly named in the linker script. +LDFLAGS_vmlinux += --orphan-handling=warn + ifeq ($(CONFIG_ARM64_USE_LSE_ATOMICS), y) ifneq ($(CONFIG_ARM64_LSE_ATOMICS), y) $(warning LSE atomics not supported by binutils) @@ -47,13 +51,16 @@ endif KBUILD_CFLAGS += -mgeneral-regs-only \ $(compat_vdso) $(cc_has_k_constraint) -KBUILD_CFLAGS += -fno-asynchronous-unwind-tables KBUILD_CFLAGS += $(call cc-disable-warning, psabi) KBUILD_AFLAGS += $(compat_vdso) KBUILD_CFLAGS += $(call cc-option,-mabi=lp64) KBUILD_AFLAGS += $(call cc-option,-mabi=lp64) +# Avoid generating .eh_frame* sections. +KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables +KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables + ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) prepare: stack_protector_prepare stack_protector_prepare: prepare0 diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S index 1f93809528a4..d62447964ed9 100644 --- a/arch/arm64/kernel/smccc-call.S +++ b/arch/arm64/kernel/smccc-call.S @@ -9,7 +9,6 @@ #include <asm/assembler.h> .macro SMCCC instr - .cfi_startproc \instr #0 ldr x4, [sp] stp x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS] @@ -21,7 +20,6 @@ b.ne 1f str x6, [x4, ARM_SMCCC_QUIRK_STATE_OFFS] 1: ret - .cfi_endproc .endm /* diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 5427f502c3a6..f6c781768f83 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -94,7 +94,8 @@ SECTIONS /DISCARD/ : { *(.interp .dynamic) *(.dynsym .dynstr .hash .gnu.hash) - *(.eh_frame) + *(.plt) *(.data.rel.ro) + *(.igot.*) *(.iplt) } . = KIMAGE_VADDR + TEXT_OFFSET; @@ -244,8 +245,16 @@ SECTIONS _end = .; STABS_DEBUG + DWARF_DEBUG HEAD_SYMBOLS + + /* + * Make sure that the .got.plt is either completely empty or it + * contains only the lazy dispatch entries. + */ + .got.plt (INFO) : { *(.got.plt) } + ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, ".got.plt not empty") } #include "image-vars.h" diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 1df25f26571d..dce024ea6084 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -42,7 +42,7 @@ u64 idmap_t0sz = TCR_T0SZ(VA_BITS); u64 idmap_ptrs_per_pgd = PTRS_PER_PGD; -u64 __section(".mmuoff.data.write") vabits_actual; +u64 __section(.mmuoff.data.write) vabits_actual; EXPORT_SYMBOL(vabits_actual); u64 kimage_voffset __ro_after_init; -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-06-24 1:50 UTC|newest] Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-06-24 1:49 [PATCH v3 0/9] Warn on orphan section placement Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 1:49 ` [PATCH v3 1/9] vmlinux.lds.h: Add .gnu.version* to DISCARDS Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 1:49 ` [PATCH v3 2/9] vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to STABS_DEBUG Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 15:39 ` Arvind Sankar 2020-06-24 15:39 ` Arvind Sankar 2020-06-24 15:39 ` Arvind Sankar 2020-06-24 16:16 ` Fangrui Song 2020-06-24 16:16 ` Fangrui Song 2020-06-24 17:11 ` Arvind Sankar 2020-06-24 17:11 ` Arvind Sankar 2020-06-24 17:11 ` Arvind Sankar 2020-06-24 17:26 ` Fangrui Song 2020-06-24 17:26 ` Fangrui Song 2020-06-24 17:35 ` Arvind Sankar 2020-06-24 17:35 ` Arvind Sankar 2020-06-24 17:35 ` Arvind Sankar 2020-06-24 1:49 ` [PATCH v3 3/9] efi/libstub: Remove .note.gnu.property Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 3:31 ` Fangrui Song 2020-06-24 3:31 ` Fangrui Song 2020-06-24 4:44 ` Kees Cook 2020-06-24 4:44 ` Kees Cook 2020-06-24 10:43 ` Will Deacon 2020-06-24 10:43 ` Will Deacon 2020-06-24 10:46 ` Ard Biesheuvel 2020-06-24 10:46 ` Ard Biesheuvel 2020-06-24 10:46 ` Ard Biesheuvel 2020-06-24 11:26 ` Will Deacon 2020-06-24 11:26 ` Will Deacon 2020-06-24 11:26 ` Will Deacon 2020-06-24 13:48 ` Dave Martin 2020-06-24 13:48 ` Dave Martin 2020-06-24 13:48 ` Dave Martin 2020-06-24 15:26 ` Will Deacon 2020-06-24 15:26 ` Will Deacon 2020-06-24 15:26 ` Will Deacon 2020-06-24 16:26 ` Dave Martin 2020-06-24 16:26 ` Dave Martin 2020-06-24 16:26 ` Dave Martin 2020-06-24 15:21 ` Kees Cook 2020-06-24 15:21 ` Kees Cook 2020-06-24 15:21 ` Kees Cook 2020-06-24 15:31 ` Ard Biesheuvel 2020-06-24 15:31 ` Ard Biesheuvel 2020-06-24 15:31 ` Ard Biesheuvel 2020-06-24 15:45 ` Kees Cook 2020-06-24 15:45 ` Kees Cook 2020-06-24 15:45 ` Kees Cook 2020-06-24 15:48 ` Ard Biesheuvel 2020-06-24 15:48 ` Ard Biesheuvel 2020-06-24 15:48 ` Ard Biesheuvel 2020-06-24 16:29 ` Dave Martin 2020-06-24 16:29 ` Dave Martin 2020-06-24 16:29 ` Dave Martin 2020-06-24 16:40 ` Ard Biesheuvel 2020-06-24 16:40 ` Ard Biesheuvel 2020-06-24 16:40 ` Ard Biesheuvel 2020-06-24 17:16 ` Dave Martin 2020-06-24 17:16 ` Dave Martin 2020-06-24 17:16 ` Dave Martin 2020-06-24 18:23 ` Ard Biesheuvel 2020-06-24 18:23 ` Ard Biesheuvel 2020-06-24 18:23 ` Ard Biesheuvel 2020-06-24 18:57 ` Ard Biesheuvel 2020-06-24 18:57 ` Ard Biesheuvel 2020-06-24 18:57 ` Ard Biesheuvel 2020-06-24 1:49 ` [PATCH v3 4/9] x86/build: Warn on orphan section placement Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 18:36 ` kernel test robot 2020-06-27 15:44 ` Kees Cook 2020-06-27 15:44 ` Kees Cook 2020-06-29 14:54 ` Marco Elver 2020-06-29 14:54 ` Marco Elver 2020-06-29 15:26 ` Kees Cook 2020-06-29 15:26 ` Kees Cook 2020-06-24 1:49 ` [PATCH v3 5/9] x86/boot: " Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 1:49 ` [PATCH v3 6/9] arm/build: " Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 1:49 ` [PATCH v3 7/9] arm/boot: " Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 1:49 ` [PATCH v3 8/9] arm64/build: Use common DISCARDS in linker script Kees Cook 2020-06-24 1:49 ` Kees Cook 2020-06-24 1:49 ` Kees Cook [this message] 2020-06-24 1:49 ` [PATCH v3 9/9] arm64/build: Warn on orphan section placement Kees Cook 2020-06-24 7:57 ` Will Deacon 2020-06-24 7:57 ` Will Deacon 2020-06-24 15:36 ` Kees Cook 2020-06-24 15:36 ` Kees Cook
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