[PATCH v4 16/17] x86/build: Warn on orphan section placement
From: Kees Cook <hidden>
Date: 2020-06-29 20:58:03
Also in:
linux-arch, linux-efi, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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. Discards the unused rela, plt, and got sections that are not needed in the final vmlinux, stop emitting kprobe sections without kprobes, and enable orphan section warnings. Signed-off-by: Kees Cook <redacted> --- arch/x86/Makefile | 4 ++++ arch/x86/include/asm/asm.h | 6 +++++- arch/x86/kernel/vmlinux.lds.S | 6 ++++++ 3 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 00e378de8bc0..f8a5b2333729 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile@@ -51,6 +51,10 @@ ifdef CONFIG_X86_NEED_RELOCS LDFLAGS_vmlinux := --emit-relocs --discard-none 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 + # # Prevent GCC from generating any FP code by mistake. #
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index 0f63585edf5f..92feec0f0a12 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h@@ -138,11 +138,15 @@ # define _ASM_EXTABLE_FAULT(from, to) \ _ASM_EXTABLE_HANDLE(from, to, ex_handler_fault) -# define _ASM_NOKPROBE(entry) \ +# ifdef CONFIG_KPROBES +# define _ASM_NOKPROBE(entry) \ .pushsection "_kprobe_blacklist","aw" ; \ _ASM_ALIGN ; \ _ASM_PTR (entry); \ .popsection +# else +# define _ASM_NOKPROBE(entry) +# endif #else # define _EXPAND_EXTABLE_HANDLE(x) #x
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 504d16968ed8..52e2b4952a0b 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S@@ -413,6 +413,12 @@ SECTIONS ELF_DETAILS DISCARDS + /DISCARD/ : { + *(.rela.*) *(.rela_*) + *(.rel.*) *(.rel_*) + *(.got) *(.got.*) + *(.igot.*) *(.iplt) + } }
--
2.25.1
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