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objtool: Fix noinstr vs KCOV

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Since many compilers cannot disable KCOV with a function attribute,
help it to NOP out any __sanitizer_cov_*() calls injected in noinstr
code.

This turns:

12:   e8 00 00 00 00          callq  17 <lockdep_hardirqs_on+0x17>
		13: R_X86_64_PLT32      __sanitizer_cov_trace_pc-0x4

into:

12:   0f 1f 44 00 00          nopl   0x0(%rax,%rax,1)
		13: R_X86_64_NONE      __sanitizer_cov_trace_pc-0x4

Just like recordmcount does.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
This commit is contained in:
Peter Zijlstra
2020-06-12 16:05:26 +02:00
parent fdabdd0b05
commit 0f1441b44e
5 changed files with 46 additions and 1 deletions
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18
tools/objtool/arch/x86/decode.c
View File

@@ -565,3 +565,21 @@ void arch_initial_func_cfi_state(struct cfi_init_state *state)
state->regs[16].base = CFI_CFA;
state->regs[16].offset = -8;
}
const char *arch_nop_insn(int len)
{
static const char nops[5][5] = {
/* 1 */ { 0x90 },
/* 2 */ { 0x66, 0x90 },
/* 3 */ { 0x0f, 0x1f, 0x00 },
/* 4 */ { 0x0f, 0x1f, 0x40, 0x00 },
/* 5 */ { 0x0f, 0x1f, 0x44, 0x00, 0x00 },
};
if (len < 1 || len > 5) {
WARN("invalid NOP size: %d\n", len);
return NULL;
}
return nops[len-1];
}

6
tools/objtool/arch/x86/include/arch_elf.h Normal file
View File

@@ -0,0 +1,6 @@
#ifndef _OBJTOOL_ARCH_ELF
#define _OBJTOOL_ARCH_ELF
#define R_NONE R_X86_64_NONE
#endif /* _OBJTOOL_ARCH_ELF */