Commit 0f1441b4 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

objtool: Fix noinstr vs KCOV 



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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarDmitry Vyukov <dvyukov@google.com>
parent fdabdd0b

arch/x86/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ config X86 
	select ARCH_HAS_FILTER_PGPROT

	select ARCH_HAS_FORTIFY_SOURCE

	select ARCH_HAS_GCOV_PROFILE_ALL

	select ARCH_HAS_KCOV			if X86_64

	select ARCH_HAS_KCOV			if X86_64 && STACK_VALIDATION

	select ARCH_HAS_MEM_ENCRYPT

	select ARCH_HAS_MEMBARRIER_SYNC_CORE

	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE

tools/objtool/arch.h

+2 −0
Original line number Diff line number Diff line
@@ -84,4 +84,6 @@ unsigned long arch_jump_destination(struct instruction *insn); 


unsigned long arch_dest_rela_offset(int addend);



const char *arch_nop_insn(int len);



#endif /* _ARCH_H */

tools/objtool/arch/x86/decode.c

+18 −0
Original line number Diff line number Diff line
@@ -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];

}

tools/objtool/arch/x86/include/arch_elf.h

0 → 100644
+6 −0
Original line number Diff line number Diff line 
#ifndef _OBJTOOL_ARCH_ELF

#define _OBJTOOL_ARCH_ELF



#define R_NONE R_X86_64_NONE



#endif /* _OBJTOOL_ARCH_ELF */

tools/objtool/check.c

+19 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include "check.h"

#include "special.h"

#include "warn.h"

#include "arch_elf.h"



#include <linux/hashtable.h>

#include <linux/kernel.h>
@@ -765,6 +766,24 @@ static int add_call_destinations(struct objtool_file *file) 
		} else

			insn->call_dest = rela->sym;



		/*

		 * Many compilers cannot disable KCOV with a function attribute

		 * so they need a little help, NOP out any KCOV calls from noinstr

		 * text.

		 */

		if (insn->sec->noinstr &&

		    !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {

			if (rela) {

				rela->type = R_NONE;

				elf_write_rela(file->elf, rela);

			}



			elf_write_insn(file->elf, insn->sec,

				       insn->offset, insn->len,

				       arch_nop_insn(insn->len));

			insn->type = INSN_NOP;

		}



		/*

		 * Whatever stack impact regular CALLs have, should be undone

		 * by the RETURN of the called function.

CRA Git | Maintained and supported by SUSTech CRA and CCSE