[RFC][PATCH v5 41/51] objtool: mcount: Convert nop writes to elf_write_insn()

From: Matt Helsley
Date: Thu Jun 18 2020 - 16:40:41 EST


objtool's elf_write_insn() does extra checking when writing to
an instruction so use that rather than a plain memcpy().

Signed-off-by: Matt Helsley <mhelsley@xxxxxxxxxx>
---
tools/objtool/mcount.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/tools/objtool/mcount.c b/tools/objtool/mcount.c
index 629eb7222ef3..029e6e72c972 100644
--- a/tools/objtool/mcount.c
+++ b/tools/objtool/mcount.c
@@ -66,9 +66,7 @@ static int make_nop_x86(struct section *txts, size_t const offset)
if (memcmp(op, ip_relative_call_x86, 5) != 0)
return -1;

- /* convert to nop */
- memcpy(op, ideal_nop, 5);
- return 0;
+ return elf_write_insn(lf, txts, offset, 5, ideal_nop);
}

static const char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
@@ -117,7 +115,8 @@ static int make_nop_arm(struct section *txts, size_t const offset)

/* Convert to nop */
do {
- memcpy(map + off, ideal_nop, nop_size);
+ if (elf_write_insn(lf, txts, off, nop_size, ideal_nop))
+ return -1;
off += nop_size;
} while (--cnt > 0);

@@ -136,8 +135,7 @@ static int make_nop_arm64(struct section *txts, size_t const offset)
return -1;

/* Convert to nop */
- memcpy(map + offset, ideal_nop, 4);
- return 0;
+ return elf_write_insn(lf, txts, offset, 4, ideal_nop);
}

/* Names of the sections that could contain calls to mcount. */
--
2.20.1