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create-diff-object: check arg2 and arg3 on all arches for line detection

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For x86, we already check arg2 and arg3 for `__LINE__` immediate load
detection.  For parity, do the same thing for the other two arches.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
This commit is contained in:
Josh Poimboeuf 2022-04-05 12:11:58 -07:00
parent e6b1664d0e
commit 79fd60b28d
1 changed files with 23 additions and 8 deletions
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31
kpatch-build/create-diff-object.c
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@ -617,8 +617,13 @@ static unsigned int insn_length(struct kpatch_elf *kelf, void *addr)
* ok, we'll find them later when someone notices a function falsely being
* reported as changed ;-)
*
* (Alternatively we may want to consider just checking all registers which can
* be used as function arguments.)
* Right now we're only checking immediate loads to the registers corresponding
* to function arguments 2 and 3 for each respective arch's calling convention.
* (Argument 1 is typically the printf format string). Eventually we might
* want to consider just checking *all* registers which could conceivably be
* used as function arguments. But in practice, arg2 and arg3 seem to be the
* main ones, so for now, take a more conservative approach at the risk of
* failing to detect some of the more obscure __LINE__-only changed functions.
*/
static bool insn_is_load_immediate(struct kpatch_elf *kelf, void *addr)
{
@ -627,12 +632,12 @@ static bool insn_is_load_immediate(struct kpatch_elf *kelf, void *addr)
switch(kelf->arch) {
case X86_64:
/* mov $imm, %edx */
if (insn[0] == 0xba)
/* arg2: mov $imm, %esi */
if (insn[0] == 0xbe)
return true;
/* mov $imm, %esi */
if (insn[0] == 0xbe)
/* arg3: mov $imm, %edx */
if (insn[0] == 0xba)
return true;
break;
@ -641,19 +646,29 @@ static bool insn_is_load_immediate(struct kpatch_elf *kelf, void *addr)
/*
* ppc64le insns are LE-encoded:
*
* 0a 00 80 38 li r4,10
* 47 14 a0 38 li r5,5191
*/
/* li r5, imm */
/* arg2: li r4, imm */
if (insn[3] == 0x38 && insn[2] == 0x80)
return true;
/* arg3: li r5, imm */
if (insn[3] == 0x38 && insn[2] == 0xa0)
return true;
break;
case S390:
/* lghi %r4, imm */
/* arg2: lghi %r3, imm */
if (insn[0] == 0xa7 && insn[1] == 0x39)
return true;
/* arg3: lghi %r4, imm */
if (insn[0] == 0xa7 && insn[1] == 0x49)
return true;
break;
default: