[PATCH -tip] kprobes/x86: Remove unneeded casting from immediate value

From: Masami Hiramatsu (Google)
Date: Thu Feb 09 2023 - 10:37:43 EST


From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

Remove unneeded casting from immediate value assignments for relative
jump offset. Since the immediate values in the 'insn' data structure are
assigned from immediate bytes as a signed value to insn.immediate.value
by insn_field_set(). Thus, if we need to access that value as a signed
value (in this kprobe's case), we don't need to cast it.
This is a kind of clean up (should not change behavior) follows Nadav's
bugfix.

Link: https://lore.kernel.org/all/20230208071708.4048-1-namit@xxxxxxxxxx/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
---
arch/x86/kernel/kprobes/core.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 695873c0f50b..2440e736d0e4 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -607,19 +607,19 @@ static int prepare_emulation(struct kprobe *p, struct insn *insn)
case 0xe8: /* near call relative */
p->ainsn.emulate_op = kprobe_emulate_call;
if (insn->immediate.nbytes == 2)
- p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
+ p->ainsn.rel32 = insn->immediate.value;
else
- p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
+ p->ainsn.rel32 = insn->immediate.value;
break;
case 0xeb: /* short jump relative */
case 0xe9: /* near jump relative */
p->ainsn.emulate_op = kprobe_emulate_jmp;
if (insn->immediate.nbytes == 1)
- p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
+ p->ainsn.rel32 = insn->immediate.value;
else if (insn->immediate.nbytes == 2)
- p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
+ p->ainsn.rel32 = insn->immediate.value;
else
- p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
+ p->ainsn.rel32 = insn->immediate.value;
break;
case 0x70 ... 0x7f:
/* 1 byte conditional jump */
@@ -634,9 +634,9 @@ static int prepare_emulation(struct kprobe *p, struct insn *insn)
p->ainsn.emulate_op = kprobe_emulate_jcc;
p->ainsn.jcc.type = opcode & 0xf;
if (insn->immediate.nbytes == 2)
- p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
+ p->ainsn.rel32 = insn->immediate.value;
else
- p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
+ p->ainsn.rel32 = insn->immediate.value;
} else if (opcode == 0x01 &&
X86_MODRM_REG(insn->modrm.bytes[0]) == 0 &&
X86_MODRM_MOD(insn->modrm.bytes[0]) == 3) {
@@ -651,7 +651,7 @@ static int prepare_emulation(struct kprobe *p, struct insn *insn)
p->ainsn.emulate_op = kprobe_emulate_loop;
p->ainsn.loop.type = opcode & 0x3;
p->ainsn.loop.asize = insn->addr_bytes * 8;
- p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
+ p->ainsn.rel32 = insn->immediate.value;
break;
case 0xff:
/*