The following commit has been merged into the core/static_call branch of tip:
Commit-ID: c43a43e439e00ad2a4d98716895d961ade6bbbfc
Gitweb: https://git.kernel.org/tip/c43a43e439e00ad2a4d98716895d961ade6bbbfc
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 18 Aug 2020 15:57:47 +02:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 01 Sep 2020 09:58:05 +02:00
x86/alternatives: Teach text_poke_bp() to emulate RET
Future patches will need to poke a RET instruction, provide the
infrastructure required for this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200818135804.982214828@xxxxxxxxxxxxx
---
arch/x86/include/asm/text-patching.h | 19 +++++++++++++++++++
arch/x86/kernel/alternative.c | 5 +++++
2 files changed, 24 insertions(+)
diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h
index 6593b42..b742178 100644
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -53,6 +53,9 @@ extern void text_poke_finish(void);
#define INT3_INSN_SIZE 1
#define INT3_INSN_OPCODE 0xCC
+#define RET_INSN_SIZE 1
+#define RET_INSN_OPCODE 0xC3
+
#define CALL_INSN_SIZE 5
#define CALL_INSN_OPCODE 0xE8
@@ -73,6 +76,7 @@ static __always_inline int text_opcode_size(u8 opcode)
switch(opcode) {
__CASE(INT3);
+ __CASE(RET);
__CASE(CALL);
__CASE(JMP32);
__CASE(JMP8);
@@ -141,11 +145,26 @@ void int3_emulate_push(struct pt_regs *regs, unsigned long val)
}
static __always_inline
+unsigned long int3_emulate_pop(struct pt_regs *regs)
+{
+ unsigned long val = *(unsigned long *)regs->sp;
+ regs->sp += sizeof(unsigned long);
+ return val;
+}
+
+static __always_inline
void int3_emulate_call(struct pt_regs *regs, unsigned long func)
{
int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
int3_emulate_jmp(regs, func);
}
+
+static __always_inline
+void int3_emulate_ret(struct pt_regs *regs)
+{
+ unsigned long ip = int3_emulate_pop(regs);
+ int3_emulate_jmp(regs, ip);
+}
#endif /* !CONFIG_UML_X86 */
#endif /* _ASM_X86_TEXT_PATCHING_H */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index cdaab30..4adbe65 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1103,6 +1103,10 @@ noinstr int poke_int3_handler(struct pt_regs *regs)
*/
goto out_put;
+ case RET_INSN_OPCODE:
+ int3_emulate_ret(regs);
+ break;
+
case CALL_INSN_OPCODE:
int3_emulate_call(regs, (long)ip + tp->rel32);
break;
@@ -1277,6 +1281,7 @@ static void text_poke_loc_init(struct text_poke_loc *tp, void *addr,
switch (tp->opcode) {
case INT3_INSN_OPCODE:
+ case RET_INSN_OPCODE:
break;
case CALL_INSN_OPCODE:
|