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x86/ftrace: Implement DYNAMIC_FTRACE_WITH_JMP

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Implement the DYNAMIC_FTRACE_WITH_JMP for x86_64. In ftrace_call_replace,
we will use JMP32_INSN_OPCODE instead of CALL_INSN_OPCODE if the address
should use "jmp".

Meanwhile, adjust the direct call in the ftrace_regs_caller. The RSB is
balanced in the "jmp" mode. Take the function "foo" for example:

 original_caller:
 call foo -> foo:
         call fentry -> fentry:
                 [do ftrace callbacks ]
                 move tramp_addr to stack
                 RET -> tramp_addr
                         tramp_addr:
                         [..]
                         call foo_body -> foo_body:
                                 [..]
                                 RET -> back to tramp_addr
                         [..]
                         RET -> back to original_caller

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20251118123639.688444-3-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Menglong Dong
2025-11-18 20:36:30 +08:00
committed by Alexei Starovoitov
parent 25e4e3565d
commit 0c3772a8db
3 changed files with 18 additions and 2 deletions
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1
arch/x86/Kconfig
View File

@@ -230,6 +230,7 @@ config X86
select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
select HAVE_FTRACE_REGS_HAVING_PT_REGS if X86_64
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_DYNAMIC_FTRACE_WITH_JMP if X86_64
select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
select HAVE_EBPF_JIT

7
arch/x86/kernel/ftrace.c
View File

@@ -74,7 +74,12 @@ static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
* No need to translate into a callthunk. The trampoline does
* the depth accounting itself.
*/
return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
if (ftrace_is_jmp(addr)) {
addr = ftrace_jmp_get(addr);
return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr);
} else {
return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
}
}
static int ftrace_verify_code(unsigned long ip, const char *old_code)

12
arch/x86/kernel/ftrace_64.S
View File

@@ -285,8 +285,18 @@ SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
ANNOTATE_NOENDBR
RET
1:
testb $1, %al
jz 2f
andq $0xfffffffffffffffe, %rax
movq %rax, MCOUNT_REG_SIZE+8(%rsp)
restore_mcount_regs
/* Restore flags */
popfq
RET
/* Swap the flags with orig_rax */
1: movq MCOUNT_REG_SIZE(%rsp), %rdi
2: movq MCOUNT_REG_SIZE(%rsp), %rdi
movq %rdi, MCOUNT_REG_SIZE-8(%rsp)
movq %rax, MCOUNT_REG_SIZE(%rsp)