diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2022-09-15 13:11:37 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-10-17 16:41:19 +0200 |
| commit | ee3e2469b3463d28ca4cde20e0283319ac6a562d (patch) | |
| tree | 958265de2b1865d821630bc175df913052ac7f25 /arch/x86/kernel/ftrace.c | |
| parent | 36b64f101219dd9e6e4f0ea880b64e8a90da547b (diff) | |
x86/ftrace: Make it call depth tracking aware
Since ftrace has trampolines, don't use thunks for the __fentry__ site
but instead require that every function called from there includes
accounting. This very much includes all the direct-call functions.
Additionally, ftrace uses ROP tricks in two places:
- return_to_handler(), and
- ftrace_regs_caller() when pt_regs->orig_ax is set by a direct-call.
return_to_handler() already uses a retpoline to replace an
indirect-jump to defeat IBT, since this is a jump-type retpoline, make
sure there is no accounting done and ALTERNATIVE the RET into a ret.
ftrace_regs_caller() does much the same and gets the same treatment.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111148.927545073@infradead.org
Diffstat (limited to 'arch/x86/kernel/ftrace.c')
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 4ac6692d5ef8..cf15ef5aecff 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -69,6 +69,10 @@ static const char *ftrace_nop_replace(void) 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); } @@ -317,7 +321,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) unsigned long size; unsigned long *ptr; void *trampoline; - void *ip; + void *ip, *dest; /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */ unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 }; unsigned const char retq[] = { RET_INSN_OPCODE, INT3_INSN_OPCODE }; @@ -404,10 +408,14 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) /* put in the call to the function */ mutex_lock(&text_mutex); call_offset -= start_offset; + /* + * No need to translate into a callthunk. The trampoline does + * the depth accounting before the call already. + */ + dest = ftrace_ops_get_func(ops); memcpy(trampoline + call_offset, - text_gen_insn(CALL_INSN_OPCODE, - trampoline + call_offset, - ftrace_ops_get_func(ops)), CALL_INSN_SIZE); + text_gen_insn(CALL_INSN_OPCODE, trampoline + call_offset, dest), + CALL_INSN_SIZE); mutex_unlock(&text_mutex); /* ALLOC_TRAMP flags lets us know we created it */ |