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| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2019-11-08 16:51:00 -0600 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-11-13 09:36:50 -0500 |
| commit | 77ac117b3a82251b109ffc5daf7d1c5392734be3 (patch) | |
| tree | 2ece11020db1a9ad22aad0ea14c718e5a15519e5 | |
| parent | a3ad1a7e39689005cb04a4f2adb82f9d55b4724f (diff) | |
| download | linux-77ac117b3a82251b109ffc5daf7d1c5392734be3.tar.bz2 | |
ftrace/x86: Tell objtool to ignore nondeterministic ftrace stack layout
Objtool complains about the new ftrace direct trampoline code:
arch/x86/kernel/ftrace_64.o: warning: objtool: ftrace_regs_caller()+0x190: stack state mismatch: cfa1=7+16 cfa2=7+24
Typically, code has a deterministic stack layout, such that at a given
instruction address, the stack frame size is always the same.
That's not the case for the new ftrace_regs_caller() code after it
adjusts the stack for the direct case. Just plead ignorance and assume
it's always the non-direct path. Note this creates a tiny window for
ORC to get confused.
Link: http://lkml.kernel.org/r/20191108225100.ea3bhsbdf6oerj6g@treble
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
| -rw-r--r-- | arch/x86/include/asm/unwind_hints.h | 8 | ||||
| -rw-r--r-- | arch/x86/kernel/ftrace_64.S | 12 |
2 files changed, 19 insertions, 1 deletions
diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h index 0bcdb1279361..f5e2eb12cb71 100644 --- a/arch/x86/include/asm/unwind_hints.h +++ b/arch/x86/include/asm/unwind_hints.h @@ -86,6 +86,14 @@ UNWIND_HINT sp_offset=\sp_offset .endm +.macro UNWIND_HINT_SAVE + UNWIND_HINT type=UNWIND_HINT_TYPE_SAVE +.endm + +.macro UNWIND_HINT_RESTORE + UNWIND_HINT type=UNWIND_HINT_TYPE_RESTORE +.endm + #else /* !__ASSEMBLY__ */ #define UNWIND_HINT(sp_reg, sp_offset, type, end) \ diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index 6ac7ff304886..b33abdd0a2db 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -178,6 +178,8 @@ ENTRY(ftrace_regs_caller) /* Save the current flags before any operations that can change them */ pushfq + UNWIND_HINT_SAVE + /* added 8 bytes to save flags */ save_mcount_regs 8 /* save_mcount_regs fills in first two parameters */ @@ -250,8 +252,16 @@ GLOBAL(ftrace_regs_call) 1: restore_mcount_regs +2: + /* + * The stack layout is nondetermistic here, depending on which path was + * taken. This confuses objtool and ORC, rightfully so. For now, + * pretend the stack always looks like the non-direct case. + */ + UNWIND_HINT_RESTORE + /* Restore flags */ -2: popfq + popfq /* * As this jmp to ftrace_epilogue can be a short jump |