From 77ac117b3a82251b109ffc5daf7d1c5392734be3 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 8 Nov 2019 16:51:00 -0600 Subject: [PATCH] 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 Signed-off-by: Josh Poimboeuf Signed-off-by: Steven Rostedt (VMware) --- arch/x86/include/asm/unwind_hints.h | 8 ++++++++ arch/x86/kernel/ftrace_64.S | 12 +++++++++++- 2 files changed, 19 insertions(+), 1 deletion(-) 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 -- 2.11.0