ftrace/x86: Tell objtool to ignore nondeterministic ftrace stack layout (77ac117b) · Commits · 戴 / test

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>

arch/x86/include/asm/unwind_hints.h

+8 −0

Original line number	Diff line number	Diff line
		@@ -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) \

arch/x86/kernel/ftrace_64.S

+11 −1

Original line number	Diff line number	Diff line
		@@ -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

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