x86/ftrace: Make non direct case the default in ftrace_regs_caller (0b4f8ddc) · Commits · 戴 / test

If a direct function is hooked along with one of the ftrace registered functions, then the ftrace_regs_caller is attached to the function that shares the direct hook as well as the ftrace hook. The ftrace_regs_caller will call ftrace_ops_list_func() that iterates through all the registered ftrace callbacks, and if there's a direct callback attached to that function, the direct ftrace_ops callback is called to notify that ftrace_regs_caller to return to the direct caller instead of going back to the function that called it. But this is a very uncommon case. Currently, the code has it as the default case. Modify ftrace_regs_caller to make the default case (the non jump) to just return normally, and have the jump to the handling of the direct caller. Link: http://lkml.kernel.org/r/20200422162750.350373278@goodmis.org Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by:

Steven Rostedt (VMware) <rostedt@goodmis.org>

arch/x86/kernel/ftrace_64.S

+15 −16

Original line number	Diff line number	Diff line
		@@ -241,22 +241,9 @@ SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL)
		*/
		movq ORIG_RAX(%rsp), %rax
		testq %rax, %rax
		jz 1f
		jnz 1f

		/* Swap the flags with orig_rax */
		movq MCOUNT_REG_SIZE(%rsp), %rdi
		movq %rdi, MCOUNT_REG_SIZE-8(%rsp)
		movq %rax, MCOUNT_REG_SIZE(%rsp)

		restore_mcount_regs 8
		/* Restore flags */
		popfq

		SYM_INNER_LABEL(ftrace_regs_caller_ret, SYM_L_GLOBAL);
		UNWIND_HINT_RET_OFFSET
		jmp ftrace_epilogue

		1: restore_mcount_regs
		restore_mcount_regs
		/* Restore flags */
		popfq

		@@ -266,7 +253,19 @@ SYM_INNER_LABEL(ftrace_regs_caller_ret, SYM_L_GLOBAL);
		* The trampoline will add the code to jump
		* to the return.
		*/
		SYM_INNER_LABEL(ftrace_regs_caller_ret, SYM_L_GLOBAL)
		jmp ftrace_epilogue

		/* Swap the flags with orig_rax */
		1: movq MCOUNT_REG_SIZE(%rsp), %rdi
		movq %rdi, MCOUNT_REG_SIZE-8(%rsp)
		movq %rax, MCOUNT_REG_SIZE(%rsp)

		restore_mcount_regs 8
		/* Restore flags */
		popfq
		SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
		UNWIND_HINT_RET_OFFSET
		jmp ftrace_epilogue

		SYM_FUNC_END(ftrace_regs_caller)

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