@@ -45,6 +45,39 @@ END(function_hook)
#endif
.endm
+#ifdef CONFIG_FRAME_POINTER
+/*
+ * Stack traces will stop at the ftrace trampoline if the frame pointer
+ * is not set up properly. If fentry is used, we need to save a frame
+ * pointer for the parent as well as the function traced, because the
+ * fentry is called before the stack frame is set up, where as mcount
+ * is called afterward.
+ */
+.macro create_frame parent rip
+#ifdef CC_USING_FENTRY
+ pushq \parent
+ pushq %rbp
+ movq %rsp, %rbp
+#endif
+ pushq \rip
+ pushq %rbp
+ movq %rsp, %rbp
+.endm
+
+.macro restore_frame
+#ifdef CC_USING_FENTRY
+ addq $16, %rsp
+#endif
+ popq %rbp
+ addq $8, %rsp
+.endm
+#else
+.macro create_frame parent rip
+.endm
+.macro restore_frame
+.endm
+#endif /* CONFIG_FRAME_POINTER */
+
ENTRY(ftrace_caller)
/* Check if tracing was disabled (quick check) */
cmpl $0, function_trace_stop
@@ -54,9 +87,13 @@ ENTRY(ftrace_caller)
/* regs go into 4th parameter (but make it NULL) */
movq $0, %rcx
+ create_frame %rsi, %rdi
+
GLOBAL(ftrace_call)
call ftrace_stub
+ restore_frame
+
MCOUNT_RESTORE_FRAME
ftrace_return:
@@ -104,9 +141,13 @@ ENTRY(ftrace_regs_caller)
/* regs go into 4th parameter */
leaq (%rsp), %rcx
+ create_frame %rsi, %rdi
+
GLOBAL(ftrace_regs_call)
call ftrace_stub
+ restore_frame
+
/* Copy flags back to SS, to restore them */
movq EFLAGS(%rsp), %rax
movq %rax, SS(%rsp)
This is a note to let you know that I have just added a patch titled ftrace/x86: Add frames pointers to trampoline as necessary to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue This patch is scheduled to be released in version 3.16.7-ckt4. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From f79290b67a009d7d621df01db0a0e9ce0f4b3ee2 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org> Date: Tue, 18 Nov 2014 19:13:25 -0500 Subject: ftrace/x86: Add frames pointers to trampoline as necessary commit 9960efeb80f73bd073483dab0855ee0ddc27085c upstream. When CONFIG_FRAME_POINTERS are enabled, it is required that the ftrace_caller and ftrace_regs_caller trampolines set up frame pointers otherwise a stack trace from a function call wont print the functions that called the trampoline. This is due to a check in __save_stack_address(): #ifdef CONFIG_FRAME_POINTER if (!reliable) return; #endif The "reliable" variable is only set if the function address is equal to contents of the address before the address the frame pointer register points to. If the frame pointer is not set up for the ftrace caller then this will fail the reliable test. It will miss the function that called the trampoline. Worse yet, if fentry is used (gcc 4.6 and beyond), it will also miss the parent, as the fentry is called before the stack frame is set up. That means the bp frame pointer points to the stack of just before the parent function was called. Link: http://lkml.kernel.org/r/20141119034829.355440340@goodmis.org Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- arch/x86/kernel/mcount_64.S | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) -- 2.1.4