Commit 0687c36e authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
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ftrace/x86: Have save_mcount_regs macro also save stack frames if needed 

The save_mcount_regs macro saves and restores the required mcount regs that
need to be saved before calling C code. It is done for all the function hook
utilities (static tracing, dynamic tracing, regs, function graph).

When frame pointers are enabled, the ftrace trampolines need to set up
frames and pointers such that a back trace (dump stack) can continue passed
them. Currently, a separate macro is used (create_frame) to do this, but
it's only done for the ftrace_caller and ftrace_reg_caller functions. It
is not done for the static tracer or function graph tracing.

Instead of having a separate macro doing the recording of the frames,
have the save_mcount_regs perform this task. This also has all tracers
saving the frame pointers when needed.

Link: http://lkml.kernel.org/r/CA+55aFwF+qCGSKdGaEgW4p6N65GZ5_XTV=1NbtWDvxnd5yYLiw@mail.gmail.com
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1411262304010.3961@nanos



Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 85f6f029

arch/x86/kernel/mcount_64.S

+67 −51
Original line number Diff line number Diff line
@@ -21,8 +21,22 @@ 
# define function_hook	mcount

#endif



/* All cases save the original rbp (8 bytes) */

#ifdef CONFIG_FRAME_POINTER

# ifdef CC_USING_FENTRY

/* Save parent and function stack frames (rip and rbp) */

#  define MCOUNT_FRAME_SIZE	(8+16*2)

# else

/* Save just function stack frame (rip and rbp) */

#  define MCOUNT_FRAME_SIZE	(8+16)

# endif

#else

/* No need to save a stack frame */

# define MCOUNT_FRAME_SIZE	8

#endif /* CONFIG_FRAME_POINTER */



/* Size of stack used to save mcount regs in save_mcount_regs */

#define MCOUNT_REG_SIZE		(SS+8)

#define MCOUNT_REG_SIZE		(SS+8 + MCOUNT_FRAME_SIZE)



/*

 * gcc -pg option adds a call to 'mcount' in most functions.
@@ -42,10 +56,37 @@ 


/* @added: the amount of stack added before calling this */

.macro save_mcount_regs added=0



	/* Always save the original rbp */

	pushq %rbp



#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.

	 */

#ifdef CC_USING_FENTRY

	/* Save the parent pointer (skip orig rbp and our return address) */

	pushq \added+8*2(%rsp)

	pushq %rbp

	movq %rsp, %rbp

	/* Save the return address (now skip orig rbp, rbp and parent) */

	pushq \added+8*3(%rsp)

#else

	/* Can't assume that rip is before this (unless added was zero) */

	pushq \added+8(%rsp)

#endif

	pushq %rbp

	movq %rsp, %rbp

#endif /* CONFIG_FRAME_POINTER */



	/*

	 * We add enough stack to save all regs.

	 */

	subq $MCOUNT_REG_SIZE, %rsp

	subq $(MCOUNT_REG_SIZE - MCOUNT_FRAME_SIZE), %rsp

	movq %rax, RAX(%rsp)

	movq %rcx, RCX(%rsp)

	movq %rdx, RDX(%rsp)
@@ -53,6 +94,13 @@ 
	movq %rdi, RDI(%rsp)

	movq %r8, R8(%rsp)

	movq %r9, R9(%rsp)

	/*

	 * Save the original RBP. Even though the mcount ABI does not

	 * require this, it helps out callers.

	 */

	movq MCOUNT_REG_SIZE-8(%rsp), %rdx

	movq %rdx, RBP(%rsp)



	 /* Move RIP to its proper location */

	movq MCOUNT_REG_SIZE+\added(%rsp), %rdi

	movq %rdi, RIP(%rsp)
@@ -66,7 +114,12 @@ 
	movq RDX(%rsp), %rdx

	movq RCX(%rsp), %rcx

	movq RAX(%rsp), %rax



	/* ftrace_regs_caller can modify %rbp */

	movq RBP(%rsp), %rbp



	addq $MCOUNT_REG_SIZE, %rsp



	.endm



/* skip is set if stack has been adjusted */
@@ -84,7 +137,10 @@ GLOBAL(\trace_label) 
#ifdef CC_USING_FENTRY

	movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi

#else

	movq 8+\added(%rbp), %rsi

	/* Need to grab the original %rbp */

	movq RBP(%rsp), %rsi

	/* Now parent address is 8 above original %rbp */

	movq 8(%rsi), %rsi

#endif

.endm
@@ -94,51 +150,14 @@ ENTRY(function_hook) 
	retq

END(function_hook)



#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)

	ftrace_caller_setup ftrace_caller_op_ptr

	/* regs go into 4th parameter (but make it NULL) */

	movq $0, %rcx



	create_frame %rsi, %rdi



GLOBAL(ftrace_call)

	call ftrace_stub



	restore_frame



	restore_mcount_regs



	/*
@@ -172,7 +191,6 @@ ENTRY(ftrace_regs_caller) 
	movq %r12, R12(%rsp)

	movq %r11, R11(%rsp)

	movq %r10, R10(%rsp)

	movq %rbp, RBP(%rsp)

	movq %rbx, RBX(%rsp)

	/* Copy saved flags */

	movq MCOUNT_REG_SIZE(%rsp), %rcx
@@ -189,13 +207,9 @@ 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, MCOUNT_REG_SIZE(%rsp)
@@ -210,7 +224,6 @@ GLOBAL(ftrace_regs_call) 
	movq R13(%rsp), %r13

	movq R12(%rsp), %r12

	movq R10(%rsp), %r10

	movq RBP(%rsp), %rbp

	movq RBX(%rsp), %rbx



	restore_mcount_regs
@@ -269,8 +282,11 @@ ENTRY(ftrace_graph_caller) 
	leaq MCOUNT_REG_SIZE+8(%rsp), %rdi

	movq $0, %rdx	/* No framepointers needed */

#else

	leaq 8(%rbp), %rdi

	movq (%rbp), %rdx

	/* Need to grab the original %rbp */

	movq RBP(%rsp), %rdx

	/* Now parent address is 8 above original %rbp */

	leaq 8(%rdx), %rdi

	movq (%rdx), %rdx

#endif

	movq RIP(%rsp), %rsi

	subq $MCOUNT_INSN_SIZE, %rsi

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