Commit 0a37605c authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
Browse files

ftrace: x86 mcount stub 



x86 now sets up the mcount locations through the build and no longer
needs to record the ip when the function is executed. This patch changes
the initial mcount to simply return. There's no need to do any other work.
If the ftrace start up test fails, the original mcount will be what everything
will use, so having this as fast as possible is a good thing.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e4b2b886

arch/x86/kernel/entry_32.S

+0 −14
Original line number Diff line number Diff line
@@ -1153,20 +1153,6 @@ ENDPROC(xen_failsafe_callback) 
#ifdef CONFIG_DYNAMIC_FTRACE



ENTRY(mcount)

	pushl %eax

	pushl %ecx

	pushl %edx

	movl 0xc(%esp), %eax

	subl $MCOUNT_INSN_SIZE, %eax



.globl mcount_call

mcount_call:

	call ftrace_stub



	popl %edx

	popl %ecx

	popl %eax



	ret

END(mcount)

arch/x86/kernel/entry_64.S

+0 −26
Original line number Diff line number Diff line
@@ -64,32 +64,6 @@ 
#ifdef CONFIG_FTRACE

#ifdef CONFIG_DYNAMIC_FTRACE

ENTRY(mcount)



	subq $0x38, %rsp

	movq %rax, (%rsp)

	movq %rcx, 8(%rsp)

	movq %rdx, 16(%rsp)

	movq %rsi, 24(%rsp)

	movq %rdi, 32(%rsp)

	movq %r8, 40(%rsp)

	movq %r9, 48(%rsp)



	movq 0x38(%rsp), %rdi

	subq $MCOUNT_INSN_SIZE, %rdi



.globl mcount_call

mcount_call:

	call ftrace_stub



	movq 48(%rsp), %r9

	movq 40(%rsp), %r8

	movq 32(%rsp), %rdi

	movq 24(%rsp), %rsi

	movq 16(%rsp), %rdx

	movq 8(%rsp), %rcx

	movq (%rsp), %rax

	addq $0x38, %rsp



	retq

END(mcount)

arch/x86/kernel/ftrace.c

+2 −12
Original line number Diff line number Diff line
@@ -112,18 +112,8 @@ notrace int ftrace_update_ftrace_func(ftrace_func_t func) 


notrace int ftrace_mcount_set(unsigned long *data)

{

	unsigned long ip = (long)(&mcount_call);

	unsigned long *addr = data;

	unsigned char old[MCOUNT_INSN_SIZE], *new;



	/*

	 * Replace the mcount stub with a pointer to the

	 * ip recorder function.

	 */

	memcpy(old, &mcount_call, MCOUNT_INSN_SIZE);

	new = ftrace_call_replace(ip, *addr);

	*addr = ftrace_modify_code(ip, old, new);



	/* mcount is initialized as a nop */

	*data = 0;

	return 0;

}

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