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ftrace: x86 mcount stub

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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: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt 2008-08-14 15:45:12 -04:00 committed by Ingo Molnar
parent e4b2b88661
commit 0a37605c22
3 changed files with 2 additions and 52 deletions
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14
arch/x86/kernel/entry_32.S
View File

@ -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)

26
arch/x86/kernel/entry_64.S
View File

@ -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)

14
arch/x86/kernel/ftrace.c
View File

@ -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;
}