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author | Steven Rostedt <srostedt@redhat.com> | 2008-05-12 21:20:43 +0200 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2008-05-23 20:33:47 +0200 |
commit | d61f82d06672f57fca410da6f7fffd15867db622 (patch) | |
tree | 62ef5573934eaa638c0d39a45d789691aecbd7d3 /arch/x86/kernel/ftrace.c | |
parent | 3c1720f00bb619302ba19d55986ab565e74d06db (diff) | |
download | linux-d61f82d06672f57fca410da6f7fffd15867db622.tar.gz linux-d61f82d06672f57fca410da6f7fffd15867db622.tar.bz2 linux-d61f82d06672f57fca410da6f7fffd15867db622.zip |
ftrace: use dynamic patching for updating mcount calls
This patch replaces the indirect call to the mcount function
pointer with a direct call that will be patched by the
dynamic ftrace routines.
On boot up, the mcount function calls the ftace_stub function.
When the dynamic ftrace code is initialized, the ftrace_stub
is replaced with a call to the ftrace_record_ip, which records
the instruction pointers of the locations that call it.
Later, the ftraced daemon will call kstop_machine and patch all
the locations to nops.
When a ftrace is enabled, the original calls to mcount will now
be set top call ftrace_caller, which will do a direct call
to the registered ftrace function. This direct call is also patched
when the function that should be called is updated.
All patching is performed by a kstop_machine routine to prevent any
type of race conditions that is associated with modifying code
on the fly.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/kernel/ftrace.c')
-rw-r--r-- | arch/x86/kernel/ftrace.c | 41 |
1 files changed, 40 insertions, 1 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index b69795efa226..9f44623e0072 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -109,10 +109,49 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code, return faulted; } -int __init ftrace_dyn_arch_init(void) +notrace int ftrace_update_ftrace_func(ftrace_func_t func) +{ + unsigned long ip = (unsigned long)(&ftrace_call); + unsigned char old[5], *new; + int ret; + + ip += CALL_BACK; + + memcpy(old, &ftrace_call, 5); + new = ftrace_call_replace(ip, (unsigned long)func); + ret = ftrace_modify_code(ip, old, new); + + return ret; +} + +notrace int ftrace_mcount_set(unsigned long *data) +{ + unsigned long ip = (long)(&mcount_call); + unsigned long *addr = data; + unsigned char old[5], *new; + + /* ip is at the location, but modify code will subtact this */ + ip += CALL_BACK; + + /* + * Replace the mcount stub with a pointer to the + * ip recorder function. + */ + memcpy(old, &mcount_call, 5); + new = ftrace_call_replace(ip, *addr); + *addr = ftrace_modify_code(ip, old, new); + + return 0; +} + +int __init ftrace_dyn_arch_init(void *data) { const unsigned char *const *noptable = find_nop_table(); + /* This is running in kstop_machine */ + + ftrace_mcount_set(data); + ftrace_nop = (unsigned long *)noptable[CALL_BACK]; return 0; |