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>
This commit is contained in:
Steven Rostedt
Thomas Gleixner
Родитель
3c1720f00b
Коммит
d61f82d066
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@ -1110,10 +1110,50 @@ ENDPROC(xen_failsafe_callback)
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#endif /* CONFIG_XEN */
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#ifdef CONFIG_FTRACE
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#ifdef CONFIG_DYNAMIC_FTRACE
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ENTRY(mcount)
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pushl %eax
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pushl %ecx
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pushl %edx
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movl 0xc(%esp), %eax
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.globl mcount_call
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mcount_call:
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call ftrace_stub
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popl %edx
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popl %ecx
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popl %eax
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ret
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END(mcount)
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ENTRY(ftrace_caller)
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pushl %eax
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pushl %ecx
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pushl %edx
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movl 0xc(%esp), %eax
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movl 0x4(%ebp), %edx
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.globl ftrace_call
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ftrace_call:
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call ftrace_stub
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popl %edx
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popl %ecx
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popl %eax
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.globl ftrace_stub
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ftrace_stub:
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ret
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END(ftrace_caller)
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#else /* ! CONFIG_DYNAMIC_FTRACE */
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ENTRY(mcount)
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cmpl $ftrace_stub, ftrace_trace_function
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jnz trace
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.globl ftrace_stub
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ftrace_stub:
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ret
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@ -1126,7 +1166,7 @@ trace:
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movl 0xc(%esp), %eax
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movl 0x4(%ebp), %edx
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call *ftrace_trace_function
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call *ftrace_trace_function
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popl %edx
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popl %ecx
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@ -1134,7 +1174,8 @@ trace:
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jmp ftrace_stub
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END(mcount)
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#endif
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#endif /* CONFIG_FTRACE */
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.section .rodata,"a"
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#include "syscall_table_32.S"
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@ -55,6 +55,70 @@
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.code64
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#ifdef CONFIG_FTRACE
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#ifdef CONFIG_DYNAMIC_FTRACE
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ENTRY(mcount)
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subq $0x38, %rsp
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movq %rax, (%rsp)
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movq %rcx, 8(%rsp)
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movq %rdx, 16(%rsp)
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movq %rsi, 24(%rsp)
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movq %rdi, 32(%rsp)
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movq %r8, 40(%rsp)
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movq %r9, 48(%rsp)
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movq 0x38(%rsp), %rdi
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.globl mcount_call
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mcount_call:
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call ftrace_stub
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movq 48(%rsp), %r9
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movq 40(%rsp), %r8
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movq 32(%rsp), %rdi
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movq 24(%rsp), %rsi
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movq 16(%rsp), %rdx
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movq 8(%rsp), %rcx
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movq (%rsp), %rax
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addq $0x38, %rsp
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retq
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END(mcount)
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ENTRY(ftrace_caller)
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/* taken from glibc */
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subq $0x38, %rsp
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movq %rax, (%rsp)
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movq %rcx, 8(%rsp)
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movq %rdx, 16(%rsp)
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movq %rsi, 24(%rsp)
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movq %rdi, 32(%rsp)
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movq %r8, 40(%rsp)
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movq %r9, 48(%rsp)
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movq 0x38(%rsp), %rdi
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movq 8(%rbp), %rsi
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.globl ftrace_call
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ftrace_call:
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call ftrace_stub
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movq 48(%rsp), %r9
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movq 40(%rsp), %r8
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movq 32(%rsp), %rdi
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movq 24(%rsp), %rsi
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movq 16(%rsp), %rdx
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movq 8(%rsp), %rcx
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movq (%rsp), %rax
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addq $0x38, %rsp
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.globl ftrace_stub
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ftrace_stub:
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retq
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END(ftrace_caller)
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#else /* ! CONFIG_DYNAMIC_FTRACE */
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ENTRY(mcount)
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cmpq $ftrace_stub, ftrace_trace_function
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jnz trace
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@ -89,7 +153,8 @@ trace:
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jmp ftrace_stub
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END(mcount)
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#endif
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#endif /* CONFIG_FTRACE */
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#ifndef CONFIG_PREEMPT
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#define retint_kernel retint_restore_args
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@ -109,10 +109,49 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
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return faulted;
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}
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int __init ftrace_dyn_arch_init(void)
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notrace int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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unsigned long ip = (unsigned long)(&ftrace_call);
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unsigned char old[5], *new;
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int ret;
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ip += CALL_BACK;
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memcpy(old, &ftrace_call, 5);
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new = ftrace_call_replace(ip, (unsigned long)func);
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ret = ftrace_modify_code(ip, old, new);
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return ret;
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}
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notrace int ftrace_mcount_set(unsigned long *data)
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{
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unsigned long ip = (long)(&mcount_call);
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unsigned long *addr = data;
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unsigned char old[5], *new;
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/* ip is at the location, but modify code will subtact this */
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ip += CALL_BACK;
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/*
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* Replace the mcount stub with a pointer to the
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* ip recorder function.
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*/
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memcpy(old, &mcount_call, 5);
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new = ftrace_call_replace(ip, *addr);
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*addr = ftrace_modify_code(ip, old, new);
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return 0;
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}
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int __init ftrace_dyn_arch_init(void *data)
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{
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const unsigned char *const *noptable = find_nop_table();
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/* This is running in kstop_machine */
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ftrace_mcount_set(data);
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ftrace_nop = (unsigned long *)noptable[CALL_BACK];
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return 0;
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@ -56,9 +56,14 @@ struct dyn_ftrace {
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extern int ftrace_ip_converted(unsigned long ip);
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extern unsigned char *ftrace_nop_replace(void);
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extern unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr);
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extern int ftrace_dyn_arch_init(void);
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extern int ftrace_dyn_arch_init(void *data);
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extern int ftrace_mcount_set(unsigned long *data);
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extern int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
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unsigned char *new_code);
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extern int ftrace_update_ftrace_func(ftrace_func_t func);
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extern void ftrace_caller(void);
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extern void ftrace_call(void);
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extern void mcount_call(void);
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#endif
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#ifdef CONFIG_FRAME_POINTER
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@ -26,14 +26,8 @@
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#include "trace.h"
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#ifdef CONFIG_DYNAMIC_FTRACE
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# define FTRACE_ENABLED_INIT 1
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#else
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# define FTRACE_ENABLED_INIT 0
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#endif
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int ftrace_enabled = FTRACE_ENABLED_INIT;
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static int last_ftrace_enabled = FTRACE_ENABLED_INIT;
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int ftrace_enabled;
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static int last_ftrace_enabled;
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static DEFINE_SPINLOCK(ftrace_lock);
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static DEFINE_MUTEX(ftrace_sysctl_lock);
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@ -149,6 +143,14 @@ static int notrace __unregister_ftrace_function(struct ftrace_ops *ops)
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#ifdef CONFIG_DYNAMIC_FTRACE
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enum {
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FTRACE_ENABLE_CALLS = (1 << 0),
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FTRACE_DISABLE_CALLS = (1 << 1),
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FTRACE_UPDATE_TRACE_FUNC = (1 << 2),
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FTRACE_ENABLE_MCOUNT = (1 << 3),
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FTRACE_DISABLE_MCOUNT = (1 << 4),
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};
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static struct hlist_head ftrace_hash[FTRACE_HASHSIZE];
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static DEFINE_PER_CPU(int, ftrace_shutdown_disable_cpu);
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@ -199,12 +201,8 @@ ftrace_add_hash(struct dyn_ftrace *node, unsigned long key)
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hlist_add_head(&node->node, &ftrace_hash[key]);
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}
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static notrace struct dyn_ftrace *ftrace_alloc_shutdown_node(unsigned long ip)
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static notrace struct dyn_ftrace *ftrace_alloc_dyn_node(unsigned long ip)
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{
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/* If this was already converted, skip it */
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if (ftrace_ip_converted(ip))
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return NULL;
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if (ftrace_pages->index == ENTRIES_PER_PAGE) {
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if (!ftrace_pages->next)
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return NULL;
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@ -215,7 +213,7 @@ static notrace struct dyn_ftrace *ftrace_alloc_shutdown_node(unsigned long ip)
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}
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static void notrace
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ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
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ftrace_record_ip(unsigned long ip)
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{
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struct dyn_ftrace *node;
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unsigned long flags;
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@ -223,6 +221,9 @@ ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
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int resched;
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int atomic;
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if (!ftrace_enabled)
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return;
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resched = need_resched();
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preempt_disable_notrace();
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@ -251,11 +252,12 @@ ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
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/*
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* There's a slight race that the ftraced will update the
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* hash and reset here. The arch alloc is responsible
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* for seeing if the IP has already changed, and if
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* it has, the alloc will fail.
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* hash and reset here. If it is already converted, skip it.
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*/
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node = ftrace_alloc_shutdown_node(ip);
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if (ftrace_ip_converted(ip))
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goto out_unlock;
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node = ftrace_alloc_dyn_node(ip);
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if (!node)
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goto out_unlock;
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@ -277,11 +279,7 @@ ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
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preempt_enable_notrace();
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}
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static struct ftrace_ops ftrace_shutdown_ops __read_mostly =
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{
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.func = ftrace_record_ip,
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};
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#define FTRACE_ADDR ((long)(&ftrace_caller))
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#define MCOUNT_ADDR ((long)(&mcount))
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static void notrace ftrace_replace_code(int saved)
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@ -309,9 +307,9 @@ static void notrace ftrace_replace_code(int saved)
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ip = rec->ip;
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if (saved)
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new = ftrace_call_replace(ip, MCOUNT_ADDR);
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new = ftrace_call_replace(ip, FTRACE_ADDR);
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else
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old = ftrace_call_replace(ip, MCOUNT_ADDR);
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old = ftrace_call_replace(ip, FTRACE_ADDR);
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failed = ftrace_modify_code(ip, old, new);
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if (failed)
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@ -320,16 +318,6 @@ static void notrace ftrace_replace_code(int saved)
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}
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}
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static notrace void ftrace_startup_code(void)
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{
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ftrace_replace_code(1);
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}
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static notrace void ftrace_shutdown_code(void)
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{
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ftrace_replace_code(0);
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}
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static notrace void ftrace_shutdown_replenish(void)
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{
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if (ftrace_pages->next)
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@ -339,16 +327,8 @@ static notrace void ftrace_shutdown_replenish(void)
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ftrace_pages->next = (void *)get_zeroed_page(GFP_KERNEL);
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}
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static int notrace __ftrace_modify_code(void *data)
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{
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void (*func)(void) = data;
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func();
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return 0;
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}
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static notrace void
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ftrace_code_disable(struct dyn_ftrace *rec, unsigned long addr)
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ftrace_code_disable(struct dyn_ftrace *rec)
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{
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unsigned long ip;
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unsigned char *nop, *call;
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@ -357,67 +337,113 @@ ftrace_code_disable(struct dyn_ftrace *rec, unsigned long addr)
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ip = rec->ip;
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nop = ftrace_nop_replace();
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call = ftrace_call_replace(ip, addr);
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call = ftrace_call_replace(ip, MCOUNT_ADDR);
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failed = ftrace_modify_code(ip, call, nop);
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if (failed)
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rec->flags |= FTRACE_FL_FAILED;
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}
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static void notrace ftrace_run_startup_code(void)
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static int notrace __ftrace_modify_code(void *data)
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{
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stop_machine_run(__ftrace_modify_code, ftrace_startup_code, NR_CPUS);
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unsigned long addr;
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int *command = data;
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if (*command & FTRACE_ENABLE_CALLS)
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ftrace_replace_code(1);
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else if (*command & FTRACE_DISABLE_CALLS)
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ftrace_replace_code(0);
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if (*command & FTRACE_UPDATE_TRACE_FUNC)
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ftrace_update_ftrace_func(ftrace_trace_function);
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if (*command & FTRACE_ENABLE_MCOUNT) {
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addr = (unsigned long)ftrace_record_ip;
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ftrace_mcount_set(&addr);
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} else if (*command & FTRACE_DISABLE_MCOUNT) {
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addr = (unsigned long)ftrace_stub;
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ftrace_mcount_set(&addr);
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}
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return 0;
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}
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static void notrace ftrace_run_shutdown_code(void)
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static void notrace ftrace_run_update_code(int command)
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{
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stop_machine_run(__ftrace_modify_code, ftrace_shutdown_code, NR_CPUS);
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stop_machine_run(__ftrace_modify_code, &command, NR_CPUS);
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}
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static ftrace_func_t saved_ftrace_func;
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static void notrace ftrace_startup(void)
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{
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int command = 0;
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mutex_lock(&ftraced_lock);
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ftraced_suspend++;
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if (ftraced_suspend != 1)
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goto out;
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__unregister_ftrace_function(&ftrace_shutdown_ops);
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if (ftraced_suspend == 1)
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command |= FTRACE_ENABLE_CALLS;
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if (ftrace_enabled)
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ftrace_run_startup_code();
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if (saved_ftrace_func != ftrace_trace_function) {
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saved_ftrace_func = ftrace_trace_function;
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command |= FTRACE_UPDATE_TRACE_FUNC;
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}
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if (!command || !ftrace_enabled)
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goto out;
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ftrace_run_update_code(command);
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out:
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mutex_unlock(&ftraced_lock);
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}
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static void notrace ftrace_shutdown(void)
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{
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int command = 0;
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mutex_lock(&ftraced_lock);
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ftraced_suspend--;
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if (ftraced_suspend)
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if (!ftraced_suspend)
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command |= FTRACE_DISABLE_CALLS;
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if (saved_ftrace_func != ftrace_trace_function) {
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saved_ftrace_func = ftrace_trace_function;
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command |= FTRACE_UPDATE_TRACE_FUNC;
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}
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if (!command || !ftrace_enabled)
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goto out;
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if (ftrace_enabled)
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ftrace_run_shutdown_code();
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__register_ftrace_function(&ftrace_shutdown_ops);
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ftrace_run_update_code(command);
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out:
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mutex_unlock(&ftraced_lock);
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}
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static void notrace ftrace_startup_sysctl(void)
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{
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int command = FTRACE_ENABLE_MCOUNT;
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mutex_lock(&ftraced_lock);
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/* Force update next time */
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saved_ftrace_func = NULL;
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/* ftraced_suspend is true if we want ftrace running */
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if (ftraced_suspend)
|
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ftrace_run_startup_code();
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command |= FTRACE_ENABLE_CALLS;
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ftrace_run_update_code(command);
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mutex_unlock(&ftraced_lock);
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}
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|
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static void notrace ftrace_shutdown_sysctl(void)
|
||||
{
|
||||
int command = FTRACE_DISABLE_MCOUNT;
|
||||
|
||||
mutex_lock(&ftraced_lock);
|
||||
/* ftraced_suspend is true if ftrace is running */
|
||||
if (ftraced_suspend)
|
||||
ftrace_run_shutdown_code();
|
||||
command |= FTRACE_DISABLE_CALLS;
|
||||
|
||||
ftrace_run_update_code(command);
|
||||
mutex_unlock(&ftraced_lock);
|
||||
}
|
||||
|
||||
|
|
@ -430,11 +456,13 @@ static int notrace __ftrace_update_code(void *ignore)
|
|||
struct dyn_ftrace *p;
|
||||
struct hlist_head head;
|
||||
struct hlist_node *t;
|
||||
int save_ftrace_enabled;
|
||||
cycle_t start, stop;
|
||||
int i;
|
||||
|
||||
/* Don't be calling ftrace ops now */
|
||||
__unregister_ftrace_function(&ftrace_shutdown_ops);
|
||||
/* Don't be recording funcs now */
|
||||
save_ftrace_enabled = ftrace_enabled;
|
||||
ftrace_enabled = 0;
|
||||
|
||||
start = now(raw_smp_processor_id());
|
||||
ftrace_update_cnt = 0;
|
||||
|
|
@ -449,7 +477,7 @@ static int notrace __ftrace_update_code(void *ignore)
|
|||
|
||||
/* all CPUS are stopped, we are safe to modify code */
|
||||
hlist_for_each_entry(p, t, &head, node) {
|
||||
ftrace_code_disable(p, MCOUNT_ADDR);
|
||||
ftrace_code_disable(p);
|
||||
ftrace_update_cnt++;
|
||||
}
|
||||
|
||||
|
|
@ -459,7 +487,7 @@ static int notrace __ftrace_update_code(void *ignore)
|
|||
ftrace_update_time = stop - start;
|
||||
ftrace_update_tot_cnt += ftrace_update_cnt;
|
||||
|
||||
__register_ftrace_function(&ftrace_shutdown_ops);
|
||||
ftrace_enabled = save_ftrace_enabled;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
|
@ -515,11 +543,6 @@ static int __init ftrace_dyn_table_alloc(void)
|
|||
struct ftrace_page *pg;
|
||||
int cnt;
|
||||
int i;
|
||||
int ret;
|
||||
|
||||
ret = ftrace_dyn_arch_init();
|
||||
if (ret)
|
||||
return ret;
|
||||
|
||||
/* allocate a few pages */
|
||||
ftrace_pages_start = (void *)get_zeroed_page(GFP_KERNEL);
|
||||
|
|
@ -557,11 +580,19 @@ static int __init ftrace_dyn_table_alloc(void)
|
|||
return 0;
|
||||
}
|
||||
|
||||
static int __init notrace ftrace_shutdown_init(void)
|
||||
static int __init notrace ftrace_dynamic_init(void)
|
||||
{
|
||||
struct task_struct *p;
|
||||
unsigned long addr;
|
||||
int ret;
|
||||
|
||||
addr = (unsigned long)ftrace_record_ip;
|
||||
stop_machine_run(ftrace_dyn_arch_init, &addr, NR_CPUS);
|
||||
|
||||
/* ftrace_dyn_arch_init places the return code in addr */
|
||||
if (addr)
|
||||
return addr;
|
||||
|
||||
ret = ftrace_dyn_table_alloc();
|
||||
if (ret)
|
||||
return ret;
|
||||
|
|
@ -570,12 +601,12 @@ static int __init notrace ftrace_shutdown_init(void)
|
|||
if (IS_ERR(p))
|
||||
return -1;
|
||||
|
||||
__register_ftrace_function(&ftrace_shutdown_ops);
|
||||
last_ftrace_enabled = ftrace_enabled = 1;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
core_initcall(ftrace_shutdown_init);
|
||||
core_initcall(ftrace_dynamic_init);
|
||||
#else
|
||||
# define ftrace_startup() do { } while (0)
|
||||
# define ftrace_shutdown() do { } while (0)
|
||||
|
|
@ -599,9 +630,8 @@ int register_ftrace_function(struct ftrace_ops *ops)
|
|||
int ret;
|
||||
|
||||
mutex_lock(&ftrace_sysctl_lock);
|
||||
ftrace_startup();
|
||||
|
||||
ret = __register_ftrace_function(ops);
|
||||
ftrace_startup();
|
||||
mutex_unlock(&ftrace_sysctl_lock);
|
||||
|
||||
return ret;
|
||||
|
|
@ -619,10 +649,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
|
|||
|
||||
mutex_lock(&ftrace_sysctl_lock);
|
||||
ret = __unregister_ftrace_function(ops);
|
||||
|
||||
if (ftrace_list == &ftrace_list_end)
|
||||
ftrace_shutdown();
|
||||
|
||||
ftrace_shutdown();
|
||||
mutex_unlock(&ftrace_sysctl_lock);
|
||||
|
||||
return ret;
|
||||
|
|
|
|||
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