aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorSteven Rostedt <srostedt@redhat.com>2008-05-12 21:20:43 +0200
committerThomas Gleixner <tglx@linutronix.de>2008-05-23 20:33:47 +0200
commitd61f82d06672f57fca410da6f7fffd15867db622 (patch)
tree62ef5573934eaa638c0d39a45d789691aecbd7d3
parent3c1720f00bb619302ba19d55986ab565e74d06db (diff)
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>
-rw-r--r--arch/x86/kernel/entry_32.S47
-rw-r--r--arch/x86/kernel/entry_64.S67
-rw-r--r--arch/x86/kernel/ftrace.c41
-rw-r--r--include/linux/ftrace.h7
-rw-r--r--kernel/trace/ftrace.c183
5 files changed, 261 insertions, 84 deletions
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index f47b9b5440d..e6517ce0b82 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1110,10 +1110,50 @@ ENDPROC(xen_failsafe_callback)
#endif /* CONFIG_XEN */
#ifdef CONFIG_FTRACE
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+ENTRY(mcount)
+ pushl %eax
+ pushl %ecx
+ pushl %edx
+ movl 0xc(%esp), %eax
+
+.globl mcount_call
+mcount_call:
+ call ftrace_stub
+
+ popl %edx
+ popl %ecx
+ popl %eax
+
+ ret
+END(mcount)
+
+ENTRY(ftrace_caller)
+ pushl %eax
+ pushl %ecx
+ pushl %edx
+ movl 0xc(%esp), %eax
+ movl 0x4(%ebp), %edx
+
+.globl ftrace_call
+ftrace_call:
+ call ftrace_stub
+
+ popl %edx
+ popl %ecx
+ popl %eax
+
+.globl ftrace_stub
+ftrace_stub:
+ ret
+END(ftrace_caller)
+
+#else /* ! CONFIG_DYNAMIC_FTRACE */
+
ENTRY(mcount)
cmpl $ftrace_stub, ftrace_trace_function
jnz trace
-
.globl ftrace_stub
ftrace_stub:
ret
@@ -1126,7 +1166,7 @@ trace:
movl 0xc(%esp), %eax
movl 0x4(%ebp), %edx
- call *ftrace_trace_function
+ call *ftrace_trace_function
popl %edx
popl %ecx
@@ -1134,7 +1174,8 @@ trace:
jmp ftrace_stub
END(mcount)
-#endif
+#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_FTRACE */
.section .rodata,"a"
#include "syscall_table_32.S"
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index f046e0c6488..fe25e5febca 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -55,6 +55,70 @@
.code64
#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
+
+.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)
+
+ENTRY(ftrace_caller)
+
+ /* taken from glibc */
+ 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
+ movq 8(%rbp), %rsi
+
+.globl ftrace_call
+ftrace_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
+
+.globl ftrace_stub
+ftrace_stub:
+ retq
+END(ftrace_caller)
+
+#else /* ! CONFIG_DYNAMIC_FTRACE */
ENTRY(mcount)
cmpq $ftrace_stub, ftrace_trace_function
jnz trace
@@ -89,7 +153,8 @@ trace:
jmp ftrace_stub
END(mcount)
-#endif
+#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_FTRACE */
#ifndef CONFIG_PREEMPT
#define retint_kernel retint_restore_args
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index b69795efa22..9f44623e007 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;
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index d509ad6c9cb..b0dd0093058 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -56,9 +56,14 @@ struct dyn_ftrace {
extern int ftrace_ip_converted(unsigned long ip);
extern unsigned char *ftrace_nop_replace(void);
extern unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr);
-extern int ftrace_dyn_arch_init(void);
+extern int ftrace_dyn_arch_init(void *data);
+extern int ftrace_mcount_set(unsigned long *data);
extern int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code);
+extern int ftrace_update_ftrace_func(ftrace_func_t func);
+extern void ftrace_caller(void);
+extern void ftrace_call(void);
+extern void mcount_call(void);
#endif
#ifdef CONFIG_FRAME_POINTER
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f6d9af3bf66..88544f9bc0e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -26,14 +26,8 @@
#include "trace.h"
-#ifdef CONFIG_DYNAMIC_FTRACE
-# define FTRACE_ENABLED_INIT 1
-#else
-# define FTRACE_ENABLED_INIT 0
-#endif
-
-int ftrace_enabled = FTRACE_ENABLED_INIT;
-static int last_ftrace_enabled = FTRACE_ENABLED_INIT;
+int ftrace_enabled;
+static int last_ftrace_enabled;
static DEFINE_SPINLOCK(ftrace_lock);
static DEFINE_MUTEX(ftrace_sysctl_lock);
@@ -149,6 +143,14 @@ static int notrace __unregister_ftrace_function(struct ftrace_ops *ops)
#ifdef CONFIG_DYNAMIC_FTRACE
+enum {
+ FTRACE_ENABLE_CALLS = (1 << 0),
+ FTRACE_DISABLE_CALLS = (1 << 1),
+ FTRACE_UPDATE_TRACE_FUNC = (1 << 2),
+ FTRACE_ENABLE_MCOUNT = (1 << 3),
+ FTRACE_DISABLE_MCOUNT = (1 << 4),
+};
+
static struct hlist_head ftrace_hash[FTRACE_HASHSIZE];
static DEFINE_PER_CPU(int, ftrace_shutdown_disable_cpu);
@@ -199,12 +201,8 @@ ftrace_add_hash(struct dyn_ftrace *node, unsigned long key)
hlist_add_head(&node->node, &ftrace_hash[key]);
}
-static notrace struct dyn_ftrace *ftrace_alloc_shutdown_node(unsigned long ip)
+static notrace struct dyn_ftrace *ftrace_alloc_dyn_node(unsigned long ip)
{
- /* If this was already converted, skip it */
- if (ftrace_ip_converted(ip))
- return NULL;
-
if (ftrace_pages->index == ENTRIES_PER_PAGE) {
if (!ftrace_pages->next)
return NULL;
@@ -215,7 +213,7 @@ static notrace struct dyn_ftrace *ftrace_alloc_shutdown_node(unsigned long ip)
}
static void notrace
-ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
+ftrace_record_ip(unsigned long ip)
{
struct dyn_ftrace *node;
unsigned long flags;
@@ -223,6 +221,9 @@ ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
int resched;
int atomic;
+ if (!ftrace_enabled)
+ return;
+
resched = need_resched();
preempt_disable_notrace();
@@ -251,11 +252,12 @@ ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
/*
* There's a slight race that the ftraced will update the
- * hash and reset here. The arch alloc is responsible
- * for seeing if the IP has already changed, and if
- * it has, the alloc will fail.
+ * hash and reset here. If it is already converted, skip it.
*/
- node = ftrace_alloc_shutdown_node(ip);
+ if (ftrace_ip_converted(ip))
+ goto out_unlock;
+
+ node = ftrace_alloc_dyn_node(ip);
if (!node)
goto out_unlock;
@@ -277,11 +279,7 @@ ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
preempt_enable_notrace();
}
-static struct ftrace_ops ftrace_shutdown_ops __read_mostly =
-{
- .func = ftrace_record_ip,
-};
-
+#define FTRACE_ADDR ((long)(&ftrace_caller))
#define MCOUNT_ADDR ((long)(&mcount))
static void notrace ftrace_replace_code(int saved)
@@ -309,9 +307,9 @@ static void notrace ftrace_replace_code(int saved)
ip = rec->ip;
if (saved)
- new = ftrace_call_replace(ip, MCOUNT_ADDR);
+ new = ftrace_call_replace(ip, FTRACE_ADDR);
else
- old = ftrace_call_replace(ip, MCOUNT_ADDR);
+ old = ftrace_call_replace(ip, FTRACE_ADDR);
failed = ftrace_modify_code(ip, old, new);
if (failed)
@@ -320,16 +318,6 @@ static void notrace ftrace_replace_code(int saved)
}
}
-static notrace void ftrace_startup_code(void)
-{
- ftrace_replace_code(1);
-}
-
-static notrace void ftrace_shutdown_code(void)
-{
- ftrace_replace_code(0);
-}
-
static notrace void ftrace_shutdown_replenish(void)
{
if (ftrace_pages->next)
@@ -339,16 +327,8 @@ static notrace void ftrace_shutdown_replenish(void)
ftrace_pages->next = (void *)get_zeroed_page(GFP_KERNEL);
}
-static int notrace __ftrace_modify_code(void *data)
-{
- void (*func)(void) = data;
-
- func();
- return 0;
-}
-
static notrace void
-ftrace_code_disable(struct dyn_ftrace *rec, unsigned long addr)
+ftrace_code_disable(struct dyn_ftrace *rec)
{
unsigned long ip;
unsigned char *nop, *call;
@@ -357,67 +337,113 @@ ftrace_code_disable(struct dyn_ftrace *rec, unsigned long addr)
ip = rec->ip;
nop = ftrace_nop_replace();
- call = ftrace_call_replace(ip, addr);
+ call = ftrace_call_replace(ip, MCOUNT_ADDR);
failed = ftrace_modify_code(ip, call, nop);
if (failed)
rec->flags |= FTRACE_FL_FAILED;
}
-static void notrace ftrace_run_startup_code(void)
+static int notrace __ftrace_modify_code(void *data)
{
- stop_machine_run(__ftrace_modify_code, ftrace_startup_code, NR_CPUS);
+ unsigned long addr;
+ int *command = data;
+
+ if (*command & FTRACE_ENABLE_CALLS)
+ ftrace_replace_code(1);
+ else if (*command & FTRACE_DISABLE_CALLS)
+ ftrace_replace_code(0);
+
+ if (*command & FTRACE_UPDATE_TRACE_FUNC)
+ ftrace_update_ftrace_func(ftrace_trace_function);
+
+ if (*command & FTRACE_ENABLE_MCOUNT) {
+ addr = (unsigned long)ftrace_record_ip;
+ ftrace_mcount_set(&addr);
+ } else if (*command & FTRACE_DISABLE_MCOUNT) {
+ addr = (unsigned long)ftrace_stub;
+ ftrace_mcount_set(&addr);
+ }
+
+ return 0;
}
-static void notrace ftrace_run_shutdown_code(void)
+static void notrace ftrace_run_update_code(int command)
{
- stop_machine_run(__ftrace_modify_code, ftrace_shutdown_code, NR_CPUS);
+ stop_machine_run(__ftrace_modify_code, &command, NR_CPUS);
}
+static ftrace_func_t saved_ftrace_func;
+
static void notrace ftrace_startup(void)
{
+ int command = 0;
+
mutex_lock(&ftraced_lock);
ftraced_suspend++;
- if (ftraced_suspend != 1)
+ if (ftraced_suspend == 1)
+ command |= FTRACE_ENABLE_CALLS;
+
+ if (saved_ftrace_func != ftrace_trace_function) {
+ saved_ftrace_func = ftrace_trace_function;
+ command |= FTRACE_UPDATE_TRACE_FUNC;
+ }
+
+ if (!command || !ftrace_enabled)
goto out;
- __unregister_ftrace_function(&ftrace_shutdown_ops);
- if (ftrace_enabled)
- ftrace_run_startup_code();
+ ftrace_run_update_code(command);
out:
mutex_unlock(&ftraced_lock);
}
static void notrace ftrace_shutdown(void)
{
+ int command = 0;
+
mutex_lock(&ftraced_lock);
ftraced_suspend--;
- if (ftraced_suspend)
- goto out;
+ if (!ftraced_suspend)
+ command |= FTRACE_DISABLE_CALLS;
- if (ftrace_enabled)
- ftrace_run_shutdown_code();
+ if (saved_ftrace_func != ftrace_trace_function) {
+ saved_ftrace_func = ftrace_trace_function;
+ command |= FTRACE_UPDATE_TRACE_FUNC;
+ }
- __register_ftrace_function(&ftrace_shutdown_ops);
+ if (!command || !ftrace_enabled)
+ goto out;
+
+ ftrace_run_update_code(command);
out:
mutex_unlock(&ftraced_lock);
}
static void notrace ftrace_startup_sysctl(void)
{
+ int command = FTRACE_ENABLE_MCOUNT;
+
mutex_lock(&ftraced_lock);
+ /* Force update next time */
+ saved_ftrace_func = NULL;
/* ftraced_suspend is true if we want ftrace running */
if (ftraced_suspend)
- ftrace_run_startup_code();
+ command |= FTRACE_ENABLE_CALLS;
+
+ ftrace_run_update_code(command);
mutex_unlock(&ftraced_lock);
}
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;