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authorFrederic Weisbecker <fweisbec@gmail.com>2008-11-11 07:03:45 +0100
committerIngo Molnar <mingo@elte.hu>2008-11-11 10:29:11 +0100
commitcaf4b323b02a16c92fba449952ac6515ddc76d7a (patch)
tree6fc234d00faca192248344996a168afb253e5f40 /arch
parentd844222a54c33a960755b44b934cd1b01b05dceb (diff)
tracing, x86: add low level support for ftrace return tracing
Impact: add infrastructure for function-return tracing Add low level support for ftrace return tracing. This plug-in stores return addresses on the thread_info structure of the current task. The index of the current return address is initialized when the task is the first one (init) and when a process forks (the child). It is not needed when a task does a sys_execve because after this syscall, it still needs to return on the kernel functions it called. Note that the code of return_to_handler has been suggested by Steven Rostedt as almost all of the ideas of improvements in this V3. For purpose of security, arch/x86/kernel/process_32.c is not traced because __switch_to() changes the current task during its execution. That could cause inconsistency in the stored return address of this function even if I didn't have any crash after testing with tracing on this function enabled. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/Kconfig1
-rw-r--r--arch/x86/include/asm/ftrace.h26
-rw-r--r--arch/x86/include/asm/thread_info.h24
-rw-r--r--arch/x86/kernel/Makefile6
-rw-r--r--arch/x86/kernel/entry_32.S33
-rw-r--r--arch/x86/kernel/ftrace.c181
6 files changed, 264 insertions, 7 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 27b8a3a3991..ca91e50bdb1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -11,6 +11,7 @@ config 64BIT
config X86_32
def_bool !64BIT
+ select HAVE_FUNCTION_RET_TRACER
config X86_64
def_bool 64BIT
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index f8173ed1c97..9b6a1fa19e7 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -20,4 +20,30 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_TRACER */
+#ifdef CONFIG_FUNCTION_RET_TRACER
+#define FTRACE_RET_STACK_SIZE 20
+
+#ifndef __ASSEMBLY__
+
+/*
+ * Stack of return addresses for functions
+ * of a thread.
+ * Used in struct thread_info
+ */
+struct ftrace_ret_stack {
+ unsigned long ret;
+ unsigned long func;
+ unsigned long long calltime;
+};
+
+/*
+ * Primary handler of a function return.
+ * It relays on ftrace_return_to_handler.
+ * Defined in entry32.S
+ */
+extern void return_to_handler(void);
+
+#endif /* __ASSEMBLY__ */
+#endif /* CONFIG_FUNCTION_RET_TRACER */
+
#endif /* _ASM_X86_FTRACE_H */
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index e44d379faad..a71158369fd 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -20,6 +20,7 @@
struct task_struct;
struct exec_domain;
#include <asm/processor.h>
+#include <asm/ftrace.h>
struct thread_info {
struct task_struct *task; /* main task structure */
@@ -38,8 +39,30 @@ struct thread_info {
*/
__u8 supervisor_stack[0];
#endif
+
+#ifdef CONFIG_FUNCTION_RET_TRACER
+ /* Index of current stored adress in ret_stack */
+ int curr_ret_stack;
+ /* Stack of return addresses for return function tracing */
+ struct ftrace_ret_stack ret_stack[FTRACE_RET_STACK_SIZE];
+#endif
};
+#ifdef CONFIG_FUNCTION_RET_TRACER
+#define INIT_THREAD_INFO(tsk) \
+{ \
+ .task = &tsk, \
+ .exec_domain = &default_exec_domain, \
+ .flags = 0, \
+ .cpu = 0, \
+ .preempt_count = 1, \
+ .addr_limit = KERNEL_DS, \
+ .restart_block = { \
+ .fn = do_no_restart_syscall, \
+ }, \
+ .curr_ret_stack = -1,\
+}
+#else
#define INIT_THREAD_INFO(tsk) \
{ \
.task = &tsk, \
@@ -52,6 +75,7 @@ struct thread_info {
.fn = do_no_restart_syscall, \
}, \
}
+#endif
#define init_thread_info (init_thread_union.thread_info)
#define init_stack (init_thread_union.stack)
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index e489ff9cb3e..1d8ed95da84 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -14,6 +14,11 @@ CFLAGS_REMOVE_paravirt-spinlocks.o = -pg
CFLAGS_REMOVE_ftrace.o = -pg
endif
+ifdef CONFIG_FUNCTION_RET_TRACER
+# Don't trace __switch_to() but let it for function tracer
+CFLAGS_REMOVE_process_32.o = -pg
+endif
+
#
# vsyscalls (which work on the user stack) should have
# no stack-protector checks:
@@ -65,6 +70,7 @@ obj-$(CONFIG_X86_LOCAL_APIC) += apic.o nmi.o
obj-$(CONFIG_X86_IO_APIC) += io_apic.o
obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o
obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
+obj-$(CONFIG_FUNCTION_RET_TRACER) += ftrace.o
obj-$(CONFIG_KEXEC) += machine_kexec_$(BITS).o
obj-$(CONFIG_KEXEC) += relocate_kernel_$(BITS).o crash.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump_$(BITS).o
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 9134de814c9..9a0ac85946d 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1188,6 +1188,10 @@ ENTRY(mcount)
cmpl $ftrace_stub, ftrace_trace_function
jnz trace
+#ifdef CONFIG_FUNCTION_RET_TRACER
+ cmpl $ftrace_stub, ftrace_function_return
+ jnz trace_return
+#endif
.globl ftrace_stub
ftrace_stub:
ret
@@ -1206,8 +1210,37 @@ trace:
popl %edx
popl %ecx
popl %eax
+ jmp ftrace_stub
+#ifdef CONFIG_FUNCTION_RET_TRACER
+trace_return:
+ pushl %eax
+ pushl %ecx
+ pushl %edx
+ movl 0xc(%esp), %eax
+ pushl %eax
+ lea 0x4(%ebp), %eax
+ pushl %eax
+ call prepare_ftrace_return
+ addl $8, %esp
+ popl %edx
+ popl %ecx
+ popl %eax
jmp ftrace_stub
+
+.globl return_to_handler
+return_to_handler:
+ pushl $0
+ pushl %eax
+ pushl %ecx
+ pushl %edx
+ call ftrace_return_to_handler
+ movl %eax, 0xc(%esp)
+ popl %edx
+ popl %ecx
+ popl %eax
+ ret
+#endif /* CONFIG_FUNCTION_RET_TRACER */
END(mcount)
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_TRACER */
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 69149337f2f..d68033bba22 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -18,10 +18,173 @@
#include <linux/list.h>
#include <asm/ftrace.h>
+#include <linux/ftrace.h>
#include <asm/nops.h>
+#include <asm/nmi.h>
-static unsigned char ftrace_nop[MCOUNT_INSN_SIZE];
+
+#ifdef CONFIG_FUNCTION_RET_TRACER
+
+/*
+ * These functions are picked from those used on
+ * this page for dynamic ftrace. They have been
+ * simplified to ignore all traces in NMI context.
+ */
+static atomic_t in_nmi;
+
+void ftrace_nmi_enter(void)
+{
+ atomic_inc(&in_nmi);
+}
+
+void ftrace_nmi_exit(void)
+{
+ atomic_dec(&in_nmi);
+}
+
+/*
+ * Synchronize accesses to return adresses stack with
+ * interrupts.
+ */
+static raw_spinlock_t ret_stack_lock;
+
+/* Add a function return address to the trace stack on thread info.*/
+static int push_return_trace(unsigned long ret, unsigned long long time,
+ unsigned long func)
+{
+ int index;
+ struct thread_info *ti;
+ unsigned long flags;
+ int err = 0;
+
+ raw_local_irq_save(flags);
+ __raw_spin_lock(&ret_stack_lock);
+
+ ti = current_thread_info();
+ /* The return trace stack is full */
+ if (ti->curr_ret_stack == FTRACE_RET_STACK_SIZE - 1) {
+ err = -EBUSY;
+ goto out;
+ }
+
+ index = ++ti->curr_ret_stack;
+ ti->ret_stack[index].ret = ret;
+ ti->ret_stack[index].func = func;
+ ti->ret_stack[index].calltime = time;
+
+out:
+ __raw_spin_unlock(&ret_stack_lock);
+ raw_local_irq_restore(flags);
+ return err;
+}
+
+/* Retrieve a function return address to the trace stack on thread info.*/
+static void pop_return_trace(unsigned long *ret, unsigned long long *time,
+ unsigned long *func)
+{
+ struct thread_info *ti;
+ int index;
+ unsigned long flags;
+
+ raw_local_irq_save(flags);
+ __raw_spin_lock(&ret_stack_lock);
+
+ ti = current_thread_info();
+ index = ti->curr_ret_stack;
+ *ret = ti->ret_stack[index].ret;
+ *func = ti->ret_stack[index].func;
+ *time = ti->ret_stack[index].calltime;
+ ti->curr_ret_stack--;
+
+ __raw_spin_unlock(&ret_stack_lock);
+ raw_local_irq_restore(flags);
+}
+
+/*
+ * Send the trace to the ring-buffer.
+ * @return the original return address.
+ */
+unsigned long ftrace_return_to_handler(void)
+{
+ struct ftrace_retfunc trace;
+ pop_return_trace(&trace.ret, &trace.calltime, &trace.func);
+ trace.rettime = cpu_clock(raw_smp_processor_id());
+ ftrace_function_return(&trace);
+
+ return trace.ret;
+}
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info.
+ */
+asmlinkage
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
+{
+ unsigned long old;
+ unsigned long long calltime;
+ int faulted;
+ unsigned long return_hooker = (unsigned long)
+ &return_to_handler;
+
+ /* Nmi's are currently unsupported */
+ if (atomic_read(&in_nmi))
+ return;
+
+ /*
+ * Protect against fault, even if it shouldn't
+ * happen. This tool is too much intrusive to
+ * ignore such a protection.
+ */
+ asm volatile(
+ "1: movl (%[parent_old]), %[old]\n"
+ "2: movl %[return_hooker], (%[parent_replaced])\n"
+ " movl $0, %[faulted]\n"
+
+ ".section .fixup, \"ax\"\n"
+ "3: movl $1, %[faulted]\n"
+ ".previous\n"
+
+ ".section __ex_table, \"a\"\n"
+ " .long 1b, 3b\n"
+ " .long 2b, 3b\n"
+ ".previous\n"
+
+ : [parent_replaced] "=rm" (parent), [old] "=r" (old),
+ [faulted] "=r" (faulted)
+ : [parent_old] "0" (parent), [return_hooker] "r" (return_hooker)
+ : "memory"
+ );
+
+ if (WARN_ON(faulted)) {
+ unregister_ftrace_return();
+ return;
+ }
+
+ if (WARN_ON(!__kernel_text_address(old))) {
+ unregister_ftrace_return();
+ *parent = old;
+ return;
+ }
+
+ calltime = cpu_clock(raw_smp_processor_id());
+
+ if (push_return_trace(old, calltime, self_addr) == -EBUSY)
+ *parent = old;
+}
+
+static int __init init_ftrace_function_return(void)
+{
+ ret_stack_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
+ return 0;
+}
+device_initcall(init_ftrace_function_return);
+
+
+#endif
+
+#ifdef CONFIG_DYNAMIC_FTRACE
union ftrace_code_union {
char code[MCOUNT_INSN_SIZE];
@@ -31,17 +194,11 @@ union ftrace_code_union {
} __attribute__((packed));
};
-
static int ftrace_calc_offset(long ip, long addr)
{
return (int)(addr - ip);
}
-unsigned char *ftrace_nop_replace(void)
-{
- return ftrace_nop;
-}
-
unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
static union ftrace_code_union calc;
@@ -183,6 +340,15 @@ do_ftrace_mod_code(unsigned long ip, void *new_code)
}
+
+
+static unsigned char ftrace_nop[MCOUNT_INSN_SIZE];
+
+unsigned char *ftrace_nop_replace(void)
+{
+ return ftrace_nop;
+}
+
int
ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code)
@@ -292,3 +458,4 @@ int __init ftrace_dyn_arch_init(void *data)
return 0;
}
+#endif