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authorSteven Rostedt <rostedt@goodmis.org>2008-11-26 00:16:24 -0500
committerIngo Molnar <mingo@elte.hu>2008-11-26 06:52:54 +0100
commit5a45cfe1c64862e8cd3b0d79d7c4ba71c3118915 (patch)
tree0a7edf3a9dc88d74b7c7053445ac8aff033a75fa /arch/x86/kernel/ftrace.c
parentdf4fc31558dd2a3a30292ddb3a64c2a5befcec73 (diff)
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ftrace: use code patching for ftrace graph tracer
Impact: more efficient code for ftrace graph tracer This patch uses the dynamic patching, when available, to patch the function graph code into the kernel. This patch will ease the way for letting both function tracing and function graph tracing run together. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/ftrace.c')
-rw-r--r--arch/x86/kernel/ftrace.c48
1 files changed, 46 insertions, 2 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 26b2d92d48b3..7ef914e6a2f6 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -111,7 +111,6 @@ static void ftrace_mod_code(void)
*/
mod_code_status = probe_kernel_write(mod_code_ip, mod_code_newcode,
MCOUNT_INSN_SIZE);
-
}
void ftrace_nmi_enter(void)
@@ -325,7 +324,51 @@ int __init ftrace_dyn_arch_init(void *data)
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-#ifndef CONFIG_DYNAMIC_FTRACE
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern void ftrace_graph_call(void);
+
+static int ftrace_mod_jmp(unsigned long ip,
+ int old_offset, int new_offset)
+{
+ unsigned char code[MCOUNT_INSN_SIZE];
+
+ if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
+ return -EFAULT;
+
+ if (code[0] != 0xe9 || old_offset != *(int *)(&code[1]))
+ return -EINVAL;
+
+ *(int *)(&code[1]) = new_offset;
+
+ if (do_ftrace_mod_code(ip, &code))
+ return -EPERM;
+
+ return 0;
+}
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ unsigned long ip = (unsigned long)(&ftrace_graph_call);
+ int old_offset, new_offset;
+
+ old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
+ new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
+
+ return ftrace_mod_jmp(ip, old_offset, new_offset);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ unsigned long ip = (unsigned long)(&ftrace_graph_call);
+ int old_offset, new_offset;
+
+ old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
+ new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
+
+ return ftrace_mod_jmp(ip, old_offset, new_offset);
+}
+
+#else /* CONFIG_DYNAMIC_FTRACE */
/*
* These functions are picked from those used on
@@ -343,6 +386,7 @@ void ftrace_nmi_exit(void)
{
atomic_dec(&in_nmi);
}
+
#endif /* !CONFIG_DYNAMIC_FTRACE */
/* Add a function return address to the trace stack on thread info.*/