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authorSteven Rostedt <srostedt@redhat.com>2008-11-14 16:21:20 -0800
committerSteven Rostedt <srostedt@redhat.com>2008-11-20 10:52:04 -0800
commite4486fe316895e87672a563c4f36393218f84ff1 (patch)
tree8cb8e68228e9a9a7c6acf8455d79b3484c8a78a4 /arch/powerpc/kernel/ftrace.c
parent8fd6e5a8c81e2e9b912ea33c8425a10729db469b (diff)
powerpc: ftrace, use probe_kernel API to modify code
Impact: use cleaner probe_kernel API over assembly Using probe_kernel_read/write interface is a much cleaner approach than the current assembly version. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Diffstat (limited to 'arch/powerpc/kernel/ftrace.c')
-rw-r--r--arch/powerpc/kernel/ftrace.c53
1 files changed, 21 insertions, 32 deletions
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 24c023a5cae..1adfbb268d8 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -9,6 +9,7 @@
#include <linux/spinlock.h>
#include <linux/hardirq.h>
+#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/init.h>
@@ -72,45 +73,33 @@ static int
ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code)
{
- unsigned replaced;
- unsigned old = *(unsigned *)old_code;
- unsigned new = *(unsigned *)new_code;
- int faulted = 0;
+ unsigned char replaced[MCOUNT_INSN_SIZE];
/*
* Note: Due to modules and __init, code can
* disappear and change, we need to protect against faulting
- * as well as code changing.
+ * as well as code changing. We do this by using the
+ * probe_kernel_* functions.
*
* No real locking needed, this code is run through
- * kstop_machine.
+ * kstop_machine, or before SMP starts.
*/
- asm volatile (
- "1: lwz %1, 0(%2)\n"
- " cmpw %1, %5\n"
- " bne 2f\n"
- " stwu %3, 0(%2)\n"
- "2:\n"
- ".section .fixup, \"ax\"\n"
- "3: li %0, 1\n"
- " b 2b\n"
- ".previous\n"
- ".section __ex_table,\"a\"\n"
- _ASM_ALIGN "\n"
- _ASM_PTR "1b, 3b\n"
- ".previous"
- : "=r"(faulted), "=r"(replaced)
- : "r"(ip), "r"(new),
- "0"(faulted), "r"(old)
- : "memory");
-
- if (replaced != old && replaced != new)
- faulted = 2;
-
- if (!faulted)
- flush_icache_range(ip, ip + 8);
-
- return faulted;
+
+ /* read the text we want to modify */
+ if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
+ return -EFAULT;
+
+ /* Make sure it is what we expect it to be */
+ if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
+ return -EINVAL;
+
+ /* replace the text with the new text */
+ if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
+ return -EPERM;
+
+ flush_icache_range(ip, ip + 8);
+
+ return 0;
}
static int test_24bit_addr(unsigned long ip, unsigned long addr)