@@ -50,32 +50,39 @@ ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
return op;
}
-static inline int
-ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
+static inline int ftrace_read_inst(unsigned long ip, ppc_inst_t *op)
{
- ppc_inst_t replaced;
-
- /*
- * Note:
- * We are paranoid about modifying text, as if a bug was to happen, it
- * could cause us to read or write to someplace that could cause harm.
- * Carefully read and modify the code with probe_kernel_*(), and make
- * sure what we read is what we expected it to be before modifying it.
- */
-
- /* read the text we want to modify */
- if (copy_inst_from_kernel_nofault(&replaced, (void *)ip))
+ if (copy_inst_from_kernel_nofault(op, (void *)ip)) {
+ pr_err("0x%lx: fetching instruction failed\n", ip);
return -EFAULT;
-
- /* Make sure it is what we expect it to be */
- if (!ppc_inst_equal(replaced, old)) {
- pr_err("%p: replaced (%08lx) != old (%08lx)", (void *)ip,
- ppc_inst_as_ulong(replaced), ppc_inst_as_ulong(old));
- return -EINVAL;
}
- /* replace the text with the new text */
- return patch_instruction((u32 *)ip, new);
+ return 0;
+}
+
+static inline int ftrace_validate_inst(unsigned long ip, ppc_inst_t inst)
+{
+ ppc_inst_t op;
+ int ret;
+
+ ret = ftrace_read_inst(ip, &op);
+ if (!ret && !ppc_inst_equal(op, inst)) {
+ pr_err("0x%lx: expected (%08lx) != found (%08lx)\n",
+ ip, ppc_inst_as_ulong(inst), ppc_inst_as_ulong(op));
+ ret = -EINVAL;
+ }
+
+ return ret;
+}
+
+static inline int ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
+{
+ int ret = ftrace_validate_inst(ip, old);
+
+ if (!ret)
+ ret = patch_instruction((u32 *)ip, new);
+
+ return ret;
}
/*
Split up ftrace_modify_code() into a few helpers for future use. Also update error messages accordingly. Signed-off-by: Naveen N Rao <naveen@kernel.org> --- arch/powerpc/kernel/trace/ftrace.c | 51 +++++++++++++++++------------- 1 file changed, 29 insertions(+), 22 deletions(-)