powerpc/ftrace: Use module loader helpers to parse trampolines

Now we have is_module_trampoline() and module_trampoline_target()
we can remove a bunch of intimate kernel module trampoline
knowledge from ftrace.

Signed-off-by: Anton Blanchard <anton@samba.org>

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 6a014c763cc71da4a9a5fd523649f105bf5fdc10..78cdd7fbecd008cfd3b4fe4c8baa7d4868225eaf 100644 (file)
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -105,11 +105,9 @@ __ftrace_make_nop(struct module *mod,
                  struct dyn_ftrace *rec, unsigned long addr)
 {
        unsigned int op;
-       unsigned int jmp[5];
        unsigned long ptr;
        unsigned long ip = rec->ip;
-       unsigned long tramp;
-       int offset;
+       void *tramp;
 
        /* read where this goes */
        if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
@@ -122,96 +120,41 @@ __ftrace_make_nop(struct module *mod,
        }
 
        /* lets find where the pointer goes */
-       tramp = find_bl_target(ip, op);
-
-       /*
-        * On PPC64 the trampoline looks like:
-        * 0x3d, 0x82, 0x00, 0x00,    addis   r12,r2, <high>
-        * 0x39, 0x8c, 0x00, 0x00,    addi    r12,r12, <low>
-        *   Where the bytes 2,3,6 and 7 make up the 32bit offset
-        *   to the TOC that holds the pointer.
-        *   to jump to.
-        * 0xf8, 0x41, 0x00, 0x28,    std     r2,40(r1)
-        * 0xe9, 0x6c, 0x00, 0x20,    ld      r11,32(r12)
-        *   The actually address is 32 bytes from the offset
-        *   into the TOC.
-        * 0xe8, 0x4c, 0x00, 0x28,    ld      r2,40(r12)
-        */
+       tramp = (void *)find_bl_target(ip, op);
 
-       pr_devel("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);
+       pr_devel("ip:%lx jumps to %p", ip, tramp);
 
-       /* Find where the trampoline jumps to */
-       if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
-               printk(KERN_ERR "Failed to read %lx\n", tramp);
-               return -EFAULT;
-       }
-
-       pr_devel(" %08x %08x", jmp[0], jmp[1]);
-
-       /* verify that this is what we expect it to be */
-       if (((jmp[0] & 0xffff0000) != 0x3d820000) ||
-           ((jmp[1] & 0xffff0000) != 0x398c0000) ||
-           (jmp[2] != 0xf8410028) ||
-           (jmp[3] != 0xe96c0020) ||
-           (jmp[4] != 0xe84c0028)) {
+       if (!is_module_trampoline(tramp)) {
                printk(KERN_ERR "Not a trampoline\n");
                return -EINVAL;
        }
 
-       /* The bottom half is signed extended */
-       offset = ((unsigned)((unsigned short)jmp[0]) << 16) +
-               (int)((short)jmp[1]);
-
-       pr_devel(" %x ", offset);
-
-       /* get the address this jumps too */
-       tramp = mod->arch.toc + offset + 32;
-       pr_devel("toc: %lx", tramp);
-
-       if (probe_kernel_read(jmp, (void *)tramp, 8)) {
-               printk(KERN_ERR "Failed to read %lx\n", tramp);
+       if (module_trampoline_target(mod, tramp, &ptr)) {
+               printk(KERN_ERR "Failed to get trampoline target\n");
                return -EFAULT;
        }
 
-       pr_devel(" %08x %08x\n", jmp[0], jmp[1]);
-
-#ifdef __LITTLE_ENDIAN__
-       ptr = ((unsigned long)jmp[1] << 32) + jmp[0];
-#else
-       ptr = ((unsigned long)jmp[0] << 32) + jmp[1];
-#endif
+       pr_devel("trampoline target %lx", ptr);
 
        /* This should match what was called */
        if (ptr != ppc_function_entry((void *)addr)) {
-               printk(KERN_ERR "addr does not match %lx\n", ptr);
+               printk(KERN_ERR "addr %lx does not match expected %lx\n",
+                       ptr, ppc_function_entry((void *)addr));
                return -EINVAL;
        }
 
        /*
-        * We want to nop the line, but the next line is
-        *  0xe8, 0x41, 0x00, 0x28   ld r2,40(r1)
-        * This needs to be turned to a nop too.
-        */
-       if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE))
-               return -EFAULT;
-
-       if (op != 0xe8410028) {
-               printk(KERN_ERR "Next line is not ld! (%08x)\n", op);
-               return -EINVAL;
-       }
-
-       /*
-        * Milton Miller pointed out that we can not blindly do nops.
-        * If a task was preempted when calling a trace function,
-        * the nops will remove the way to restore the TOC in r2
-        * and the r2 TOC will get corrupted.
-        */
-
-       /*
-        * Replace:
-        *   bl <tramp>  <==== will be replaced with "b 1f"
-        *   ld r2,40(r1)
-        *  1:
+        * Our original call site looks like:
+        *
+        * bl <tramp>
+        * ld r2,XX(r1)
+        *
+        * Milton Miller pointed out that we can not simply nop the branch.
+        * If a task was preempted when calling a trace function, the nops
+        * will remove the way to restore the TOC in r2 and the r2 TOC will
+        * get corrupted.
+        *
+        * Use a b +8 to jump over the load.
         */
        op = 0x48000008;        /* b +8 */