1 files changed, 39 insertions, 98 deletions

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 6a014c763cc7..f202d0731b06 100644
--- 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)
-         */
-
-        pr_devel("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);
-
-        /* 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;
-        }
+        tramp = (void *)find_bl_target(ip, op);
 
-        pr_devel(" %08x %08x", jmp[0], jmp[1]);
+        pr_devel("ip:%lx jumps to %p", ip, tramp);
 
-        /* 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 */
 
@@ -349,19 +292,24 @@ static int
 __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
         unsigned int op[2];
-        unsigned long ip = rec->ip;
+        void *ip = (void *)rec->ip;
 
         /* read where this goes */
-        if (probe_kernel_read(op, (void *)ip, MCOUNT_INSN_SIZE * 2))
+        if (probe_kernel_read(op, ip, sizeof(op)))
                 return -EFAULT;
 
         /*
-         * It should be pointing to two nops or
-         *  b +8; ld r2,40(r1)
+         * We expect to see:
+         *
+         * b +8
+         * ld r2,XX(r1)
+         *
+         * The load offset is different depending on the ABI. For simplicity
+         * just mask it out when doing the compare.
          */
-        if (((op[0] != 0x48000008) || (op[1] != 0xe8410028)) &&
-            ((op[0] != PPC_INST_NOP) || (op[1] != PPC_INST_NOP))) {
-                printk(KERN_ERR "Expected NOPs but have %x %x\n", op[0], op[1]);
+        if ((op[0] != 0x48000008) || ((op[1] & 0xffff00000) != 0xe8410000)) {
+                printk(KERN_ERR "Unexpected call sequence: %x %x\n",
+                        op[0], op[1]);
                 return -EINVAL;
         }
 
@@ -371,23 +319,16 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
                 return -EINVAL;
         }
 
-        /* create the branch to the trampoline */
-        op[0] = create_branch((unsigned int *)ip,
-                              rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
-        if (!op[0]) {
-                printk(KERN_ERR "REL24 out of range!\n");
+        /* Ensure branch is within 24 bits */
+        if (create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
+                printk(KERN_ERR "Branch out of range");
                 return -EINVAL;
         }
 
-        /* ld r2,40(r1) */
-        op[1] = 0xe8410028;
-
-        pr_devel("write to %lx\n", rec->ip);
-
-        if (probe_kernel_write((void *)ip, op, MCOUNT_INSN_SIZE * 2))
-                return -EPERM;
-
-        flush_icache_range(ip, ip + 8);
+        if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
+                printk(KERN_ERR "REL24 out of range!\n");
+                return -EINVAL;
+        }
 
         return 0;
 }