powerpc: ftrace, use create_branch

Impact: clean up

Paul Mackerras pointed out that the code to determine if the branch
can reach the destination is incorrect. Michael Ellerman suggested
to pull out the code from create_branch and use that.

Simply using create_branch is probably the best.

Reported-by: Michael Ellerman <michael@ellerman.id.au>
Reported-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index a4640e4..5355244 100644 (file)
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -114,19 +114,9 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
  */
 static int test_24bit_addr(unsigned long ip, unsigned long addr)
 {
-       long diff;
 
-       /*
-        * Can we get to addr from ip in 24 bits?
-        *  (26 really, since we mulitply by 4 for 4 byte alignment)
-        */
-       diff = addr - ip;
-
-       /*
-        * Return true if diff is less than 1 << 25
-        *  and greater than -1 << 26.
-        */
-       return (diff < (1 << 25)) && (diff > (-1 << 26));
+       /* use the create_branch to verify that this offset can be branched */
+       return create_branch((unsigned int *)ip, addr, 0);
 }
 
 static int is_bl_op(unsigned int op)
@@ -134,11 +124,6 @@ static int is_bl_op(unsigned int op)
        return (op & 0xfc000003) == 0x48000001;
 }
 
-static int test_offset(unsigned long offset)
-{
-       return (offset + 0x2000000 > 0x3ffffff) || ((offset & 3) != 0);
-}
-
 static unsigned long find_bl_target(unsigned long ip, unsigned int op)
 {
        static int offset;
@@ -151,12 +136,6 @@ static unsigned long find_bl_target(unsigned long ip, unsigned int op)
        return ip + (long)offset;
 }
 
-static unsigned int branch_offset(unsigned long offset)
-{
-       /* return "bl ip+offset" */
-       return 0x48000001 | (offset & 0x03fffffc);
-}
-
 #ifdef CONFIG_PPC64
 static int
 __ftrace_make_nop(struct module *mod,
@@ -402,7 +381,6 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
        unsigned int op[2];
        unsigned long ip = rec->ip;
-       unsigned long offset;
 
        /* read where this goes */
        if (probe_kernel_read(op, (void *)ip, MCOUNT_INSN_SIZE * 2))
@@ -424,17 +402,14 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
                return -EINVAL;
        }
 
-       /* now calculate a jump to the ftrace caller trampoline */
-       offset = rec->arch.mod->arch.tramp - ip;
-
-       if (test_offset(offset)) {
-               printk(KERN_ERR "REL24 %li out of range!\n",
-                      (long int)offset);
+       /* 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");
                return -EINVAL;
        }
 
-       /* Set to "bl addr" */
-       op[0] = branch_offset(offset);
        /* ld r2,40(r1) */
        op[1] = 0xe8410028;
 
@@ -453,7 +428,6 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
        unsigned int op;
        unsigned long ip = rec->ip;
-       unsigned long offset;
 
        /* read where this goes */
        if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
@@ -471,18 +445,14 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
                return -EINVAL;
        }
 
-       /* now calculate a jump to the ftrace caller trampoline */
-       offset = rec->arch.mod->arch.tramp - ip;
-
-       if (test_offset(offset)) {
-               printk(KERN_ERR "REL24 %li out of range!\n",
-                      (long int)offset);
+       /* create the branch to the trampoline */
+       op = create_branch((unsigned int *)ip,
+                          rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
+       if (!op) {
+               printk(KERN_ERR "REL24 out of range!\n");
                return -EINVAL;
        }
 
-       /* Set to "bl addr" */
-       op = branch_offset(offset);
-
        DEBUGP("write to %lx\n", rec->ip);
 
        if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))