[PATCH 4/5] powerpc: ftrace, use create_branch

Steven Rostedt
2008-11-26T22:05:57Z

[-- Attachment #1: 0004-powerpc-ftrace-use-create_branch.patch --]
[-- Type: text/plain, Size: 3922 bytes --]

From: Steven Rostedt <srostedt@redhat.com>

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>
---
arch/powerpc/kernel/ftrace.c | 54 +++++++++--------------------------------
1 files changed, 12 insertions(+), 42 deletions(-)

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index a4640e4..5355244 100644
--- 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))
--
1.5.6.5

--