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Subject[PATCH -mm 1/2] kprobes: indirectly call kprobe_target
Call kprobe_target indirectly. This prevents gcc to unroll
a noinline function in caller function.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
CC: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
CC: Jim Keniston <jkenisto@us.ibm.com>
CC: David Miller <davem@davemloft.net>
---
I ported patches which had been discussed on
http://sources.redhat.com/bugzilla/show_bug.cgi?id=3542

tests/test_kprobes.c | 21 ++++++---------------
1 file changed, 6 insertions(+), 15 deletions(-)

Index: 2.6.26-rc2-mm1/tests/test_kprobes.c
===================================================================
--- 2.6.26-rc2-mm1.orig/tests/test_kprobes.c
+++ 2.6.26-rc2-mm1/tests/test_kprobes.c
@@ -22,21 +22,10 @@

static u32 rand1, preh_val, posth_val, jph_val;
static int errors, handler_errors, num_tests;
+static u32 (*target)(u32 value);

static noinline u32 kprobe_target(u32 value)
{
- /*
- * gcc ignores noinline on some architectures unless we stuff
- * sufficient lard into the function. The get_kprobe() here is
- * just for that.
- *
- * NOTE: We aren't concerned about the correctness of get_kprobe()
- * here; hence, this call is neither under !preempt nor with the
- * kprobe_mutex held. This is fine(tm)
- */
- if (get_kprobe((void *)0xdeadbeef))
- printk(KERN_INFO "Kprobe smoke test: probe on 0xdeadbeef!\n");
-
return (value / div_factor);
}

@@ -74,7 +63,7 @@ static int test_kprobe(void)
return ret;
}

- ret = kprobe_target(rand1);
+ ret = target(rand1);
unregister_kprobe(&kp);

if (preh_val == 0) {
@@ -121,7 +110,7 @@ static int test_jprobe(void)
return ret;
}

- ret = kprobe_target(rand1);
+ ret = target(rand1);
unregister_jprobe(&jp);
if (jph_val == 0) {
printk(KERN_ERR "Kprobe smoke test failed: "
@@ -177,7 +166,7 @@ static int test_kretprobe(void)
return ret;
}

- ret = kprobe_target(rand1);
+ ret = target(rand1);
unregister_kretprobe(&rp);
if (krph_val != rand1) {
printk(KERN_ERR "Kprobe smoke test failed: "
@@ -193,6 +182,8 @@ int init_test_probes(void)
{
int ret;

+ target = kprobe_target;
+
do {
rand1 = random32();
} while (rand1 <= div_factor);
--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com



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