From c9becf58d935265919bf1cb348b2c04492c8949d Mon Sep 17 00:00:00 2001
From: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp>
Date: Sun, 26 Mar 2006 01:38:19 -0800
Subject: [PATCH] kretprobe: kretprobe-booster
In normal operation, kretprobe makes a target function return to trampoline
code. A kprobe (called trampoline_probe) has been inserted in the trampoline
code. When the kernel hits this kprobe, it calls kretprobe's handler and it
returns to the original return address.
Kretprobe-booster removes the trampoline_probe. It allows the trampoline code
to call kretprobe's handler directly instead of invoking kprobe. The
trampoline code returns to the original return address.
(changelog from Chuck Ebbert <76306.1226@compuserve.com> - thanks ;))
Signed-off-by: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
arch/i386/kernel/kprobes.c | 61 +++++++++++++++++++++++++++++-----------------
1 file changed, 39 insertions(+), 22 deletions(-)
(limited to 'arch')
diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 137bf61..acdcc64 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -333,17 +333,44 @@ no_kprobe:
* here. When a retprobed function returns, this probe is hit and
* trampoline_probe_handler() runs, calling the kretprobe's handler.
*/
- void kretprobe_trampoline_holder(void)
+ void __kprobes kretprobe_trampoline_holder(void)
{
- asm volatile ( ".global kretprobe_trampoline\n"
+ asm volatile ( ".global kretprobe_trampoline\n"
"kretprobe_trampoline: \n"
- "nop\n");
- }
+ " pushf\n"
+ /* skip cs, eip, orig_eax, es, ds */
+ " subl $20, %esp\n"
+ " pushl %eax\n"
+ " pushl %ebp\n"
+ " pushl %edi\n"
+ " pushl %esi\n"
+ " pushl %edx\n"
+ " pushl %ecx\n"
+ " pushl %ebx\n"
+ " movl %esp, %eax\n"
+ " call trampoline_handler\n"
+ /* move eflags to cs */
+ " movl 48(%esp), %edx\n"
+ " movl %edx, 44(%esp)\n"
+ /* save true return address on eflags */
+ " movl %eax, 48(%esp)\n"
+ " popl %ebx\n"
+ " popl %ecx\n"
+ " popl %edx\n"
+ " popl %esi\n"
+ " popl %edi\n"
+ " popl %ebp\n"
+ " popl %eax\n"
+ /* skip eip, orig_eax, es, ds */
+ " addl $16, %esp\n"
+ " popf\n"
+ " ret\n");
+}
/*
- * Called when we hit the probe point at kretprobe_trampoline
+ * Called from kretprobe_trampoline
*/
-int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
{
struct kretprobe_instance *ri = NULL;
struct hlist_head *head;
@@ -372,8 +399,11 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
/* another task is sharing our hash bucket */
continue;
- if (ri->rp && ri->rp->handler)
+ if (ri->rp && ri->rp->handler){
+ __get_cpu_var(current_kprobe) = &ri->rp->kp;
ri->rp->handler(ri, regs);
+ __get_cpu_var(current_kprobe) = NULL;
+ }
orig_ret_address = (unsigned long)ri->ret_addr;
recycle_rp_inst(ri);
@@ -388,18 +418,10 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
}
BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
- regs->eip = orig_ret_address;
- reset_current_kprobe();
spin_unlock_irqrestore(&kretprobe_lock, flags);
- preempt_enable_no_resched();
- /*
- * By returning a non-zero value, we are telling
- * kprobe_handler() that we don't want the post_handler
- * to run (and have re-enabled preemption)
- */
- return 1;
+ return (void*)orig_ret_address;
}
/*
@@ -646,12 +668,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
return 0;
}
-static struct kprobe trampoline_p = {
- .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
- .pre_handler = trampoline_probe_handler
-};
-
int __init arch_init_kprobes(void)
{
- return register_kprobe(&trampoline_p);
+ return 0;
}
--
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