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[PATCH] kretprobe: kretprobe-booster

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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>
This commit is contained in:
Masami Hiramatsu 2006-03-26 01:38:19 -08:00 committed by Linus Torvalds
parent 311ac88fd2
commit c9becf58d9
1 changed files with 39 additions and 22 deletions
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61
arch/i386/kernel/kprobes.c
View file

@ -333,17 +333,44 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
* 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;
}