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[Patch][kretprobe] fix kretprobe-booster to save regs and set status
- From: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- To: Andrew Morton <akpm at osdl dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, "Keshavamurthy, Anil S" <anil dot s dot keshavamurthy at intel dot com>, Prasanna S Panchamukhi <prasanna at in dot ibm dot com>
- Cc: linux-kernel <linux-kernel at vger dot kernel dot org>, SystemTAP <systemtap at sources dot redhat dot com>, Jim Keniston <jkenisto at us dot ibm dot com>, Satoshi Oshima <soshima at redhat dot com>, Hideo Aoki <haoki at redhat dot com>, Yumiko Sugita <yumiko dot sugita dot yf at hitachi dot com>
- Date: Wed, 08 Nov 2006 10:26:05 +0900
- Subject: [Patch][kretprobe] fix kretprobe-booster to save regs and set status
- Organization: Systems Development Lab., Hitachi, Ltd., Japan
Hi Andrew,
Here is a patch to fix bugs in the kretprobe-booster.
There are two bugs in the kretprobe-booster.
1) It doesn't make room for gs registers.
2) It doesn't change status of the current kprobe. This
status will effect the fault handling.
This patch fixes these bugs and, additionally, saves
skipped registers for compatibility with the original
kretprobe.
--
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
arch/i386/kernel/kprobes.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
Index: linux-2.6.19-rc4-mm2/arch/i386/kernel/kprobes.c
===================================================================
--- linux-2.6.19-rc4-mm2.orig/arch/i386/kernel/kprobes.c
+++ linux-2.6.19-rc4-mm2/arch/i386/kernel/kprobes.c
@@ -361,8 +361,11 @@ no_kprobe:
asm volatile ( ".global kretprobe_trampoline\n"
"kretprobe_trampoline: \n"
" pushf\n"
- /* skip cs, eip, orig_eax, es, ds */
- " subl $20, %esp\n"
+ /* skip cs, eip, orig_eax */
+ " subl $12, %esp\n"
+ " pushl %gs\n"
+ " pushl %ds\n"
+ " pushl %es\n"
" pushl %eax\n"
" pushl %ebp\n"
" pushl %edi\n"
@@ -373,10 +376,10 @@ no_kprobe:
" movl %esp, %eax\n"
" call trampoline_handler\n"
/* move eflags to cs */
- " movl 48(%esp), %edx\n"
- " movl %edx, 44(%esp)\n"
+ " movl 52(%esp), %edx\n"
+ " movl %edx, 48(%esp)\n"
/* save true return address on eflags */
- " movl %eax, 48(%esp)\n"
+ " movl %eax, 52(%esp)\n"
" popl %ebx\n"
" popl %ecx\n"
" popl %edx\n"
@@ -384,8 +387,8 @@ no_kprobe:
" popl %edi\n"
" popl %ebp\n"
" popl %eax\n"
- /* skip eip, orig_eax, es, ds */
- " addl $16, %esp\n"
+ /* skip eip, orig_eax, es, ds, gs */
+ " addl $20, %esp\n"
" popf\n"
" ret\n");
}
@@ -404,6 +407,10 @@ fastcall void *__kprobes trampoline_hand
INIT_HLIST_HEAD(&empty_rp);
spin_lock_irqsave(&kretprobe_lock, flags);
head = kretprobe_inst_table_head(current);
+ /* fixup registers */
+ regs->xcs = __KERNEL_CS;
+ regs->eip = trampoline_address;
+ regs->orig_eax = 0xffffffff;
/*
* It is possible to have multiple instances associated with a given
@@ -425,6 +432,7 @@ fastcall void *__kprobes trampoline_hand
if (ri->rp && ri->rp->handler){
__get_cpu_var(current_kprobe) = &ri->rp->kp;
+ get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
ri->rp->handler(ri, regs);
__get_cpu_var(current_kprobe) = NULL;
}