[Patch] kprobes exception notifier fix 2.6.9-rc2

From: Prasanna S Panchamukhi
Date: Thu Sep 23 2004 - 00:34:09 EST

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In order to make other debuggers use exception notifiers, kprobes
notifier return values are required to be modified. This patch modifies the
return values of kprobes notifier return values in a clean way.

Please let me know your comments.

Thanks
Prasanna
--

Prasanna S Panchamukhi
Linux Technology Center
India Software Labs, IBM Bangalore
Ph: 91-80-25044636
<prasanna@xxxxxxxxxx>

This patch modifies the return value of kprobes exceptions notify handler.
The kprobes exception notifier returns NOTIFY_STOP on handling notification.
This patch helps other debuggers to co-exists with the Kprobes. Other debuggers
registered for exceptions notification must return NOTIFY_STOP on handling
the notification.

Signed-off by : Prasanna S Panchamukhi <prasanna@xxxxxxxxxx>

---

linux-2.6.9-rc2-prasanna/arch/i386/kernel/kprobes.c | 10 +++++-----
linux-2.6.9-rc2-prasanna/arch/i386/kernel/traps.c | 18 +++++++++---------
linux-2.6.9-rc2-prasanna/arch/i386/mm/fault.c | 2 +-
linux-2.6.9-rc2-prasanna/include/linux/notifier.h | 4 ++++
linux-2.6.9-rc2-prasanna/kernel/kprobes.c | 3 +++
5 files changed, 22 insertions(+), 15 deletions(-)

diff -puN arch/i386/kernel/kprobes.c~kprobes-exceptions-nofitier-fix arch/i386/kernel/kprobes.c
--- linux-2.6.9-rc2/arch/i386/kernel/kprobes.c~kprobes-exceptions-nofitier-fix 2004-09-21 15:06:22.000000000 +0530
+++ linux-2.6.9-rc2-prasanna/arch/i386/kernel/kprobes.c 2004-09-21 15:06:22.000000000 +0530
@@ -267,26 +267,26 @@ int kprobe_exceptions_notify(struct noti
switch (val) {
case DIE_INT3:
if (kprobe_handler(args->regs))
- return NOTIFY_OK;
+ return NOTIFY_STOP;
break;
case DIE_DEBUG:
if (post_kprobe_handler(args->regs))
- return NOTIFY_OK;
+ return NOTIFY_STOP;
break;
case DIE_GPF:
if (kprobe_running() &&
kprobe_fault_handler(args->regs, args->trapnr))
- return NOTIFY_OK;
+ return NOTIFY_STOP;
break;
case DIE_PAGE_FAULT:
if (kprobe_running() &&
kprobe_fault_handler(args->regs, args->trapnr))
- return NOTIFY_OK;
+ return NOTIFY_STOP;
break;
default:
break;
}
- return NOTIFY_BAD;
+ return NOTIFY_DONE;
}

int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
diff -puN arch/i386/kernel/traps.c~kprobes-exceptions-nofitier-fix arch/i386/kernel/traps.c
--- linux-2.6.9-rc2/arch/i386/kernel/traps.c~kprobes-exceptions-nofitier-fix 2004-09-21 15:06:22.000000000 +0530
+++ linux-2.6.9-rc2-prasanna/arch/i386/kernel/traps.c 2004-09-21 15:06:22.000000000 +0530
@@ -422,7 +422,7 @@ static inline void do_trap(int trapnr, i
asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
{ \
if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
- == NOTIFY_OK) \
+ == NOTIFY_STOP) \
return; \
do_trap(trapnr, signr, str, 0, regs, error_code, NULL); \
}
@@ -436,7 +436,7 @@ asmlinkage void do_##name(struct pt_regs
info.si_code = sicode; \
info.si_addr = (void __user *)siaddr; \
if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
- == NOTIFY_BAD) \
+ == NOTIFY_STOP) \
return; \
do_trap(trapnr, signr, str, 0, regs, error_code, &info); \
}
@@ -445,7 +445,7 @@ asmlinkage void do_##name(struct pt_regs
asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
{ \
if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
- == NOTIFY_OK) \
+ == NOTIFY_STOP) \
return; \
do_trap(trapnr, signr, str, 1, regs, error_code, NULL); \
}
@@ -459,7 +459,7 @@ asmlinkage void do_##name(struct pt_regs
info.si_code = sicode; \
info.si_addr = (void __user *)siaddr; \
if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
- == NOTIFY_OK) \
+ == NOTIFY_STOP) \
return; \
do_trap(trapnr, signr, str, 1, regs, error_code, &info); \
}
@@ -498,7 +498,7 @@ gp_in_vm86:
gp_in_kernel:
if (!fixup_exception(regs)) {
if (notify_die(DIE_GPF, "general protection fault", regs,
- error_code, 13, SIGSEGV) == NOTIFY_OK);
+ error_code, 13, SIGSEGV) == NOTIFY_STOP);
return;
die("general protection fault", regs, error_code);
}
@@ -572,7 +572,7 @@ static void default_do_nmi(struct pt_reg

if (!(reason & 0xc0)) {
if (notify_die(DIE_NMI_IPI, "nmi_ipi", regs, reason, 0, SIGINT)
- == NOTIFY_BAD)
+ == NOTIFY_STOP)
return;
#ifdef CONFIG_X86_LOCAL_APIC
/*
@@ -587,7 +587,7 @@ static void default_do_nmi(struct pt_reg
unknown_nmi_error(reason, regs);
return;
}
- if (notify_die(DIE_NMI, "nmi", regs, reason, 0, SIGINT) == NOTIFY_BAD)
+ if (notify_die(DIE_NMI, "nmi", regs, reason, 0, SIGINT) == NOTIFY_STOP)
return;
if (reason & 0x80)
mem_parity_error(reason, regs);
@@ -636,7 +636,7 @@ void unset_nmi_callback(void)
asmlinkage int do_int3(struct pt_regs *regs, long error_code)
{
if (notify_die(DIE_INT3, "int3", regs, error_code, 3, SIGTRAP)
- == NOTIFY_OK)
+ == NOTIFY_STOP)
return 1;
/* This is an interrupt gate, because kprobes wants interrupts
disabled. Normal trap handlers don't. */
@@ -677,7 +677,7 @@ asmlinkage void do_debug(struct pt_regs
__asm__ __volatile__("movl %%db6,%0" : "=r" (condition));

if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
- SIGTRAP) == NOTIFY_OK)
+ SIGTRAP) == NOTIFY_STOP)
return;
/* It's safe to allow irq's after DR6 has been saved */
if (regs->eflags & X86_EFLAGS_IF)
diff -puN arch/i386/mm/fault.c~kprobes-exceptions-nofitier-fix arch/i386/mm/fault.c
--- linux-2.6.9-rc2/arch/i386/mm/fault.c~kprobes-exceptions-nofitier-fix 2004-09-21 15:06:22.000000000 +0530
+++ linux-2.6.9-rc2-prasanna/arch/i386/mm/fault.c 2004-09-21 15:06:22.000000000 +0530
@@ -227,7 +227,7 @@ asmlinkage void do_page_fault(struct pt_
__asm__("movl %%cr2,%0":"=r" (address));

if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
- SIGSEGV) == NOTIFY_OK)
+ SIGSEGV) == NOTIFY_STOP)
return;
/* It's safe to allow irq's after cr2 has been saved */
if (regs->eflags & (X86_EFLAGS_IF|VM_MASK))
diff -puN kernel/kprobes.c~kprobes-exceptions-nofitier-fix kernel/kprobes.c
--- linux-2.6.9-rc2/kernel/kprobes.c~kprobes-exceptions-nofitier-fix 2004-09-21 15:06:22.000000000 +0530
+++ linux-2.6.9-rc2-prasanna/kernel/kprobes.c 2004-09-21 15:06:22.000000000 +0530
@@ -25,6 +25,8 @@
* hlists and exceptions notifier as suggested by Andi Kleen.
* 2004-July Suparna Bhattacharya <suparna@xxxxxxxxxx> added jumper probes
* interface to access function arguments.
+ * 2004-Sep Prasanna S Panchamukhi <prasanna@xxxxxxxxxx> Changed Kprobes
+ * exceptions notifier to be first on the priority list.
*/
#include <linux/kprobes.h>
#include <linux/spinlock.h>
@@ -108,6 +110,7 @@ void unregister_kprobe(struct kprobe *p)

static struct notifier_block kprobe_exceptions_nb = {
.notifier_call = kprobe_exceptions_notify,
+ .priority = 0x7fffffff /* we need to notified first */
};

int register_jprobe(struct jprobe *jp)
diff -puN include/linux/notifier.h~kprobes-exceptions-nofitier-fix include/linux/notifier.h
--- linux-2.6.9-rc2/include/linux/notifier.h~kprobes-exceptions-nofitier-fix 2004-09-21 15:06:22.000000000 +0530
+++ linux-2.6.9-rc2-prasanna/include/linux/notifier.h 2004-09-21 15:07:21.000000000 +0530
@@ -29,6 +29,10 @@ extern int notifier_call_chain(struct no
#define NOTIFY_OK 0x0001 /* Suits me */
#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) /* Bad/Veto action */
+/*
+ * Clean way to return from the notifier and stop further calls.
+ */
+#define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)

/*
* Declared notifiers so far. I can imagine quite a few more chains

_

Next message: Peter Williams: "Re: 2.6.9-rc2-mm2"
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