Re: [PATCH]kprobe handler discard user space trap

[bibo mao <bibo_mao@linux.intel.com>]

This patch removes code in kprobe_handler() function which calculates 
user space int3 trap address in i386 architecture. And this patch is 
based on kprobe-handler-discard-user-space-trap.patch, against 
2.6.16-rc5-mm1.

Signed-off-by: bibo mao <bibo.mao@intel.com>

--- a/arch/i386/kernel/kprobes.c	2006-03-01 12:48:54.000000000 +0800
+++ b/arch/i386/kernel/kprobes.c	2006-03-01 14:08:12.000000000 +0800
@@ -203,7 +203,7 @@ static int __kprobes kprobe_handler(stru
 {
 	struct kprobe *p;
 	int ret = 0;
-	kprobe_opcode_t *addr = NULL;
+	kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->eip - 
sizeof(kprobe_opcode_t));
 	unsigned long *lp;
 	struct kprobe_ctlblk *kcb;
 #ifdef CONFIG_PREEMPT
@@ -217,17 +217,6 @@ static int __kprobes kprobe_handler(stru
 	preempt_disable();
 	kcb = get_kprobe_ctlblk();

-	/* Check if the application is using LDT entry for its code segment and
-	 * calculate the address by reading the base address from the LDT entry.
-	 */
-	if ((regs->xcs & 4) && (current->mm)) {
-		lp = (unsigned long *) ((unsigned long)((regs->xcs >> 3) * 8)
-					+ (char *) current->mm->context.ldt);
-		addr = (kprobe_opcode_t *) (get_desc_base(lp) + regs->eip -
-						sizeof(kprobe_opcode_t));
-	} else {
-		addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
-	}
 	/* Check we're not actually recursing */
 	if (kprobe_running()) {
 		p = get_kprobe(addr);

Prasanna S Panchamukhi wrote:
> On Tue, Feb 28, 2006 at 03:23:12PM +0800, bibo,mao wrote:
> > Currently kprobe handler traps only happen in kernel space, so function
> > kprobe_exceptions_notify should skip traps which happen in user space.
> > This patch modifies this, and it is based on 2.6.16-rc4.
>
> You need to remove the code which calculates the
> user space address in kprobe_handler() and also you need 
> to remove the code that checks for VM86 in i386, since
> your patch check if user/vm86 at the top level.
>
> Thanks
> Prasanna
>
> > Signed-off-by: bibo mao <bibo.mao@intel.com>
> >
> > diff -Nruap a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
> > --- a/arch/i386/kernel/kprobes.c    2006-02-25 17:08:52.000000000 +0800
> > +++ b/arch/i386/kernel/kprobes.c    2006-03-01 10:37:50.000000000 +0800
> > @@ -463,6 +463,9 @@ int __kprobes kprobe_exceptions_notify(s
> >      struct die_args *args = (struct die_args *)data;
> >      int ret = NOTIFY_DONE;
> >
> > +    if (user_mode(args->regs))
> > +        return ret;
> > +
> >      switch (val) {
> >      case DIE_INT3:
> >          if (kprobe_handler(args->regs))
> > diff -Nruap a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
> > --- a/arch/ia64/kernel/kprobes.c    2006-02-25 17:08:53.000000000 +0800
> > +++ b/arch/ia64/kernel/kprobes.c    2006-03-01 10:39:15.000000000 +0800
> > @@ -740,6 +740,9 @@ int __kprobes kprobe_exceptions_notify(s
> >      struct die_args *args = (struct die_args *)data;
> >      int ret = NOTIFY_DONE;
> >
> > +    if (user_mode(args->regs))
> > +        return ret;
> > +
> >      switch(val) {
> >      case DIE_BREAK:
> >          /* err is break number from ia64_bad_break() */
> > diff -Nruap a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> > --- a/arch/powerpc/kernel/kprobes.c    2006-02-25 17:08:52.000000000 +0800
> > +++ b/arch/powerpc/kernel/kprobes.c    2006-03-01 10:39:53.000000000 +0800
> > @@ -397,6 +397,9 @@ int __kprobes kprobe_exceptions_notify(s
> >      struct die_args *args = (struct die_args *)data;
> >      int ret = NOTIFY_DONE;
> >
> > +    if (user_mode(args->regs))
> > +        return ret;
> > +
> >      switch (val) {
> >      case DIE_BPT:
> >          if (kprobe_handler(args->regs))
> > diff -Nruap a/arch/sparc64/kernel/kprobes.c b/arch/sparc64/kernel/kprobes.c
> > --- a/arch/sparc64/kernel/kprobes.c    2006-02-25 17:08:52.000000000 +0800
> > +++ b/arch/sparc64/kernel/kprobes.c    2006-03-01 10:40:16.000000000 +0800
> > @@ -324,6 +324,9 @@ int __kprobes kprobe_exceptions_notify(s
> >      struct die_args *args = (struct die_args *)data;
> >      int ret = NOTIFY_DONE;
> >
> > +    if (user_mode(args->regs))
> > +        return ret;
> > +
> >      switch (val) {
> >      case DIE_DEBUG:
> >          if (kprobe_handler(args->regs))
> > diff -Nruap a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
> > --- a/arch/x86_64/kernel/kprobes.c    2006-02-25 17:08:52.000000000 +0800
> > +++ b/arch/x86_64/kernel/kprobes.c    2006-03-01 10:38:48.000000000 +0800
> > @@ -601,6 +601,9 @@ int __kprobes kprobe_exceptions_notify(s
> >      struct die_args *args = (struct die_args *)data;
> >      int ret = NOTIFY_DONE;
> >
> > +    if (user_mode(args->regs))
> > +        return ret;
> > +
> >      switch (val) {
> >      case DIE_INT3:
> >          if (kprobe_handler(args->regs))

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