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jprobes: make jprobes a little safer for users

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I realise jprobes are a razor-blades-included type of interface, but that
doesn't mean we can't try and make them safer to use.  This guy I know once
wrote code like this:

struct jprobe jp = { .kp.symbol_name = "foo", .entry = "jprobe_foo" };

And then his kernel exploded. Oops.

This patch adds an arch hook, arch_deref_entry_point() (I don't like it
either) which takes the void * in a struct jprobe, and gives back the text
address that it represents.

We can then use that in register_jprobe() to check that the entry point we're
passed is actually in the kernel text, rather than just some random value.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michael Ellerman
2007-07-19 01:48:11 -07:00
committed by Linus Torvalds
parent 9e367d8592
commit 3d7e33825d
4 changed files with 24 additions and 4 deletions
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11
arch/powerpc/kernel/kprobes.c
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@@ -492,6 +492,13 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
return ret;
}
#ifdef CONFIG_PPC64
unsigned long arch_deref_entry_point(void *entry)
{
return (unsigned long)(((func_descr_t *)entry)->entry);
}
#endif
int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
struct jprobe *jp = container_of(p, struct jprobe, kp);
@@ -500,11 +507,9 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
/* setup return addr to the jprobe handler routine */
regs->nip = arch_deref_entry_point(jp->entry);
#ifdef CONFIG_PPC64
regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
#else
regs->nip = (unsigned long)jp->entry;
#endif
return 1;