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x86/kprobes: Drop removed INT3 handling code

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Drop removed INT3 handling code from kprobe_int3_handler() because this
case (get_kprobe() doesn't return corresponding kprobe AND the INT3 is
removed) must not happen with the kprobe managed INT3, but can happen
with the non-kprobe INT3, which should be handled by other callbacks.

For the kprobe managed INT3, it is already safe. The commit 5c02ece818
("x86/kprobes: Fix ordering while text-patching") introduced
text_poke_sync() to the arch_disarm_kprobe() right after removing INT3.
Since this text_poke_sync() uses IPI to call sync_core() on all online
cpus, that ensures that all running INT3 exception handlers have done.
And, the unregister_kprobe() will remove the kprobe from the hash table
after arch_disarm_kprobe().

Thus, when the kprobe managed INT3 hits, kprobe_int3_handler() should
be able to find corresponding kprobe always by get_kprobe(). If it can
not find any kprobe, this means that is NOT a kprobe managed INT3.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/166981518895.1131462.4693062055762912734.stgit@devnote3
This commit is contained in:
Masami Hiramatsu (Google) 2022-11-30 22:33:09 +09:00 committed by Ingo Molnar
parent 03c4c7f887
commit 8e791f7eba
1 changed files with 0 additions and 14 deletions
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14
arch/x86/kernel/kprobes/core.c
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@ -986,20 +986,6 @@ int kprobe_int3_handler(struct pt_regs *regs)
kprobe_post_process(p, regs, kcb);
return 1;
}
}
if (*addr != INT3_INSN_OPCODE) {
/*
* The breakpoint instruction was removed right
* after we hit it. Another cpu has removed
* either a probepoint or a debugger breakpoint
* at this address. In either case, no further
* handling of this interrupt is appropriate.
* Back up over the (now missing) int3 and run
* the original instruction.
*/
regs->ip = (unsigned long)addr;
return 1;
} /* else: not a kprobe fault; let the kernel handle it */
return 0;