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Message-Id: <166938748740.2964025.7215038423815144481.stgit@devnote3>
Date: Fri, 25 Nov 2022 23:44:47 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: x86@...nel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Peter Zijlstra <peterz@...radead.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
Huacai Chen <chenhuacai@...ngson.cn>,
Jinyang He <hejinyang@...ngson.cn>,
Tiezhu Yang <yangtiezhu@...ngson.cn>,
"Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>
Subject: [PATCH -tip] x86/kprobes: Drop removed INT3 handling code
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
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, the arch_disarm_kprobe() removes the INT3
and then calls text_poke_sync(). 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@...nel.org>
---
arch/x86/kernel/kprobes/core.c | 14 --------------
1 file changed, 14 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 66299682b6b7..33390ed4dcf3 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -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;
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