linux-kernel - [tip: perf/core] x86/kprobes: Drop removed INT3 handling code

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Date:   Sat, 07 Jan 2023 11:36:24 -0000
From:   "tip-bot2 for Masami Hiramatsu (Google)" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/core] x86/kprobes: Drop removed INT3 handling code

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     8e791f7eba4c7711f56616ae163ee3cbc00b1bf4
Gitweb:        https://git.kernel.org/tip/8e791f7eba4c7711f56616ae163ee3cbc00b1bf4
Author:        Masami Hiramatsu (Google) <mhiramat@...nel.org>
AuthorDate:    Wed, 30 Nov 2022 22:33:09 +09:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Sat, 07 Jan 2023 12:29:08 +01:00

x86/kprobes: Drop removed INT3 handling code

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 5c02ece81848d
("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@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Link: https://lore.kernel.org/r/166981518895.1131462.4693062055762912734.stgit@devnote3
---
 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 6629968..33390ed 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;