From 8e791f7eba4c7711f56616ae163ee3cbc00b1bf4 Mon Sep 17 00:00:00 2001 From: "Masami Hiramatsu (Google)" Date: Wed, 30 Nov 2022 22:33:09 +0900 Subject: [PATCH] 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) Signed-off-by: Ingo Molnar Reviewed-by: Steven Rostedt (Google) 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; -- 2.7.4