perf/x86/64: Simplify regs_user->abi setting code in get_regs_user() (32caa060) · Commits · 戴 / test

user_64bit_mode(regs) basically checks regs->cs to point to a 64-bit segment. This check used to be unreliable here because regs->cs was not always correct in syscalls. Now regs->cs is always correct: in syscalls, in interrupts, in exceptions. No need to emply heuristics here. Signed-off-by:

Denys Vlasenko <dvlasenk@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1428671219-29341-3-git-send-email-dvlasenk@redhat.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/perf_regs.c

+2 −16

Original line number	Diff line number	Diff line
		@@ -166,22 +166,8 @@ void perf_get_regs_user(struct perf_regs *regs_user,
		* be careful not to look at any other percpu variables that might
		* change during context switches.
		*/
		if (IS_ENABLED(CONFIG_IA32_EMULATION) &&
		task_thread_info(current)->status & TS_COMPAT) {
		/* Easy case: we're in a compat syscall. */
		regs_user->abi = PERF_SAMPLE_REGS_ABI_32;
		} else if (user_regs->orig_ax != -1) {
		/*
		* We're probably in a 64-bit syscall.
		* Warning: this code is severely racy. At least it's better
		* than just blindly copying user_regs.
		*/
		regs_user->abi = PERF_SAMPLE_REGS_ABI_64;
		} else {
		/* We're probably in an interrupt or exception. */
		regs_user->abi = user_64bit_mode(user_regs) ?
		PERF_SAMPLE_REGS_ABI_64 : PERF_SAMPLE_REGS_ABI_32;
		}

		regs_user->regs = regs_user_copy;
		}

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