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perf/x86/64: Simplify regs_user->abi setting code in get_regs_user()

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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>
This commit is contained in:
Denys Vlasenko 2015-04-10 15:06:58 +02:00 committed by Ingo Molnar
parent 5df71b396b
commit 32caa06091
1 changed files with 2 additions and 16 deletions
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18
arch/x86/kernel/perf_regs.c
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@ -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->abi = user_64bit_mode(user_regs) ?
PERF_SAMPLE_REGS_ABI_64 : PERF_SAMPLE_REGS_ABI_32;
regs_user->regs = regs_user_copy;
}