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Subject[PATCH 3/4] perf/x86_64: get_regs_user: Simplify regs_user->abi setting code
Date
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: Jiri Olsa <jolsa@redhat.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Paul Mackerras <paulus@samba.org>
CC: Ingo Molnar <mingo@redhat.com>
CC: Arnaldo Carvalho de Melo <acme@kernel.org>
CC: x86@kernel.org
CC: linux-kernel@vger.kernel.org
---
arch/x86/kernel/perf_regs.c | 18 ++----------------
1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c
index a8d4e48..8157d39 100644
--- a/arch/x86/kernel/perf_regs.c
+++ b/arch/x86/kernel/perf_regs.c
@@ -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;
}
--
1.8.1.4


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