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perf/x86/64: Do not guess user_regs->cs, ss, sp in get_regs_user() 

After recent changes to syscall entry points,
user_regs->{cs,ss,sp} are always correct. (They used to be
undefined while in syscalls).

We can report them reliably, without guessing.

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/1428671219-29341-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Denys Vlasenko 2015-04-10 15:06:56 +02:00 committed by Ingo Molnar
parent 54cfa458b4
commit aa21df0424
1 changed files with 9 additions and 14 deletions
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23
arch/x86/kernel/perf_regs.c
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@ -131,8 +131,8 @@ void perf_get_regs_user(struct perf_regs *regs_user,
}
/*
* RIP, flags, and the argument registers are usually saved.
* orig_ax is probably okay, too.
* These registers are always saved on 64-bit syscall entry.
* On 32-bit entry points, they are saved too except r8..r11.
*/
regs_user_copy->ip = user_regs->ip;
regs_user_copy->cx = user_regs->cx;
@ -145,9 +145,12 @@ void perf_get_regs_user(struct perf_regs *regs_user,
regs_user_copy->r11 = user_regs->r11;
regs_user_copy->orig_ax = user_regs->orig_ax;
regs_user_copy->flags = user_regs->flags;
regs_user_copy->sp = user_regs->sp;
regs_user_copy->cs = user_regs->cs;
regs_user_copy->ss = user_regs->ss;
/*
* Don't even try to report the "rest" regs.
* Most system calls don't save these registers, don't report them.
*/
regs_user_copy->bx = -1;
regs_user_copy->bp = -1;
@ -158,7 +161,7 @@ void perf_get_regs_user(struct perf_regs *regs_user,
/*
* For this to be at all useful, we need a reasonable guess for
* sp and the ABI. Be careful: we're in NMI context, and we're
* the ABI. Be careful: we're in NMI context, and we're
* considering current to be the current task, so we should
* be careful not to look at any other percpu variables that might
* change during context switches.
@ -167,9 +170,6 @@ void perf_get_regs_user(struct perf_regs *regs_user,
task_thread_info(current)->status & TS_COMPAT) {
/* Easy case: we're in a compat syscall. */
regs_user->abi = PERF_SAMPLE_REGS_ABI_32;
regs_user_copy->sp = user_regs->sp;
regs_user_copy->cs = user_regs->cs;
regs_user_copy->ss = user_regs->ss;
} else if (user_regs->orig_ax != -1) {
/*
* We're probably in a 64-bit syscall.
@ -177,17 +177,12 @@ void perf_get_regs_user(struct perf_regs *regs_user,
* than just blindly copying user_regs.
*/
regs_user->abi = PERF_SAMPLE_REGS_ABI_64;
regs_user_copy->sp = user_regs->sp;
regs_user_copy->cs = __USER_CS;
regs_user_copy->ss = __USER_DS;
regs_user_copy->cx = -1; /* usually contains garbage */
/* usually contains return address (same as ->ip) */
regs_user_copy->cx = -1;
} 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_copy->sp = user_regs->sp;
regs_user_copy->cs = user_regs->cs;
regs_user_copy->ss = user_regs->ss;
}
regs_user->regs = regs_user_copy;