perf/x86/64: Report regs_user->ax too in get_regs_user()

[mirror_ubuntu-artful-kernel.git] / arch / x86 / kernel / perf_regs.c

diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c
index 781861cc5ee8d7b9bbd27e9b13c380da59bb06c0..da8cb987b97312f6b37b5a967ce70fc5e75e0205 100644 (file)
--- a/arch/x86/kernel/perf_regs.c
+++ b/arch/x86/kernel/perf_regs.c
@@ -131,10 +131,11 @@ 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->ax = user_regs->ax;
        regs_user_copy->cx = user_regs->cx;
        regs_user_copy->dx = user_regs->dx;
        regs_user_copy->si = user_regs->si;
@@ -145,9 +146,12 @@ 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;
@@ -158,37 +162,13 @@ 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.
         */
-       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;
-               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.
-                * 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;
-               regs_user_copy->sp = this_cpu_read(old_rsp);
-               regs_user_copy->cs = __USER_CS;
-               regs_user_copy->ss = __USER_DS;
-               regs_user_copy->cx = -1;  /* usually contains garbage */
-       } 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->abi = user_64bit_mode(user_regs) ?
+               PERF_SAMPLE_REGS_ABI_64 : PERF_SAMPLE_REGS_ABI_32;
 
        regs_user->regs = regs_user_copy;
 }