1 files changed, 10 insertions, 30 deletions

diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c
index 781861cc5ee8..da8cb987b973 100644
--- 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;
 }