[XRay][compiler-rt][x86_64] Align the stack before and after calling handlers

Summary:
This change fixes the XRay trampolines aside from the __xray_CustomEvent
trampoline to align the stack to 16-byte boundaries before calling the
handler. Before this change we've not been explicitly aligning the stack
to 16-byte boundaries, which makes it dangerous when calling handlers
that leave the stack in a state that isn't strictly 16-byte aligned
after calling the handlers.

We add a test that makes sure we can handle these cases appropriately
after the changes, and prevents us from regressing the state moving
forward.

Fixes http://llvm.org/PR35294.

Reviewers: pelikan, pcc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D40004

llvm-svn: 318261

2 files changed, 79 insertions, 16 deletions

diff --git a/compiler-rt/lib/xray/xray_trampoline_x86_64.S b/compiler-rt/lib/xray/xray_trampoline_x86_64.S
index ffbfb5c7e91..33fa0e79d11 100644
--- a/compiler-rt/lib/xray/xray_trampoline_x86_64.S
+++ b/compiler-rt/lib/xray/xray_trampoline_x86_64.S
@@ -60,6 +60,20 @@
 	.cfi_def_cfa_offset 8
 .endm
 
+.macro ALIGNED_CALL_RAX
+	// Call the logging handler, after aligning the stack to a 16-byte boundary.
+	// The approach we're taking here uses additional stack space to stash the
+	// stack pointer twice before aligning the pointer to 16-bytes. If the stack
+	// was 8-byte aligned, it will become 16-byte aligned -- when restoring the
+	// pointer, we can always look -8 bytes from the current position to get
+	// either of the values we've stashed in the first place.
+	pushq %rsp
+	pushq (%rsp)
+	andq $-0x10, %rsp
+  callq *%rax
+	movq 8(%rsp), %rsp
+.endm
+
 	.text
 	.file "xray_trampoline_x86.S"
 
@@ -82,7 +96,8 @@ __xray_FunctionEntry:
 	// The patched function prolog puts its xray_instr_map index into %r10d.
 	movl	%r10d, %edi
 	xor	%esi,%esi
-	callq	*%rax
+	ALIGNED_CALL_RAX
+
 .Ltmp0:
 	RESTORE_REGISTERS
 	retq
@@ -113,7 +128,8 @@ __xray_FunctionExit:
 
 	movl	%r10d, %edi
 	movl	$1, %esi
-	callq	*%rax
+  ALIGNED_CALL_RAX
+
 .Ltmp2:
 	// Restore the important registers.
 	movq  48(%rsp), %rbp
@@ -143,7 +159,8 @@ __xray_FunctionTailExit:
 
 	movl	%r10d, %edi
 	movl	$2, %esi
-	callq	*%rax
+
+  ALIGNED_CALL_RAX
 
 .Ltmp4:
 	RESTORE_REGISTERS
@@ -181,7 +198,7 @@ __xray_ArgLoggerEntry:
 
 	// 32-bit function ID becomes the first
 	movl	%r10d, %edi
-	callq	*%rax
+	ALIGNED_CALL_RAX
 
 .Larg1entryFail:
 	RESTORE_REGISTERS
@@ -207,18 +224,7 @@ __xray_CustomEvent:
 	testq %rax,%rax
 	je .LcustomEventCleanup
 
-	// At this point we know that rcx and rdx already has the data, so we just
-	// call the logging handler, after aligning the stack to a 16-byte boundary.
-	// The approach we're taking here uses additional stack space to stash the
-	// stack pointer twice before aligning the pointer to 16-bytes. If the stack
-	// was 8-byte aligned, it will become 16-byte aligned -- when restoring the
-	// pointer, we can always look -8 bytes from the current position to get
-	// either of the values we've stashed in the first place.
-	pushq %rsp
-	pushq (%rsp)
-	andq $-0x10, %rsp
-  callq *%rax
-	movq 8(%rsp), %rsp
+	ALIGNED_CALL_RAX
 
 .LcustomEventCleanup:
 	RESTORE_REGISTERS
diff --git a/compiler-rt/test/xray/TestCases/Linux/common-trampoline-alignment.cc b/compiler-rt/test/xray/TestCases/Linux/common-trampoline-alignment.cc
new file mode 100644
index 00000000000..5d1cc1e9b45
--- /dev/null
+++ b/compiler-rt/test/xray/TestCases/Linux/common-trampoline-alignment.cc
@@ -0,0 +1,57 @@
+// Make sure that we're aligning the stack properly to support handlers that
+// expect 16-byte alignment of the stack.
+//
+// RUN: %clangxx_xray -std=c++11 %s -o %t
+// RUN: XRAY_OPTIONS="patch_premain=false verbosity=1 xray_naive_log=false" \
+// RUN:     %run %t 2>&1
+// REQUIRES: x86_64-linux
+// REQUIRES: built-in-llvm-tree
+#include "xray/xray_interface.h"
+#include <stdio.h>
+#include <xmmintrin.h>
+
+[[clang::xray_never_instrument]] __attribute__((weak)) __m128 f(__m128 *i) {
+  return *i;
+}
+
+[[clang::xray_always_instrument]] __attribute__((noinline)) void noarg() {
+  __m128 v = {};
+  f(&v);
+}
+
+[[ clang::xray_always_instrument, clang::xray_log_args(1) ]]
+__attribute__((noinline)) void arg1(int) {
+  __m128 v = {};
+  f(&v);
+}
+
+[[clang::xray_always_instrument]] __attribute__((noinline))
+void no_alignment() {}
+
+[[clang::xray_never_instrument]] void noarg_handler(int32_t,
+                                                        XRayEntryType) {
+  printf("noarg handler called\n");
+  __m128 v = {};
+  f(&v);
+}
+
+[[clang::xray_never_instrument]] void arg1_handler(int32_t, XRayEntryType,
+                                                   uint64_t) {
+  printf("arg1 handler called\n");
+  __m128 v = {};
+  f(&v);
+}
+
+int main(int argc, char *argv[]) {
+  __xray_set_handler(noarg_handler);
+  __xray_set_handler_arg1(arg1_handler);
+  __xray_patch();
+  noarg();    // CHECK: noarg handler called
+  arg1(argc); // CHECK: arg1 handler called
+  no_alignment();
+  __xray_unpatch();
+  __xray_remove_handler();
+  __xray_remove_handler_arg1();
+  noarg();
+  arg1(argc);
+}