[compiler-rt] r277124 - [compiler-rt][XRay] Address follow-up comments to initial interface and initialisation code
Dean Michael Berris via llvm-commits
llvm-commits at lists.llvm.org
Fri Jul 29 00:11:59 PDT 2016
Author: dberris
Date: Fri Jul 29 02:11:58 2016
New Revision: 277124
URL: http://llvm.org/viewvc/llvm-project?rev=277124&view=rev
Log:
[compiler-rt][XRay] Address follow-up comments to initial interface and initialisation code
This addresses some comments from D21612, which contains the following changes:
- Update __xray_patch() and __xray_unpatch() API documentation to not imply asynchrony.
- Introduce a scope cleanup mechanism to make sure we can roll-back changes to the XRayPatching global atomic.
- Introduce a few more comments for potential extension points for other platforms (for the implementation details of patching and un-patching).
Reviewers: eugenis, rnk, kcc, echristo, majnemer
Subscribers: llvm-commits, mehdi_amini
Differential Revision: https://reviews.llvm.org/D22911
Modified:
compiler-rt/trunk/include/xray/xray_interface.h
compiler-rt/trunk/lib/xray/xray_init.cc
compiler-rt/trunk/lib/xray/xray_interface.cc
Modified: compiler-rt/trunk/include/xray/xray_interface.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/include/xray/xray_interface.h?rev=277124&r1=277123&r2=277124&view=diff
==============================================================================
--- compiler-rt/trunk/include/xray/xray_interface.h (original)
+++ compiler-rt/trunk/include/xray/xray_interface.h Fri Jul 29 02:11:58 2016
@@ -41,26 +41,18 @@ extern int __xray_remove_handler();
enum XRayPatchingStatus {
NOT_INITIALIZED = 0,
- NOTIFIED = 1,
+ SUCCESS = 1,
ONGOING = 2,
- FAILED = 3
+ FAILED = 3,
};
-// This tells XRay to patch the instrumentation points. This is an asynchronous
-// process, and returns the following status in specific cases:
-//
-// - 0 : XRay is not initialized.
-// - 1 : We've done the notification.
-// - 2 : Patching / un-patching is on-going.
+// This tells XRay to patch the instrumentation points. See XRayPatchingStatus
+// for possible result values.
extern XRayPatchingStatus __xray_patch();
-// Reverses the effect of __xray_patch(). This is an asynchronous process, and
-// returns the following status in specific cases.
-//
-// - 0 : XRay is not initialized.
-// - 1 : We've done the notification.
-// - 2 : Patching / un-patching is on-going.
-extern int __xray_unpatch();
+// Reverses the effect of __xray_patch(). See XRayPatchingStatus for possible
+// result values.
+extern XRayPatchingStatus __xray_unpatch();
}
#endif
Modified: compiler-rt/trunk/lib/xray/xray_init.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/xray/xray_init.cc?rev=277124&r1=277123&r2=277124&view=diff
==============================================================================
--- compiler-rt/trunk/lib/xray/xray_init.cc (original)
+++ compiler-rt/trunk/lib/xray/xray_init.cc Fri Jul 29 02:11:58 2016
@@ -22,18 +22,20 @@
#include "xray_interface_internal.h"
extern "C" {
-extern void __xray_init();
+void __xray_init();
extern const XRaySledEntry __start_xray_instr_map[] __attribute__((weak));
extern const XRaySledEntry __stop_xray_instr_map[] __attribute__((weak));
}
using namespace __xray;
-// We initialize some global variables that pertain to specific sections of XRay
-// data structures in the binary. We do this for the current process using
-// /proc/curproc/map and make sure that we're able to get it. We signal failure
-// via a global atomic boolean to indicate whether we've initialized properly.
+// When set to 'true' this means the XRay runtime has been initialised. We use
+// the weak symbols defined above (__start_xray_inst_map and
+// __stop_xray_instr_map) to initialise the instrumentation map that XRay uses
+// for runtime patching/unpatching of instrumentation points.
//
+// FIXME: Support DSO instrumentation maps too. The current solution only works
+// for statically linked executables.
std::atomic<bool> XRayInitialized{false};
// This should always be updated before XRayInitialized is updated.
Modified: compiler-rt/trunk/lib/xray/xray_interface.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/xray/xray_interface.cc?rev=277124&r1=277123&r2=277124&view=diff
==============================================================================
--- compiler-rt/trunk/lib/xray/xray_interface.cc (original)
+++ compiler-rt/trunk/lib/xray/xray_interface.cc Fri Jul 29 02:11:58 2016
@@ -14,6 +14,7 @@
//===----------------------------------------------------------------------===//
#include "xray_interface_internal.h"
+
#include <atomic>
#include <cstdint>
#include <cstdio>
@@ -21,6 +22,8 @@
#include <limits>
#include <sys/mman.h>
+#include "sanitizer_common/sanitizer_common.h"
+
namespace __xray {
// This is the function to call when we encounter the entry or exit sleds.
@@ -83,8 +86,25 @@ std::atomic<bool> XRayPatching{false};
using namespace __xray;
+// FIXME: Figure out whether we can move this class to sanitizer_common instead
+// as a generic "scope guard".
+template <class Function> class CleanupInvoker {
+ Function Fn;
+
+public:
+ explicit CleanupInvoker(Function Fn) : Fn(Fn) {}
+ CleanupInvoker(const CleanupInvoker &) = default;
+ CleanupInvoker(CleanupInvoker &&) = default;
+ CleanupInvoker &operator=(const CleanupInvoker &) = delete;
+ CleanupInvoker &operator=(CleanupInvoker &&) = delete;
+ ~CleanupInvoker() { Fn(); }
+};
+
+template <class Function> CleanupInvoker<Function> ScopeCleanup(Function Fn) {
+ return CleanupInvoker<Function>{Fn};
+}
+
XRayPatchingStatus __xray_patch() {
- // FIXME: Make this happen asynchronously. For now just do this sequentially.
if (!XRayInitialized.load(std::memory_order_acquire))
return XRayPatchingStatus::NOT_INITIALIZED; // Not initialized.
@@ -95,6 +115,13 @@ XRayPatchingStatus __xray_patch() {
return XRayPatchingStatus::ONGOING; // Already patching.
}
+ bool PatchingSuccess = false;
+ auto XRayPatchingStatusResetter = ScopeCleanup([&PatchingSuccess] {
+ if (!PatchingSuccess) {
+ XRayPatching.store(false, std::memory_order_release);
+ }
+ });
+
// Step 1: Compute the function id, as a unique identifier per function in the
// instrumentation map.
XRaySledMap InstrMap = XRayInstrMap.load(std::memory_order_acquire);
@@ -131,6 +158,7 @@ XRayPatchingStatus __xray_patch() {
static constexpr int64_t MinOffset{std::numeric_limits<int32_t>::min()};
static constexpr int64_t MaxOffset{std::numeric_limits<int32_t>::max()};
if (Sled.Kind == XRayEntryType::ENTRY) {
+ // FIXME: Implement this in a more extensible manner, per-platform.
// Here we do the dance of replacing the following sled:
//
// xray_sled_n:
@@ -157,7 +185,10 @@ XRayPatchingStatus __xray_patch() {
reinterpret_cast<int64_t>(__xray_FunctionEntry) -
(static_cast<int64_t>(Sled.Address) + 11);
if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) {
- // FIXME: Print out an error here.
+ Report("XRay Entry trampoline (%p) too far from sled (%p); distance = "
+ "%ld\n",
+ __xray_FunctionEntry, reinterpret_cast<void *>(Sled.Address),
+ TrampolineOffset);
continue;
}
*reinterpret_cast<uint32_t *>(Sled.Address + 2) = FuncId;
@@ -169,6 +200,7 @@ XRayPatchingStatus __xray_patch() {
}
if (Sled.Kind == XRayEntryType::EXIT) {
+ // FIXME: Implement this in a more extensible manner, per-platform.
// Here we do the dance of replacing the following sled:
//
// xray_sled_n:
@@ -193,7 +225,10 @@ XRayPatchingStatus __xray_patch() {
reinterpret_cast<int64_t>(__xray_FunctionExit) -
(static_cast<int64_t>(Sled.Address) + 11);
if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) {
- // FIXME: Print out an error here.
+ Report("XRay Exit trampoline (%p) too far from sled (%p); distance = "
+ "%ld\n",
+ __xray_FunctionExit, reinterpret_cast<void *>(Sled.Address),
+ TrampolineOffset);
continue;
}
*reinterpret_cast<uint32_t *>(Sled.Address + 2) = FuncId;
@@ -205,5 +240,6 @@ XRayPatchingStatus __xray_patch() {
}
}
XRayPatching.store(false, std::memory_order_release);
- return XRayPatchingStatus::NOTIFIED;
+ PatchingSuccess = true;
+ return XRayPatchingStatus::SUCCESS;
}
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