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Adopt JmpCtxScope for setting stack walk siglongjmp protection #758

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Merged
zhengyu123 merged 1 commit into from
Aug 27, 2026
+14 −18
Merged

Adopt JmpCtxScope for setting stack walk siglongjmp protection #758

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15 changes: 7 additions & 8 deletions ddprof-lib/src/main/cpp/hotspot/hotspotSupport.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -279,7 +279,7 @@ __attribute__((no_sanitize("address"))) int HotspotSupport::walkVM(void* ucontex
// then we end up with multiple HotspotSupport::walkVM() calls on stack,
// each one sets up sigjmp_buf, they need to be chained to jump back to
// correct location.
sigjmp_buf* prev_jmp_buf = prof_thread->getJmpCtx();
JmpCtxScope jmp_scope(prof_thread);
// Should be preserved across sigsetjmp/siglongjmp
volatile int depth = 0;
int actual_max_depth = truncated ? max_depth + 1 : max_depth;
Expand All @@ -288,7 +288,7 @@ __attribute__((no_sanitize("address"))) int HotspotSupport::walkVM(void* ucontex
// checkFault() does a siglongjmp from inside segvHandler, bypassing
// segvHandler's SignalHandlerScope destructor. Compensate.
SIGNAL_HANDLER_UNWIND_AFTER_LONGJMP();
prof_thread->setJmpCtx(prev_jmp_buf);
jmp_scope.restore();
if (depth < max_depth) {
fillFrame(frames[depth++], BCI_ERROR, "break_not_walkable");
}
Expand All @@ -301,7 +301,7 @@ __attribute__((no_sanitize("address"))) int HotspotSupport::walkVM(void* ucontex
return depth;
}

prof_thread->setJmpCtx(&crash_protection_ctx);
jmp_scope.install(&crash_protection_ctx);
VMThread* vm_thread = VMThread::current();
if (vm_thread != NULL && !vm_thread->isThreadAccessible()) {
Counters::increment(WALKVM_THREAD_INACCESSIBLE);
Expand Down Expand Up @@ -991,7 +991,7 @@ __attribute__((no_sanitize("address"))) int HotspotSupport::walkVM(void* ucontex
}

done:
prof_thread->setJmpCtx(prev_jmp_buf);
jmp_scope.restore();

// Drop unknown leaf frame - it provides no useful information and breaks
// aggregation by lumping unrelated samples under a single "unknown" entry
Expand Down Expand Up @@ -1263,13 +1263,13 @@ int HotspotSupport::walkJavaStack(StackWalkRequest& request) {
}
const bool prev_unwinding_java = prof_thread->is_unwinding_Java();
sigjmp_buf crash_protection_ctx;
sigjmp_buf* prev_jmp_buf = prof_thread->getJmpCtx();
JmpCtxScope jmp_scope(prof_thread);

if (sigsetjmp(crash_protection_ctx, 1) != 0) {
// checkFault() does a siglongjmp from inside segvHandler, bypassing
// segvHandler's SignalHandlerScope destructor. Compensate.
SIGNAL_HANDLER_UNWIND_AFTER_LONGJMP();
prof_thread->setJmpCtx(prev_jmp_buf);
jmp_scope.restore();
// A recovered siglongjmp bypasses AsyncSampleMutex destructors, so restore
// the per-thread guard to its pre-walk value.
prof_thread->set_unwinding_Java(prev_unwinding_java);
Expand All @@ -1278,7 +1278,7 @@ int HotspotSupport::walkJavaStack(StackWalkRequest& request) {
}
return java_frames;
}
prof_thread->setJmpCtx(&crash_protection_ctx);
jmp_scope.install(&crash_protection_ctx);

if (features.mixed) {
java_frames = walkVM(ucontext, frames, max_depth, features, eventTypeFromBCI(request.event_type), lock_index, truncated);
Expand Down Expand Up @@ -1332,7 +1332,6 @@ int HotspotSupport::walkJavaStack(StackWalkRequest& request) {
}
}

prof_thread->setJmpCtx(prev_jmp_buf);
return java_frames;
}

Expand Down
17 changes: 7 additions & 10 deletions ddprof-lib/src/main/cpp/stackWalker.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
#include "stackWalker.inline.h"
#include "dwarf.h"
#include "faultInjection.h"
#include "guards.h"
#include "profiler.h"
#include "stackFrame.h"
#include "symbols.h"
Expand Down Expand Up @@ -52,13 +53,13 @@ int StackWalker::walkFP(void* ucontext, const void** callchain, int max_depth, S
}

sigjmp_buf crash_protection_ctx;
sigjmp_buf* prev_jmp_buf = prof_thread->getJmpCtx();
JmpCtxScope jmp_scope(prof_thread);

if (sigsetjmp(crash_protection_ctx, 1) != 0) {
// checkFault() does a siglongjmp from inside segvHandler, bypassing
// segvHandler's SignalHandlerScope destructor. Compensate.
SIGNAL_HANDLER_UNWIND_AFTER_LONGJMP();
prof_thread->setJmpCtx(prev_jmp_buf);
jmp_scope.restore();
if (truncated) {
*truncated = true;
if (depth > max_depth) {
Expand All @@ -67,7 +68,7 @@ int StackWalker::walkFP(void* ucontext, const void** callchain, int max_depth, S
}
return depth;
}
prof_thread->setJmpCtx(&crash_protection_ctx);
jmp_scope.install(&crash_protection_ctx);

// Walk until the bottom of the stack or until the first Java frame
while (depth < actual_max_depth) {
Expand Down Expand Up @@ -98,8 +99,6 @@ int StackWalker::walkFP(void* ucontext, const void** callchain, int max_depth, S
fp = (uintptr_t)SafeAccess::load(INJECT_FAULT_ADDRESS_LIKELY((void**)fp));
}

prof_thread->setJmpCtx(prev_jmp_buf);

if (truncated && depth > max_depth) {
*truncated = true;
depth = max_depth;
Expand Down Expand Up @@ -140,13 +139,13 @@ int StackWalker::walkDwarf(void* ucontext, const void** callchain, int max_depth
}

sigjmp_buf crash_protection_ctx;
sigjmp_buf* prev_jmp_buf = prof_thread->getJmpCtx();
JmpCtxScope jmp_scope(prof_thread);

if (sigsetjmp(crash_protection_ctx, 1) != 0) {
// checkFault() does a siglongjmp from inside segvHandler, bypassing
// segvHandler's SignalHandlerScope destructor. Compensate.
SIGNAL_HANDLER_UNWIND_AFTER_LONGJMP();
prof_thread->setJmpCtx(prev_jmp_buf);
jmp_scope.restore();
if (truncated) {
*truncated = true;
if (depth > max_depth) {
Expand All @@ -155,7 +154,7 @@ int StackWalker::walkDwarf(void* ucontext, const void** callchain, int max_depth
}
return depth;
}
prof_thread->setJmpCtx(&crash_protection_ctx);
jmp_scope.install(&crash_protection_ctx);

// Walk until the bottom of the stack or until the first Java frame
while (depth < actual_max_depth) {
Expand Down Expand Up @@ -233,8 +232,6 @@ int StackWalker::walkDwarf(void* ucontext, const void** callchain, int max_depth
}
}

prof_thread->setJmpCtx(prev_jmp_buf);

if (truncated && depth > max_depth) {
*truncated = true;
depth = max_depth;
Expand Down
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