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SOS: read macOS arm64 thread metadata from a valid address #5953

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Merged
max-charlamb merged 3 commits into from
Aug 10, 2026
Merged

SOS: read macOS arm64 thread metadata from a valid address #5953

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bd015d7
SOS: read arm64 thread info from a 47-bit address
max-charlamb Aug 6, 2026
c7ae442
SOS: align arm64 thread info address
max-charlamb Aug 6, 2026
55bc898
Address PR review feedback
max-charlamb Aug 7, 2026
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9 changes: 9 additions & 0 deletions src/SOS/inc/specialthreadinfo.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,16 @@

#define SPECIAL_THREADINFO_SIGNATURE "THREADINFO"

#if defined(HOST_ARM64) || defined(__arm64__) || defined(__aarch64__)
// Apple Silicon (arm64) macOS user-space VM is 47 bits. lldb's core reader
// rejects segments above 0x7FFF_FFFF_FFFF, so use a 47-bit-valid address.
// The legacy address is still probed for dumps produced by older createdump binaries.
const uint64_t SpecialThreadInfoAddress = 0x00007ffffff00000;
const uint64_t SpecialThreadInfoLegacyAddress = 0x7fffffff00000000;
#else
const uint64_t SpecialThreadInfoAddress = 0x7fffffff00000000;
const uint64_t SpecialThreadInfoLegacyAddress = 0x7fffffff00000000;
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#endif

struct SpecialThreadInfoHeader
{
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14 changes: 12 additions & 2 deletions src/SOS/lldbplugin/services.cpp
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Expand Up @@ -2756,7 +2756,17 @@ LLDBServices::InitializeThreadInfo(lldb::SBProcess process)
}
SpecialThreadInfoHeader header;
lldb::SBError error;
size_t read = process.ReadMemory(SpecialThreadInfoAddress, &header, sizeof(SpecialThreadInfoHeader), error);
uint64_t threadInfoAddress = SpecialThreadInfoAddress;
size_t read = process.ReadMemory(threadInfoAddress, &header, sizeof(SpecialThreadInfoHeader), error);
if ((error.Fail() || read != sizeof(header) ||
strncmp(header.signature, SPECIAL_THREADINFO_SIGNATURE, sizeof(SPECIAL_THREADINFO_SIGNATURE)) != 0)
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max-charlamb marked this conversation as resolved.
&& SpecialThreadInfoAddress != SpecialThreadInfoLegacyAddress)
{
// Fall back to the legacy address for dumps produced by older createdump binaries.
error.Clear();
threadInfoAddress = SpecialThreadInfoLegacyAddress;
read = process.ReadMemory(threadInfoAddress, &header, sizeof(SpecialThreadInfoHeader), error);
}
if (error.Fail() || read != sizeof(header))
{
return;
Expand All @@ -2775,7 +2785,7 @@ LLDBServices::InitializeThreadInfo(lldb::SBProcess process)
m_processId = header.pid;
m_threadInfos.clear();

uint64_t address = SpecialThreadInfoAddress + sizeof(header);
uint64_t address = threadInfoAddress + sizeof(header);
for (int index = 0; index < number; index++)
{
SpecialThreadInfoEntry entry;
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