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Merged
mchoo7 merged 9 commits into from
Feb 18, 2026
Merged

[lldb][Process/FreeBSDKernel] Fix broken debugging on aarch64 #180222

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cdb644c
[lldb][Process/FreeBSDKernel] Fix broken debugging on aarch64
mchoo7 Feb 6, 2026
11882f4
fixup! [lldb][Process/FreeBSDKernel] Fix broken debugging on aarch64
mchoo7 Feb 6, 2026
1798331
fixup! [lldb][Process/FreeBSDKernel] Fix broken debugging on aarch64
mchoo7 Feb 9, 2026
4e0d1c9
fixup! [lldb][Process/FreeBSDKernel] Fix broken debugging on aarch64
mchoo7 Feb 12, 2026
ad34bcf
Merge branch 'main' into arm
mchoo7 Feb 12, 2026
b242e6a
fixup! [lldb][Process/FreeBSDKernel] Fix broken debugging on aarch64
mchoo7 Feb 12, 2026
cfe96c0
fixup! [lldb][Process/FreeBSDKernel] Fix broken debugging on aarch64
mchoo7 Feb 12, 2026
a5ab620
fixup! [lldb][Process/FreeBSDKernel] Fix broken debugging on aarch64
mchoo7 Feb 18, 2026
d25eb3c
fixup! [lldb][Process/FreeBSDKernel] Fix broken debugging on aarch64
mchoo7 Feb 18, 2026
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192 changes: 142 additions & 50 deletions lldb/source/Plugins/Process/FreeBSDKernel/RegisterContextFreeBSDKernel_arm64.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,8 +9,12 @@
#include "RegisterContextFreeBSDKernel_arm64.h"
#include "Plugins/Process/Utility/lldb-arm64-register-enums.h"

#include "lldb/Symbol/Symbol.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/Thread.h"
#include "lldb/Utility/LLDBLog.h"
#include "lldb/Utility/Log.h"
#include "lldb/Utility/RegisterValue.h"
#include "llvm/Support/Endian.h"

Expand Down Expand Up @@ -43,64 +47,120 @@ bool RegisterContextFreeBSDKernel_arm64::ReadRegister(
return false;

// https://cgit.freebsd.org/src/tree/sys/arm64/include/pcb.h
struct {
llvm::support::ulittle64_t x[12];
llvm::support::ulittle64_t sp;
} pcb;

// https://cgit.freebsd.org/src/tree/sys/arm64/include/pcb.h?h=stable%2F13
struct {
llvm::support::ulittle64_t x[30];
llvm::support::ulittle64_t lr;
llvm::support::ulittle64_t _reserved;
llvm::support::ulittle64_t sp;
} pcb;
} pcb13;

Status error;
size_t rd =
m_thread.GetProcess()->ReadMemory(m_pcb_addr, &pcb, sizeof(pcb), error);
if (rd != sizeof(pcb))
return false;
constexpr int FBSD14 = 1400084;
int osreldate = FBSD14;

uint32_t reg = reg_info->kinds[lldb::eRegisterKindLLDB];
switch (reg) {
case gpr_x0_arm64:
case gpr_x1_arm64:
case gpr_x2_arm64:
case gpr_x3_arm64:
case gpr_x4_arm64:
case gpr_x5_arm64:
case gpr_x6_arm64:
case gpr_x7_arm64:
case gpr_x8_arm64:
case gpr_x9_arm64:
case gpr_x10_arm64:
case gpr_x11_arm64:
case gpr_x12_arm64:
case gpr_x13_arm64:
case gpr_x14_arm64:
case gpr_x15_arm64:
case gpr_x16_arm64:
case gpr_x17_arm64:
case gpr_x18_arm64:
case gpr_x19_arm64:
case gpr_x20_arm64:
case gpr_x21_arm64:
case gpr_x22_arm64:
case gpr_x23_arm64:
case gpr_x24_arm64:
case gpr_x25_arm64:
case gpr_x26_arm64:
case gpr_x27_arm64:
case gpr_x28_arm64:
case gpr_fp_arm64:
static_assert(gpr_fp_arm64 - gpr_x0_arm64 == 29,
"nonconsecutive arm64 register numbers");
value = pcb.x[reg - gpr_x0_arm64];
break;
case gpr_sp_arm64:
value = pcb.sp;
break;
case gpr_pc_arm64:
// The pc of crashing thread is stored in lr.
value = pcb.lr;
break;
default:
return false;
if (auto osreldate_or_null = GetOsreldate())
osreldate = *osreldate_or_null;
else
LLDB_LOGF(GetLog(LLDBLog::Object),
"Cannot find osreldate. Defaulting to %d.", FBSD14);

// TODO: LLVM 24: Remove FreeBSD 13 support
if (osreldate >= FBSD14) {
constexpr uint32_t PCB_FP = 10;
constexpr uint32_t PCB_LR = 11;
size_t rd =
m_thread.GetProcess()->ReadMemory(m_pcb_addr, &pcb, sizeof(pcb), error);
if (rd != sizeof(pcb))
return false;

uint32_t reg = reg_info->kinds[lldb::eRegisterKindLLDB];
switch (reg) {
case gpr_x19_arm64:
case gpr_x20_arm64:
case gpr_x21_arm64:
case gpr_x22_arm64:
case gpr_x23_arm64:
case gpr_x24_arm64:
case gpr_x25_arm64:
case gpr_x26_arm64:
case gpr_x27_arm64:
case gpr_x28_arm64:
case gpr_fp_arm64:
static_assert(gpr_fp_arm64 - gpr_x19_arm64 == PCB_FP,
"nonconsecutive arm64 register numbers");
value = pcb.x[reg - gpr_x19_arm64];
break;
case gpr_lr_arm64:
case gpr_pc_arm64:
// The pc of crashing thread is stored in lr.
static_assert(gpr_lr_arm64 - gpr_x19_arm64 == PCB_LR,
"nonconsecutive arm64 register numbers");
value = pcb.x[reg - gpr_x19_arm64];
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@jrtc27 jrtc27 Feb 28, 2026

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This does the wrong thing for gpr_pc_arm64, it's one past the end, so reads sp. Presumably this is meant to be always gpr_lr_arm64 - gpr_x19_arm64, i.e. PCB_LR?

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@mchoo7 mchoo7 Feb 28, 2026

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I created fix for this at #183947

break;
case gpr_sp_arm64:
value = pcb.sp;
break;
default:
return false;
}
} else {
size_t rd = m_thread.GetProcess()->ReadMemory(m_pcb_addr, &pcb13,
sizeof(pcb13), error);
if (rd != sizeof(pcb13))
return false;

uint32_t reg = reg_info->kinds[lldb::eRegisterKindLLDB];
switch (reg) {
case gpr_x0_arm64:
case gpr_x1_arm64:
case gpr_x2_arm64:
case gpr_x3_arm64:
case gpr_x4_arm64:
case gpr_x5_arm64:
case gpr_x6_arm64:
case gpr_x7_arm64:
case gpr_x8_arm64:
case gpr_x9_arm64:
case gpr_x10_arm64:
case gpr_x11_arm64:
case gpr_x12_arm64:
case gpr_x13_arm64:
case gpr_x14_arm64:
case gpr_x15_arm64:
case gpr_x16_arm64:
case gpr_x17_arm64:
case gpr_x18_arm64:
case gpr_x19_arm64:
case gpr_x20_arm64:
case gpr_x21_arm64:
case gpr_x22_arm64:
case gpr_x23_arm64:
case gpr_x24_arm64:
case gpr_x25_arm64:
case gpr_x26_arm64:
case gpr_x27_arm64:
case gpr_x28_arm64:
case gpr_fp_arm64:
static_assert(gpr_fp_arm64 - gpr_x0_arm64 == 29,
"nonconsecutive arm64 register numbers");
value = pcb13.x[reg - gpr_x0_arm64];
break;
case gpr_sp_arm64:
value = pcb13.sp;
break;
case gpr_pc_arm64:
// The pc of crashing thread is stored in lr.
value = pcb13.lr;
break;
default:
return false;
}
}
return true;
}
Expand All @@ -109,3 +169,35 @@ bool RegisterContextFreeBSDKernel_arm64::WriteRegister(
const RegisterInfo *reg_info, const RegisterValue &value) {
return false;
}

std::optional<int> RegisterContextFreeBSDKernel_arm64::GetOsreldate() {
ProcessSP process_sp = m_thread.GetProcess();
if (!process_sp)
return std::nullopt;

Target &target = process_sp->GetTarget();

SymbolContextList sc_list;
target.GetImages().FindSymbolsWithNameAndType(ConstString("osreldate"),
lldb::eSymbolTypeData, sc_list);
if (sc_list.GetSize() == 0)
return std::nullopt;

SymbolContext sc;
sc_list.GetContextAtIndex(0, sc);
if (!sc.symbol)
return std::nullopt;

lldb::addr_t addr = sc.symbol->GetLoadAddress(&target);
if (addr == LLDB_INVALID_ADDRESS)
return std::nullopt;

Status error;
int osreldate = 0;
size_t bytes_read =
process_sp->ReadMemory(addr, &osreldate, sizeof(osreldate), error);
if (bytes_read == sizeof(osreldate) && error.Success())
return osreldate;

return std::nullopt;
}
4 changes: 4 additions & 0 deletions lldb/source/Plugins/Process/FreeBSDKernel/RegisterContextFreeBSDKernel_arm64.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,8 @@
#include "Plugins/Process/Utility/RegisterContextPOSIX_arm64.h"
#include "Plugins/Process/elf-core/RegisterUtilities.h"

#include <optional>

class RegisterContextFreeBSDKernel_arm64 : public RegisterContextPOSIX_arm64 {
public:
RegisterContextFreeBSDKernel_arm64(
Expand All @@ -36,6 +38,8 @@ class RegisterContextFreeBSDKernel_arm64 : public RegisterContextPOSIX_arm64 {

private:
lldb::addr_t m_pcb_addr;

std::optional<int> GetOsreldate();
};

#endif // LLDB_SOURCE_PLUGINS_PROCESS_FREEBSDKERNEL_REGISTERCONTEXTFREEBSDKERNEL_ARM64_H