Advertise pointer authentication support to GDB

src/ExtraRegisters.cc

@@ -275,6 +275,21 @@ size_t ExtraRegisters::read_register(uint8_t* buf, GdbServerRegister regno,
     } else if (regno == DREG_FPCR) {
       reg_data = RegData(offsetof(ARM64Arch::user_fpsimd_state, fpcr),
                          sizeof(uint32_t));
+#ifdef __aarch64__
+    } else if (regno == DREG_PAUTH_DMASK || regno == DREG_PAUTH_CMASK) {
+      uint64_t ptr = 1ULL << 55;
+      // The XPAC instruction will copy bit 55 of the argument into the PAC mask
+      // bits, so ptr will be set to the mask plus bit 55.
+      if (regno == DREG_PAUTH_DMASK) {
+        __asm__ __volatile__("xpacd %0" : "+r"(ptr));
+      } else {
+        __asm__ __volatile__("xpaci %0" : "+r"(ptr));
+      }
+      uint64_t mask = ptr & ~(1ULL << 55);
+      *defined = true;
+      memcpy(buf, &mask, sizeof(mask));
+      return sizeof(mask);
+#endif
     } else {
       *defined = false;
       return 0;

src/GdbServer.cc

@@ -2332,6 +2332,7 @@ const vector<GdbServerRegister>& GdbServer::target_registers(
   bool have_PKU = dbg->cpu_features() & GdbServerConnection::CPU_PKU;
   bool have_AVX = dbg->cpu_features() & GdbServerConnection::CPU_AVX;
   bool have_AVX512 = dbg->cpu_features() & GdbServerConnection::CPU_AVX512;
+  bool have_PAUTH = dbg->cpu_features() & GdbServerConnection::CPU_PAUTH;
   switch (arch) {
     case x86: {
       add_range(GdbServerRegister(0), GdbServerRegister(DREG_ORIG_EAX));
@@ -2368,7 +2369,11 @@ const vector<GdbServerRegister>& GdbServer::target_registers(
     }
     case aarch64:
       add_range(GdbServerRegister::DREG_X0,
-                GdbServerRegister::DREG_NUM_LINUX_AARCH64);
+                GdbServerRegister::DREG_FPCR);
+      if (have_PAUTH) {
+        register_description.push_back(DREG_PAUTH_DMASK);
+        register_description.push_back(DREG_PAUTH_CMASK);
+      }
       break;
     default:
       FATAL() << "Unknown architecture";

src/GdbServerConnection.cc

@@ -18,6 +18,7 @@
 #include <poll.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <sys/auxv.h>
 #include <sys/mman.h>
 #include <sys/socket.h>
 #include <sys/types.h>
@@ -32,6 +33,7 @@
 #include "ScopedFd.h"
 #include "TargetDescription.h"
 #include "core.h"
+#include "kernel_supplement.h"
 #include "log.h"
 
 using namespace std;
@@ -106,6 +108,11 @@ static uint32_t get_cpu_features(SupportedArch arch) {
     }
     case aarch64:
       cpu_features = GdbServerConnection::CPU_AARCH64;
+#ifdef __aarch64__
+      if (getauxval(AT_HWCAP) & HWCAP_PACA) {
+        cpu_features |= GdbServerConnection::CPU_PAUTH;
+      }
+#endif
       break;
     default:
       FATAL() << "Unknown architecture";

src/GdbServerConnection.h

@@ -752,7 +752,8 @@ class GdbServerConnection {
     CPU_AVX = 1 << 1,
     CPU_AARCH64 = 1 << 2,
     CPU_PKU = 1 << 3,
-    CPU_AVX512 = 1 << 4
+    CPU_AVX512 = 1 << 4,
+    CPU_PAUTH = 1 << 5
   };
 
   void set_cpu_features(SupportedArch arch);

src/GdbServerRegister.h

@@ -320,7 +320,11 @@ enum GdbServerRegister {
   DREG_FPSR,
   DREG_FPCR,
 
-  DREG_NUM_LINUX_AARCH64 = DREG_FPCR + 1,
+  // aarch64-pauth.xml
+  DREG_PAUTH_DMASK,
+  DREG_PAUTH_CMASK,
+
+  DREG_NUM_LINUX_AARCH64,
 };
 
 } // namespace rr

src/TargetDescription.cc

@@ -78,6 +78,9 @@ FeatureStream& operator<<(FeatureStream& stream, TargetFeature feature) {
     case TargetFeature::FPU:
       stream << "fpu.xml";
       break;
+    case TargetFeature::PAuth:
+      stream << "pauth.xml";
+      break;
   }
   stream << R"("/>)" << '\n';
   return stream;
@@ -103,6 +106,9 @@ TargetDescription::TargetDescription(rr::SupportedArch arch,
     case rr::aarch64:
       target_features.push_back(TargetFeature::Core);
       target_features.push_back(TargetFeature::FPU);
+      if (cpu_features & rr::GdbServerConnection::CPU_PAUTH) {
+        target_features.push_back(TargetFeature::PAuth);
+      }
       break;
   }
 

src/TargetDescription.h

@@ -20,6 +20,7 @@ enum class TargetFeature : uint32_t {
   AVX512,
   PKeys,
   FPU,
+  PAuth,
 };
 
 class TargetDescription {

src/kernel_supplement.h

@@ -148,6 +148,10 @@ enum _ptrace_get_syscall_info_op {
 #define NT_ARM_PACG_KEYS 0x408
 #endif
 
+#ifndef HWCAP_PACA
+#define HWCAP_PACA (1 << 30)
+#endif
+
 // These are defined by the include/linux/errno.h in the kernel tree.
 // Since userspace doesn't see these errnos in normal operation, that
 // header apparently isn't distributed with libc.