[libunwind][Haiku] Fix signal frame unwinding (#135367)

The current unwinding implementation on Haiku is messy and broken.
1. It searches weird paths for private headers, which is breaking builds
in consuming projects, such as dotnet/runtime.
2. It does not even work, due to relying on incorrect private offsets.

This commit strips all references to private headers and ports a working
signal frame implementation. It has been tested against
`tests/signal_unwind.pass.cpp` and can go pass the signal frame.

libunwind/src/CMakeLists.txt

@@ -118,22 +118,6 @@ if (HAIKU)
 
   add_compile_flags("-D_DEFAULT_SOURCE")
   add_compile_flags("-DPT_GNU_EH_FRAME=PT_EH_FRAME")
-
-  find_path(LIBUNWIND_HAIKU_PRIVATE_HEADERS
-            "commpage_defs.h"
-            PATHS ${CMAKE_SYSTEM_INCLUDE_PATH}
-            PATH_SUFFIXES "/private/system"
-            NO_DEFAULT_PATH
-            REQUIRED)
-
-  include_directories(SYSTEM "${LIBUNWIND_HAIKU_PRIVATE_HEADERS}")
-  if (LIBUNWIND_TARGET_TRIPLE)
-    if (${LIBUNWIND_TARGET_TRIPLE} MATCHES "^x86_64")
-      include_directories(SYSTEM "${LIBUNWIND_HAIKU_PRIVATE_HEADERS}/arch/x86_64")
-    endif()
-  else()
-    include_directories(SYSTEM "${LIBUNWIND_HAIKU_PRIVATE_HEADERS}/arch/${CMAKE_SYSTEM_PROCESSOR}")
-  endif()
 endif ()
 
 string(REPLACE ";" " " LIBUNWIND_COMPILE_FLAGS "${LIBUNWIND_COMPILE_FLAGS}")

libunwind/src/UnwindCursor.hpp

@@ -41,6 +41,12 @@
 #define _LIBUNWIND_CHECK_LINUX_SIGRETURN 1
 #endif
 
+#if defined(_LIBUNWIND_TARGET_HAIKU) && defined(_LIBUNWIND_TARGET_X86_64)
+#include <OS.h>
+#include <signal.h>
+#define _LIBUNWIND_CHECK_HAIKU_SIGRETURN 1
+#endif
+
 #include "AddressSpace.hpp"
 #include "CompactUnwinder.hpp"
 #include "config.h"
@@ -1031,7 +1037,7 @@ private:
   template <typename Registers> int stepThroughSigReturn(Registers &) {
     return UNW_STEP_END;
   }
-#elif defined(_LIBUNWIND_TARGET_HAIKU)
+#elif defined(_LIBUNWIND_CHECK_HAIKU_SIGRETURN)
   bool setInfoForSigReturn();
   int stepThroughSigReturn();
 #endif
@@ -2630,7 +2636,7 @@ int UnwindCursor<A, R>::stepWithTBTable(pint_t pc, tbtable *TBTable,
 template <typename A, typename R>
 void UnwindCursor<A, R>::setInfoBasedOnIPRegister(bool isReturnAddress) {
 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) ||                               \
-    defined(_LIBUNWIND_TARGET_HAIKU)
+    defined(_LIBUNWIND_CHECK_HAIKU_SIGRETURN)
   _isSigReturn = false;
 #endif
 
@@ -2755,7 +2761,7 @@ void UnwindCursor<A, R>::setInfoBasedOnIPRegister(bool isReturnAddress) {
 #endif // #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 
 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) ||                               \
-    defined(_LIBUNWIND_TARGET_HAIKU)
+    defined(_LIBUNWIND_CHECK_HAIKU_SIGRETURN)
   if (setInfoForSigReturn())
     return;
 #endif
@@ -2831,63 +2837,6 @@ int UnwindCursor<A, R>::stepThroughSigReturn(Registers_arm64 &) {
   _isSignalFrame = true;
   return UNW_STEP_SUCCESS;
 }
-
-#elif defined(_LIBUNWIND_TARGET_HAIKU) && defined(_LIBUNWIND_TARGET_X86_64)
-#include <commpage_defs.h>
-#include <signal.h>
-
-extern "C" {
-extern void *__gCommPageAddress;
-}
-
-template <typename A, typename R>
-bool UnwindCursor<A, R>::setInfoForSigReturn() {
-#if defined(_LIBUNWIND_TARGET_X86_64)
-  addr_t signal_handler =
-      (((addr_t *)__gCommPageAddress)[COMMPAGE_ENTRY_X86_SIGNAL_HANDLER] +
-       (addr_t)__gCommPageAddress);
-  addr_t signal_handler_ret = signal_handler + 45;
-#endif
-  pint_t pc = static_cast<pint_t>(this->getReg(UNW_REG_IP));
-  if (pc == signal_handler_ret) {
-    _info = {};
-    _info.start_ip = signal_handler;
-    _info.end_ip = signal_handler_ret;
-    _isSigReturn = true;
-    return true;
-  }
-  return false;
-}
-
-template <typename A, typename R>
-int UnwindCursor<A, R>::stepThroughSigReturn() {
-  _isSignalFrame = true;
-  pint_t sp = _registers.getSP();
-#if defined(_LIBUNWIND_TARGET_X86_64)
-  vregs *regs = (vregs *)(sp + 0x70);
-
-  _registers.setRegister(UNW_REG_IP, regs->rip);
-  _registers.setRegister(UNW_REG_SP, regs->rsp);
-  _registers.setRegister(UNW_X86_64_RAX, regs->rax);
-  _registers.setRegister(UNW_X86_64_RDX, regs->rdx);
-  _registers.setRegister(UNW_X86_64_RCX, regs->rcx);
-  _registers.setRegister(UNW_X86_64_RBX, regs->rbx);
-  _registers.setRegister(UNW_X86_64_RSI, regs->rsi);
-  _registers.setRegister(UNW_X86_64_RDI, regs->rdi);
-  _registers.setRegister(UNW_X86_64_RBP, regs->rbp);
-  _registers.setRegister(UNW_X86_64_R8, regs->r8);
-  _registers.setRegister(UNW_X86_64_R9, regs->r9);
-  _registers.setRegister(UNW_X86_64_R10, regs->r10);
-  _registers.setRegister(UNW_X86_64_R11, regs->r11);
-  _registers.setRegister(UNW_X86_64_R12, regs->r12);
-  _registers.setRegister(UNW_X86_64_R13, regs->r13);
-  _registers.setRegister(UNW_X86_64_R14, regs->r14);
-  _registers.setRegister(UNW_X86_64_R15, regs->r15);
-  // TODO: XMM
-#endif
-
-  return UNW_STEP_SUCCESS;
-}
 #endif // defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) &&
        // defined(_LIBUNWIND_TARGET_AARCH64)
 
@@ -3103,6 +3052,96 @@ int UnwindCursor<A, R>::stepThroughSigReturn(Registers_s390x &) {
 #endif // defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) &&
        // defined(_LIBUNWIND_TARGET_S390X)
 
+#if defined(_LIBUNWIND_CHECK_HAIKU_SIGRETURN)
+template <typename A, typename R>
+bool UnwindCursor<A, R>::setInfoForSigReturn() {
+  Dl_info dlinfo;
+  const auto isSignalHandler = [&](pint_t addr) {
+    if (!dladdr(reinterpret_cast<void *>(addr), &dlinfo))
+      return false;
+    if (strcmp(dlinfo.dli_fname, "commpage"))
+      return false;
+    if (dlinfo.dli_sname == NULL ||
+        strcmp(dlinfo.dli_sname, "commpage_signal_handler"))
+      return false;
+    return true;
+  };
+
+  pint_t pc = static_cast<pint_t>(this->getReg(UNW_REG_IP));
+  if (!isSignalHandler(pc))
+    return false;
+
+  pint_t start = reinterpret_cast<pint_t>(dlinfo.dli_saddr);
+
+  static size_t signalHandlerSize = 0;
+  if (signalHandlerSize == 0) {
+    size_t boundLow = 0;
+    size_t boundHigh = static_cast<size_t>(-1);
+
+    area_info areaInfo;
+    if (get_area_info(area_for(dlinfo.dli_saddr), &areaInfo) == B_OK)
+      boundHigh = areaInfo.size;
+
+    while (boundLow < boundHigh) {
+      size_t boundMid = boundLow + ((boundHigh - boundLow) / 2);
+      pint_t test = start + boundMid;
+      if (test >= start && isSignalHandler(test))
+        boundLow = boundMid + 1;
+      else
+        boundHigh = boundMid;
+    }
+
+    signalHandlerSize = boundHigh;
+  }
+
+  _info = {};
+  _info.start_ip = start;
+  _info.end_ip = start + signalHandlerSize;
+  _isSigReturn = true;
+
+  return true;
+}
+
+template <typename A, typename R>
+int UnwindCursor<A, R>::stepThroughSigReturn() {
+  _isSignalFrame = true;
+
+#if defined(_LIBUNWIND_TARGET_X86_64)
+  // Layout of the stack before function call:
+  // - signal_frame_data
+  //   + siginfo_t    (public struct, fairly stable)
+  //   + ucontext_t   (public struct, fairly stable)
+  //     - mcontext_t -> Offset 0x70, this is what we want.
+  // - frame->ip (8 bytes)
+  // - frame->bp (8 bytes). Not written by the kernel,
+  //   but the signal handler has a "push %rbp" instruction.
+  pint_t bp = this->getReg(UNW_X86_64_RBP);
+  vregs *regs = (vregs *)(bp + 0x70);
+
+  _registers.setRegister(UNW_REG_IP, regs->rip);
+  _registers.setRegister(UNW_REG_SP, regs->rsp);
+  _registers.setRegister(UNW_X86_64_RAX, regs->rax);
+  _registers.setRegister(UNW_X86_64_RDX, regs->rdx);
+  _registers.setRegister(UNW_X86_64_RCX, regs->rcx);
+  _registers.setRegister(UNW_X86_64_RBX, regs->rbx);
+  _registers.setRegister(UNW_X86_64_RSI, regs->rsi);
+  _registers.setRegister(UNW_X86_64_RDI, regs->rdi);
+  _registers.setRegister(UNW_X86_64_RBP, regs->rbp);
+  _registers.setRegister(UNW_X86_64_R8, regs->r8);
+  _registers.setRegister(UNW_X86_64_R9, regs->r9);
+  _registers.setRegister(UNW_X86_64_R10, regs->r10);
+  _registers.setRegister(UNW_X86_64_R11, regs->r11);
+  _registers.setRegister(UNW_X86_64_R12, regs->r12);
+  _registers.setRegister(UNW_X86_64_R13, regs->r13);
+  _registers.setRegister(UNW_X86_64_R14, regs->r14);
+  _registers.setRegister(UNW_X86_64_R15, regs->r15);
+  // TODO: XMM
+#endif // defined(_LIBUNWIND_TARGET_X86_64)
+
+  return UNW_STEP_SUCCESS;
+}
+#endif // defined(_LIBUNWIND_CHECK_HAIKU_SIGRETURN)
+
 template <typename A, typename R> int UnwindCursor<A, R>::step(bool stage2) {
   (void)stage2;
   // Bottom of stack is defined is when unwind info cannot be found.
@@ -3112,7 +3151,7 @@ template <typename A, typename R> int UnwindCursor<A, R>::step(bool stage2) {
   // Use unwinding info to modify register set as if function returned.
   int result;
 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) ||                               \
-    defined(_LIBUNWIND_TARGET_HAIKU)
+    defined(_LIBUNWIND_CHECK_HAIKU_SIGRETURN)
   if (_isSigReturn) {
     result = this->stepThroughSigReturn();
   } else