[libunwind][AIX] implementation of the unwinder for AIX

Summary: This patch contains the implementation of the unwinder for IBM AIX. AIX does not support the eh_frame section. Instead, the traceback table located at the end of each function provides the information for stack unwinding and EH. In this patch macro _LIBUNWIND_SUPPORT_TBTAB_UNWIND is used to guard code for AIX traceback table based unwinding. Function getInfoFromTBTable() and stepWithTBTable() are added to get the EH information from the traceback table and to step up the stack respectively. There are two kinds of LSDA information for EH on AIX, the state table and the range table. The state table is used by the previous version of the IBM XL compiler, i.e., xlC and xlclang++. The DWARF based range table is used by AIX clang++. The traceback table has flags to differentiate these cases. For the range table, relative addresses are calculated using a base of DW_EH_PE_datarel, which is the TOC base of the module where the function of the current frame belongs. Two personality routines are employed to handle these two different LSDAs, __xlcxx_personality_v0() for the state table and __xlcxx_personality_v1() for the range table. Since the traceback table does not have the information of the personality for the state table approach, its personality __xlcxx_personality_v0() is dynamically resolved as the handler for the state table. For the range table, the locations of the LSDA and its associated personality routine are found in the traceback table. Assembly code for 32- and 64-bit PowerPC in UnwindRegistersRestore.S and UnwindRegistersSave.S are modified so that it can be consumed by the GNU flavor assembler and the AIX assembler. The restoration of vector registers does not check VRSAVE on AIX because VRSAVE is not used in the AIX ABI. Reviewed by: MaskRay, compnerd, cebowleratibm, sfertile, libunwind Differential Revision: https://reviews.llvm.org/D100132
intel · Apr 13, 2022 · a85da64 · a85da64
1 parent 0424b51
commit a85da64
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Showing 15 changed files with 848 additions and 81 deletions.
diff --git a/libunwind/include/libunwind.h b/libunwind/include/libunwind.h
@@ -120,6 +120,9 @@ extern int unw_resume(unw_cursor_t *) LIBUNWIND_AVAIL;
 extern void unw_save_vfp_as_X(unw_cursor_t *) LIBUNWIND_AVAIL;
 #endif
 
+#ifdef _AIX
+extern uintptr_t unw_get_data_rel_base(unw_cursor_t *) LIBUNWIND_AVAIL;
+#endif
 
 extern const char *unw_regname(unw_cursor_t *, unw_regnum_t) LIBUNWIND_AVAIL;
 extern int unw_get_proc_info(unw_cursor_t *, unw_proc_info_t *) LIBUNWIND_AVAIL;

diff --git a/libunwind/include/unwind.h b/libunwind/include/unwind.h
@@ -160,7 +160,7 @@ extern const void *_Unwind_Find_FDE(const void *pc, struct dwarf_eh_bases *);
 extern void *_Unwind_FindEnclosingFunction(void *pc);
 
 // Mac OS X does not support text-rel and data-rel addressing so these functions
-// are unimplemented
+// are unimplemented.
 extern uintptr_t _Unwind_GetDataRelBase(struct _Unwind_Context *context)
     LIBUNWIND_UNAVAIL;
 extern uintptr_t _Unwind_GetTextRelBase(struct _Unwind_Context *context)

diff --git a/libunwind/src/AddressSpace.hpp b/libunwind/src/AddressSpace.hpp
@@ -24,11 +24,11 @@
 #include "Registers.hpp"
 
 #ifndef _LIBUNWIND_USE_DLADDR
-  #if !defined(_LIBUNWIND_IS_BAREMETAL) && !defined(_WIN32)
-    #define _LIBUNWIND_USE_DLADDR 1
-  #else
-    #define _LIBUNWIND_USE_DLADDR 0
-  #endif
+#if !(defined(_LIBUNWIND_IS_BAREMETAL) || defined(_WIN32) || defined(_AIX))
+#define _LIBUNWIND_USE_DLADDR 1
+#else
+#define _LIBUNWIND_USE_DLADDR 0
+#endif
 #endif
 
 #if _LIBUNWIND_USE_DLADDR
@@ -45,6 +45,13 @@ struct EHABIIndexEntry {
 };
 #endif
 
+#if defined(_AIX)
+namespace libunwind {
+char *getFuncNameFromTBTable(uintptr_t pc, uint16_t &NameLen,
+                             unw_word_t *offset);
+}
+#endif
+
 #ifdef __APPLE__
 
   struct dyld_unwind_sections
@@ -580,6 +587,11 @@ inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
   (void)targetAddr;
   (void)info;
   return true;
+#elif defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
+  // The traceback table is used for unwinding.
+  (void)targetAddr;
+  (void)info;
+  return true;
 #elif defined(_LIBUNWIND_USE_DL_UNWIND_FIND_EXIDX)
   int length = 0;
   info.arm_section =
@@ -596,7 +608,6 @@ inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
   return false;
 }
 
-
 inline bool LocalAddressSpace::findOtherFDE(pint_t targetAddr, pint_t &fde) {
   // TO DO: if OS has way to dynamically register FDEs, check that.
   (void)targetAddr;
@@ -616,6 +627,13 @@ inline bool LocalAddressSpace::findFunctionName(pint_t addr, char *buf,
       return true;
     }
   }
+#elif defined(_AIX)
+  uint16_t nameLen;
+  char *funcName = getFuncNameFromTBTable(addr, nameLen, offset);
+  if (funcName != NULL) {
+    snprintf(buf, bufLen, "%.*s", nameLen, funcName);
+    return true;
+  }
 #else
   (void)addr;
   (void)buf;

diff --git a/libunwind/src/CMakeLists.txt b/libunwind/src/CMakeLists.txt
@@ -11,6 +11,12 @@ if(APPLE)
     )
 endif()
 
+if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+  list(APPEND LIBUNWIND_CXX_SOURCES
+    Unwind_AIXExtras.cpp
+    )
+endif()
+
 set(LIBUNWIND_C_SOURCES
     UnwindLevel1.c
     UnwindLevel1-gcc-ext.c
@@ -26,7 +32,11 @@ set(LIBUNWIND_ASM_SOURCES
     )
 
 # See add_asm_sources() in compiler-rt for explanation of this workaround.
-if((APPLE AND CMAKE_VERSION VERSION_LESS 3.19) OR (MINGW AND CMAKE_VERSION VERSION_LESS 3.17))
+# CMake doesn't work correctly with assembly on AIX. Workaround by compiling
+# as C files as well.
+if((APPLE AND CMAKE_VERSION VERSION_LESS 3.19) OR
+   (MINGW AND CMAKE_VERSION VERSION_LESS 3.17) OR
+   (${CMAKE_SYSTEM_NAME} MATCHES "AIX"))
   set_source_files_properties(${LIBUNWIND_ASM_SOURCES} PROPERTIES LANGUAGE C)
 endif()
 

diff --git a/libunwind/src/Registers.hpp b/libunwind/src/Registers.hpp
@@ -609,6 +609,8 @@ class _LIBUNWIND_HIDDEN Registers_ppc {
   void      setSP(uint32_t value) { _registers.__r1 = value; }
   uint64_t  getIP() const         { return _registers.__srr0; }
   void      setIP(uint32_t value) { _registers.__srr0 = value; }
+  uint64_t  getCR() const         { return _registers.__cr; }
+  void      setCR(uint32_t value) { _registers.__cr = value; }
 
 private:
   struct ppc_thread_state_t {
@@ -1175,6 +1177,8 @@ class _LIBUNWIND_HIDDEN Registers_ppc64 {
   void      setSP(uint64_t value) { _registers.__r1 = value; }
   uint64_t  getIP() const         { return _registers.__srr0; }
   void      setIP(uint64_t value) { _registers.__srr0 = value; }
+  uint64_t  getCR() const         { return _registers.__cr; }
+  void      setCR(uint64_t value) { _registers.__cr = value; }
 
 private:
   struct ppc64_thread_state_t {