[libunwind] Minor fixes in libunwind

[rprichard]

Summary

• When _LIBUNWIND_SUPPORT_COMPACT_UNWIND is defined in config.h, define it to "1" like the other macros. These macros are still checked using "#if defined(...)", however.
• Include libunwind.h in AddressSpace.hpp before using _LIBUNWIND_ARM_EHABI.
• Rename ProcessFrameHeaderCache to TheFrameHeaderCache, because some configurations (e.g. Android / hermetic static libraries) can have one cache per shared object in the process. (When there are more copies, it's more important not to waste memory in the cache.)
• Add 3 missing header files to LIBUNWIND_HEADERS.

[rprichard]

Revert edit that crept in from a later patch: SECTION -> UNWIND.

[saugustine]

Looks good from the FrameHeaderCache side.

[compnerd]

Can you please verify that findUnwindSectionsByPhdr was not exposed previously? This seems like it could be an ABI break.

[rprichard]

There is a libunwind::findUnwindSectionsByPhdr as of 11.x. When I build 11.x libunwind.so for glibc (I tested arm and x86_64), the symbol is exposed:

$ readelf --dyn-syms unwind-arm/lib/libunwind.so.1.0 | grep findUnwind
    35: 00000f24   204 FUNC    GLOBAL DEFAULT    11 _ZN9libunwind24findUnwindSectionsByPhdrEP12dl_phdr_infojPv

$ readelf --dyn-syms unwind-x86_64/lib/libunwind.so.1.0 | grep findUnwind
    46: 0000000000002c30   854 FUNC    GLOBAL DEFAULT    12 _ZN9libunwind24findUnwindSectionsByPhdrEP12dl_phdr_infomPv

In previous releases, the function was a lambda instead, and the lambda was a hidden symbol (because LocalAddressSpace is marked with _LIBUNWIND_HIDDEN, which is __attribute__((visibility("hidden"))).)

$ readelf -s unwind-arm/src/CMakeFiles/unwind_shared.dir/libunwind.cpp.o | grep findUnwind
     5: 00000000     0 SECTION LOCAL  DEFAULT    23 .text._ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEjRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infojPvE_4_FUNES4_jS5_
     7: 00000000     0 SECTION LOCAL  DEFAULT    24 .ARM.extab.text._ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEjRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infojPvE_4_FUNES4_jS5_
     8: 00000000     0 SECTION LOCAL  DEFAULT    25 .ARM.exidx.text._ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEjRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infojPvE_4_FUNES4_jS5_
   265: 00000000   204 FUNC    WEAK   HIDDEN     23 _ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEjRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infojPvE_4_FUNES4_jS5_

$ readelf -s unwind-x86_64/src/CMakeFiles/unwind_shared.dir/libunwind.cpp.o | grep findUnwind
    38: 0000000000000000     0 SECTION LOCAL  DEFAULT    80 .text._ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEmRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infomPvE_4_FUNES4_mS5_
   249: 0000000000000000   313 FUNC    WEAK   HIDDEN     80 _ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEmRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infomPvE_4_FUNES4_mS5_

The hidden symbol doesn't make it into the shared object's .dynsym table.

11.0.0-final isn't released yet, so maybe this can be fixed still?

I suspect this function is currently only ever defined in libunwind.cpp.

[compnerd]

Please ensure that the fix goes into 11 before release (CC: @hans), but the remainder of the change is fine.

[rprichard]

Break the "Make findUnwindSectionsByPhdr static" change into its own patch.

[rprichard]

Update summary.

[hans]

In D86254#2230647, @compnerd wrote:

Please ensure that the fix goes into 11 before release (CC: @hans), but the remainder of the change is fine.

Just to make sure I get it right, the fix need for 11 is https://reviews.llvm.org/D86372, right?

[rprichard]

In D86254#2234248, @hans wrote:

In D86254#2230647, @compnerd wrote:

Please ensure that the fix goes into 11 before release (CC: @hans), but the remainder of the change is fine.

Just to make sure I get it right, the fix need for 11 is https://reviews.llvm.org/D86372, right?

Correct. Only D86372, containing the findUnwindSectionsByPhdr change, is needed for 11. After I broke that change out, this differential revision (D86254) isn't needed for 11 anymore.

libunwind/src/AddressSpace.hpp

 #ifndef __ADDRESSSPACE_HPP__
 #define __ADDRESSSPACE_HPP__
 
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include "libunwind.h"
+#include "config.h"
+#include "dwarf2.h"
+#include "EHHeaderParser.hpp"
+#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
 #endif
 
 #if _LIBUNWIND_USE_DLADDR
 #include <dlfcn.h>
 #if defined(__ELF__) && defined(_LIBUNWIND_LINK_DL_LIB)
 #pragma comment(lib, "dl")
 #endif
 #endif
 
 #if defined(_LIBUNWIND_ARM_EHABI)
 struct EHABIIndexEntry {
   uint32_t functionOffset;
   uint32_t data;
 };
 #endif
 
-#include "libunwind.h"
-#include "config.h"
-#include "dwarf2.h"
-#include "EHHeaderParser.hpp"
-#include "Registers.hpp"
-
 #ifdef __APPLE__
 
   struct dyld_unwind_sections
   {
     const struct mach_header*   mh;
     const void*                 dwarf_section;
     uintptr_t                   dwarf_section_length;
     const void*                 compact_unwind_section;

 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
   #if !defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
     #error "_LIBUNWIND_SUPPORT_DWARF_UNWIND requires _LIBUNWIND_SUPPORT_DWARF_INDEX on this platform."
   #endif
 
 #if defined(_LIBUNWIND_USE_FRAME_HEADER_CACHE)
 #include "FrameHeaderCache.hpp"
 
-// There should be just one of these per process.
-static FrameHeaderCache ProcessFrameHeaderCache;
+// Typically there is one cache per process, but when libunwind is built as a
+// hermetic static library, then each shared object may have its own cache.
+static FrameHeaderCache TheFrameHeaderCache;
 #endif
 
 static bool checkAddrInSegment(const Elf_Phdr *phdr, size_t image_base,
                                dl_iterate_cb_data *cbdata) {
   if (phdr->p_type == PT_LOAD) {
     uintptr_t begin = image_base + phdr->p_vaddr;
     uintptr_t end = begin + phdr->p_memsz;
     if (cbdata->targetAddr >= begin && cbdata->targetAddr < end) {
       cbdata->sects->dso_base = begin;
       cbdata->sects->dwarf_section_length = phdr->p_memsz;
       return true;
     }
   }
   return false;
 }
 
-int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t pinfo_size,
-                             void *data) {
+static int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo,
+                                    size_t pinfo_size, void *data) {
   auto cbdata = static_cast<dl_iterate_cb_data *>(data);
   if (pinfo->dlpi_phnum == 0 || cbdata->targetAddr < pinfo->dlpi_addr)
     return 0;
 #if defined(_LIBUNWIND_USE_FRAME_HEADER_CACHE)
-  if (ProcessFrameHeaderCache.find(pinfo, pinfo_size, data))
+  if (TheFrameHeaderCache.find(pinfo, pinfo_size, data))
     return 1;
 #endif
 
   Elf_Addr image_base = calculateImageBase(pinfo);
   bool found_obj = false;
   bool found_hdr = false;
 
   // Third phdr is usually the executable phdr.
if (!found_hdr && phdr->p_type == PT_GNU_EH_FRAME) {
           hdrInfo);
       if (found_hdr)
         cbdata->sects->dwarf_section = hdrInfo.eh_frame_ptr;
     } else if (!found_obj) {
       found_obj = checkAddrInSegment(phdr, image_base, cbdata);
     }
     if (found_obj && found_hdr) {
 #if defined(_LIBUNWIND_USE_FRAME_HEADER_CACHE)
-      ProcessFrameHeaderCache.add(cbdata->sects);
+      TheFrameHeaderCache.add(cbdata->sects);
 #endif
       return 1;
     }
   }
   cbdata->sects->dwarf_section_length = 0;
   return 0;
 }
 
 #else  // defined(LIBUNWIND_SUPPORT_DWARF_UNWIND)
 // Given all the #ifdef's above, the code here is for
 // defined(LIBUNWIND_ARM_EHABI)
 
-int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
+static int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t,
+                                    void *data) {
   auto *cbdata = static_cast<dl_iterate_cb_data *>(data);
   bool found_obj = false;
   bool found_hdr = false;
 
   assert(cbdata);
   assert(cbdata->sects);
 
   if (cbdata->targetAddr < pinfo->dlpi_addr)

libunwind/src/CMakeLists.txt

 set(LIBUNWIND_HEADERS
     AddressSpace.hpp
     assembly.h
     CompactUnwinder.hpp
     config.h
     dwarf2.h
     DwarfInstructions.hpp
     DwarfParser.hpp
+    EHHeaderParser.hpp
+    FrameHeaderCache.hpp
     libunwind_ext.h
     Registers.hpp
     RWMutex.hpp
+    Unwind-EHABI.h
     UnwindCursor.hpp
     ../include/libunwind.h
     ../include/unwind.h
     )
 if(APPLE)
   list(APPEND LIBUNWIND_HEADERS
     ../include/mach-o/compact_unwind_encoding.h
     )

libunwind/src/config.h

 //===----------------------------- config.h -------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //
 //  Defines macros used within libunwind project.
 //
#if !(__has_feature(cxx_static_assert)) && !defined(static_assert)
   #define static_assert(__b, __m) \
       extern int compile_time_assert_failed[ ( __b ) ? 1 : -1 ]  \
                                                   __attribute__( ( unused ) );
 #endif
 
 // Platform specific configuration defines.
 #ifdef __APPLE__
   #if defined(FOR_DYLD)
-    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND
+    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 1
   #else
-    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND
-    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND   1
+    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 1
+    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
   #endif
 #elif defined(_WIN32)
   #ifdef __SEH__
     #define _LIBUNWIND_SUPPORT_SEH_UNWIND 1
   #else
     #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
   #endif
 #else