[PATCH] D86748: [libunwind] Bare-metal DWARF: set dso_base to 0

[Ryan Prichard via Phabricator via llvm-commits]

rprichard created this revision.
rprichard added reviewers: compnerd, mstorsjo, whitequark.
Herald added subscribers: libcxx-commits, llvm-commits, aprantl.
Herald added projects: LLVM, libunwind.
Herald added a reviewer: libunwind.
rprichard requested review of this revision.

DwarfFDECache::findFDE normally uses mh==0 as a flag indicating that it
should search the entire cache, including dynamically-registered FDEs.
Replace this sentinel value with a bool parameter.

Fixes PR47335.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D86748

Files:
  libunwind/src/AddressSpace.hpp
  libunwind/src/UnwindCursor.hpp


Index: libunwind/src/UnwindCursor.hpp
===================================================================
--- libunwind/src/UnwindCursor.hpp
+++ libunwind/src/UnwindCursor.hpp
@@ -81,7 +81,7 @@
 class _LIBUNWIND_HIDDEN DwarfFDECache {
   typedef typename A::pint_t pint_t;
 public:
-  static pint_t findFDE(pint_t mh, pint_t pc);
+  static pint_t findFDE(pint_t mh, bool ignore_mh, pint_t pc);
   static void add(pint_t mh, pint_t ip_start, pint_t ip_end, pint_t fde);
   static void removeAllIn(pint_t mh);
   static void iterateCacheEntries(void (*func)(unw_word_t ip_start,
@@ -134,11 +134,12 @@
 #endif
 
 template <typename A>
-typename A::pint_t DwarfFDECache<A>::findFDE(pint_t mh, pint_t pc) {
+typename A::pint_t DwarfFDECache<A>::findFDE(pint_t mh, bool ignore_mh,
+                                             pint_t pc) {
   pint_t result = 0;
   _LIBUNWIND_LOG_IF_FALSE(_lock.lock_shared());
   for (entry *p = _buffer; p < _bufferUsed; ++p) {
-    if ((mh == p->mh) || (mh == 0)) {
+    if ((mh == p->mh) || ignore_mh) {
       if ((p->ip_start <= pc) && (pc < p->ip_end)) {
         result = p->fde;
         break;
@@ -1529,7 +1530,7 @@
 #endif
   if (!foundFDE) {
     // otherwise, search cache of previously found FDEs.
-    pint_t cachedFDE = DwarfFDECache<A>::findFDE(sects.dso_base, pc);
+    pint_t cachedFDE = DwarfFDECache<A>::findFDE(sects.dso_base, false, pc);
     if (cachedFDE != 0) {
       foundFDE =
           CFI_Parser<A>::findFDE(_addressSpace, pc, sects.dwarf_section,
@@ -1945,7 +1946,7 @@
 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
   // There is no static unwind info for this pc. Look to see if an FDE was
   // dynamically registered for it.
-  pint_t cachedFDE = DwarfFDECache<A>::findFDE(0, pc);
+  pint_t cachedFDE = DwarfFDECache<A>::findFDE(0, true, pc);
   if (cachedFDE != 0) {
     typename CFI_Parser<A>::FDE_Info fdeInfo;
     typename CFI_Parser<A>::CIE_Info cieInfo;
Index: libunwind/src/AddressSpace.hpp
===================================================================
--- libunwind/src/AddressSpace.hpp
+++ libunwind/src/AddressSpace.hpp
@@ -535,6 +535,7 @@
     return true;
   }
 #elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_LIBUNWIND_IS_BAREMETAL)
+  info.dso_base = 0;
   // Bare metal is statically linked, so no need to ask the dynamic loader
   info.dwarf_section_length = (uintptr_t)(&__eh_frame_end - &__eh_frame_start);
   info.dwarf_section =        (uintptr_t)(&__eh_frame_start);


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