[NFC][libunwind] Fix uintptr_t vs size_t confusion for lengths

These two are not conceptually the same; the former is a pointer shoved
in an integer, the latter is an offset or length. On the architectures
supported by libunwind, these two have the same underlying type, namely
unsigned int on ILP32, unsigned long on LP64 and unsigned long long on
LLP64. However, on CHERI, and thus Arm's Morello, they are not the same,
as pointers are hardware capabilities that carry additional metadata
including bounds and permissions, which is preserved in uintptr_t but
not in size_t. Thus, fix all length variables to be of type size_t not
uintptr_t, as we have done downstream for a while in CHERI LLVM but did
not get round to upstreaming.

Note that dyld_unwind_sections is currently defined in Apple's headers
as genuinely using uintptr_t to represent lengths. This is a bad API and
should be fixed, which would be totally API and ABI compatible due to
size_t and uintptr_t being the same type on all supported Apple systems,
but our definition is left matching theirs until such a time as they fix
their bogus types.

This is intended to be an NFC change on all architectures supported by
LLVM upstream, only being a functional change for CHERI downstream in
CHERI LLVM.

Author: jrtc27

libunwind/src/AddressSpace.hpp

@@ -121,23 +121,23 @@ struct UnwindInfoSections {
   uintptr_t       dso_base;
 #endif
 #if defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
-  uintptr_t       text_segment_length;
+  size_t          text_segment_length;
 #endif
 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
   uintptr_t       dwarf_section;
-  uintptr_t       dwarf_section_length;
+  size_t          dwarf_section_length;
 #endif
 #if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
   uintptr_t       dwarf_index_section;
-  uintptr_t       dwarf_index_section_length;
+  size_t          dwarf_index_section_length;
 #endif
 #if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
   uintptr_t       compact_unwind_section;
-  uintptr_t       compact_unwind_section_length;
+  size_t          compact_unwind_section_length;
 #endif
 #if defined(_LIBUNWIND_ARM_EHABI)
   uintptr_t       arm_section;
-  uintptr_t       arm_section_length;
+  size_t          arm_section_length;
 #endif
 };
 
@@ -430,7 +430,7 @@ static bool checkForUnwindInfoSegment(const Elf_Phdr *phdr, size_t image_base,
       // .eh_frame_hdr records the start of .eh_frame, but not its size.
       // Rely on a zero terminator to find the end of the section.
       cbdata->sects->dwarf_section = hdrInfo.eh_frame_ptr;
-      cbdata->sects->dwarf_section_length = UINTPTR_MAX;
+      cbdata->sects->dwarf_section_length = SIZE_MAX;
       return true;
     }
   }
@@ -506,22 +506,22 @@ inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
     info.dso_base                      = (uintptr_t)dyldInfo.mh;
  #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
     info.dwarf_section                 = (uintptr_t)dyldInfo.dwarf_section;
-    info.dwarf_section_length          = dyldInfo.dwarf_section_length;
+    info.dwarf_section_length          = (size_t)dyldInfo.dwarf_section_length;
  #endif
     info.compact_unwind_section        = (uintptr_t)dyldInfo.compact_unwind_section;
-    info.compact_unwind_section_length = dyldInfo.compact_unwind_section_length;
+    info.compact_unwind_section_length = (size_t)dyldInfo.compact_unwind_section_length;
     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_length = (size_t)(&__eh_frame_end - &__eh_frame_start);
   info.dwarf_section =        (uintptr_t)(&__eh_frame_start);
   _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %p length %p",
                              (void *)info.dwarf_section, (void *)info.dwarf_section_length);
 #if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
   info.dwarf_index_section =        (uintptr_t)(&__eh_frame_hdr_start);
-  info.dwarf_index_section_length = (uintptr_t)(&__eh_frame_hdr_end - &__eh_frame_hdr_start);
+  info.dwarf_index_section_length = (size_t)(&__eh_frame_hdr_end - &__eh_frame_hdr_start);
   _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: index section %p length %p",
                              (void *)info.dwarf_index_section, (void *)info.dwarf_index_section_length);
 #endif
@@ -530,7 +530,7 @@ inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
 #elif defined(_LIBUNWIND_ARM_EHABI) && defined(_LIBUNWIND_IS_BAREMETAL)
   // Bare metal is statically linked, so no need to ask the dynamic loader
   info.arm_section =        (uintptr_t)(&__exidx_start);
-  info.arm_section_length = (uintptr_t)(&__exidx_end - &__exidx_start);
+  info.arm_section_length = (size_t)(&__exidx_end - &__exidx_start);
   _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %p length %p",
                              (void *)info.arm_section, (void *)info.arm_section_length);
   if (info.arm_section && info.arm_section_length)
@@ -584,7 +584,7 @@ inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
   int length = 0;
   info.arm_section =
       (uintptr_t)dl_unwind_find_exidx((_Unwind_Ptr)targetAddr, &length);
-  info.arm_section_length = (uintptr_t)length * sizeof(EHABIIndexEntry);
+  info.arm_section_length = (size_t)length * sizeof(EHABIIndexEntry);
   if (info.arm_section && info.arm_section_length)
     return true;
 #elif defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)

libunwind/src/DwarfParser.hpp

@@ -151,7 +151,7 @@ class CFI_Parser {
   };
 
   static bool findFDE(A &addressSpace, pint_t pc, pint_t ehSectionStart,
-                      uintptr_t sectionLength, pint_t fdeHint, FDE_Info *fdeInfo,
+                      size_t sectionLength, pint_t fdeHint, FDE_Info *fdeInfo,
                       CIE_Info *cieInfo);
   static const char *decodeFDE(A &addressSpace, pint_t fdeStart,
                                FDE_Info *fdeInfo, CIE_Info *cieInfo,
@@ -230,11 +230,11 @@ const char *CFI_Parser<A>::decodeFDE(A &addressSpace, pint_t fdeStart,
 /// Scan an eh_frame section to find an FDE for a pc
 template <typename A>
 bool CFI_Parser<A>::findFDE(A &addressSpace, pint_t pc, pint_t ehSectionStart,
-                            uintptr_t sectionLength, pint_t fdeHint,
+                            size_t sectionLength, pint_t fdeHint,
                             FDE_Info *fdeInfo, CIE_Info *cieInfo) {
   //fprintf(stderr, "findFDE(0x%llX)\n", (long long)pc);
   pint_t p = (fdeHint != 0) ? fdeHint : ehSectionStart;
-  const pint_t ehSectionEnd = (sectionLength == UINTPTR_MAX)
+  const pint_t ehSectionEnd = (sectionLength == SIZE_MAX)
                                   ? static_cast<pint_t>(-1)
                                   : (ehSectionStart + sectionLength);
   while (p < ehSectionEnd) {