libunwind: limit stack usage in unwind cursor

[emaste]

Summary

From FreeBSD r302475

[compnerd]

include/__libunwind_config.h

50

Uh, this looks like the DWARF number as 64-95 represent the VFP register set in modern ARM toolchains. Please rename the macros to _LIBUNWIND_HIGHEST_DWARF_REGISTER so that someone does not assume some silly mistake (the likes of #define ONE 2).

[emaste]

Update macro name as requested by @compnerd

[compnerd]

Im tempted to say that we should try to merge this into 3.9 as well given that its pretty low risk, and we also have the other alignment issue that we are going to carry over. Mind merging or pinging Hans for this change?

[rmaprath]

Thanks for this!

I was on holidays, couldn't respond sooner.

/ Asiri

include/__libunwind_config.h

 #define _LIBUNWIND_ARM_EHABI 0
 #endif
 
 #if defined(_LIBUNWIND_IS_NATIVE_ONLY)
 # if defined(__i386__)
 #  define _LIBUNWIND_TARGET_I386 1
 #  define _LIBUNWIND_CONTEXT_SIZE 8
 #  define _LIBUNWIND_CURSOR_SIZE 19
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 9
 # elif defined(__x86_64__)
 #  define _LIBUNWIND_TARGET_X86_64 1
 #  define _LIBUNWIND_CONTEXT_SIZE 21
 #  define _LIBUNWIND_CURSOR_SIZE 33
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 17
 # elif defined(__ppc__)
 #  define _LIBUNWIND_TARGET_PPC 1
 #  define _LIBUNWIND_CONTEXT_SIZE 117
 #  define _LIBUNWIND_CURSOR_SIZE 128
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 113
 # elif defined(__aarch64__)
 #  define _LIBUNWIND_TARGET_AARCH64 1
 #  define _LIBUNWIND_CONTEXT_SIZE 66
 #  define _LIBUNWIND_CURSOR_SIZE 78
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 96
 # elif defined(__arm__)
 #  define _LIBUNWIND_TARGET_ARM 1
 #  if defined(__ARM_WMMX)
 #    define _LIBUNWIND_CONTEXT_SIZE 60
 #    define _LIBUNWIND_CURSOR_SIZE 67
 #  else
 #    define _LIBUNWIND_CONTEXT_SIZE 42
 #    define _LIBUNWIND_CURSOR_SIZE 49
 #  endif
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 96
 # elif defined(__or1k__)
 #  define _LIBUNWIND_TARGET_OR1K 1
 #  define _LIBUNWIND_CONTEXT_SIZE 16
 #  define _LIBUNWIND_CURSOR_SIZE 28
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER 32
 # else
 #  error "Unsupported architecture."
 # endif
 #else // !_LIBUNWIND_IS_NATIVE_ONLY
 # define _LIBUNWIND_TARGET_I386 1
 # define _LIBUNWIND_TARGET_X86_64 1
 # define _LIBUNWIND_TARGET_PPC 1
 # define _LIBUNWIND_TARGET_AARCH64 1
 # define _LIBUNWIND_TARGET_ARM 1
 # define _LIBUNWIND_TARGET_OR1K 1
 # define _LIBUNWIND_CONTEXT_SIZE 128
 # define _LIBUNWIND_CURSOR_SIZE 140
+# define _LIBUNWIND_HIGHEST_DWARF_REGISTER 120
 #endif // _LIBUNWIND_IS_NATIVE_ONLY
 
 #endif // ____LIBUNWIND_CONFIG_H__

src/DwarfParser.hpp

struct FDE_Info {
     pint_t  fdeLength;
     pint_t  fdeInstructions;
     pint_t  pcStart;
     pint_t  pcEnd;
     pint_t  lsda;
   };
 
   enum {
-    kMaxRegisterNumber = 120
+    kMaxRegisterNumber = _LIBUNWIND_HIGHEST_DWARF_REGISTER
   };
   enum RegisterSavedWhere {
     kRegisterUnused,
     kRegisterInCFA,
     kRegisterOffsetFromCFA,
     kRegisterInRegister,
     kRegisterAtExpression,
     kRegisterIsExpression