diff options
Diffstat (limited to 'source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.h')
| -rw-r--r-- | source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.h | 37 |
1 files changed, 17 insertions, 20 deletions
diff --git a/source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.h b/source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.h index a2eee280fa38..43784a5c9111 100644 --- a/source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.h +++ b/source/Plugins/ABI/MacOSX-i386/ABIMacOSX_i386.h @@ -71,24 +71,25 @@ public: return true; } + // The Darwin i386 ABI requires that stack frames be 16 byte aligned. + // When there is a trap handler on the stack, e.g. _sigtramp in userland + // code, we've seen that the stack pointer is often not aligned properly + // before the handler is invoked. This means that lldb will stop the unwind + // early -- before the function which caused the trap. + // + // To work around this, we relax that alignment to be just word-size (4-bytes). + // Whitelisting the trap handlers for user space would be easy (_sigtramp) but + // in other environments there can be a large number of different functions + // involved in async traps. + // + // If we were to enforce 16-byte alignment, we also need to relax to 4-byte + // alignment for non-darwin i386 targets. virtual bool CallFrameAddressIsValid (lldb::addr_t cfa) { - // Darwin call frame addresses must be 16-byte aligned, but other OS's - // only need 4-byte alignment. Otherwise the ABI matches, so we have - // this one minor override here. - if (target_is_darwin) - { - // Make sure the stack call frame addresses are are 16 byte aligned - if (cfa & (16ull - 1ull)) - return false; // Not 16 byte aligned - } - else - { - // Make sure the stack call frame addresses are are 4 byte aligned - if (cfa & (4ull - 1ull)) - return false; // Not 4 byte aligned - } + // Make sure the stack call frame addresses are are 4 byte aligned + if (cfa & (4ull - 1ull)) + return false; // Not 4 byte aligned if (cfa == 0) return false; // Zero is not a valid stack address return true; @@ -139,11 +140,7 @@ protected: RegisterIsCalleeSaved (const lldb_private::RegisterInfo *reg_info); private: - ABIMacOSX_i386(bool is_darwin) : lldb_private::ABI(), - target_is_darwin(is_darwin) - { } // Call CreateInstance instead. - - bool target_is_darwin; + ABIMacOSX_i386() : lldb_private::ABI() { } // Call CreateInstance instead. }; |