From 3b72a2c9d1d656c74c691a45689e1d637f669e3a Mon Sep 17 00:00:00 2001 From: Kenneth Graunke Date: Fri, 3 Jan 2014 15:08:33 -0800 Subject: Force XCB event structures with 64-bit extended fields to be packed. With the advent of the Present extension, some events (such as PresentCompleteNotify) now use native 64-bit types on the wire. For XGE events, we insert an extra "uint32_t full_sequence" field immediately after the first 32 bytes of data. Normally, this causes the subsequent fields to be shifted over by 4 bytes, and the structure to grow in size by 4 bytes. Everything works fine. However, if event contains 64-bit extended fields, this may result in the compiler adding an extra 4 bytes of padding so that those fields remain aligned on 64-bit boundaries. This causes the structure to grow by 8 bytes, not 4. Unfortunately, XCB doesn't realize this, and always believes that the length only increased by 4. read_packet() then fails to malloc enough memory to hold the event, and the event processing code uses the wrong offsets. To fix this, mark any event structures containing 64-bit extended fields with __attribute__((__packed__)). v2: Use any(...) instead of True in (...), as suggested by Daniel Martin. v3 (Alan Coopersmith): Fix build with Solaris Studio 12.3 by moving the attribute to after the structure definition. Signed-off-by: Kenneth Graunke Reviewed-by: Keith Packard [v1] Reviewed-by: Josh Triplett [v1] Reviewed-by: Daniel Martin Signed-off-by: Alan Coopersmith --- src/c_client.py | 12 +++++++++--- src/xcb.h | 2 ++ 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/src/c_client.py b/src/c_client.py index 99fd307..45de544 100644 --- a/src/c_client.py +++ b/src/c_client.py @@ -1762,7 +1762,7 @@ def c_simple(self, name): # Iterator _c_iterator(self, name) -def _c_complex(self): +def _c_complex(self, force_packed = False): ''' Helper function for handling all structure types. Called for all structs, requests, replies, events, errors. @@ -1817,7 +1817,7 @@ def _c_complex(self): if b.type.has_name: _h(' } %s;', b.c_field_name) - _h('} %s;', self.c_type) + _h('} %s%s;', 'XCB_PACKED ' if force_packed else '', self.c_type) def c_struct(self, name): ''' @@ -2902,6 +2902,7 @@ def c_event(self, name): # events while generating the structure for them. Otherwise we would read # garbage (the internal full_sequence) when accessing normal event fields # there. + force_packed = False if hasattr(self, 'is_ge_event') and self.is_ge_event and self.name == name: event_size = 0 for field in self.fields: @@ -2911,6 +2912,11 @@ def c_event(self, name): full_sequence = Field(tcard32, tcard32.name, 'full_sequence', False, True, True) idx = self.fields.index(field) self.fields.insert(idx + 1, full_sequence) + + # If the event contains any 64-bit extended fields, they need + # to remain aligned on a 64-bit boundary. Adding full_sequence + # would normally break that; force the struct to be packed. + force_packed = any(f.type.size == 8 and f.type.is_simple for f in self.fields[(idx+1):]) break _c_type_setup(self, name, ('event',)) @@ -2920,7 +2926,7 @@ def c_event(self, name): if self.name == name: # Structure definition - _c_complex(self) + _c_complex(self, force_packed) else: # Typedef _h('') diff --git a/src/xcb.h b/src/xcb.h index e62c985..73c77a3 100644 --- a/src/xcb.h +++ b/src/xcb.h @@ -51,6 +51,8 @@ extern "C" { * @file xcb.h */ +#define XCB_PACKED __attribute__((__packed__)) + /** * @defgroup XCB_Core_API XCB Core API * @brief Core API of the XCB library. -- cgit v1.2.3