https://bugs.freedesktop.org/show_bug.cgi?id=80673
Priority: medium Bug ID: 80673 Assignee: dri-devel@lists.freedesktop.org Summary: XCOM: Enemy Unknown - Wrong read access when starting the game Severity: normal Classification: Unclassified OS: Linux (All) Reporter: freedesktop@psydk.org Hardware: x86-64 (AMD64) Status: NEW Version: 10.1 Component: Drivers/Gallium/r600 Product: Mesa
Created attachment 101971 --> https://bugs.freedesktop.org/attachment.cgi?id=101971&action=edit callstack of the wrong read access
Some background: I am trying to understand why "XCOM: Enemy Uknown" (a game that was released for Linux x64 last week on Steam), leads to crashes when running with the open source Radeon driver. The people who did the port do not officialy support the open source driver but seems to be open to the idea of making it run on it.
My system: Ubuntu 14.04 x64 Readon HD 4870 Mesa 10.1.3
Unfortunately that Radeon model is not supported by AMD's closed source driver. However, the game runs very well with the open source driver, with the exception of several random crashes. This bug report is one of the problem I have found and for which I have some information.
The main crash I was experimenting was corrupting the heap, so I used a tool to detect illegal read and write accesses. The first problem it found is an illegal read access at the start of the game, after the different logos, when the main menu is about to appear.
What is happening is that a memcpy with a size of 1360 bytes is made with a source buffer of only 1280 bytes in u_upload_data(). I will attach the callstack to this ticket.
In that context, the entry point in the driver is: vbo_exec_DrawRangeElementsBaseVertex(GLenum mode, GLuint start, GLuint end, GLsizei count, GLenum type, const GLvoid *indices, GLint basevertex)
Here are the values of the parameters:
--------------------------------------------------------------- mode: 4 (GL_TRIANGLES) start: 0 end: 16 count: 24 type: 5123 (GL_UNSIGNED_SHORT) indices: 72 bytes: 00 00 02 00 03 00 00 00 01 00 02 00 04 00 06 00 07 00 04 00 05 00 06 00 08 00 0a 00 0b 00 08 00 09 00 0a 00 0c 00 0e 00 0f 00 0c 00 0d 00 0e 00 00 00 04 00 06 00 00 00 06 00 02 00 01 00 03 00 07 00 01 00 07 00 05 00 reordered as 36 u16: 0000 0002 0003 0000 0001 0002 0004 0006 0007 0004 0005 0006 0008 000a 000b 0008 0009 000a 000c 000e 000f 000c 000d 000e 0000 0004 0006 0000 0006 0002 0001 0003 0007 0001 0007 0005
basevertex: 0 --------------------------------------------------------------- Now I'm no expert in OpenGL and it is the first time I look at Mesa code, so I can't identify the main reason for the error. Hopefully you will have a clue.
A tip to debug the game: if you have Steam and the game, I renamed the main exectuable in ".../Steam/SteamApps/common/XCom-Enemy-Unknown/binaries/linux/" named "game.x86_64" as "game.x86_64_real" and created a shell script named "game.x86_64" that performs necessary settings for debugging and then launch "game.x86_64_real". In my case I am setting LD_PRELOAD with a library that catches malloc() calls and fences the buffer before returning it.