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Matt Turner authored
Prior to this patch sizeof(linear_header) was 20 bytes in a non-debug build on 32-bit platforms. We do some pointer arithmetic to calculate the next available location with ptr = (linear_size_chunk *)((char *)&latest[1] + latest->offset); in linear_alloc_child(). The &latest[1] adds 20 bytes, so an allocation would only be 4-byte aligned. On 32-bit SPARC a 'sttw' instruction (which stores a consecutive pair of 4-byte registers to memory) requires an 8-byte aligned address. Such an instruction is used to store to an 8-byte integer type, like intmax_t which is used in glcpp's expression_value_t struct. As a result of the 4-byte alignment returned by linear_alloc_child() we would generate a SIGBUS (unaligned exception) on SPARC. According to the GNU libc manual malloc() always returns memory that has at least an alignment of 8-bytes [1]. I think our allocator should do the same. So, simple fix with two parts: (1) Increase SUBALLOC_ALIGNMENT to 8 unconditionally. (2) Mark linear_header with an aligned attribute, which will cause its sizeof to be rounded up to that alignment. (We already do this for ralloc_header) With this done, all Mesa's unit tests now pass on SPARC. [1] https://www.gnu.org/software/libc/manual/html_node/Aligned-Memory-Blocks.html Fixes: 47e17586 ("glcpp: use the linear allocator for most objects") Bug: https://bugs.gentoo.org/636326 Reviewed-by: Eric Anholt <eric@anholt.net>
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