ewah: support platforms that require aligned reads
The caller may hand us an unaligned buffer (e.g., because it is an mmap of a file with many ewah bitmaps). On some platforms (like SPARC) this can cause a bus error. We can fix it with a combination of get_be32 and moving the data into an aligned buffer (which we would do anyway, but we can move it before fixing the endianness). Signed-off-by: Vicent Marti <tanoku@gmail.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Vicent Marti committed
Jan 23, 2014 at 16:27 UTC
a201c20b41a2f0725977bcb89a2a66135d776ba2
1 file changed
+24
-9
ewah/ewah_io.c
+24
-9
@@ -112,23 +112,38 @@ int ewah_serialize(struct ewah_bitmap *self, int fd)
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int ewah_read_mmap(struct ewah_bitmap *self, void *map, size_t len)
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{
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- uint32_t *read32 = map;
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- eword_t *read64;
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- size_t i;
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+ uint8_t *ptr = map;
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+
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+ self->bit_size = get_be32(ptr);
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+ ptr += sizeof(uint32_t);
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+
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+ self->buffer_size = self->alloc_size = get_be32(ptr);
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+ ptr += sizeof(uint32_t);
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- self->bit_size = ntohl(*read32++);
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- self->buffer_size = self->alloc_size = ntohl(*read32++);
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self->buffer = ewah_realloc(self->buffer,
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self->alloc_size * sizeof(eword_t));
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if (!self->buffer)
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return -1;
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- for (i = 0, read64 = (void *)read32; i < self->buffer_size; ++i)
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- self->buffer[i] = ntohll(*read64++);
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+ /*
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+ * Copy the raw data for the bitmap as a whole chunk;
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+ * if we're in a little-endian platform, we'll perform
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+ * the endianness conversion in a separate pass to ensure
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+ * we're loading 8-byte aligned words.
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+ */
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+ memcpy(self->buffer, ptr, self->buffer_size * sizeof(uint64_t));
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+ ptr += self->buffer_size * sizeof(uint64_t);
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+
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+#if __BYTE_ORDER != __BIG_ENDIAN
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+ {
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+ size_t i;
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+ for (i = 0; i < self->buffer_size; ++i)
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+ self->buffer[i] = ntohll(self->buffer[i]);
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+ }
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+#endif
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- read32 = (void *)read64;
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- self->rlw = self->buffer + ntohl(*read32++);
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+ self->rlw = self->buffer + get_be32(ptr);
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return (3 * 4) + (self->buffer_size * 8);
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}