If a transfer to or from a floppy disk crosses a 64k boundary, we have to
use a bounce buffer for the actual transfer to avoid crossing a 64k boundary. To do this, we malloc a buffer twice as big as we need and then find an aligned block within that buffer to do the transfer. The check to see which part of the block we use used the wrong variable for part of the condition meaning that in certain edge cases we would ask the BIOS to cross a 64k boundary. The BIOS request would then fail resulting in file transfers that just magically fail in the middle without any apparent reason. Specifically, my tests for the splitfs boot floppies managed to trigger this edge case. MFC after: 1 week X-MFC-info: along with fixes to libstand filesystems
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@ -867,7 +867,7 @@ bd_read(struct open_disk *od, daddr_t dblk, int blks, caddr_t dest)
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*/
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x = min(FLOPPY_BOUNCEBUF, (unsigned)blks);
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bbuf = malloc(x * 2 * BIOSDISK_SECSIZE);
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if (((u_int32_t)VTOP(bbuf) & 0xffff0000) == ((u_int32_t)VTOP(dest + x * BIOSDISK_SECSIZE) & 0xffff0000)) {
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if (((u_int32_t)VTOP(bbuf) & 0xffff0000) == ((u_int32_t)VTOP(bbuf + x * BIOSDISK_SECSIZE) & 0xffff0000)) {
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breg = bbuf;
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} else {
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breg = bbuf + x * BIOSDISK_SECSIZE;
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@ -1000,7 +1000,7 @@ bd_write(struct open_disk *od, daddr_t dblk, int blks, caddr_t dest)
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x = min(FLOPPY_BOUNCEBUF, (unsigned)blks);
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bbuf = malloc(x * 2 * BIOSDISK_SECSIZE);
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if (((u_int32_t)VTOP(bbuf) & 0xffff0000) == ((u_int32_t)VTOP(dest + x * BIOSDISK_SECSIZE) & 0xffff0000)) {
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if (((u_int32_t)VTOP(bbuf) & 0xffff0000) == ((u_int32_t)VTOP(bbuf + x * BIOSDISK_SECSIZE) & 0xffff0000)) {
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breg = bbuf;
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} else {
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breg = bbuf + x * BIOSDISK_SECSIZE;
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