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| author | Shao Miller <shao.miller@yrdsb.edu.on.ca> | 2011-01-26 20:10:24 -0500 |
|---|---|---|
| committer | Gene Cumm <gene.cumm@gmail.com> | 2011-01-26 20:40:41 -0500 |
| commit | 61df6e617c2d755ef8cac91c8c4b9bc2710b2bee (patch) | |
| tree | f9e9d15c56d597fe44981a3910830959a335b427 | |
| parent | 558087bfd62e8f74f58157e885cecc00feba836a (diff) | |
| download | syslinux-61df6e617c2d755ef8cac91c8c4b9bc2710b2bee.tar.gz | |
memdisk/dskprobe.c: Additional checks in INT13h AH08h and AH41h
Some BIOSs lie and don't set CF when they should.
Additional comments from Shao:
Fix INT 0x13, AH==0x08 disk drive probe.
This function might return CF==0 ("success"), but could return a
standard response no matter which drive number is passed in DL, but
based only on DL's bit 7. Fortunately, AH should be 0 for an existent
drive and 01h for a non-existent drive. Now we check AH.
Fix INT 0x13, AH==0x41 disk drive probe
This function might return CF==0 ("success"), but could also include BX
left unchanged. If extensions are present, BX should be returned with
0xAA55. So we now check for this special value in our determination of
a drive's presence.
Signed-off-by: Gene Cumm <gene.cumm@gmail.com>
| -rw-r--r-- | memdisk/dskprobe.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/memdisk/dskprobe.c b/memdisk/dskprobe.c index 84400a83..ee7be12d 100644 --- a/memdisk/dskprobe.c +++ b/memdisk/dskprobe.c @@ -57,7 +57,7 @@ static int probe_int13h_08h(uint8_t drive, com32sys_t * regs) memset(regs, 0, sizeof *regs); probe_any(0x08, drive, regs); - present = !(regs->eflags.l & 1); + present = !(regs->eflags.l & 1) && !regs->eax.b[1]; dskprobe_printf(" AH08: CF%d BL%02x DL%02x\n", regs->eflags.l & 1, regs->ebx.b[0], regs->edx.b[0]); return present; @@ -88,7 +88,7 @@ static int probe_int13h_41h(uint8_t drive, com32sys_t * regs) memset(regs, 0, sizeof *regs); regs->ebx.w[0] = 0x55AA; /* BX == 0x55AA */ probe_any(0x41, drive, regs); - present = !(regs->eflags.l & 1); + present = !(regs->eflags.l & 1) && (regs->ebx.w[0] == 0xAA55); dskprobe_printf(" AH41: CF%d BX%04x AH%02x DH%02x\n", regs->eflags.l & 1, regs->ebx.w[0], regs->eax.b[1], regs->edx.b[1]); return present; |