ahc_linux_map_seg() compile/style/data corruption fixes

William Lee Irwin III
2003-05-14T04:37:04Z

ahc_linux_map_seg() has several style and compile-time issues:

(1) if (sizeof(bus_addr_t) > 4 && ...) linewraps oddly
(2) ~0xFFFFFFFF is always 0; the check for being above 4GB never succeeds
(3) 0x100000000 overflows int and hence vanishes, causing a compile error
on gcc-3.3 and effectively being identical to its replacement here
(4) constants describing the upper byte of the length are not used
(5) return is a keyword, not a function
(6) uint32_t used instead of u32 (contrary to Linux conventions)
(7) it's randomly panicking in a driver; at least complain in a comment

This is basically a compilefix for axel@pearbough.net's compile failure,
with some added cleanup. (2) should cause data corruption on x440,
NUMA-Q, and ES7000 almost every time this is called, so I guess this
qualifies as a runtime bugfix too. Oddly, I'm not seeing any even on
64GB NUMA-Q, so it's probably bouncing due to some other bug.

For the connoisseur, I've attached before/after disassemblies
demonstrating that the if () whose failure is caused by (2) is a very,
very, very real problem. In order to isolate the code, I uninlined
ahc_linux_map_seg() so the code could be isolated from the rest of
everything. It's clear well over half the function was missing before.
Also note the calls to panic() are made by jmps to the end of the
function. This is 5f in the -'s, and f3 in the +'s. i.e. you can
very easily tell from the disassembly that one of the panic()'s is
missing, i.e. the if () in question is compiled out.

--- ../disasm.old 2003-05-13 21:24:42.000000000 -0700
+++ ../disasm.new 2003-05-13 21:24:23.000000000 -0700
@@ -1,38 +1,80 @@
<ahc_linux_map_seg>:
55 push %ebp
89 e5 mov %esp,%ebp
-83 ec 10 sub $0x10,%esp
-89 75 f8 mov %esi,0xfffffff8(%ebp)
-8b 55 14 mov 0x14(%ebp),%edx
-8b 75 0c mov 0xc(%ebp),%esi
+83 ec 14 sub $0x14,%esp
89 5d f4 mov %ebx,0xfffffff4(%ebp)
-8b 4d 18 mov 0x18(%ebp),%ecx
-8b 5d 1c mov 0x1c(%ebp),%ebx
+8b 55 0c mov 0xc(%ebp),%edx
+8b 5d 14 mov 0x14(%ebp),%ebx
+89 75 f8 mov %esi,0xfffffff8(%ebp)
+8b 75 18 mov 0x18(%ebp),%esi
89 7d fc mov %edi,0xfffffffc(%ebp)
-8b 7d 10 mov 0x10(%ebp),%edi
-8b 46 34 mov 0x34(%esi),%eax
+8b 7d 1c mov 0x1c(%ebp),%edi
+8b 42 34 mov 0x34(%edx),%eax
40 inc %eax
3d 80 00 00 00 cmp $0x80,%eax
-77 36 ja c02654ef <ahc_linux_map_seg+0x5f>
-89 17 mov %edx,(%edi)
-8b 46 20 mov 0x20(%esi),%eax
-01 58 0c add %ebx,0xc(%eax)
+0f 87 c9 00 00 00 ja c0265583 <ahc_linux_map_seg+0xf3>
+c7 45 f0 01 00 00 00 movl $0x1,0xfffffff0(%ebp)
+8b 45 10 mov 0x10(%ebp),%eax
+89 18 mov %ebx,(%eax)
+8b 55 0c mov 0xc(%ebp),%edx
+8b 42 20 mov 0x20(%edx),%eax
+01 78 0c add %edi,0xc(%eax)
8b 45 08 mov 0x8(%ebp),%eax
f6 80 17 01 00 00 01 testb $0x1,0x117(%eax)
-74 0d je c02654da <ahc_linux_map_seg+0x4a>
-0f ac ca 08 shrd $0x8,%ecx,%edx
-89 d0 mov %edx,%eax
+0f 84 8e 00 00 00 je c026556d <ahc_linux_map_seg+0xdd>
+89 f2 mov %esi,%edx
+89 d8 mov %ebx,%eax
+c1 ea 1e shr $0x1e,%edx
+0f ac f0 1e shrd $0x1e,%esi,%eax
+83 fa 00 cmp $0x0,%edx
+77 71 ja c0265560 <ahc_linux_map_seg+0xd0>
+83 f8 03 cmp $0x3,%eax
+77 6c ja c0265560 <ahc_linux_map_seg+0xd0>
+89 f8 mov %edi,%eax
+31 d2 xor %edx,%edx
+01 d8 add %ebx,%eax
+11 f2 adc %esi,%edx
+83 c0 ff add $0xffffffff,%eax
+83 d2 ff adc $0xffffffff,%edx
+0f ac d0 1e shrd $0x1e,%edx,%eax
+c1 ea 1e shr $0x1e,%edx
+83 fa 00 cmp $0x0,%edx
+77 05 ja c0265513 <ahc_linux_map_seg+0x83>
+83 f8 03 cmp $0x3,%eax
+76 4d jbe c0265560 <ahc_linux_map_seg+0xd0>
+c7 04 24 66 57 31 c0 movl $0xc0315766,(%esp,1)
+e8 11 d8 eb ff call c0122d30 <printk>
+8b 55 0c mov 0xc(%ebp),%edx
+8b 42 34 mov 0x34(%edx),%eax
+83 c0 02 add $0x2,%eax
+3d 80 00 00 00 cmp $0x80,%eax
+77 54 ja c0265583 <ahc_linux_map_seg+0xf3>
+c7 45 f0 02 00 00 00 movl $0x2,0xfffffff0(%ebp)
+8b 45 10 mov 0x10(%ebp),%eax
+89 da mov %ebx,%edx
+0f ac f2 08 shrd $0x8,%esi,%edx
+81 c2 00 00 00 01 add $0x1000000,%edx
+81 e2 00 00 00 7f and $0x7f000000,%edx
+c7 40 08 00 00 00 00 movl $0x0,0x8(%eax)
+89 d8 mov %ebx,%eax
+f7 d8 neg %eax
+29 c7 sub %eax,%edi
+09 d0 or %edx,%eax
+8b 55 10 mov 0x10(%ebp),%edx
+89 42 0c mov %eax,0xc(%edx)
+0f ac f3 08 shrd $0x8,%esi,%ebx
+89 d8 mov %ebx,%eax
25 00 00 00 7f and $0x7f000000,%eax
-09 c3 or %eax,%ebx
-89 5f 04 mov %ebx,0x4(%edi)
+09 c7 or %eax,%edi
+8b 45 10 mov 0x10(%ebp),%eax
+89 78 04 mov %edi,0x4(%eax)
+8b 45 f0 mov 0xfffffff0(%ebp),%eax
8b 5d f4 mov 0xfffffff4(%ebp),%ebx
-b8 01 00 00 00 mov $0x1,%eax
8b 75 f8 mov 0xfffffff8(%ebp),%esi
8b 7d fc mov 0xfffffffc(%ebp),%edi
89 ec mov %ebp,%esp
5d pop %ebp
c3 ret
-c7 04 24 80 38 32 c0 movl $0xc0323880,(%esp,1)
-e8 75 cf eb ff call c0122470 <panic>
+c7 04 24 00 39 32 c0 movl $0xc0323900,(%esp,1)
+e8 e1 ce eb ff call c0122470 <panic>
90 nop
-8d 74 26 00 lea 0x0(%esi,1),%esi

Applies cleanly to 2.5.69-bk8 and/or current bk.

-- wli

diff -prauN linux-2.5.69-bk8-1/drivers/scsi/aic7xxx/aic7xxx_osm.c linux-2.5.69-bk8-2/drivers/scsi/aic7xxx/aic7xxx_osm.c
--- linux-2.5.69-bk8-1/drivers/scsi/aic7xxx/aic7xxx_osm.c 2003-05-13 17:26:56.000000000 -0700
+++ linux-2.5.69-bk8-2/drivers/scsi/aic7xxx/aic7xxx_osm.c 2003-05-13 20:22:22.000000000 -0700
@@ -744,18 +744,20 @@ ahc_linux_map_seg(struct ahc_softc *ahc,
"Increase AHC_NSEG\n");

consumed = 1;
- sg->addr = ahc_htole32(addr & 0xFFFFFFFF);
+ sg->addr = ahc_htole32((u32)addr);
scb->platform_data->xfer_len += len;
- if (sizeof(bus_addr_t) > 4
- && (ahc->flags & AHC_39BIT_ADDRESSING) != 0) {
+ if (sizeof(bus_addr_t) > 4 &&
+ (ahc->flags & AHC_39BIT_ADDRESSING) != 0) {
/*
- * Due to DAC restrictions, we can't
- * cross a 4GB boundary.
+ * Due to DAC restrictions, we can't cross 4GB boundaries.
+ * Right shift by 30 to find GB-granularity placement
+ * without getting tripped up by anal compilers.
*/
- if ((addr ^ (addr + len - 1)) & ~0xFFFFFFFF) {
+ if ((addr >> 30) < 4 && ((addr + len - 1) >> 30) >= 4) {
struct ahc_dma_seg *next_sg;
- uint32_t next_len;
+ u32 next_len;

+ /* somebody clean this up to return an error */
printf("Crossed Seg\n");
if ((scb->sg_count + 2) > AHC_NSEG)
panic("Too few segs for dma mapping. "
@@ -764,15 +766,25 @@ ahc_linux_map_seg(struct ahc_softc *ahc,
consumed++;
next_sg = sg + 1;
next_sg->addr = 0;
- next_len = 0x100000000 - (addr & 0xFFFFFFFF);
+
+ /*
+ * 2's complement arithmetic assumed.
+ * We want: 4GB - low 32 bits of addr
+ * to find the length of the low segment
+ * and to subtract it out from the high
+ */
+ next_len = -((u32)addr);
len -= next_len;
- next_len |= ((addr >> 8) + 0x1000000) & 0x7F000000;
+
+ /* c.f. struct ahc_dma_seg for meaning of high byte */
+ next_len |= ((addr >> 8) + AHC_SG_LEN_MASK + 1)
+ & AHC_SG_HIGH_ADDR_MASK;
next_sg->len = ahc_htole32(next_len);
}
- len |= (addr >> 8) & 0x7F000000;
+ len |= (addr >> 8) & AHC_SG_HIGH_ADDR_MASK;
}
sg->len = ahc_htole32(len);
- return (consumed);
+ return consumed;
}

/************************ Host template entry points *************************/