Date: Tue, 22 Oct 2002 12:13:55 +0900 (JST) From: Mitsuru IWASAKI <iwasaki@jp.FreeBSD.org> To: bde@zeta.org.au Cc: current@FreeBSD.ORG Subject: Re: [PATCH] Workaround for bogus INT 12H BIOS service implementation Message-ID: <20021022.121355.78702461.iwasaki@jp.FreeBSD.org> In-Reply-To: <20021022103609.V12732-100000@gamplex.bde.org> References: <20021022.003512.15273101.iwasaki@jp.FreeBSD.org> <20021022103609.V12732-100000@gamplex.bde.org>
next in thread | previous in thread | raw e-mail | index | archive | help
> > - vm86_intcall(0x12, &vmf);
> > - basemem = vmf.vmf_ax;
> > + if ((basemem = rtcin(RTC_BASELO) + (rtcin(RTC_BASEHI)<<8)) > 640)
> > + basemem = 640;
> > +
> > + if (basemem == 0) {
> > + vm86_intcall(0x12, &vmf);
> > + basemem = vmf.vmf_ax;
> > + }
> > +
> > if (basemem > 640) {
> > printf("Preposterous BIOS basemem of %uK, truncating to 640K\n",
> > basemem);
> >
>
> This would reintroduce a large bug. The RTC gives the hardware memory
> size, but the interrupt gives the software memory size. These differ
> for one of two machines under my desk (both have Award BIOSes). The
> BIOS often steals some of the base memory. It's hard to tell whether
> this memory will be used after FreeBSD determines the memory size. It
> might be used for VM86 or (much more magically) for SMM.
>
> Reading the memory size from BIOS RAM (offset 0x413) would be safer.
> I'm not sure how standard this is. I thought that it is less standard
> than INT 0x12.
OK, RELENG_3 GENERIC kernel might have problems with base memory, RTC
was used there...
How about this? It's my original idea.
Thanks
Index: machdep.c
===================================================================
RCS file: /home/ncvs/src/sys/i386/i386/machdep.c,v
retrieving revision 1.542
diff -u -r1.542 machdep.c
--- machdep.c 12 Oct 2002 05:32:23 -0000 1.542
+++ machdep.c 22 Oct 2002 03:04:15 -0000
@@ -1281,49 +1281,7 @@
bzero(&vmf, sizeof(struct vm86frame));
bzero(physmap, sizeof(physmap));
-
- /*
- * Perform "base memory" related probes & setup
- */
- vm86_intcall(0x12, &vmf);
- basemem = vmf.vmf_ax;
- if (basemem > 640) {
- printf("Preposterous BIOS basemem of %uK, truncating to 640K\n",
- basemem);
- basemem = 640;
- }
-
- /*
- * XXX if biosbasemem is now < 640, there is a `hole'
- * between the end of base memory and the start of
- * ISA memory. The hole may be empty or it may
- * contain BIOS code or data. Map it read/write so
- * that the BIOS can write to it. (Memory from 0 to
- * the physical end of the kernel is mapped read-only
- * to begin with and then parts of it are remapped.
- * The parts that aren't remapped form holes that
- * remain read-only and are unused by the kernel.
- * The base memory area is below the physical end of
- * the kernel and right now forms a read-only hole.
- * The part of it from PAGE_SIZE to
- * (trunc_page(biosbasemem * 1024) - 1) will be
- * remapped and used by the kernel later.)
- *
- * This code is similar to the code used in
- * pmap_mapdev, but since no memory needs to be
- * allocated we simply change the mapping.
- */
- for (pa = trunc_page(basemem * 1024);
- pa < ISA_HOLE_START; pa += PAGE_SIZE)
- pmap_kenter(KERNBASE + pa, pa);
-
- /*
- * if basemem != 640, map pages r/w into vm86 page table so
- * that the bios can scribble on it.
- */
- pte = (pt_entry_t *)vm86paddr;
- for (i = basemem / 4; i < 160; i++)
- pte[i] = (i << PAGE_SHIFT) | PG_V | PG_RW | PG_U;
+ basemem = 0;
/*
* map page 1 R/W into the kernel page table so we can use it
@@ -1391,6 +1349,60 @@
physmap[physmap_idx + 1] = smap->base + smap->length;
next_run: ;
} while (vmf.vmf_ebx != 0);
+
+ /*
+ * Perform "base memory" related probes & setup
+ */
+ for (i = 0; i <= physmap_idx; i += 2) {
+ if (physmap[i] == 0x00000000) {
+ basemem = physmap[i + 1] / 1024;
+ break;
+ }
+ }
+
+ /* Fall back to the old compatibility function for base memory */
+ if (basemem == 0) {
+ vm86_intcall(0x12, &vmf);
+ basemem = vmf.vmf_ax;
+ }
+
+ if (basemem > 640) {
+ printf("Preposterous BIOS basemem of %uK, truncating to 640K\n",
+ basemem);
+ basemem = 640;
+ }
+
+ /*
+ * XXX if biosbasemem is now < 640, there is a `hole'
+ * between the end of base memory and the start of
+ * ISA memory. The hole may be empty or it may
+ * contain BIOS code or data. Map it read/write so
+ * that the BIOS can write to it. (Memory from 0 to
+ * the physical end of the kernel is mapped read-only
+ * to begin with and then parts of it are remapped.
+ * The parts that aren't remapped form holes that
+ * remain read-only and are unused by the kernel.
+ * The base memory area is below the physical end of
+ * the kernel and right now forms a read-only hole.
+ * The part of it from PAGE_SIZE to
+ * (trunc_page(biosbasemem * 1024) - 1) will be
+ * remapped and used by the kernel later.)
+ *
+ * This code is similar to the code used in
+ * pmap_mapdev, but since no memory needs to be
+ * allocated we simply change the mapping.
+ */
+ for (pa = trunc_page(basemem * 1024);
+ pa < ISA_HOLE_START; pa += PAGE_SIZE)
+ pmap_kenter(KERNBASE + pa, pa);
+
+ /*
+ * if basemem != 640, map pages r/w into vm86 page table so
+ * that the bios can scribble on it.
+ */
+ pte = (pt_entry_t *)vm86paddr;
+ for (i = basemem / 4; i < 160; i++)
+ pte[i] = (i << PAGE_SHIFT) | PG_V | PG_RW | PG_U;
if (physmap[1] != 0)
goto physmap_done;
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20021022.121355.78702461.iwasaki>