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SubjectRe: 2.6.18-mm2 boot failure on x86-64
On Fri, Oct 06, 2006 at 01:03:50PM -0500, Steve Fox wrote:
> On Fri, 2006-10-06 at 18:11 +0100, Mel Gorman wrote:
> > On (06/10/06 11:36), Vivek Goyal didst pronounce:
> > > Where is bss placed in physical memory? I guess bss_start and bss_stop
> > > from System.map will tell us. That will confirm that above memset step is
> > > stomping over bss. Then we have to just find that somewhere probably
> > > we allocated wrong physical memory area for bootmem allocator map.
> > >
> >
> > BSS is at 0x643000 -> 0x777BC4
> > init_bootmem wipes from 0x777000 -> 0x8F7000
> >
> > So the BSS bytes from 0x777000 ->0x777BC4 (which looks very suspiciously
> > pile a page alignment of addr & PAGE_MASK) gets set to 0xFF. One possible
> > fix is below. It adds a check in bad_addr() to see if the BSS section is
> > about to be used for bootmap. It Seems To Work For Me (tm) and illustrates
> > the source of the problem even if it's not the 100% correct fix.
>
> I was able to boot the machine with Mel's patch applied on top of
> -git22.


Please have a look at the attached patch. Does it make some sense.

Steve, can you please give this patch a try if it fixes the problem?

Thanks
Vivek




o Currently some code pieces assume that address returned by find_e820_area()
are page aligned. But looks like find_e820_area() had no such intention
and hence one might end up stomping over some of the data. One such
case is bootmem allocator initialization code stomped over bss.

o This patch modified find_e820_area() to return page aligned address. This
might be little wasteful of memory but at the same time probably it is
easier to handle page aligned memory.

Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
---
arch/x86_64/kernel/e820.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff -puN arch/x86_64/kernel/e820.c~x86_64-return-page-aligned-phy-addr-from-find-e820-area arch/x86_64/kernel/e820.c
--- linux-2.6.19-rc1-1M/arch/x86_64/kernel/e820.c~x86_64-return-page-aligned-phy-addr-from-find-e820-area 2006-10-06 15:28:13.000000000 -0400
+++ linux-2.6.19-rc1-1M-root/arch/x86_64/kernel/e820.c 2006-10-06 15:44:45.000000000 -0400
@@ -54,13 +54,13 @@ static inline int bad_addr(unsigned long

/* various gunk below that needed for SMP startup */
if (addr < 0x8000) {
- *addrp = 0x8000;
+ *addrp = PAGE_ALIGN(0x8000);
return 1;
}

/* direct mapping tables of the kernel */
if (last >= table_start<<PAGE_SHIFT && addr < table_end<<PAGE_SHIFT) {
- *addrp = table_end << PAGE_SHIFT;
+ *addrp = PAGE_ALIGN(table_end << PAGE_SHIFT);
return 1;
}

@@ -68,18 +68,18 @@ static inline int bad_addr(unsigned long
#ifdef CONFIG_BLK_DEV_INITRD
if (LOADER_TYPE && INITRD_START && last >= INITRD_START &&
addr < INITRD_START+INITRD_SIZE) {
- *addrp = INITRD_START + INITRD_SIZE;
+ *addrp = PAGE_ALIGN(INITRD_START + INITRD_SIZE);
return 1;
}
#endif
/* kernel code */
- if (last >= __pa_symbol(&_text) && last < __pa_symbol(&_end)) {
- *addrp = __pa_symbol(&_end);
+ if (last >= __pa_symbol(&_text) && addr < __pa_symbol(&_end)) {
+ *addrp = PAGE_ALIGN(__pa_symbol(&_end));
return 1;
}

if (last >= ebda_addr && addr < ebda_addr + ebda_size) {
- *addrp = ebda_addr + ebda_size;
+ *addrp = PAGE_ALIGN(ebda_addr + ebda_size);
return 1;
}

@@ -152,7 +152,7 @@ unsigned long __init find_e820_area(unsi
continue;
while (bad_addr(&addr, size) && addr+size <= ei->addr+ei->size)
;
- last = addr + size;
+ last = PAGE_ALIGN(addr) + size;
if (last > ei->addr + ei->size)
continue;
if (last > end)
_
-
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