2.6.3: PnPBIOS hangs with S875WP1 BIOS

2.6.3: PnPBIOS hangs with S875WP1 BIOS

[Meelis Roos]

I run a 2.6.3 kernel on Intel S875WP1 mainboard. When I enable PnPBIOS
in kernel config, the kernel gets general protection fault 0 just after
telling it found PnP BIOS. No backtrace. Disabling PnPBIOS in kernel
works around the problem.

-- 
Meelis Roos (mroos@linux.ee)

Re: 2.6.3: PnPBIOS hangs with S875WP1 BIOS

[Brian Gerst]

[-- Attachment #1: Type: text/plain, Size: 304 bytes --]

Meelis Roos wrote:
> I run a 2.6.3 kernel on Intel S875WP1 mainboard. When I enable PnPBIOS
> in kernel config, the kernel gets general protection fault 0 just after
> telling it found PnP BIOS. No backtrace. Disabling PnPBIOS in kernel
> works around the problem.
> 

Try this patch

--
				Brian Gerst

[-- Attachment #2: pnpsegs-1 --]
[-- Type: text/plain, Size: 524 bytes --]

diff -urN linux-bk/arch/i386/mm/extable.c linux/arch/i386/mm/extable.c
--- linux-bk/arch/i386/mm/extable.c	2004-02-15 00:41:41.000000000 -0500
+++ linux/arch/i386/mm/extable.c	2004-03-04 08:42:12.169000128 -0500
@@ -12,7 +12,7 @@
 	const struct exception_table_entry *fixup;
 
 #ifdef CONFIG_PNPBIOS
-	if (unlikely((regs->xcs | 8) == 0x88)) /* 0x80 or 0x88 */
+	if (unlikely((regs->xcs & ~15) == (GDT_ENTRY_PNPBIOS_BASE << 3)))
 	{
 		extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
 		extern u32 pnp_bios_is_utter_crap;

Re: 2.6.3: PnPBIOS hangs with S875WP1 BIOS

[Meelis Roos]

> Try this patch

Well, it gets a little further. No oops but a different hang:

Linux Plug and Play Support v0.97 (c) Adam Belay
PnPBIOS: Scanning system for PnP BIOS support...
PnPBIOS: Found PnP BIOS installation structure at 0xc00f3e90
PnPBIOS: PnP BIOS version 1.0, entry 0xf0000:0x44ba, dseg 0xf0000
PNPBIOS fault.. attempting recovery.
double fault, gdt at c0488100 [255 bytes]
double fault, tss at c0530800
eip = f7fa1ea6, esp = 00000028
eax = 00000028, ebx = f7fa1ea6, ecx = c048c5d4, edx = 00000086
esi = 00000000, edi = c010c958

-- 
Meelis Roos (mroos@ut.ee)      http://www.cs.ut.ee/~mroos/

Re: 2.6.3: PnPBIOS hangs with S875WP1 BIOS

[Brian Gerst]

Meelis Roos wrote:

>>Try this patch
> 
> 
> Well, it gets a little further. No oops but a different hang:
> 
> Linux Plug and Play Support v0.97 (c) Adam Belay
> PnPBIOS: Scanning system for PnP BIOS support...
> PnPBIOS: Found PnP BIOS installation structure at 0xc00f3e90
> PnPBIOS: PnP BIOS version 1.0, entry 0xf0000:0x44ba, dseg 0xf0000
> PNPBIOS fault.. attempting recovery.
> double fault, gdt at c0488100 [255 bytes]
> double fault, tss at c0530800
> eip = f7fa1ea6, esp = 00000028

Looks like the BIOS trashed the stack.  I don't think there is anything 
that can be done other than a BIOS update.

--
				Brian Gerst

Re: 2.6.3: PnPBIOS hangs with S875WP1 BIOS

[Meelis Roos]

> > PNPBIOS fault.. attempting recovery.
> > double fault, gdt at c0488100 [255 bytes]
> > double fault, tss at c0530800
> > eip = f7fa1ea6, esp = 00000028
>
> Looks like the BIOS trashed the stack.  I don't think there is anything
> that can be done other than a BIOS update.

This is the latest BIOS (P12) so I reported it to Intel.

-- 
Meelis Roos (mroos@linux.ee)

[PATCH] PnP BIOS exception fixes

[Brian Gerst]

[-- Attachment #1: Type: text/plain, Size: 205 bytes --]

This patch fixes two errors in fixup_exception() for PnP BIOS faults:
- Check for the correct segments used for the BIOS
- Fix asm constraints so that EIP and ESP are properly reloaded

--
				Brian Gerst

[-- Attachment #2: pnpsegs-2 --]
[-- Type: text/plain, Size: 777 bytes --]

diff -urN linux-bk/arch/i386/mm/extable.c linux/arch/i386/mm/extable.c
--- linux-bk/arch/i386/mm/extable.c	2004-02-15 00:41:41.000000000 -0500
+++ linux/arch/i386/mm/extable.c	2004-03-04 10:45:32.988904488 -0500
@@ -12,7 +12,7 @@
 	const struct exception_table_entry *fixup;
 
 #ifdef CONFIG_PNPBIOS
-	if (unlikely((regs->xcs | 8) == 0x88)) /* 0x80 or 0x88 */
+	if (unlikely((regs->xcs & ~15) == (GDT_ENTRY_PNPBIOS_BASE << 3)))
 	{
 		extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
 		extern u32 pnp_bios_is_utter_crap;
@@ -21,7 +21,7 @@
 		__asm__ volatile(
 			"movl %0, %%esp\n\t"
 			"jmp *%1\n\t"
-			: "=a" (pnp_bios_fault_esp), "=b" (pnp_bios_fault_eip));
+			: : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
 		panic("do_trap: can't hit this");
 	}
 #endif

Re: [PATCH] PnP BIOS exception fixes

[Linus Torvalds]

On Thu, 4 Mar 2004, Brian Gerst wrote:
>
> This patch fixes two errors in fixup_exception() for PnP BIOS faults:
> - Check for the correct segments used for the BIOS
> - Fix asm constraints so that EIP and ESP are properly reloaded

I'm almost certain that you should NOT use "g" as a constraint, since that 
allows the address to be on the stack frame, so when we compile without 
frame pointers and the compiler uses a %esp-relative thing for the branch 
address, that will totally screw up when we just re-loaded %esp inside the 
asm.

Can you use "r" instead, and test that it all works for you, and send an 
updated patch? Or just explain why I'm wrong.

		Linus

Re: [PATCH] PnP BIOS exception fixes

[Brian Gerst]

Linus Torvalds wrote:
> 
> On Thu, 4 Mar 2004, Brian Gerst wrote:
> 
>>This patch fixes two errors in fixup_exception() for PnP BIOS faults:
>>- Check for the correct segments used for the BIOS
>>- Fix asm constraints so that EIP and ESP are properly reloaded
> 
> 
> I'm almost certain that you should NOT use "g" as a constraint, since that 
> allows the address to be on the stack frame, so when we compile without 
> frame pointers and the compiler uses a %esp-relative thing for the branch 
> address, that will totally screw up when we just re-loaded %esp inside the 
> asm.
> 
> Can you use "r" instead, and test that it all works for you, and send an 
> updated patch? Or just explain why I'm wrong.
> 
> 		Linus
> 

The inputs are global variables, with absolute addresses.

--
				Brian Gerst