According to BIOS32 specification
(http://members.datafast.net.au/dft0802/specs/bios32.pdf), at most two
pages per BIOS32 service should be set executable and no pages need to
be writeable. This patch modifies bios32_service() to set proper page
access permissions at time of service discovery, as described in the
specification.
Further, hardcoded protection of memory area between 640k to 1Mb have
been removed from static_protections(), since only pages mentioned
above need to be executable, not whole BIOS region.
The patch have been developed for Linux 2.6.30 x86 by Siarhei Liakh
<[email protected]> and Xuxian Jiang <[email protected]>.
---
Signed-off-by: Siarhei Liakh <[email protected]>
Signed-off-by: Xuxian Jiang <[email protected]>
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index e17efed..9ce45d2 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -254,13 +254,6 @@ static inline pgprot_t
static_protections(pgprot_t prot, unsigned long address,
pgprot_t forbidden = __pgprot(0);
/*
- * The BIOS area between 640k and 1Mb needs to be executable for
- * PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
- */
- if (within(pfn, BIOS_BEGIN >> PAGE_SHIFT, BIOS_END >> PAGE_SHIFT))
- pgprot_val(forbidden) |= _PAGE_NX;
-
- /*
* The kernel text needs to be executable for obvious reasons
* Does not cover __inittext since that is gone later on. On
* 64bit we do not enforce !NX on the low mapping
diff --git a/arch/x86/pci/pcbios.c b/arch/x86/pci/pcbios.c
index 1c975cc..31a2653 100644
--- a/arch/x86/pci/pcbios.c
+++ b/arch/x86/pci/pcbios.c
@@ -8,6 +8,7 @@
#include <linux/uaccess.h>
#include <asm/pci_x86.h>
#include <asm/pci-functions.h>
+#include <asm/cacheflush.h>
/* BIOS32 signature: "_32_" */
#define BIOS32_SIGNATURE (('_' << 0) + ('3' << 8) + ('2' << 16) + ('_' << 24))
@@ -69,6 +70,7 @@ static unsigned long bios32_service(unsigned long service)
unsigned long length; /* %ecx */
unsigned long entry; /* %edx */
unsigned long flags;
+ unsigned long pg_address;
local_irq_save(flags);
__asm__("lcall *(%%edi); cld"
@@ -82,15 +84,21 @@ static unsigned long bios32_service(unsigned long service)
local_irq_restore(flags);
switch (return_code) {
- case 0:
- return address + entry;
- case 0x80: /* Not present */
- printk(KERN_WARNING "bios32_service(0x%lx): not present\n", service);
- return 0;
- default: /* Shouldn't happen */
- printk(KERN_WARNING "bios32_service(0x%lx): returned 0x%x -- BIOS bug!\n",
- service, return_code);
- return 0;
+ case 0: /* Service present, set proper page access */
+ address += entry;
+ pg_address = PFN_DOWN(address + PAGE_OFFSET) << PAGE_SHIFT;
+ set_memory_ro(pg_address, 2);
+ set_memory_x(pg_address, 2);
+ return address;
+ case 0x80: /* Not present */
+ printk(KERN_WARNING "bios32_service(0x%lx): not present\n",
+ service);
+ return 0;
+ default: /* Shouldn't happen */
+ printk(KERN_WARNING "bios32_service(0x%lx): "
+ "returned 0x%x -- BIOS bug!\n",
+ service, return_code);
+ return 0;
}
}
Siarhei Liakh wrote:
> According to BIOS32 specification
> (http://members.datafast.net.au/dft0802/specs/bios32.pdf), at most two
> pages per BIOS32 service should be set executable and no pages need to
> be writeable. This patch modifies bios32_service() to set proper page
> access permissions at time of service discovery, as described in the
> specification.
> Further, hardcoded protection of memory area between 640k to 1Mb have
> been removed from static_protections(), since only pages mentioned
> above need to be executable, not whole BIOS region.
>
> The patch have been developed for Linux 2.6.30 x86 by Siarhei Liakh
> <[email protected]> and Xuxian Jiang <[email protected]>.
>
Specifications mean little in the BIOS space, unfortunately. Do we have
any notion about how many machines this has been tested on?
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
For now I have only tested it on my home system and qemu. Actuallym in
both cases, I had to compile kernel with only CONFIG_PCI_GOBIOS=y,
since Kernel prefers other ways to access PCI when possible (with
CONFIG_PCI_GOANY=y).
On Sun, Jul 19, 2009 at 8:53 PM, H. Peter Anvin<[email protected]> wrote:
> Siarhei Liakh wrote:
>> According to BIOS32 specification
>> (http://members.datafast.net.au/dft0802/specs/bios32.pdf), at most two
>> pages per BIOS32 service should be set executable and no pages need to
>> be writeable. This patch modifies bios32_service() to set proper page
>> access permissions at time of service discovery, as described in the
>> specification.
>> Further, hardcoded protection of memory area between 640k to 1Mb have
>> been removed from static_protections(), since only pages mentioned
>> above need to be executable, not whole BIOS region.
>>
>> The patch have been developed for Linux 2.6.30 x86 by Siarhei Liakh
>> <[email protected]> and Xuxian Jiang <[email protected]>.
>>
>
> Specifications mean little in the BIOS space, unfortunately. ?Do we have
> any notion about how many machines this has been tested on?
>
> ? ? ? ?-hpa
>
> --
> H. Peter Anvin, Intel Open Source Technology Center
> I work for Intel. ?I don't speak on their behalf.
>
>