similar to: [PATCH 2/3] Pnp bios gdt fix

PnP BIOS data, code, and 32-bit entry segments all have fixed limits as well; set them in the GDT rather than adding more code. It would be nice to add these fixups to the boot GDT rather than setting the GDT for each CPU; perhaps I can wiggle this in later, but getting it in before the subsys init looks tricky. Also, make some progress on deprecating the ugly Q_SET_SEL macros. Signed-off-by:

PnP BIOS data, code, and 32-bit entry segments all have fixed limits as well; set them in the GDT rather than adding more code. It would be nice to add these fixups to the boot GDT rather than setting the GDT for each CPU; perhaps I can wiggle this in later, but getting it in before the subsys init looks tricky. Also, make some progress on deprecating the ugly Q_SET_SEL macros. Signed-off-by:

Move PnP BIOS segment definitions into segment.h; the segments are reserved here, so they might as well be defined here as well. Note I didn't do this for APM BIOS, as Macintosh and other systems use those values to emulate APM in some scary way I don't want to understand. Signed-off-by: Zachary Amsden <zach@vmware.com> Index: linux-2.6.14-zach-work/include/asm-i386/segment.h

Move PnP BIOS segment definitions into segment.h; the segments are reserved here, so they might as well be defined here as well. Note I didn't do this for APM BIOS, as Macintosh and other systems use those values to emulate APM in some scary way I don't want to understand. Signed-off-by: Zachary Amsden <zach@vmware.com> Index: linux-2.6.14-zach-work/include/asm-i386/segment.h

Make GDT page aligned and page padded to support running inside of a hypervisor. This prevents false sharing of the GDT page with other hot data, which is not allowed in Xen, and causes performance problems in VMware. Rather than go back to the old method of statically allocating the GDT (which wastes unneded space for non-present CPUs), the GDT for APs is allocated dynamically. Signed-off-by:

Make GDT page aligned and page padded to support running inside of a hypervisor. This prevents false sharing of the GDT page with other hot data, which is not allowed in Xen, and causes performance problems in VMware. Rather than go back to the old method of statically allocating the GDT (which wastes unneded space for non-present CPUs), the GDT for APs is allocated dynamically. Signed-off-by:

Both the APM BIOS and PnP BIOS code use a segment hack to simulate real mode selector 0x40 (which points to the BIOS data area at 0x00400 in real mode). Several broken BIOSen use selector 0x40 as if they were running in real mode, which we make work by faking up selector 0x40 in the GDT to point to physical memory starting at 0x400. We limit the access to the remainder of this physical page

Both the APM BIOS and PnP BIOS code use a segment hack to simulate real mode selector 0x40 (which points to the BIOS data area at 0x00400 in real mode). Several broken BIOSen use selector 0x40 as if they were running in real mode, which we make work by faking up selector 0x40 in the GDT to point to physical memory starting at 0x400. We limit the access to the remainder of this physical page

Andrew Morton's fix for PnP BIOS. Signed-off-by: Zachary Amsden <zach@vmware.com> Index: linux-2.6.14-rc1/drivers/pnp/pnpbios/bioscalls.c =================================================================== --- linux-2.6.14-rc1.orig/drivers/pnp/pnpbios/bioscalls.c 2005-08-28 16:41:01.000000000 -0700 +++ linux-2.6.14-rc1/drivers/pnp/pnpbios/bioscalls.c 2005-09-28 13:13:42.000000000 -0700

Andrew Morton's fix for PnP BIOS. Signed-off-by: Zachary Amsden <zach@vmware.com> Index: linux-2.6.14-rc1/drivers/pnp/pnpbios/bioscalls.c =================================================================== --- linux-2.6.14-rc1.orig/drivers/pnp/pnpbios/bioscalls.c 2005-08-28 16:41:01.000000000 -0700 +++ linux-2.6.14-rc1/drivers/pnp/pnpbios/bioscalls.c 2005-09-28 13:13:42.000000000 -0700

Ancient inline assembler that manipulates descriptor tables is unreadable and has no type checking. Doing this in C actually generates better code, saves code space, and improves readability. The fact that you must cast descriptors to (char *) for the inline assembler to work properly caused me no end of grief working on these patches. Note that GCC does not generate rotations to utilize

Ancient inline assembler that manipulates descriptor tables is unreadable and has no type checking. Doing this in C actually generates better code, saves code space, and improves readability. The fact that you must cast descriptors to (char *) for the inline assembler to work properly caused me no end of grief working on these patches. Note that GCC does not generate rotations to utilize

It is impossible to have a zero length segment in descriptor tables using "normal" segments. One of many ways to properly protect segments to zero length is to map the base to an umapped page. Create a nicer way to do this, and stop subtracting 1 from the length passed to set_limit (note calling set limit with a zero limit does something very bad! - not anymore). Signed-off-by:

It is impossible to have a zero length segment in descriptor tables using "normal" segments. One of many ways to properly protect segments to zero length is to map the base to an umapped page. Create a nicer way to do this, and stop subtracting 1 from the length passed to set_limit (note calling set limit with a zero limit does something very bad! - not anymore). Signed-off-by:

In-Reply-To: <20060803002518.190834642@xensource.com> On Wed, 02 Aug 2006 17:25:13 -0700, Jeremy Fitzhardinge wrote: > We allow for the fact that the guest kernel may not run in ring 0. > This requires some abstraction in a few places when setting %cs or > checking privilege level (user vs kernel). I made some changes: a. Added some comments about the SEGMENT_IS_*_CODE() macros.

In-Reply-To: <20060803002518.190834642@xensource.com> On Wed, 02 Aug 2006 17:25:13 -0700, Jeremy Fitzhardinge wrote: > We allow for the fact that the guest kernel may not run in ring 0. > This requires some abstraction in a few places when setting %cs or > checking privilege level (user vs kernel). I made some changes: a. Added some comments about the SEGMENT_IS_*_CODE() macros.

Clean up of patch for letting kernel run other than ring 0: a. Add some comments about the SEGMENT_IS_*_CODE() macros. b. Add a USER_RPL macro. (Code was comparing a value to a mask in some places and to the magic number 3 in other places.) c. Add macros for table indicator field and use them. d. Change the entry.S tests for LDT stack segment to use the macros. Signed-off-by: Chuck Ebbert

Clean up of patch for letting kernel run other than ring 0: a. Add some comments about the SEGMENT_IS_*_CODE() macros. b. Add a USER_RPL macro. (Code was comparing a value to a mask in some places and to the magic number 3 in other places.) c. Add macros for table indicator field and use them. d. Change the entry.S tests for LDT stack segment to use the macros. Signed-off-by: Chuck Ebbert

I discovered an even more subtle problem; the PnP BIOS code is saving the %fs and %gs segments in inline assembler, yet it also uses the same hack for patching in a fake real mode selector for the BIOS data area. Note that the protected mode selector 0x40 overlaps the user TLS area in the GDT; this means that badly timed PnP BIOS calls could come in, save %fs, come back, and restore %fs -- to

I discovered an even more subtle problem; the PnP BIOS code is saving the %fs and %gs segments in inline assembler, yet it also uses the same hack for patching in a fake real mode selector for the BIOS data area. Note that the protected mode selector 0x40 overlaps the user TLS area in the GDT; this means that badly timed PnP BIOS calls could come in, save %fs, come back, and restore %fs -- to