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| author | Rusty Russell <rusty@rustcorp.com.au> | 2006-09-26 10:52:39 +0200 |
|---|---|---|
| committer | Andi Kleen <andi@basil.nowhere.org> | 2006-09-26 10:52:39 +0200 |
| commit | 78be3706b21a232310590fe00258b224177ac05f (patch) | |
| tree | 57dbe444e57241613067145b04c0e15c98278cd6 /include | |
| parent | [PATCH] i386: Abstract sensitive instructions (diff) | |
| download | linux-78be3706b21a232310590fe00258b224177ac05f.tar.xz linux-78be3706b21a232310590fe00258b224177ac05f.zip | |
[PATCH] i386: Allow a kernel not to be in ring 0
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).
This is Chris' [RFC PATCH 15/33] move segment checks to subarch, except rather
than using #define USER_MODE_MASK which depends on a config option, we use
Zach's more flexible approach of assuming ring 3 == userspace. I also used
"get_kernel_rpl()" over "get_kernel_cs()" because I think it reads better in
the code...
1) Remove the hardcoded 3 and introduce #define SEGMENT_RPL_MASK 3 2) Add a
get_kernel_rpl() macro, and don't assume it's zero.
And:
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: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Diffstat (limited to 'include')
| -rw-r--r-- | include/asm-i386/ptrace.h | 5 | ||||
| -rw-r--r-- | include/asm-i386/segment.h | 17 |
2 files changed, 20 insertions, 2 deletions
diff --git a/include/asm-i386/ptrace.h b/include/asm-i386/ptrace.h index 30a442ec2059..21bb91679c82 100644 --- a/include/asm-i386/ptrace.h +++ b/include/asm-i386/ptrace.h @@ -60,6 +60,7 @@ struct pt_regs { #ifdef __KERNEL__ #include <asm/vm86.h> +#include <asm/segment.h> struct task_struct; extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code); @@ -73,11 +74,11 @@ extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int erro */ static inline int user_mode(struct pt_regs *regs) { - return (regs->xcs & 3) != 0; + return (regs->xcs & SEGMENT_RPL_MASK) == USER_RPL; } static inline int user_mode_vm(struct pt_regs *regs) { - return ((regs->xcs & 3) | (regs->eflags & VM_MASK)) != 0; + return ((regs->xcs & SEGMENT_RPL_MASK) | (regs->eflags & VM_MASK)) >= USER_RPL; } #define instruction_pointer(regs) ((regs)->eip) extern unsigned long profile_pc(struct pt_regs *regs); diff --git a/include/asm-i386/segment.h b/include/asm-i386/segment.h index faf995307b9e..b7ab59685ba7 100644 --- a/include/asm-i386/segment.h +++ b/include/asm-i386/segment.h @@ -83,6 +83,11 @@ #define GDT_SIZE (GDT_ENTRIES * 8) +/* Matches __KERNEL_CS and __USER_CS (they must be 2 entries apart) */ +#define SEGMENT_IS_FLAT_CODE(x) (((x) & 0xec) == GDT_ENTRY_KERNEL_CS * 8) +/* Matches PNP_CS32 and PNP_CS16 (they must be consecutive) */ +#define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == GDT_ENTRY_PNPBIOS_BASE * 8) + /* Simple and small GDT entries for booting only */ #define GDT_ENTRY_BOOT_CS 2 @@ -112,4 +117,16 @@ */ #define IDT_ENTRIES 256 +/* Bottom two bits of selector give the ring privilege level */ +#define SEGMENT_RPL_MASK 0x3 +/* Bit 2 is table indicator (LDT/GDT) */ +#define SEGMENT_TI_MASK 0x4 + +/* User mode is privilege level 3 */ +#define USER_RPL 0x3 +/* LDT segment has TI set, GDT has it cleared */ +#define SEGMENT_LDT 0x4 +#define SEGMENT_GDT 0x0 + +#define get_kernel_rpl() 0 #endif |