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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 /arch/i386/kernel | |
| parent | 0da5db313317e3195482d3e660a1074857374a89 (diff) | |
| download | blackbird-op-linux-78be3706b21a232310590fe00258b224177ac05f.tar.gz blackbird-op-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 'arch/i386/kernel')
| -rw-r--r-- | arch/i386/kernel/entry.S | 9 | ||||
| -rw-r--r-- | arch/i386/kernel/process.c | 2 |
2 files changed, 6 insertions, 5 deletions
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S index 3872fca5c74a..284f2e908ad0 100644 --- a/arch/i386/kernel/entry.S +++ b/arch/i386/kernel/entry.S @@ -240,8 +240,9 @@ ret_from_intr: check_userspace: movl EFLAGS(%esp), %eax # mix EFLAGS and CS movb CS(%esp), %al - testl $(VM_MASK | 3), %eax - jz resume_kernel + andl $(VM_MASK | SEGMENT_RPL_MASK), %eax + cmpl $USER_RPL, %eax + jb resume_kernel # not returning to v8086 or userspace ENTRY(resume_userspace) DISABLE_INTERRUPTS # make sure we don't miss an interrupt # setting need_resched or sigpending @@ -377,8 +378,8 @@ restore_all: # See comments in process.c:copy_thread() for details. movb OLDSS(%esp), %ah movb CS(%esp), %al - andl $(VM_MASK | (4 << 8) | 3), %eax - cmpl $((4 << 8) | 3), %eax + andl $(VM_MASK | (SEGMENT_TI_MASK << 8) | SEGMENT_RPL_MASK), %eax + cmpl $((SEGMENT_LDT << 8) | USER_RPL), %eax CFI_REMEMBER_STATE je ldt_ss # returning to user-space with LDT SS restore_nocheck: diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c index 220aeca59c3a..8c190ca7ae44 100644 --- a/arch/i386/kernel/process.c +++ b/arch/i386/kernel/process.c @@ -338,7 +338,7 @@ int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags) regs.xes = __USER_DS; regs.orig_eax = -1; regs.eip = (unsigned long) kernel_thread_helper; - regs.xcs = __KERNEL_CS; + regs.xcs = __KERNEL_CS | get_kernel_rpl(); regs.eflags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2; /* Ok, create the new process.. */ |
