The patch titled
x86: slight cleanups for x86 ring macros
has been added to the -mm tree. Its filename is
x86-allow-a-kernel-to-not-be-in-ring-0-tidy.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: x86: slight cleanups for x86 ring macros
From: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
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 <76306.1226@xxxxxxxxxxxxxx>
Acked-by: Zachary Amsden <zach@xxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
diff -puN arch/i386/kernel/entry.S~x86-allow-a-kernel-to-not-be-in-ring-0-tidy arch/i386/kernel/entry.S
--- a/arch/i386/kernel/entry.S~x86-allow-a-kernel-to-not-be-in-ring-0-tidy
+++ a/arch/i386/kernel/entry.S
@@ -230,7 +230,7 @@ check_userspace:
movl EFLAGS(%esp), %eax # mix EFLAGS and CS
movb CS(%esp), %al
andl $(VM_MASK | SEGMENT_RPL_MASK), %eax
- cmpl $SEGMENT_RPL_MASK, %eax
+ cmpl $USER_RPL, %eax
jb resume_kernel # not returning to v8086 or userspace
ENTRY(resume_userspace)
cli # make sure we don't miss an interrupt
@@ -368,8 +368,8 @@ 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 -puN include/asm-i386/ptrace.h~x86-allow-a-kernel-to-not-be-in-ring-0-tidy include/asm-i386/ptrace.h
--- a/include/asm-i386/ptrace.h~x86-allow-a-kernel-to-not-be-in-ring-0-tidy
+++ a/include/asm-i386/ptrace.h
@@ -74,11 +74,11 @@ extern void send_sigtrap(struct task_str
*/
static inline int user_mode(struct pt_regs *regs)
{
- return (regs->xcs & SEGMENT_RPL_MASK) == 3;
+ return (regs->xcs & SEGMENT_RPL_MASK) == USER_RPL;
}
static inline int user_mode_vm(struct pt_regs *regs)
{
- return (((regs->xcs & SEGMENT_RPL_MASK) | (regs->eflags & VM_MASK)) >= 3);
+ 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 -puN include/asm-i386/segment.h~x86-allow-a-kernel-to-not-be-in-ring-0-tidy include/asm-i386/segment.h
--- a/include/asm-i386/segment.h~x86-allow-a-kernel-to-not-be-in-ring-0-tidy
+++ a/include/asm-i386/segment.h
@@ -83,10 +83,9 @@
#define GDT_SIZE (GDT_ENTRIES * 8)
-/*
- * Some tricky tests to match code segments after a fault
- */
+/* 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 */
@@ -118,8 +117,16 @@
*/
#define IDT_ENTRIES 256
-/* Bottom three bits of xcs give the ring privilege level */
-#define SEGMENT_RPL_MASK 0x3
+/* 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
_
Patches currently in -mm which might be from rusty@xxxxxxxxxxxxxxx are
fix-x86_64-mm-early-param-again.patch
fix-x86_64-mm-early-param.patch
x86-remove-locally-defined-ldt-structure-in-favour-of-standard-type.patch
x86-allow-a-kernel-to-not-be-in-ring-0.patch
x86-allow-a-kernel-to-not-be-in-ring-0-tidy.patch
x86-replace-sensitive-instructions-with-macros.patch
x86-roll-all-the-cpuid-asm-into-one-__cpuid-call.patch
x86-trivial-pgtableh-__assembly__-move.patch
x86-trivial-move-of-__have-macros-in-i386-pagetable-headers.patch
x86-trivial-move-of-ptep_set_access_flags.patch
x86-remove-unused-include-from-efi_stubs.patch
eisa-bus-modalias-attributes-support-1.patch
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