Add some convenient segment macros to the kernel. This makes the
rather obfuscated 'seg & 4' go away.
Patch-keys: i386 segment cleanup
Patch-base: 2.6.13-rc5-mm1
Signed-off-by: Zachary Amsden <[email protected]>
Index: linux-2.6.13/include/asm-i386/segment.h
===================================================================
--- linux-2.6.13.orig/include/asm-i386/segment.h 2005-08-09 19:36:36.000000000 -0700
+++ linux-2.6.13/include/asm-i386/segment.h 2005-08-09 19:43:47.000000000 -0700
@@ -98,4 +98,14 @@
*/
#define IDT_ENTRIES 256
+/*
+ * This bit is set to indicate segment selectors are in the LDT
+ */
+#define LDT_SEGMENT 4
+
+#ifndef __ASSEMBLY__
+#define segment_index(seg) ((seg) >> 3)
+#define segment_from_ldt(seg) ((seg) & LDT_SEGMENT)
+#endif
+
#endif
Index: linux-2.6.13/arch/i386/kernel/ptrace.c
===================================================================
--- linux-2.6.13.orig/arch/i386/kernel/ptrace.c 2005-08-09 19:36:36.000000000 -0700
+++ linux-2.6.13/arch/i386/kernel/ptrace.c 2005-08-10 20:40:51.000000000 -0700
@@ -146,8 +146,6 @@
return retval;
}
-#define LDT_SEGMENT 4
-
static unsigned long convert_eip_to_linear(struct task_struct *child, struct pt_regs *regs)
{
unsigned long addr, seg;
@@ -165,7 +163,7 @@
* TLS segments are used for data, and the PNPBIOS
* and APM bios ones we just ignore here.
*/
- if (seg & LDT_SEGMENT) {
+ if (segment_from_ldt(seg)) {
u32 *desc;
unsigned long base;
Index: linux-2.6.13/arch/i386/kernel/kprobes.c
===================================================================
--- linux-2.6.13.orig/arch/i386/kernel/kprobes.c 2005-08-09 19:36:36.000000000 -0700
+++ linux-2.6.13/arch/i386/kernel/kprobes.c 2005-08-10 20:42:20.000000000 -0700
@@ -163,8 +163,8 @@
/* Check if the application is using LDT entry for its code segment and
* calculate the address by reading the base address from the LDT entry.
*/
- if ((regs->xcs & 4) && (current->mm)) {
- lp = (unsigned long *) ((unsigned long)((regs->xcs >> 3) * 8)
+ if (segment_from_ldt(regs->xcs) && (current->mm)) {
+ lp = (unsigned long *) ((unsigned long)(segment_index(regs->xcs) * 8)
+ (char *) current->mm->context.ldt);
addr = (kprobe_opcode_t *) (get_desc_base(lp) + regs->eip -
sizeof(kprobe_opcode_t));
Index: linux-2.6.13/arch/i386/kernel/entry.S
===================================================================
--- linux-2.6.13.orig/arch/i386/kernel/entry.S 2005-08-09 19:36:36.000000000 -0700
+++ linux-2.6.13/arch/i386/kernel/entry.S 2005-08-09 19:43:47.000000000 -0700
@@ -268,8 +268,8 @@
# 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 | (LDT_SEGMENT << 8) | 3), %eax
+ cmpl $((LDT_SEGMENT << 8) | 3), %eax
je ldt_ss # returning to user-space with LDT SS
restore_nocheck:
RESTORE_REGS
Index: linux-2.6.13/arch/i386/mm/fault.c
===================================================================
--- linux-2.6.13.orig/arch/i386/mm/fault.c 2005-08-09 19:43:38.000000000 -0700
+++ linux-2.6.13/arch/i386/mm/fault.c 2005-08-10 20:42:20.000000000 -0700
@@ -101,7 +101,7 @@
/* Get the GDT/LDT descriptor base.
When you look for races in this code remember that
LDT and other horrors are only used in user space. */
- if (seg & (1<<2)) {
+ if (segment_from_ldt(seg)) {
/* Must lock the LDT while reading it. */
down(¤t->mm->context.sem);
desc = current->mm->context.ldt;
@@ -115,7 +115,7 @@
/* Decode the code segment base from the descriptor */
base = get_desc_base((unsigned long *)desc);
- if (seg & (1<<2)) {
+ if (segment_from_ldt(seg)) {
up(¤t->mm->context.sem);
} else
put_cpu();
-
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