[PATCH]: 4/4GB:

From: Kirill Korotaev
Date: Thu Nov 11 2004 - 11:20:43 EST


This patch fixes exception handling in RESTORE_ALL macro on returing
to user space. Incorrect values in %ds/%es can lead to incorrect behaivour and iret to kernel space address. This patch moves
exception handler from .fixup section to .entry.text and makes it
to be between int80_ret_start_marker/int80_ret_end_marker markers.

Signed-Off-By: Kirill Korotaev <dev@xxxxx>

Kirill

P.S. These 4GB split patches are against modified 2.6.8.1 kernel, but should be appliable to last Fedora kernels --- ./arch/i386/kernel/entry.S.4gbrest 2004-11-10 11:21:32.000000000 +0300
+++ ./arch/i386/kernel/entry.S 2004-11-10 12:35:24.239613040 +0300
@@ -167,7 +167,7 @@ int80_ret_start_marker: \
movl %edx, %esp; \
movl %ecx, %cr3; \
\
- __RESTORE_ALL; \
+ __RESTORE_ALL_USER; \
int80_ret_end_marker: \
2:

@@ -204,14 +204,19 @@ int80_ret_end_marker: \

#define __RESTORE_REGS \
__RESTORE_INT_REGS; \
+ popl %ds; \
+ popl %es;
+
+#define __RESTORE_REGS_USER \
+ __RESTORE_INT_REGS; \
111: popl %ds; \
222: popl %es; \
-.section .fixup,"ax"; \
+ jmp 666f; \
444: movl $0,(%esp); \
jmp 111b; \
555: movl $0,(%esp); \
jmp 222b; \
-.previous; \
+666: \
.section __ex_table,"a";\
.align 4; \
.long 111b,444b;\
@@ -220,6 +225,13 @@ int80_ret_end_marker: \

#define __RESTORE_ALL \
__RESTORE_REGS \
+ __RESTORE_IRET
+
+#define __RESTORE_ALL_USER \
+ __RESTORE_REGS_USER \
+ __RESTORE_IRET
+
+#define __RESTORE_IRET \
addl $4, %esp; \
333: iret; \
.section .fixup,"ax"; \