[PATCH] i386: espfix cleanup
Clean up the espfix code:
- Introduced PER_CPU() macro to be used from asm
- Introduced GET_DESC_BASE() macro to be used from asm
- Rewrote the fixup code in asm, as calling a C code with the altered %ss
appeared to be unsafe
- No longer altering the stack from a .fixup section
- 16bit per-cpu stack is no longer used, instead the stack segment base
is patched the way so that the high word of the kernel and user %esp
are the same.
- Added the limit-patching for the espfix segment. (Chuck Ebbert)
[jeremy@goop.org: use the x86 scaling addressing mode rather than shifting]
Signed-off-by: Stas Sergeev <stsp@aknet.ru>
Signed-off-by: Andi Kleen <ak@suse.de>
Acked-by: Zachary Amsden <zach@vmware.com>
Acked-by: Chuck Ebbert <76306.1226@compuserve.com>
Acked-by: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 5a63d6f..c38d801 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -48,6 +48,7 @@
#include <asm/smp.h>
#include <asm/page.h>
#include <asm/desc.h>
+#include <asm/percpu.h>
#include <asm/dwarf2.h>
#include "irq_vectors.h"
@@ -418,23 +419,18 @@
* This is an "official" bug of all the x86-compatible
* CPUs, which we can try to work around to make
* dosemu and wine happy. */
- subl $8, %esp # reserve space for switch16 pointer
- CFI_ADJUST_CFA_OFFSET 8
+ movl OLDESP(%esp), %eax
+ movl %esp, %edx
+ call patch_espfix_desc
+ pushl $__ESPFIX_SS
+ CFI_ADJUST_CFA_OFFSET 4
+ pushl %eax
+ CFI_ADJUST_CFA_OFFSET 4
DISABLE_INTERRUPTS
TRACE_IRQS_OFF
- movl %esp, %eax
- /* Set up the 16bit stack frame with switch32 pointer on top,
- * and a switch16 pointer on top of the current frame. */
- call setup_x86_bogus_stack
- CFI_ADJUST_CFA_OFFSET -8 # frame has moved
- TRACE_IRQS_IRET
- RESTORE_REGS
- lss 20+4(%esp), %esp # switch to 16bit stack
-1: INTERRUPT_RETURN
-.section __ex_table,"a"
- .align 4
- .long 1b,iret_exc
-.previous
+ lss (%esp), %esp
+ CFI_ADJUST_CFA_OFFSET -8
+ jmp restore_nocheck
CFI_ENDPROC
# perform work that needs to be done immediately before resumption
@@ -524,30 +520,30 @@
CFI_ENDPROC
#define FIXUP_ESPFIX_STACK \
- movl %esp, %eax; \
- /* switch to 32bit stack using the pointer on top of 16bit stack */ \
- lss %ss:CPU_16BIT_STACK_SIZE-8, %esp; \
- /* copy data from 16bit stack to 32bit stack */ \
- call fixup_x86_bogus_stack; \
- /* put ESP to the proper location */ \
- movl %eax, %esp;
-#define UNWIND_ESPFIX_STACK \
+ /* since we are on a wrong stack, we cant make it a C code :( */ \
+ GET_THREAD_INFO(%ebp); \
+ movl TI_cpu(%ebp), %ebx; \
+ PER_CPU(cpu_gdt_descr, %ebx); \
+ movl GDS_address(%ebx), %ebx; \
+ GET_DESC_BASE(GDT_ENTRY_ESPFIX_SS, %ebx, %eax, %ax, %al, %ah); \
+ addl %esp, %eax; \
+ pushl $__KERNEL_DS; \
+ CFI_ADJUST_CFA_OFFSET 4; \
pushl %eax; \
CFI_ADJUST_CFA_OFFSET 4; \
+ lss (%esp), %esp; \
+ CFI_ADJUST_CFA_OFFSET -8;
+#define UNWIND_ESPFIX_STACK \
movl %ss, %eax; \
- /* see if on 16bit stack */ \
+ /* see if on espfix stack */ \
cmpw $__ESPFIX_SS, %ax; \
- je 28f; \
-27: popl %eax; \
- CFI_ADJUST_CFA_OFFSET -4; \
-.section .fixup,"ax"; \
-28: movl $__KERNEL_DS, %eax; \
+ jne 27f; \
+ movl $__KERNEL_DS, %eax; \
movl %eax, %ds; \
movl %eax, %es; \
- /* switch to 32bit stack */ \
+ /* switch to normal stack */ \
FIXUP_ESPFIX_STACK; \
- jmp 27b; \
-.previous
+27:;
/*
* Build the entry stubs and pointer table with
@@ -614,7 +610,6 @@
pushl %eax
CFI_ADJUST_CFA_OFFSET 4
CFI_REL_OFFSET eax, 0
- xorl %eax, %eax
pushl %ebp
CFI_ADJUST_CFA_OFFSET 4
CFI_REL_OFFSET ebp, 0
@@ -627,7 +622,6 @@
pushl %edx
CFI_ADJUST_CFA_OFFSET 4
CFI_REL_OFFSET edx, 0
- decl %eax # eax = -1
pushl %ecx
CFI_ADJUST_CFA_OFFSET 4
CFI_REL_OFFSET ecx, 0
@@ -644,7 +638,7 @@
/*CFI_REGISTER es, ecx*/
movl ES(%esp), %edi # get the function address
movl ORIG_EAX(%esp), %edx # get the error code
- movl %eax, ORIG_EAX(%esp)
+ movl $-1, ORIG_EAX(%esp)
movl %ecx, ES(%esp)
/*CFI_REL_OFFSET es, ES*/
movl $(__USER_DS), %ecx
@@ -754,7 +748,7 @@
cmpw $__ESPFIX_SS, %ax
popl %eax
CFI_ADJUST_CFA_OFFSET -4
- je nmi_16bit_stack
+ je nmi_espfix_stack
cmpl $sysenter_entry,(%esp)
je nmi_stack_fixup
pushl %eax
@@ -797,7 +791,7 @@
FIX_STACK(24,nmi_stack_correct, 1)
jmp nmi_stack_correct
-nmi_16bit_stack:
+nmi_espfix_stack:
/* We have a RING0_INT_FRAME here.
*
* create the pointer to lss back
@@ -806,7 +800,6 @@
CFI_ADJUST_CFA_OFFSET 4
pushl %esp
CFI_ADJUST_CFA_OFFSET 4
- movzwl %sp, %esp
addw $4, (%esp)
/* copy the iret frame of 12 bytes */
.rept 3
@@ -817,11 +810,11 @@
CFI_ADJUST_CFA_OFFSET 4
SAVE_ALL
FIXUP_ESPFIX_STACK # %eax == %esp
- CFI_ADJUST_CFA_OFFSET -20 # the frame has now moved
xorl %edx,%edx # zero error code
call do_nmi
RESTORE_REGS
- lss 12+4(%esp), %esp # back to 16bit stack
+ lss 12+4(%esp), %esp # back to espfix stack
+ CFI_ADJUST_CFA_OFFSET -24
1: INTERRUPT_RETURN
CFI_ENDPROC
.section __ex_table,"a"