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[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>
This commit is contained in:
Stas Sergeev 2006-12-07 02:14:01 +01:00 committed by Andi Kleen
parent bb81a09e55
commit be44d2aabc
7 changed files with 103 additions and 97 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/i386/kernel/asm-offsets.c
View File

@ -58,6 +58,11 @@ void foo(void)
OFFSET(TI_sysenter_return, thread_info, sysenter_return);
BLANK();
OFFSET(GDS_size, Xgt_desc_struct, size);
OFFSET(GDS_address, Xgt_desc_struct, address);
OFFSET(GDS_pad, Xgt_desc_struct, pad);
BLANK();
OFFSET(EXEC_DOMAIN_handler, exec_domain, handler);
OFFSET(RT_SIGFRAME_sigcontext, rt_sigframe, uc.uc_mcontext);
BLANK();

11
arch/i386/kernel/cpu/common.c
View File

@ -24,9 +24,6 @@
DEFINE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
EXPORT_PER_CPU_SYMBOL(cpu_gdt_descr);
DEFINE_PER_CPU(unsigned char, cpu_16bit_stack[CPU_16BIT_STACK_SIZE]);
EXPORT_PER_CPU_SYMBOL(cpu_16bit_stack);
static int cachesize_override __cpuinitdata = -1;
static int disable_x86_fxsr __cpuinitdata;
static int disable_x86_serial_nr __cpuinitdata = 1;
@ -603,7 +600,6 @@ void __cpuinit cpu_init(void)
struct tss_struct * t = &per_cpu(init_tss, cpu);
struct thread_struct *thread = &current->thread;
struct desc_struct *gdt;
__u32 stk16_off = (__u32)&per_cpu(cpu_16bit_stack, cpu);
struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
if (cpu_test_and_set(cpu, cpu_initialized)) {
@ -651,13 +647,6 @@ old_gdt:
* and set up the GDT descriptor:
*/
memcpy(gdt, cpu_gdt_table, GDT_SIZE);
/* Set up GDT entry for 16bit stack */
*(__u64 *)(&gdt[GDT_ENTRY_ESPFIX_SS]) |=
((((__u64)stk16_off) << 16) & 0x000000ffffff0000ULL) |
((((__u64)stk16_off) << 32) & 0xff00000000000000ULL) |
(CPU_16BIT_STACK_SIZE - 1);
cpu_gdt_descr->size = GDT_SIZE - 1;
cpu_gdt_descr->address = (unsigned long)gdt;

73
arch/i386/kernel/entry.S
View File

@ -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 @@ ldt_ss:
* 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 @@ syscall_badsys:
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 @@ error_code:
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 @@ error_code:
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 @@ error_code:
/*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 @@ KPROBE_ENTRY(nmi)
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 @@ nmi_debug_stack_check:
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 @@ nmi_16bit_stack:
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 @@ nmi_16bit_stack:
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"

2
arch/i386/kernel/head.S
View File

@ -584,7 +584,7 @@ ENTRY(cpu_gdt_table)
.quad 0x00009a000000ffff /* 0xc0 APM CS 16 code (16 bit) */
.quad 0x004092000000ffff /* 0xc8 APM DS data */
.quad 0x0000920000000000 /* 0xd0 - ESPFIX 16-bit SS */
.quad 0x00c0920000000000 /* 0xd0 - ESPFIX SS */
.quad 0x0000000000000000 /* 0xd8 - unused */
.quad 0x0000000000000000 /* 0xe0 - unused */
.quad 0x0000000000000000 /* 0xe8 - unused */

57
arch/i386/kernel/traps.c
View File

@ -1088,49 +1088,24 @@ fastcall void do_spurious_interrupt_bug(struct pt_regs * regs,
#endif
}
fastcall void setup_x86_bogus_stack(unsigned char * stk)
fastcall unsigned long patch_espfix_desc(unsigned long uesp,
unsigned long kesp)
{
unsigned long *switch16_ptr, *switch32_ptr;
struct pt_regs *regs;
unsigned long stack_top, stack_bot;
unsigned short iret_frame16_off;
int cpu = smp_processor_id();
/* reserve the space on 32bit stack for the magic switch16 pointer */
memmove(stk, stk + 8, sizeof(struct pt_regs));
switch16_ptr = (unsigned long *)(stk + sizeof(struct pt_regs));
regs = (struct pt_regs *)stk;
/* now the switch32 on 16bit stack */
stack_bot = (unsigned long)&per_cpu(cpu_16bit_stack, cpu);
stack_top = stack_bot + CPU_16BIT_STACK_SIZE;
switch32_ptr = (unsigned long *)(stack_top - 8);
iret_frame16_off = CPU_16BIT_STACK_SIZE - 8 - 20;
/* copy iret frame on 16bit stack */
memcpy((void *)(stack_bot + iret_frame16_off), &regs->eip, 20);
/* fill in the switch pointers */
switch16_ptr[0] = (regs->esp & 0xffff0000) | iret_frame16_off;
switch16_ptr[1] = __ESPFIX_SS;
switch32_ptr[0] = (unsigned long)stk + sizeof(struct pt_regs) +
8 - CPU_16BIT_STACK_SIZE;
switch32_ptr[1] = __KERNEL_DS;
}
fastcall unsigned char * fixup_x86_bogus_stack(unsigned short sp)
{
unsigned long *switch32_ptr;
unsigned char *stack16, *stack32;
unsigned long stack_top, stack_bot;
int len;
int cpu = smp_processor_id();
stack_bot = (unsigned long)&per_cpu(cpu_16bit_stack, cpu);
stack_top = stack_bot + CPU_16BIT_STACK_SIZE;
switch32_ptr = (unsigned long *)(stack_top - 8);
/* copy the data from 16bit stack to 32bit stack */
len = CPU_16BIT_STACK_SIZE - 8 - sp;
stack16 = (unsigned char *)(stack_bot + sp);
stack32 = (unsigned char *)
(switch32_ptr[0] + CPU_16BIT_STACK_SIZE - 8 - len);
memcpy(stack32, stack16, len);
return stack32;
struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
struct desc_struct *gdt = (struct desc_struct *)cpu_gdt_descr->address;
unsigned long base = (kesp - uesp) & -THREAD_SIZE;
unsigned long new_kesp = kesp - base;
unsigned long lim_pages = (new_kesp | (THREAD_SIZE - 1)) >> PAGE_SHIFT;
__u64 desc = *(__u64 *)&gdt[GDT_ENTRY_ESPFIX_SS];
/* Set up base for espfix segment */
desc &= 0x00f0ff0000000000ULL;
desc |= ((((__u64)base) << 16) & 0x000000ffffff0000ULL) |
((((__u64)base) << 32) & 0xff00000000000000ULL) |
((((__u64)lim_pages) << 32) & 0x000f000000000000ULL) |
(lim_pages & 0xffff);
*(__u64 *)&gdt[GDT_ENTRY_ESPFIX_SS] = desc;
return new_kesp;
}
/*

27
include/asm-i386/desc.h
View File

@ -4,8 +4,6 @@
#include <asm/ldt.h>
#include <asm/segment.h>
#define CPU_16BIT_STACK_SIZE 1024
#ifndef __ASSEMBLY__
#include <linux/preempt.h>
@ -16,8 +14,6 @@
extern struct desc_struct cpu_gdt_table[GDT_ENTRIES];
DECLARE_PER_CPU(unsigned char, cpu_16bit_stack[CPU_16BIT_STACK_SIZE]);
struct Xgt_desc_struct {
unsigned short size;
unsigned long address __attribute__((packed));
@ -181,6 +177,29 @@ static inline unsigned long get_desc_base(unsigned long *desc)
return base;
}
#else /* __ASSEMBLY__ */
/*
* GET_DESC_BASE reads the descriptor base of the specified segment.
*
* Args:
* idx - descriptor index
* gdt - GDT pointer
* base - 32bit register to which the base will be written
* lo_w - lo word of the "base" register
* lo_b - lo byte of the "base" register
* hi_b - hi byte of the low word of the "base" register
*
* Example:
* GET_DESC_BASE(GDT_ENTRY_ESPFIX_SS, %ebx, %eax, %ax, %al, %ah)
* Will read the base address of GDT_ENTRY_ESPFIX_SS and put it into %eax.
*/
#define GET_DESC_BASE(idx, gdt, base, lo_w, lo_b, hi_b) \
movb idx*8+4(gdt), lo_b; \
movb idx*8+7(gdt), hi_b; \
shll $16, base; \
movw idx*8+2(gdt), lo_w;
#endif /* !__ASSEMBLY__ */
#endif

25
include/asm-i386/percpu.h
View File

@ -1,6 +1,31 @@
#ifndef __ARCH_I386_PERCPU__
#define __ARCH_I386_PERCPU__
#ifndef __ASSEMBLY__
#include <asm-generic/percpu.h>
#else
/*
* PER_CPU finds an address of a per-cpu variable.
*
* Args:
* var - variable name
* cpu - 32bit register containing the current CPU number
*
* The resulting address is stored in the "cpu" argument.
*
* Example:
* PER_CPU(cpu_gdt_descr, %ebx)
*/
#ifdef CONFIG_SMP
#define PER_CPU(var, cpu) \
movl __per_cpu_offset(,cpu,4), cpu; \
addl $per_cpu__/**/var, cpu;
#else /* ! SMP */
#define PER_CPU(var, cpu) \
movl $per_cpu__/**/var, cpu;
#endif /* SMP */
#endif /* !__ASSEMBLY__ */
#endif /* __ARCH_I386_PERCPU__ */