[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/traps.c b/arch/i386/kernel/traps.c
index 56655ea..f9bb1f8 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -1088,49 +1088,24 @@
#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), ®s->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;
}
/*