From: Joerg Roedel <jroedel@xxxxxxx> This makes it easier to split up the shared iret code path. Signed-off-by: Joerg Roedel <jroedel@xxxxxxx> --- arch/x86/entry/entry_32.S | 97 ++++++++++++++++++++++++----------------------- 1 file changed, 49 insertions(+), 48 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index ec288be..118420b 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -221,6 +221,54 @@ POP_GS_EX .endm +.macro CHECK_AND_APPLY_ESPFIX +#ifdef CONFIG_X86_ESPFIX32 +#define GDT_ESPFIX_SS PER_CPU_VAR(gdt_page) + (GDT_ENTRY_ESPFIX_SS * 8) + + ALTERNATIVE "jmp .Lend_\@", "", X86_BUG_ESPFIX + + movl PT_EFLAGS(%esp), %eax # mix EFLAGS, SS and CS + /* + * Warning: PT_OLDSS(%esp) contains the wrong/random values if we + * are returning to the kernel. + * See comments in process.c:copy_thread() for details. + */ + movb PT_OLDSS(%esp), %ah + movb PT_CS(%esp), %al + andl $(X86_EFLAGS_VM | (SEGMENT_TI_MASK << 8) | SEGMENT_RPL_MASK), %eax + cmpl $((SEGMENT_LDT << 8) | USER_RPL), %eax + jne .Lend_\@ # returning to user-space with LDT SS + + /* + * Setup and switch to ESPFIX stack + * + * We're returning to userspace with a 16 bit stack. The CPU will not + * restore the high word of ESP for us on executing iret... This is an + * "official" bug of all the x86-compatible CPUs, which we can work + * around to make dosemu and wine happy. We do this by preloading the + * high word of ESP with the high word of the userspace ESP while + * compensating for the offset by changing to the ESPFIX segment with + * a base address that matches for the difference. + */ + mov %esp, %edx /* load kernel esp */ + mov PT_OLDESP(%esp), %eax /* load userspace esp */ + mov %dx, %ax /* eax: new kernel esp */ + sub %eax, %edx /* offset (low word is 0) */ + shr $16, %edx + mov %dl, GDT_ESPFIX_SS + 4 /* bits 16..23 */ + mov %dh, GDT_ESPFIX_SS + 7 /* bits 24..31 */ + pushl $__ESPFIX_SS + pushl %eax /* new kernel esp */ + /* + * Disable interrupts, but do not irqtrace this section: we + * will soon execute iret and the tracer was already set to + * the irqstate after the IRET: + */ + DISABLE_INTERRUPTS(CLBR_ANY) + lss (%esp), %esp /* switch to espfix segment */ +.Lend_\@: +#endif /* CONFIG_X86_ESPFIX32 */ +.endm /* * %eax: prev task * %edx: next task @@ -547,21 +595,7 @@ ENTRY(entry_INT80_32) restore_all: TRACE_IRQS_IRET .Lrestore_all_notrace: -#ifdef CONFIG_X86_ESPFIX32 - ALTERNATIVE "jmp .Lrestore_nocheck", "", X86_BUG_ESPFIX - - movl PT_EFLAGS(%esp), %eax # mix EFLAGS, SS and CS - /* - * Warning: PT_OLDSS(%esp) contains the wrong/random values if we - * are returning to the kernel. - * See comments in process.c:copy_thread() for details. - */ - movb PT_OLDSS(%esp), %ah - movb PT_CS(%esp), %al - andl $(X86_EFLAGS_VM | (SEGMENT_TI_MASK << 8) | SEGMENT_RPL_MASK), %eax - cmpl $((SEGMENT_LDT << 8) | USER_RPL), %eax - je .Lldt_ss # returning to user-space with LDT SS -#endif + CHECK_AND_APPLY_ESPFIX .Lrestore_nocheck: RESTORE_REGS 4 # skip orig_eax/error_code .Lirq_return: @@ -579,39 +613,6 @@ ENTRY(iret_exc ) jmp common_exception .previous _ASM_EXTABLE(.Lirq_return, iret_exc) - -#ifdef CONFIG_X86_ESPFIX32 -.Lldt_ss: -/* - * Setup and switch to ESPFIX stack - * - * We're returning to userspace with a 16 bit stack. The CPU will not - * restore the high word of ESP for us on executing iret... This is an - * "official" bug of all the x86-compatible CPUs, which we can work - * around to make dosemu and wine happy. We do this by preloading the - * high word of ESP with the high word of the userspace ESP while - * compensating for the offset by changing to the ESPFIX segment with - * a base address that matches for the difference. - */ -#define GDT_ESPFIX_SS PER_CPU_VAR(gdt_page) + (GDT_ENTRY_ESPFIX_SS * 8) - mov %esp, %edx /* load kernel esp */ - mov PT_OLDESP(%esp), %eax /* load userspace esp */ - mov %dx, %ax /* eax: new kernel esp */ - sub %eax, %edx /* offset (low word is 0) */ - shr $16, %edx - mov %dl, GDT_ESPFIX_SS + 4 /* bits 16..23 */ - mov %dh, GDT_ESPFIX_SS + 7 /* bits 24..31 */ - pushl $__ESPFIX_SS - pushl %eax /* new kernel esp */ - /* - * Disable interrupts, but do not irqtrace this section: we - * will soon execute iret and the tracer was already set to - * the irqstate after the IRET: - */ - DISABLE_INTERRUPTS(CLBR_ANY) - lss (%esp), %esp /* switch to espfix segment */ - jmp .Lrestore_nocheck -#endif ENDPROC(entry_INT80_32) .macro FIXUP_ESPFIX_STACK -- 2.7.4
