Commit-ID: 7209a75d2009dbf7745e2fd354abf25c3deb3ca3 Gitweb: http://git.kernel.org/tip/7209a75d2009dbf7745e2fd354abf25c3deb3ca3 Author: Andy Lutomirski <luto@xxxxxxxxxxxxxx> AuthorDate: Wed, 23 Jul 2014 08:34:11 -0700 Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> CommitDate: Mon, 28 Jul 2014 15:25:40 -0700 x86_64/entry/xen: Do not invoke espfix64 on Xen This moves the espfix64 logic into native_iret. To make this work, it gets rid of the native patch for INTERRUPT_RETURN: INTERRUPT_RETURN on native kernels is now 'jmp native_iret'. This changes the 16-bit SS behavior on Xen from OOPSing to leaking some bits of the Xen hypervisor's RSP (I think). [ hpa: this is a nonzero cost on native, but probably not enough to measure. Xen needs to fix this in their own code, probably doing something equivalent to espfix64. ] Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/7b8f1d8ef6597cb16ae004a43c56980a7de3cf94.1406129132.git.luto@xxxxxxxxxxxxxx Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> --- arch/x86/include/asm/irqflags.h | 2 +- arch/x86/kernel/entry_64.S | 28 ++++++++++------------------ arch/x86/kernel/paravirt_patch_64.c | 2 -- 3 files changed, 11 insertions(+), 21 deletions(-) diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h index bba3cf8..0a8b519 100644 --- a/arch/x86/include/asm/irqflags.h +++ b/arch/x86/include/asm/irqflags.h @@ -129,7 +129,7 @@ static inline notrace unsigned long arch_local_irq_save(void) #define PARAVIRT_ADJUST_EXCEPTION_FRAME /* */ -#define INTERRUPT_RETURN iretq +#define INTERRUPT_RETURN jmp native_iret #define USERGS_SYSRET64 \ swapgs; \ sysretq; diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index b25ca96..c844f08 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -830,27 +830,24 @@ restore_args: RESTORE_ARGS 1,8,1 irq_return: + INTERRUPT_RETURN + +ENTRY(native_iret) /* * Are we returning to a stack segment from the LDT? Note: in * 64-bit mode SS:RSP on the exception stack is always valid. */ #ifdef CONFIG_X86_ESPFIX64 testb $4,(SS-RIP)(%rsp) - jnz irq_return_ldt + jnz native_irq_return_ldt #endif -irq_return_iret: - INTERRUPT_RETURN - _ASM_EXTABLE(irq_return_iret, bad_iret) - -#ifdef CONFIG_PARAVIRT -ENTRY(native_iret) +native_irq_return_iret: iretq - _ASM_EXTABLE(native_iret, bad_iret) -#endif + _ASM_EXTABLE(native_irq_return_iret, bad_iret) #ifdef CONFIG_X86_ESPFIX64 -irq_return_ldt: +native_irq_return_ldt: pushq_cfi %rax pushq_cfi %rdi SWAPGS @@ -872,7 +869,7 @@ irq_return_ldt: SWAPGS movq %rax,%rsp popq_cfi %rax - jmp irq_return_iret + jmp native_irq_return_iret #endif .section .fixup,"ax" @@ -956,13 +953,8 @@ __do_double_fault: cmpl $__KERNEL_CS,CS(%rdi) jne do_double_fault movq RIP(%rdi),%rax - cmpq $irq_return_iret,%rax -#ifdef CONFIG_PARAVIRT - je 1f - cmpq $native_iret,%rax -#endif + cmpq $native_irq_return_iret,%rax jne do_double_fault /* This shouldn't happen... */ -1: movq PER_CPU_VAR(kernel_stack),%rax subq $(6*8-KERNEL_STACK_OFFSET),%rax /* Reset to original stack */ movq %rax,RSP(%rdi) @@ -1428,7 +1420,7 @@ error_sti: */ error_kernelspace: incl %ebx - leaq irq_return_iret(%rip),%rcx + leaq native_irq_return_iret(%rip),%rcx cmpq %rcx,RIP+8(%rsp) je error_swapgs movl %ecx,%eax /* zero extend */ diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c index 3f08f34..a1da673 100644 --- a/arch/x86/kernel/paravirt_patch_64.c +++ b/arch/x86/kernel/paravirt_patch_64.c @@ -6,7 +6,6 @@ DEF_NATIVE(pv_irq_ops, irq_disable, "cli"); DEF_NATIVE(pv_irq_ops, irq_enable, "sti"); DEF_NATIVE(pv_irq_ops, restore_fl, "pushq %rdi; popfq"); DEF_NATIVE(pv_irq_ops, save_fl, "pushfq; popq %rax"); -DEF_NATIVE(pv_cpu_ops, iret, "iretq"); DEF_NATIVE(pv_mmu_ops, read_cr2, "movq %cr2, %rax"); DEF_NATIVE(pv_mmu_ops, read_cr3, "movq %cr3, %rax"); DEF_NATIVE(pv_mmu_ops, write_cr3, "movq %rdi, %cr3"); @@ -50,7 +49,6 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf, PATCH_SITE(pv_irq_ops, save_fl); PATCH_SITE(pv_irq_ops, irq_enable); PATCH_SITE(pv_irq_ops, irq_disable); - PATCH_SITE(pv_cpu_ops, iret); PATCH_SITE(pv_cpu_ops, irq_enable_sysexit); PATCH_SITE(pv_cpu_ops, usergs_sysret32); PATCH_SITE(pv_cpu_ops, usergs_sysret64); -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html