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x86/entry/32: Re-implement SYSENTER using the new C path
Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/5b99659e8be70f3dd10cd8970a5c90293d9ad9a7.1444091585.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski
Ingo Molnar
parent
150ac78d63
commit
5f310f739b
@ -363,7 +363,7 @@ __visible void do_int80_syscall_32(struct pt_regs *regs)
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syscall_return_slowpath(regs);
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}
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/* Returns 0 to return using IRET or 1 to return using SYSRETL. */
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/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
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__visible long do_fast_syscall_32(struct pt_regs *regs)
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{
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/*
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@ -417,7 +417,20 @@ __visible long do_fast_syscall_32(struct pt_regs *regs)
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regs->ip == landing_pad &&
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(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF)) == 0;
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#else
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return 0;
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/*
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* Opportunistic SYSEXIT: if possible, try to return using SYSEXIT.
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*
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* Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
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* because the ECX fixup above will ensure that this is essentially
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* never the case.
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*
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* We don't allow syscalls at all from VM86 mode, but we still
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* need to check VM, because we might be returning from sys_vm86.
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*/
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return static_cpu_has(X86_FEATURE_SEP) &&
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regs->cs == __USER_CS && regs->ss == __USER_DS &&
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regs->ip == landing_pad &&
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(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0;
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#endif
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}
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#endif
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@ -287,76 +287,47 @@ need_resched:
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END(resume_kernel)
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#endif
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/*
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* SYSENTER_RETURN points to after the SYSENTER instruction
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* in the vsyscall page. See vsyscall-sysentry.S, which defines
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* the symbol.
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*/
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# SYSENTER call handler stub
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ENTRY(entry_SYSENTER_32)
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movl TSS_sysenter_sp0(%esp), %esp
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sysenter_past_esp:
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pushl $__USER_DS /* pt_regs->ss */
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pushl %ecx /* pt_regs->cx */
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pushfl /* pt_regs->flags (except IF = 0) */
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orl $X86_EFLAGS_IF, (%esp) /* Fix IF */
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pushl $__USER_CS /* pt_regs->cs */
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pushl $0 /* pt_regs->ip = 0 (placeholder) */
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pushl %eax /* pt_regs->orig_ax */
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SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */
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/*
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* Interrupts are disabled here, but we can't trace it until
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* enough kernel state to call TRACE_IRQS_OFF can be called - but
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* we immediately enable interrupts at that point anyway.
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* User mode is traced as though IRQs are on, and SYSENTER
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* turned them off.
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*/
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pushl $__USER_DS
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pushl %ebp
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pushfl
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orl $X86_EFLAGS_IF, (%esp)
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pushl $__USER_CS
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/*
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* Push current_thread_info()->sysenter_return to the stack.
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* A tiny bit of offset fixup is necessary: TI_sysenter_return
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* is relative to thread_info, which is at the bottom of the
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* kernel stack page. 4*4 means the 4 words pushed above;
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* TOP_OF_KERNEL_STACK_PADDING takes us to the top of the stack;
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* and THREAD_SIZE takes us to the bottom.
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*/
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pushl ((TI_sysenter_return) - THREAD_SIZE + TOP_OF_KERNEL_STACK_PADDING + 4*4)(%esp)
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pushl %eax
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SAVE_ALL
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ENABLE_INTERRUPTS(CLBR_NONE)
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/*
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* Load the potential sixth argument from user stack.
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* Careful about security.
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*/
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cmpl $__PAGE_OFFSET-3, %ebp
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jae syscall_fault
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ASM_STAC
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1: movl (%ebp), %ebp
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ASM_CLAC
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movl %ebp, PT_EBP(%esp)
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_ASM_EXTABLE(1b, syscall_fault)
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GET_THREAD_INFO(%ebp)
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testl $_TIF_WORK_SYSCALL_ENTRY, TI_flags(%ebp)
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jnz syscall_trace_entry
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sysenter_do_call:
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cmpl $(NR_syscalls), %eax
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jae sysenter_badsys
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call *sys_call_table(, %eax, 4)
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sysenter_after_call:
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movl %eax, PT_EAX(%esp)
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LOCKDEP_SYS_EXIT
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DISABLE_INTERRUPTS(CLBR_ANY)
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TRACE_IRQS_OFF
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movl TI_flags(%ebp), %ecx
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testl $_TIF_ALLWORK_MASK, %ecx
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jnz syscall_exit_work_irqs_off
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sysenter_exit:
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/* if something modifies registers it must also disable sysexit */
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movl PT_EIP(%esp), %edx
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movl PT_OLDESP(%esp), %ecx
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xorl %ebp, %ebp
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TRACE_IRQS_ON
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movl %esp, %eax
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call do_fast_syscall_32
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testl %eax, %eax
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jz .Lsyscall_32_done
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/* Opportunistic SYSEXIT */
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TRACE_IRQS_ON /* User mode traces as IRQs on. */
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movl PT_EIP(%esp), %edx /* pt_regs->ip */
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movl PT_OLDESP(%esp), %ecx /* pt_regs->sp */
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popl %ebx /* pt_regs->bx */
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addl $2*4, %esp /* skip pt_regs->cx and pt_regs->dx */
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popl %esi /* pt_regs->si */
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popl %edi /* pt_regs->di */
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popl %ebp /* pt_regs->bp */
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popl %eax /* pt_regs->ax */
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1: mov PT_FS(%esp), %fs
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PTGS_TO_GS
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/*
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* Return back to the vDSO, which will pop ecx and edx.
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* Don't bother with DS and ES (they already contain __USER_DS).
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*/
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ENABLE_INTERRUPTS_SYSEXIT
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.pushsection .fixup, "ax"
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@ -371,7 +342,7 @@ ENDPROC(entry_SYSENTER_32)
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ENTRY(entry_INT80_32)
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ASM_CLAC
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pushl %eax /* pt_regs->orig_ax */
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SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest, load -ENOSYS into ax */
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SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */
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/*
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* User mode is traced as though IRQs are on, and the interrupt gate
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@ -381,6 +352,7 @@ ENTRY(entry_INT80_32)
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movl %esp, %eax
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call do_int80_syscall_32
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.Lsyscall_32_done:
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restore_all:
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TRACE_IRQS_IRET
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@ -457,42 +429,6 @@ ldt_ss:
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#endif
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ENDPROC(entry_INT80_32)
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# perform syscall exit tracing
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ALIGN
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syscall_trace_entry:
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movl $-ENOSYS, PT_EAX(%esp)
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movl %esp, %eax
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call syscall_trace_enter
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/* What it returned is what we'll actually use. */
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cmpl $(NR_syscalls), %eax
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jnae syscall_call
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jmp syscall_exit
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END(syscall_trace_entry)
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# perform syscall exit tracing
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ALIGN
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syscall_exit_work_irqs_off:
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TRACE_IRQS_ON
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ENABLE_INTERRUPTS(CLBR_ANY)
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syscall_exit_work:
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movl %esp, %eax
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call syscall_return_slowpath
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jmp restore_all
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END(syscall_exit_work)
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syscall_fault:
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ASM_CLAC
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GET_THREAD_INFO(%ebp)
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movl $-EFAULT, PT_EAX(%esp)
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jmp resume_userspace
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END(syscall_fault)
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sysenter_badsys:
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movl $-ENOSYS, %eax
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jmp sysenter_after_call
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END(sysenter_badsys)
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.macro FIXUP_ESPFIX_STACK
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/*
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* Switch back for ESPFIX stack to the normal zerobased stack
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@ -34,6 +34,8 @@ __kernel_vsyscall:
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/* If SYSENTER (Intel) or SYSCALL32 (AMD) is available, use it. */
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ALTERNATIVE_2 "", "sysenter", X86_FEATURE_SYSENTER32, \
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"syscall", X86_FEATURE_SYSCALL32
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#else
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ALTERNATIVE "", "sysenter", X86_FEATURE_SEP
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#endif
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/* Enter using int $0x80 */
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