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>
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 02881e5..c1c7c63 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -287,76 +287,47 @@
END(resume_kernel)
#endif
-/*
- * SYSENTER_RETURN points to after the SYSENTER instruction
- * in the vsyscall page. See vsyscall-sysentry.S, which defines
- * the symbol.
- */
-
# SYSENTER call handler stub
ENTRY(entry_SYSENTER_32)
movl TSS_sysenter_sp0(%esp), %esp
sysenter_past_esp:
+ pushl $__USER_DS /* pt_regs->ss */
+ pushl %ecx /* pt_regs->cx */
+ pushfl /* pt_regs->flags (except IF = 0) */
+ orl $X86_EFLAGS_IF, (%esp) /* Fix IF */
+ pushl $__USER_CS /* pt_regs->cs */
+ pushl $0 /* pt_regs->ip = 0 (placeholder) */
+ pushl %eax /* pt_regs->orig_ax */
+ SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */
+
/*
- * Interrupts are disabled here, but we can't trace it until
- * enough kernel state to call TRACE_IRQS_OFF can be called - but
- * we immediately enable interrupts at that point anyway.
+ * User mode is traced as though IRQs are on, and SYSENTER
+ * turned them off.
*/
- pushl $__USER_DS
- pushl %ebp
- pushfl
- orl $X86_EFLAGS_IF, (%esp)
- pushl $__USER_CS
- /*
- * Push current_thread_info()->sysenter_return to the stack.
- * A tiny bit of offset fixup is necessary: TI_sysenter_return
- * is relative to thread_info, which is at the bottom of the
- * kernel stack page. 4*4 means the 4 words pushed above;
- * TOP_OF_KERNEL_STACK_PADDING takes us to the top of the stack;
- * and THREAD_SIZE takes us to the bottom.
- */
- pushl ((TI_sysenter_return) - THREAD_SIZE + TOP_OF_KERNEL_STACK_PADDING + 4*4)(%esp)
-
- pushl %eax
- SAVE_ALL
- ENABLE_INTERRUPTS(CLBR_NONE)
-
-/*
- * Load the potential sixth argument from user stack.
- * Careful about security.
- */
- cmpl $__PAGE_OFFSET-3, %ebp
- jae syscall_fault
- ASM_STAC
-1: movl (%ebp), %ebp
- ASM_CLAC
- movl %ebp, PT_EBP(%esp)
- _ASM_EXTABLE(1b, syscall_fault)
-
- GET_THREAD_INFO(%ebp)
-
- testl $_TIF_WORK_SYSCALL_ENTRY, TI_flags(%ebp)
- jnz syscall_trace_entry
-sysenter_do_call:
- cmpl $(NR_syscalls), %eax
- jae sysenter_badsys
- call *sys_call_table(, %eax, 4)
-sysenter_after_call:
- movl %eax, PT_EAX(%esp)
- LOCKDEP_SYS_EXIT
- DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_OFF
- movl TI_flags(%ebp), %ecx
- testl $_TIF_ALLWORK_MASK, %ecx
- jnz syscall_exit_work_irqs_off
-sysenter_exit:
-/* if something modifies registers it must also disable sysexit */
- movl PT_EIP(%esp), %edx
- movl PT_OLDESP(%esp), %ecx
- xorl %ebp, %ebp
- TRACE_IRQS_ON
+
+ movl %esp, %eax
+ call do_fast_syscall_32
+ testl %eax, %eax
+ jz .Lsyscall_32_done
+
+/* Opportunistic SYSEXIT */
+ TRACE_IRQS_ON /* User mode traces as IRQs on. */
+ movl PT_EIP(%esp), %edx /* pt_regs->ip */
+ movl PT_OLDESP(%esp), %ecx /* pt_regs->sp */
+ popl %ebx /* pt_regs->bx */
+ addl $2*4, %esp /* skip pt_regs->cx and pt_regs->dx */
+ popl %esi /* pt_regs->si */
+ popl %edi /* pt_regs->di */
+ popl %ebp /* pt_regs->bp */
+ popl %eax /* pt_regs->ax */
1: mov PT_FS(%esp), %fs
PTGS_TO_GS
+
+ /*
+ * Return back to the vDSO, which will pop ecx and edx.
+ * Don't bother with DS and ES (they already contain __USER_DS).
+ */
ENABLE_INTERRUPTS_SYSEXIT
.pushsection .fixup, "ax"
@@ -371,7 +342,7 @@
ENTRY(entry_INT80_32)
ASM_CLAC
pushl %eax /* pt_regs->orig_ax */
- SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest, load -ENOSYS into ax */
+ SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */
/*
* User mode is traced as though IRQs are on, and the interrupt gate
@@ -381,6 +352,7 @@
movl %esp, %eax
call do_int80_syscall_32
+.Lsyscall_32_done:
restore_all:
TRACE_IRQS_IRET
@@ -457,42 +429,6 @@
#endif
ENDPROC(entry_INT80_32)
- # perform syscall exit tracing
- ALIGN
-syscall_trace_entry:
- movl $-ENOSYS, PT_EAX(%esp)
- movl %esp, %eax
- call syscall_trace_enter
- /* What it returned is what we'll actually use. */
- cmpl $(NR_syscalls), %eax
- jnae syscall_call
- jmp syscall_exit
-END(syscall_trace_entry)
-
- # perform syscall exit tracing
- ALIGN
-syscall_exit_work_irqs_off:
- TRACE_IRQS_ON
- ENABLE_INTERRUPTS(CLBR_ANY)
-
-syscall_exit_work:
- movl %esp, %eax
- call syscall_return_slowpath
- jmp restore_all
-END(syscall_exit_work)
-
-syscall_fault:
- ASM_CLAC
- GET_THREAD_INFO(%ebp)
- movl $-EFAULT, PT_EAX(%esp)
- jmp resume_userspace
-END(syscall_fault)
-
-sysenter_badsys:
- movl $-ENOSYS, %eax
- jmp sysenter_after_call
-END(sysenter_badsys)
-
.macro FIXUP_ESPFIX_STACK
/*
* Switch back for ESPFIX stack to the normal zerobased stack