TRACE_IRQS_ON /* user mode is traced as IRQs on */
movq RIP(%rsp), %rcx
movq EFLAGS(%rsp), %r11
- RESTORE_C_REGS_EXCEPT_RCX_R11
- movq RSP(%rsp), %rsp
+ addq $6*8, %rsp /* skip extra regs -- they were preserved */
UNWIND_HINT_EMPTY
- USERGS_SYSRET64
+ jmp .Lpop_c_regs_except_rcx_r11_and_sysret
1:
/*
call do_syscall_64 /* returns with IRQs disabled */
return_from_SYSCALL_64:
- RESTORE_EXTRA_REGS
TRACE_IRQS_IRETQ /* we're about to change IF */
/*
* Try to use SYSRET instead of IRET if we're returning to
- * a completely clean 64-bit userspace context.
+ * a completely clean 64-bit userspace context. If we're not,
+ * go to the slow exit path.
*/
movq RCX(%rsp), %rcx
movq RIP(%rsp), %r11
- cmpq %rcx, %r11 /* RCX == RIP */
- jne opportunistic_sysret_failed
+
+ cmpq %rcx, %r11 /* SYSRET requires RCX == RIP */
+ jne swapgs_restore_regs_and_return_to_usermode
/*
* On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP
/* If this changed %rcx, it was not canonical */
cmpq %rcx, %r11
- jne opportunistic_sysret_failed
+ jne swapgs_restore_regs_and_return_to_usermode
cmpq $__USER_CS, CS(%rsp) /* CS must match SYSRET */
- jne opportunistic_sysret_failed
+ jne swapgs_restore_regs_and_return_to_usermode
movq R11(%rsp), %r11
cmpq %r11, EFLAGS(%rsp) /* R11 == RFLAGS */
- jne opportunistic_sysret_failed
+ jne swapgs_restore_regs_and_return_to_usermode
/*
* SYSCALL clears RF when it saves RFLAGS in R11 and SYSRET cannot
* would never get past 'stuck_here'.
*/
testq $(X86_EFLAGS_RF|X86_EFLAGS_TF), %r11
- jnz opportunistic_sysret_failed
+ jnz swapgs_restore_regs_and_return_to_usermode
/* nothing to check for RSP */
cmpq $__USER_DS, SS(%rsp) /* SS must match SYSRET */
- jne opportunistic_sysret_failed
+ jne swapgs_restore_regs_and_return_to_usermode
/*
* We win! This label is here just for ease of understanding
*/
syscall_return_via_sysret:
/* rcx and r11 are already restored (see code above) */
- RESTORE_C_REGS_EXCEPT_RCX_R11
- movq RSP(%rsp), %rsp
UNWIND_HINT_EMPTY
+ POP_EXTRA_REGS
+.Lpop_c_regs_except_rcx_r11_and_sysret:
+ popq %rsi /* skip r11 */
+ popq %r10
+ popq %r9
+ popq %r8
+ popq %rax
+ popq %rsi /* skip rcx */
+ popq %rdx
+ popq %rsi
+ popq %rdi
+ movq RSP-ORIG_RAX(%rsp), %rsp
USERGS_SYSRET64
-
-opportunistic_sysret_failed:
- SWAPGS
- jmp restore_c_regs_and_iret
END(entry_SYSCALL_64)
ENTRY(stub_ptregs_64)
movq %rsp, %rdi
call syscall_return_slowpath /* returns with IRQs disabled */
TRACE_IRQS_ON /* user mode is traced as IRQS on */
- SWAPGS
- jmp restore_regs_and_iret
+ jmp swapgs_restore_regs_and_return_to_usermode
1:
/* kernel thread */
mov %rsp,%rdi
call prepare_exit_to_usermode
TRACE_IRQS_IRETQ
+
+GLOBAL(swapgs_restore_regs_and_return_to_usermode)
+#ifdef CONFIG_DEBUG_ENTRY
+ /* Assert that pt_regs indicates user mode. */
+ testb $3, CS(%rsp)
+ jnz 1f
+ ud2
+1:
+#endif
SWAPGS
- jmp restore_regs_and_iret
+ POP_EXTRA_REGS
+ POP_C_REGS
+ addq $8, %rsp /* skip regs->orig_ax */
+ INTERRUPT_RETURN
+
/* Returning to kernel space */
retint_kernel:
*/
TRACE_IRQS_IRETQ
-/*
- * At this label, code paths which return to kernel and to user,
- * which come from interrupts/exception and from syscalls, merge.
- */
-GLOBAL(restore_regs_and_iret)
- RESTORE_EXTRA_REGS
-restore_c_regs_and_iret:
- RESTORE_C_REGS
- REMOVE_PT_GPREGS_FROM_STACK 8
+GLOBAL(restore_regs_and_return_to_kernel)
+#ifdef CONFIG_DEBUG_ENTRY
+ /* Assert that pt_regs indicates kernel mode. */
+ testb $3, CS(%rsp)
+ jz 1f
+ ud2
+1:
+#endif
+ POP_EXTRA_REGS
+ POP_C_REGS
+ addq $8, %rsp /* skip regs->orig_ax */
INTERRUPT_RETURN
ENTRY(native_iret)
ASM_CLAC
- .ifeq \has_error_code
+ .if \has_error_code == 0
pushq $-1 /* ORIG_RAX: no syscall to restart */
.endif
idtentry stack_segment do_stack_segment has_error_code=1
#ifdef CONFIG_XEN
+idtentry xennmi do_nmi has_error_code=0
idtentry xendebug do_debug has_error_code=0
idtentry xenint3 do_int3 has_error_code=0
#endif
DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_OFF_DEBUG
testl %ebx, %ebx /* swapgs needed? */
- jnz paranoid_exit_no_swapgs
+ jnz .Lparanoid_exit_no_swapgs
TRACE_IRQS_IRETQ
SWAPGS_UNSAFE_STACK
- jmp paranoid_exit_restore
-paranoid_exit_no_swapgs:
+ jmp .Lparanoid_exit_restore
+.Lparanoid_exit_no_swapgs:
TRACE_IRQS_IRETQ_DEBUG
-paranoid_exit_restore:
- RESTORE_EXTRA_REGS
- RESTORE_C_REGS
- REMOVE_PT_GPREGS_FROM_STACK 8
- INTERRUPT_RETURN
+.Lparanoid_exit_restore:
+ jmp restore_regs_and_return_to_kernel
END(paranoid_exit)
/*
jmp retint_user
END(error_exit)
-/* Runs on exception stack */
-/* XXX: broken on Xen PV */
+/*
+ * Runs on exception stack. Xen PV does not go through this path at all,
+ * so we can use real assembly here.
+ */
ENTRY(nmi)
UNWIND_HINT_IRET_REGS
+
/*
* We allow breakpoints in NMIs. If a breakpoint occurs, then
* the iretq it performs will take us out of NMI context.
* stacks lest we corrupt the "NMI executing" variable.
*/
- SWAPGS_UNSAFE_STACK
+ swapgs
cld
movq %rsp, %rdx
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
* Return back to user mode. We must *not* do the normal exit
* work, because we don't want to enable interrupts.
*/
- SWAPGS
- jmp restore_regs_and_iret
+ jmp swapgs_restore_regs_and_return_to_usermode
.Lnmi_from_kernel:
/*
popq %rdx
/* We are returning to kernel mode, so this cannot result in a fault. */
- INTERRUPT_RETURN
+ iretq
first_nmi:
/* Restore rdx. */
pushfq /* RFLAGS */
pushq $__KERNEL_CS /* CS */
pushq $1f /* RIP */
- INTERRUPT_RETURN /* continues at repeat_nmi below */
+ iretq /* continues at repeat_nmi below */
UNWIND_HINT_IRET_REGS
1:
#endif
nmi_swapgs:
SWAPGS_UNSAFE_STACK
nmi_restore:
- RESTORE_EXTRA_REGS
- RESTORE_C_REGS
+ POP_EXTRA_REGS
+ POP_C_REGS
- /* Point RSP at the "iret" frame. */
- REMOVE_PT_GPREGS_FROM_STACK 6*8
+ /*
+ * Skip orig_ax and the "outermost" frame to point RSP at the "iret"
+ * at the "iret" frame.
+ */
+ addq $6*8, %rsp
/*
* Clear "NMI executing". Set DF first so that we can easily
* distinguish the remaining code between here and IRET from
- * the SYSCALL entry and exit paths. On a native kernel, we
- * could just inspect RIP, but, on paravirt kernels,
- * INTERRUPT_RETURN can translate into a jump into a
- * hypercall page.
+ * the SYSCALL entry and exit paths.
+ *
+ * We arguably should just inspect RIP instead, but I (Andy) wrote
+ * this code when I had the misapprehension that Xen PV supported
+ * NMIs, and Xen PV would break that approach.
*/
std
movq $0, 5*8(%rsp) /* clear "NMI executing" */
/*
- * INTERRUPT_RETURN reads the "iret" frame and exits the NMI
- * stack in a single instruction. We are returning to kernel
- * mode, so this cannot result in a fault.
+ * iretq reads the "iret" frame and exits the NMI stack in a
+ * single instruction. We are returning to kernel mode, so this
+ * cannot result in a fault. Similarly, we don't need to worry
+ * about espfix64 on the way back to kernel mode.
*/
- INTERRUPT_RETURN
+ iretq
END(nmi)
ENTRY(ignore_sysret)
projects / linux-2.6-microblaze.git / blobdiff