diff options
author | Ingo Molnar <mingo@kernel.org> | 2017-12-01 10:32:48 +0100 |
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committer | Ingo Molnar <mingo@kernel.org> | 2017-12-17 12:58:53 +0100 |
commit | 0fd2e9c53d82704a3ba87ea1980ec515188c5316 (patch) | |
tree | a828c396110053feba9e65307a4e802b00966519 /arch/x86/entry/entry_64.S | |
parent | 1784f9144b143a1e8b19fe94083b040aa559182b (diff) | |
parent | 1e4c4f610f774df6088d7c065b2dd4d22adba698 (diff) | |
download | op-kernel-dev-0fd2e9c53d82704a3ba87ea1980ec515188c5316.zip op-kernel-dev-0fd2e9c53d82704a3ba87ea1980ec515188c5316.tar.gz |
Merge commit 'upstream-x86-entry' into WIP.x86/mm
Pull in a minimal set of v4.15 entry code changes, for a base for the MM isolation patches.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/entry/entry_64.S')
-rw-r--r-- | arch/x86/entry/entry_64.S | 141 |
1 files changed, 83 insertions, 58 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index bcfc566..a2b30ec 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -221,10 +221,9 @@ entry_SYSCALL_64_fastpath: 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: /* @@ -246,17 +245,18 @@ entry_SYSCALL64_slow_path: 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 @@ -274,14 +274,14 @@ return_from_SYSCALL_64: /* 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 @@ -302,12 +302,12 @@ return_from_SYSCALL_64: * 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 @@ -315,14 +315,20 @@ return_from_SYSCALL_64: */ 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) @@ -423,8 +429,7 @@ ENTRY(ret_from_fork) 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 */ @@ -612,8 +617,21 @@ GLOBAL(retint_user) 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: @@ -633,15 +651,17 @@ 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) @@ -818,7 +838,7 @@ ENTRY(\sym) ASM_CLAC - .ifeq \has_error_code + .if \has_error_code == 0 pushq $-1 /* ORIG_RAX: no syscall to restart */ .endif @@ -1059,6 +1079,7 @@ idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK 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 @@ -1112,17 +1133,14 @@ ENTRY(paranoid_exit) 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) /* @@ -1223,10 +1241,13 @@ ENTRY(error_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. @@ -1284,7 +1305,7 @@ ENTRY(nmi) * 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 @@ -1328,8 +1349,7 @@ ENTRY(nmi) * 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: /* @@ -1450,7 +1470,7 @@ nested_nmi_out: popq %rdx /* We are returning to kernel mode, so this cannot result in a fault. */ - INTERRUPT_RETURN + iretq first_nmi: /* Restore rdx. */ @@ -1481,7 +1501,7 @@ first_nmi: 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 @@ -1544,29 +1564,34 @@ end_repeat_nmi: 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) |