diff options
Diffstat (limited to 'arch/x86/entry/entry_64.S')
| -rw-r--r-- | arch/x86/entry/entry_64.S | 117 |
1 files changed, 45 insertions, 72 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 7c5ce0a6c4d2..4d7a2d9d44cf 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -142,67 +142,6 @@ END(native_usergs_sysret64) * with them due to bugs in both AMD and Intel CPUs. */ - .pushsection .entry_trampoline, "ax" - -/* - * The code in here gets remapped into cpu_entry_area's trampoline. This means - * that the assembler and linker have the wrong idea as to where this code - * lives (and, in fact, it's mapped more than once, so it's not even at a - * fixed address). So we can't reference any symbols outside the entry - * trampoline and expect it to work. - * - * Instead, we carefully abuse %rip-relative addressing. - * _entry_trampoline(%rip) refers to the start of the remapped) entry - * trampoline. We can thus find cpu_entry_area with this macro: - */ - -#define CPU_ENTRY_AREA \ - _entry_trampoline - CPU_ENTRY_AREA_entry_trampoline(%rip) - -/* The top word of the SYSENTER stack is hot and is usable as scratch space. */ -#define RSP_SCRATCH CPU_ENTRY_AREA_entry_stack + \ - SIZEOF_entry_stack - 8 + CPU_ENTRY_AREA - -ENTRY(entry_SYSCALL_64_trampoline) - UNWIND_HINT_EMPTY - swapgs - - /* Stash the user RSP. */ - movq %rsp, RSP_SCRATCH - - /* Note: using %rsp as a scratch reg. */ - SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp - - /* Load the top of the task stack into RSP */ - movq CPU_ENTRY_AREA_tss + TSS_sp1 + CPU_ENTRY_AREA, %rsp - - /* Start building the simulated IRET frame. */ - pushq $__USER_DS /* pt_regs->ss */ - pushq RSP_SCRATCH /* pt_regs->sp */ - pushq %r11 /* pt_regs->flags */ - pushq $__USER_CS /* pt_regs->cs */ - pushq %rcx /* pt_regs->ip */ - - /* - * x86 lacks a near absolute jump, and we can't jump to the real - * entry text with a relative jump. We could push the target - * address and then use retq, but this destroys the pipeline on - * many CPUs (wasting over 20 cycles on Sandy Bridge). Instead, - * spill RDI and restore it in a second-stage trampoline. - */ - pushq %rdi - movq $entry_SYSCALL_64_stage2, %rdi - JMP_NOSPEC %rdi -END(entry_SYSCALL_64_trampoline) - - .popsection - -ENTRY(entry_SYSCALL_64_stage2) - UNWIND_HINT_EMPTY - popq %rdi - jmp entry_SYSCALL_64_after_hwframe -END(entry_SYSCALL_64_stage2) - ENTRY(entry_SYSCALL_64) UNWIND_HINT_EMPTY /* @@ -212,21 +151,19 @@ ENTRY(entry_SYSCALL_64) */ swapgs - /* - * This path is only taken when PAGE_TABLE_ISOLATION is disabled so it - * is not required to switch CR3. - */ - movq %rsp, PER_CPU_VAR(rsp_scratch) + /* tss.sp2 is scratch space. */ + movq %rsp, PER_CPU_VAR(cpu_tss_rw + TSS_sp2) + SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp /* Construct struct pt_regs on stack */ - pushq $__USER_DS /* pt_regs->ss */ - pushq PER_CPU_VAR(rsp_scratch) /* pt_regs->sp */ - pushq %r11 /* pt_regs->flags */ - pushq $__USER_CS /* pt_regs->cs */ - pushq %rcx /* pt_regs->ip */ + pushq $__USER_DS /* pt_regs->ss */ + pushq PER_CPU_VAR(cpu_tss_rw + TSS_sp2) /* pt_regs->sp */ + pushq %r11 /* pt_regs->flags */ + pushq $__USER_CS /* pt_regs->cs */ + pushq %rcx /* pt_regs->ip */ GLOBAL(entry_SYSCALL_64_after_hwframe) - pushq %rax /* pt_regs->orig_ax */ + pushq %rax /* pt_regs->orig_ax */ PUSH_AND_CLEAR_REGS rax=$-ENOSYS @@ -900,6 +837,42 @@ apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt */ #define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss_rw) + (TSS_ist + ((x) - 1) * 8) +/** + * idtentry - Generate an IDT entry stub + * @sym: Name of the generated entry point + * @do_sym: C function to be called + * @has_error_code: True if this IDT vector has an error code on the stack + * @paranoid: non-zero means that this vector may be invoked from + * kernel mode with user GSBASE and/or user CR3. + * 2 is special -- see below. + * @shift_ist: Set to an IST index if entries from kernel mode should + * decrement the IST stack so that nested entries get a + * fresh stack. (This is for #DB, which has a nasty habit + * of recursing.) + * + * idtentry generates an IDT stub that sets up a usable kernel context, + * creates struct pt_regs, and calls @do_sym. The stub has the following + * special behaviors: + * + * On an entry from user mode, the stub switches from the trampoline or + * IST stack to the normal thread stack. On an exit to user mode, the + * normal exit-to-usermode path is invoked. + * + * On an exit to kernel mode, if @paranoid == 0, we check for preemption, + * whereas we omit the preemption check if @paranoid != 0. This is purely + * because the implementation is simpler this way. The kernel only needs + * to check for asynchronous kernel preemption when IRQ handlers return. + * + * If @paranoid == 0, then the stub will handle IRET faults by pretending + * that the fault came from user mode. It will handle gs_change faults by + * pretending that the fault happened with kernel GSBASE. Since this handling + * is omitted for @paranoid != 0, the #GP, #SS, and #NP stubs must have + * @paranoid == 0. This special handling will do the wrong thing for + * espfix-induced #DF on IRET, so #DF must not use @paranoid == 0. + * + * @paranoid == 2 is special: the stub will never switch stacks. This is for + * #DF: if the thread stack is somehow unusable, we'll still get a useful OOPS. + */ .macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 ENTRY(\sym) UNWIND_HINT_IRET_REGS offset=\has_error_code*8 |