Re: [PATCH 08/62] x86/boot/compressed/64: Add IDT Infrastructure
From: Andy Lutomirski <luto@kernel.org>
Date: 2020-02-11 22:19:07
Also in:
kvm, lkml
On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel [off-list ref] wrote:
From: Joerg Roedel <redacted> Add code needed to setup an IDT in the early pre-decompression boot-code. The IDT is loaded first in startup_64, which is after EfiExitBootServices() has been called, and later reloaded when the kernel image has been relocated to the end of the decompression area. This allows to setup different IDT handlers before and after the relocation.
quoted hunk ↗ jump to hunk
diff --git a/arch/x86/boot/compressed/idt_64.c b/arch/x86/boot/compressed/idt_64.c new file mode 100644 index 000000000000..46ecea671b90 --- /dev/null +++ b/arch/x86/boot/compressed/idt_64.c@@ -0,0 +1,43 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <asm/trap_defs.h> +#include <asm/segment.h> +#include "misc.h" + +static void set_idt_entry(int vector, void (*handler)(void)) +{ + unsigned long address = (unsigned long)handler; + gate_desc entry; + + memset(&entry, 0, sizeof(entry)); + + entry.offset_low = (u16)(address & 0xffff); + entry.segment = __KERNEL_CS; + entry.bits.type = GATE_TRAP;
^^^ I realize we're not running a real kernel here, but GATE_TRAP is madness. Please use GATE_INTERRUPT.
quoted hunk ↗ jump to hunk
+ entry.bits.p = 1; + entry.offset_middle = (u16)((address >> 16) & 0xffff); + entry.offset_high = (u32)(address >> 32); + + memcpy(&boot_idt[vector], &entry, sizeof(entry)); +} + +/* Have this here so we don't need to include <asm/desc.h> */ +static void load_boot_idt(const struct desc_ptr *dtr) +{ + asm volatile("lidt %0"::"m" (*dtr)); +} + +/* Setup IDT before kernel jumping to .Lrelocated */ +void load_stage1_idt(void) +{ + boot_idt_desc.address = (unsigned long)boot_idt; + + load_boot_idt(&boot_idt_desc); +} + +/* Setup IDT after kernel jumping to .Lrelocated */ +void load_stage2_idt(void) +{ + boot_idt_desc.address = (unsigned long)boot_idt; + + load_boot_idt(&boot_idt_desc); +}diff --git a/arch/x86/boot/compressed/idt_handlers_64.S b/arch/x86/boot/compressed/idt_handlers_64.S new file mode 100644 index 000000000000..0b2b6cf747d2 --- /dev/null +++ b/arch/x86/boot/compressed/idt_handlers_64.S@@ -0,0 +1,71 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Early IDT handler entry points + * + * Copyright (C) 2019 SUSE + * + * Author: Joerg Roedel <jroedel@suse.de> + */ + +#include <asm/segment.h> + +.macro EXCEPTION_HANDLER name function error_code=0 +SYM_FUNC_START(\name) + + /* Build pt_regs */ + .if \error_code == 0 + pushq $0 + .endif
cld
+ + pushq %rdi + pushq %rsi + pushq %rdx + pushq %rcx + pushq %rax + pushq %r8 + pushq %r9 + pushq %r10 + pushq %r11 + pushq %rbx + pushq %rbp + pushq %r12 + pushq %r13 + pushq %r14 + pushq %r15 + + /* Call handler with pt_regs */ + movq %rsp, %rdi + call \function + + /* Restore regs */ + popq %r15 + popq %r14 + popq %r13 + popq %r12 + popq %rbp + popq %rbx + popq %r11 + popq %r10 + popq %r9 + popq %r8 + popq %rax + popq %rcx + popq %rdx + popq %rsi + popq %rdi
if error_code?
+ + /* Remove error code and return */ + addq $8, %rsp + + /* + * Make sure we return to __KERNEL_CS - the CS selector on + * the IRET frame might still be from an old BIOS GDT + */ + movq $__KERNEL_CS, 8(%rsp) +
If this actually happens, you have a major bug. Please sanitize all the segment registers after installing the GDT rather than hacking around it here.