gdt_idt.c

 1// SPDX-License-Identifier: GPL-2.0
 2
 3#include <linux/linkage.h>
 4#include <linux/types.h>
 5
 6#include <asm/desc.h>
 7#include <asm/init.h>
 8#include <asm/setup.h>
 9#include <asm/sev.h>
10#include <asm/trapnr.h>
11
12/*
13 * Data structures and code used for IDT setup in head_64.S. The bringup-IDT is
14 * used until the idt_table takes over. On the boot CPU this happens in
15 * x86_64_start_kernel(), on secondary CPUs in start_secondary(). In both cases
16 * this happens in the functions called from head_64.S.
17 *
18 * The idt_table can't be used that early because all the code modifying it is
19 * in idt.c and can be instrumented by tracing or KASAN, which both don't work
20 * during early CPU bringup. Also the idt_table has the runtime vectors
21 * configured which require certain CPU state to be setup already (like TSS),
22 * which also hasn't happened yet in early CPU bringup.
23 */
24static gate_desc bringup_idt_table[NUM_EXCEPTION_VECTORS] __page_aligned_data;
25
26/* This may run while still in the direct mapping */
27void startup_64_load_idt(void *vc_handler)
28{
29	struct desc_ptr desc = {
30		.address = (unsigned long)rip_rel_ptr(bringup_idt_table),
31		.size    = sizeof(bringup_idt_table) - 1,
32	};
33	struct idt_data data;
34	gate_desc idt_desc;
35
36	/* @vc_handler is set only for a VMM Communication Exception */
37	if (vc_handler) {
38		init_idt_data(&data, X86_TRAP_VC, vc_handler);
39		idt_init_desc(&idt_desc, &data);
40		native_write_idt_entry((gate_desc *)desc.address, X86_TRAP_VC, &idt_desc);
41	}
42
43	native_load_idt(&desc);
44}
45
46/*
47 * Setup boot CPU state needed before kernel switches to virtual addresses.
48 */
49void __init startup_64_setup_gdt_idt(void)
50{
51	struct gdt_page *gp = rip_rel_ptr((void *)(__force unsigned long)&gdt_page);
52	void *handler = NULL;
53
54	struct desc_ptr startup_gdt_descr = {
55		.address = (unsigned long)gp->gdt,
56		.size    = GDT_SIZE - 1,
57	};
58
59	/* Load GDT */
60	native_load_gdt(&startup_gdt_descr);
61
62	/* New GDT is live - reload data segment registers */
63	asm volatile("movl %%eax, %%ds\n"
64		     "movl %%eax, %%ss\n"
65		     "movl %%eax, %%es\n" : : "a"(__KERNEL_DS) : "memory");
66
67	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT))
68		handler = rip_rel_ptr(vc_no_ghcb);
69
70	startup_64_load_idt(handler);
71}