x86/boot/compressed/64: Add IDT Infrastructure

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.
Signed-off-by: NJoerg Roedel <jroedel@suse.de>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-14-joro@8bytes.org

arch/x86/boot/compressed/Makefile

@@ -85,6 +85,7 @@ vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $(obj)/early_serial_console.o
 vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o
 ifdef CONFIG_X86_64
 	vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr_64.o
+	vmlinux-objs-y += $(obj)/idt_64.o $(obj)/idt_handlers_64.o
 	vmlinux-objs-y += $(obj)/mem_encrypt.o
 	vmlinux-objs-y += $(obj)/pgtable_64.o
 endif

arch/x86/boot/compressed/head_64.S

@@ -33,6 +33,7 @@
 #include <asm/processor-flags.h>
 #include <asm/asm-offsets.h>
 #include <asm/bootparam.h>
+#include <asm/desc_defs.h>
 #include "pgtable.h"
 
 /*
@@ -410,6 +411,10 @@ SYM_CODE_START(startup_64)
 
 .Lon_kernel_cs:
 
+	pushq	%rsi
+	call	load_stage1_idt
+	popq	%rsi
+
 	/*
 	 * paging_prepare() sets up the trampoline and checks if we need to
 	 * enable 5-level paging.
@@ -537,6 +542,13 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
 	shrq	$3, %rcx
 	rep	stosq
 
+/*
+ * Load stage2 IDT
+ */
+	pushq	%rsi
+	call	load_stage2_idt
+	popq	%rsi
+
 /*
  * Do the extraction, and jump to the new kernel..
  */
@@ -690,10 +702,21 @@ SYM_DATA_START_LOCAL(gdt)
 	.quad   0x0000000000000000	/* TS continued */
 SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end)
 
+SYM_DATA_START(boot_idt_desc)
+	.word	boot_idt_end - boot_idt - 1
+	.quad	0
+SYM_DATA_END(boot_idt_desc)
+	.balign 8
+SYM_DATA_START(boot_idt)
+	.rept	BOOT_IDT_ENTRIES
+	.quad	0
+	.quad	0
+	.endr
+SYM_DATA_END_LABEL(boot_idt, SYM_L_GLOBAL, boot_idt_end)
+
 #ifdef CONFIG_EFI_STUB
 SYM_DATA(image_offset, .long 0)
 #endif
-
 #ifdef CONFIG_EFI_MIXED
 SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0)
 SYM_DATA(efi_is64, .byte 1)

arch/x86/boot/compressed/idt_64.c

+// SPDX-License-Identifier: GPL-2.0-only
+#include <asm/trap_pf.h>
+#include <asm/segment.h>
+#include <asm/trapnr.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;
+	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);
+}

arch/x86/boot/compressed/idt_handlers_64.S

+/* 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>
+
+/* For ORIG_RAX */
+#include "../../entry/calling.h"
+
+.macro EXCEPTION_HANDLER name function error_code=0
+SYM_FUNC_START(\name)
+
+	/* Build pt_regs */
+	.if \error_code == 0
+	pushq   $0
+	.endif
+
+	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
+	/* Error code is second parameter */
+	movq	ORIG_RAX(%rsp), %rsi
+	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
+
+	/* Remove error code and return */
+	addq    $8, %rsp
+
+	iretq
+SYM_FUNC_END(\name)
+	.endm
+
+	.text
+	.code64

arch/x86/boot/compressed/misc.h

@@ -23,6 +23,7 @@
 #include <asm/page.h>
 #include <asm/boot.h>
 #include <asm/bootparam.h>
+#include <asm/desc_defs.h>
 
 #define BOOT_CTYPE_H
 #include <linux/acpi.h>
@@ -133,4 +134,8 @@ int count_immovable_mem_regions(void);
 static inline int count_immovable_mem_regions(void) { return 0; }
 #endif
 
+/* idt_64.c */
+extern gate_desc boot_idt[BOOT_IDT_ENTRIES];
+extern struct desc_ptr boot_idt_desc;
+
 #endif /* BOOT_COMPRESSED_MISC_H */

arch/x86/include/asm/desc_defs.h

@@ -109,6 +109,9 @@ struct desc_ptr {
 
 #endif /* !__ASSEMBLY__ */
 
+/* Boot IDT definitions */
+#define	BOOT_IDT_ENTRIES	32
+
 /* Access rights as returned by LAR */
 #define AR_TYPE_RODATA		(0 * (1 << 9))
 #define AR_TYPE_RWDATA		(1 * (1 << 9))