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-rw-r--r--arch/x86/platform/pvh/head.S166
1 files changed, 166 insertions, 0 deletions
diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
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+++ b/arch/x86/platform/pvh/head.S
@@ -0,0 +1,166 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright C 2016, Oracle and/or its affiliates. All rights reserved.
+ */
+
+ .code32
+ .text
+#define _pa(x) ((x) - __START_KERNEL_map)
+
+#include <linux/elfnote.h>
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/segment.h>
+#include <asm/asm.h>
+#include <asm/boot.h>
+#include <asm/processor-flags.h>
+#include <asm/msr.h>
+#include <asm/nospec-branch.h>
+#include <xen/interface/elfnote.h>
+
+ __HEAD
+
+/*
+ * Entry point for PVH guests.
+ *
+ * Xen ABI specifies the following register state when we come here:
+ *
+ * - `ebx`: contains the physical memory address where the loader has placed
+ * the boot start info structure.
+ * - `cr0`: bit 0 (PE) must be set. All the other writeable bits are cleared.
+ * - `cr4`: all bits are cleared.
+ * - `cs `: must be a 32-bit read/execute code segment with a base of `0`
+ * and a limit of `0xFFFFFFFF`. The selector value is unspecified.
+ * - `ds`, `es`: must be a 32-bit read/write data segment with a base of
+ * `0` and a limit of `0xFFFFFFFF`. The selector values are all
+ * unspecified.
+ * - `tr`: must be a 32-bit TSS (active) with a base of '0' and a limit
+ * of '0x67'.
+ * - `eflags`: bit 17 (VM) must be cleared. Bit 9 (IF) must be cleared.
+ * Bit 8 (TF) must be cleared. Other bits are all unspecified.
+ *
+ * All other processor registers and flag bits are unspecified. The OS is in
+ * charge of setting up it's own stack, GDT and IDT.
+ */
+
+#define PVH_GDT_ENTRY_CS 1
+#define PVH_GDT_ENTRY_DS 2
+#define PVH_CS_SEL (PVH_GDT_ENTRY_CS * 8)
+#define PVH_DS_SEL (PVH_GDT_ENTRY_DS * 8)
+
+SYM_CODE_START_LOCAL(pvh_start_xen)
+ UNWIND_HINT_EMPTY
+ cld
+
+ lgdt (_pa(gdt))
+
+ mov $PVH_DS_SEL,%eax
+ mov %eax,%ds
+ mov %eax,%es
+ mov %eax,%ss
+
+ /* Stash hvm_start_info. */
+ mov $_pa(pvh_start_info), %edi
+ mov %ebx, %esi
+ mov _pa(pvh_start_info_sz), %ecx
+ shr $2,%ecx
+ rep
+ movsl
+
+ mov $_pa(early_stack_end), %esp
+
+ /* Enable PAE mode. */
+ mov %cr4, %eax
+ orl $X86_CR4_PAE, %eax
+ mov %eax, %cr4
+
+#ifdef CONFIG_X86_64
+ /* Enable Long mode. */
+ mov $MSR_EFER, %ecx
+ rdmsr
+ btsl $_EFER_LME, %eax
+ wrmsr
+
+ /* Enable pre-constructed page tables. */
+ mov $_pa(init_top_pgt), %eax
+ mov %eax, %cr3
+ mov $(X86_CR0_PG | X86_CR0_PE), %eax
+ mov %eax, %cr0
+
+ /* Jump to 64-bit mode. */
+ ljmp $PVH_CS_SEL, $_pa(1f)
+
+ /* 64-bit entry point. */
+ .code64
+1:
+ /* Set base address in stack canary descriptor. */
+ mov $MSR_GS_BASE,%ecx
+ mov $_pa(canary), %eax
+ xor %edx, %edx
+ wrmsr
+
+ call xen_prepare_pvh
+
+ /* startup_64 expects boot_params in %rsi. */
+ mov $_pa(pvh_bootparams), %rsi
+ mov $_pa(startup_64), %rax
+ ANNOTATE_RETPOLINE_SAFE
+ jmp *%rax
+
+#else /* CONFIG_X86_64 */
+
+ call mk_early_pgtbl_32
+
+ mov $_pa(initial_page_table), %eax
+ mov %eax, %cr3
+
+ mov %cr0, %eax
+ or $(X86_CR0_PG | X86_CR0_PE), %eax
+ mov %eax, %cr0
+
+ ljmp $PVH_CS_SEL, $1f
+1:
+ call xen_prepare_pvh
+ mov $_pa(pvh_bootparams), %esi
+
+ /* startup_32 doesn't expect paging and PAE to be on. */
+ ljmp $PVH_CS_SEL, $_pa(2f)
+2:
+ mov %cr0, %eax
+ and $~X86_CR0_PG, %eax
+ mov %eax, %cr0
+ mov %cr4, %eax
+ and $~X86_CR4_PAE, %eax
+ mov %eax, %cr4
+
+ ljmp $PVH_CS_SEL, $_pa(startup_32)
+#endif
+SYM_CODE_END(pvh_start_xen)
+
+ .section ".init.data","aw"
+ .balign 8
+SYM_DATA_START_LOCAL(gdt)
+ .word gdt_end - gdt_start
+ .long _pa(gdt_start)
+ .word 0
+SYM_DATA_END(gdt)
+SYM_DATA_START_LOCAL(gdt_start)
+ .quad 0x0000000000000000 /* NULL descriptor */
+#ifdef CONFIG_X86_64
+ .quad GDT_ENTRY(0xa09a, 0, 0xfffff) /* PVH_CS_SEL */
+#else
+ .quad GDT_ENTRY(0xc09a, 0, 0xfffff) /* PVH_CS_SEL */
+#endif
+ .quad GDT_ENTRY(0xc092, 0, 0xfffff) /* PVH_DS_SEL */
+SYM_DATA_END_LABEL(gdt_start, SYM_L_LOCAL, gdt_end)
+
+ .balign 16
+SYM_DATA_LOCAL(canary, .fill 48, 1, 0)
+
+SYM_DATA_START_LOCAL(early_stack)
+ .fill BOOT_STACK_SIZE, 1, 0
+SYM_DATA_END_LABEL(early_stack, SYM_L_LOCAL, early_stack_end)
+
+ ELFNOTE(Xen, XEN_ELFNOTE_PHYS32_ENTRY,
+ _ASM_PTR (pvh_start_xen - __START_KERNEL_map))