/* SPDX-License-Identifier: GPL-2.0 */ /* * linux/arch/x86/kernel/head_64.S -- start in 32bit and switch to 64bit * * Copyright (C) 2000 Andrea Arcangeli SuSE * Copyright (C) 2000 Pavel Machek * Copyright (C) 2000 Karsten Keil * Copyright (C) 2001,2002 Andi Kleen * Copyright (C) 2005 Eric Biederman */ #include #include #include #include #include #include #include #include #include #include #include #include "../entry/calling.h" #include #include #include /* * We are not able to switch in one step to the final KERNEL ADDRESS SPACE * because we need identity-mapped pages. */ #define l4_index(x) (((x) >> 39) & 511) #define pud_index(x) (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1)) L4_PAGE_OFFSET = l4_index(__PAGE_OFFSET_BASE_L4) L4_START_KERNEL = l4_index(__START_KERNEL_map) L3_START_KERNEL = pud_index(__START_KERNEL_map) .text __HEAD .code64 SYM_CODE_START_NOALIGN(startup_64) UNWIND_HINT_EMPTY /* * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0, * and someone has loaded an identity mapped page table * for us. These identity mapped page tables map all of the * kernel pages and possibly all of memory. * * %rsi holds a physical pointer to real_mode_data. * * We come here either directly from a 64bit bootloader, or from * arch/x86/boot/compressed/head_64.S. * * We only come here initially at boot nothing else comes here. * * Since we may be loaded at an address different from what we were * compiled to run at we first fixup the physical addresses in our page * tables and then reload them. */ /* Set up the stack for verify_cpu(), similar to initial_stack below */ leaq (__end_init_task - FRAME_SIZE)(%rip), %rsp leaq _text(%rip), %rdi /* * initial_gs points to initial fixed_percpu_data struct with storage for * the stack protector canary. Global pointer fixups are needed at this * stage, so apply them as is done in fixup_pointer(), and initialize %gs * such that the canary can be accessed at %gs:40 for subsequent C calls. */ movl $MSR_GS_BASE, %ecx movq initial_gs(%rip), %rax movq $_text, %rdx subq %rdx, %rax addq %rdi, %rax movq %rax, %rdx shrq $32, %rdx wrmsr pushq %rsi call startup_64_setup_env popq %rsi /* Now switch to __KERNEL_CS so IRET works reliably */ pushq $__KERNEL_CS leaq .Lon_kernel_cs(%rip), %rax pushq %rax lretq .Lon_kernel_cs: UNWIND_HINT_EMPTY #ifdef CONFIG_AMD_MEM_ENCRYPT /* * Activate SEV/SME memory encryption if supported/enabled. This needs to * be done now, since this also includes setup of the SEV-SNP CPUID table, * which needs to be done before any CPUID instructions are executed in * subsequent code. */ movq %rsi, %rdi pushq %rsi call sme_enable popq %rsi #endif /* Sanitize CPU configuration */ call verify_cpu /* * Perform pagetable fixups. Additionally, if SME is active, encrypt * the kernel and retrieve the modifier (SME encryption mask if SME * is active) to be added to the initial pgdir entry that will be * programmed into CR3. */ leaq _text(%rip), %rdi pushq %rsi call __startup_64 popq %rsi /* Form the CR3 value being sure to include the CR3 modifier */ addq $(early_top_pgt - __START_KERNEL_map), %rax jmp 1f SYM_CODE_END(startup_64) SYM_CODE_START(secondary_startup_64) UNWIND_HINT_EMPTY ANNOTATE_NOENDBR /* * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0, * and someone has loaded a mapped page table. * * %rsi holds a physical pointer to real_mode_data. * * We come here either from startup_64 (using physical addresses) * or from trampoline.S (using virtual addresses). * * Using virtual addresses from trampoline.S removes the need * to have any identity mapped pages in the kernel page table * after the boot processor executes this code. */ /* Sanitize CPU configuration */ call verify_cpu /* * The secondary_startup_64_no_verify entry point is only used by * SEV-ES guests. In those guests the call to verify_cpu() would cause * #VC exceptions which can not be handled at this stage of secondary * CPU bringup. * * All non SEV-ES systems, especially Intel systems, need to execute * verify_cpu() above to make sure NX is enabled. */ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) UNWIND_HINT_EMPTY ANNOTATE_NOENDBR /* * Retrieve the modifier (SME encryption mask if SME is active) to be * added to the initial pgdir entry that will be programmed into CR3. */ #ifdef CONFIG_AMD_MEM_ENCRYPT movq sme_me_mask, %rax #else xorq %rax, %rax #endif /* Form the CR3 value being sure to include the CR3 modifier */ addq $(init_top_pgt - __START_KERNEL_map), %rax 1: #ifdef CONFIG_X86_MCE /* * Preserve CR4.MCE if the kernel will enable #MC support. * Clearing MCE may fault in some environments (that also force #MC * support). Any machine check that occurs before #MC support is fully * configured will crash the system regardless of the CR4.MCE value set * here. */ movq %cr4, %rcx andl $X86_CR4_MCE, %ecx #else movl $0, %ecx #endif /* Enable PAE mode, PGE and LA57 */ orl $(X86_CR4_PAE | X86_CR4_PGE), %ecx #ifdef CONFIG_X86_5LEVEL testl $1, __pgtable_l5_enabled(%rip) jz 1f orl $X86_CR4_LA57, %ecx 1: #endif movq %rcx, %cr4 /* Setup early boot stage 4-/5-level pagetables. */ addq phys_base(%rip), %rax /* * For SEV guests: Verify that the C-bit is correct. A malicious * hypervisor could lie about the C-bit position to perform a ROP * attack on the guest by writing to the unencrypted stack and wait for * the next RET instruction. * %rsi carries pointer to realmode data and is callee-clobbered. Save * and restore it. */ pushq %rsi movq %rax, %rdi call sev_verify_cbit popq %rsi /* * Switch to new page-table * * For the boot CPU this switches to early_top_pgt which still has the * indentity mappings present. The secondary CPUs will switch to the * init_top_pgt here, away from the trampoline_pgd and unmap the * indentity mapped ranges. */ movq %rax, %cr3 /* * Do a global TLB flush after the CR3 switch to make sure the TLB * entries from the identity mapping are flushed. */ movq %cr4, %rcx movq %rcx, %rax xorq $X86_CR4_PGE, %rcx movq %rcx, %cr4 movq %rax, %cr4 /* Ensure I am executing from virtual addresses */ movq $1f, %rax ANNOTATE_RETPOLINE_SAFE jmp *%rax 1: UNWIND_HINT_EMPTY ANNOTATE_NOENDBR // above /* * We must switch to a new descriptor in kernel space for the GDT * because soon the kernel won't have access anymore to the userspace * addresses where we're currently running on. We have to do that here * because in 32bit we couldn't load a 64bit linear address. */ lgdt early_gdt_descr(%rip) /* set up data segments */ xorl %eax,%eax movl %eax,%ds movl %eax,%ss movl %eax,%es /* * We don't really need to load %fs or %gs, but load them anyway * to kill any stale realmode selectors. This allows execution * under VT hardware. */ movl %eax,%fs movl %eax,%gs /* Set up %gs. * * The base of %gs always points to fixed_percpu_data. If the * stack protector canary is enabled, it is located at %gs:40. * Note that, on SMP, the boot cpu uses init data section until * the per cpu areas are set up. */ movl $MSR_GS_BASE,%ecx movl initial_gs(%rip),%eax movl initial_gs+4(%rip),%edx wrmsr /* * Setup a boot time stack - Any secondary CPU will have lost its stack * by now because the cr3-switch above unmaps the real-mode stack */ movq initial_stack(%rip), %rsp /* Setup and Load IDT */ pushq %rsi call early_setup_idt popq %rsi /* Check if nx is implemented */ movl $0x80000001, %eax cpuid movl %edx,%edi /* Setup EFER (Extended Feature Enable Register) */ movl $MSR_EFER, %ecx rdmsr /* * Preserve current value of EFER for comparison and to skip * EFER writes if no change was made (for TDX guest) */ movl %eax, %edx btsl $_EFER_SCE, %eax /* Enable System Call */ btl $20,%edi /* No Execute supported? */ jnc 1f btsl $_EFER_NX, %eax btsq $_PAGE_BIT_NX,early_pmd_flags(%rip) /* Avoid writing EFER if no change was made (for TDX guest) */ 1: cmpl %edx, %eax je 1f xor %edx, %edx wrmsr /* Make changes effective */ 1: /* Setup cr0 */ movl $CR0_STATE, %eax /* Make changes effective */ movq %rax, %cr0 /* zero EFLAGS after setting rsp */ pushq $0 popfq /* rsi is pointer to real mode structure with interesting info. pass it to C */ movq %rsi, %rdi .Ljump_to_C_code: /* * Jump to run C code and to be on a real kernel address. * Since we are running on identity-mapped space we have to jump * to the full 64bit address, this is only possible as indirect * jump. In addition we need to ensure %cs is set so we make this * a far return. * * Note: do not change to far jump indirect with 64bit offset. * * AMD does not support far jump indirect with 64bit offset. * AMD64 Architecture Programmer's Manual, Volume 3: states only * JMP FAR mem16:16 FF /5 Far jump indirect, * with the target specified by a far pointer in memory. * JMP FAR mem16:32 FF /5 Far jump indirect, * with the target specified by a far pointer in memory. * * Intel64 does support 64bit offset. * Software Developer Manual Vol 2: states: * FF /5 JMP m16:16 Jump far, absolute indirect, * address given in m16:16 * FF /5 JMP m16:32 Jump far, absolute indirect, * address given in m16:32. * REX.W + FF /5 JMP m16:64 Jump far, absolute indirect, * address given in m16:64. */ pushq $.Lafter_lret # put return address on stack for unwinder xorl %ebp, %ebp # clear frame pointer movq initial_code(%rip), %rax pushq $__KERNEL_CS # set correct cs pushq %rax # target address in negative space lretq .Lafter_lret: ANNOTATE_NOENDBR SYM_CODE_END(secondary_startup_64) #include "verify_cpu.S" #include "sev_verify_cbit.S" #ifdef CONFIG_HOTPLUG_CPU /* * Boot CPU0 entry point. It's called from play_dead(). Everything has been set * up already except stack. We just set up stack here. Then call * start_secondary() via .Ljump_to_C_code. */ SYM_CODE_START(start_cpu0) ANNOTATE_NOENDBR UNWIND_HINT_EMPTY movq initial_stack(%rip), %rsp jmp .Ljump_to_C_code SYM_CODE_END(start_cpu0) #endif #ifdef CONFIG_AMD_MEM_ENCRYPT /* * VC Exception handler used during early boot when running on kernel * addresses, but before the switch to the idt_table can be made. * The early_idt_handler_array can't be used here because it calls into a lot * of __init code and this handler is also used during CPU offlining/onlining. * Therefore this handler ends up in the .text section so that it stays around * when .init.text is freed. */ SYM_CODE_START_NOALIGN(vc_boot_ghcb) UNWIND_HINT_IRET_REGS offset=8 ENDBR ANNOTATE_UNRET_END /* Build pt_regs */ PUSH_AND_CLEAR_REGS /* Call C handler */ movq %rsp, %rdi movq ORIG_RAX(%rsp), %rsi movq initial_vc_handler(%rip), %rax ANNOTATE_RETPOLINE_SAFE call *%rax /* Unwind pt_regs */ POP_REGS /* Remove Error Code */ addq $8, %rsp iretq SYM_CODE_END(vc_boot_ghcb) #endif /* Both SMP bootup and ACPI suspend change these variables */ __REFDATA .balign 8 SYM_DATA(initial_code, .quad x86_64_start_kernel) SYM_DATA(initial_gs, .quad INIT_PER_CPU_VAR(fixed_percpu_data)) #ifdef CONFIG_AMD_MEM_ENCRYPT SYM_DATA(initial_vc_handler, .quad handle_vc_boot_ghcb) #endif /* * The FRAME_SIZE gap is a convention which helps the in-kernel unwinder * reliably detect the end of the stack. */ SYM_DATA(initial_stack, .quad init_thread_union + THREAD_SIZE - FRAME_SIZE) __FINITDATA __INIT SYM_CODE_START(early_idt_handler_array) i = 0 .rept NUM_EXCEPTION_VECTORS .if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0 UNWIND_HINT_IRET_REGS ENDBR pushq $0 # Dummy error code, to make stack frame uniform .else UNWIND_HINT_IRET_REGS offset=8 ENDBR .endif pushq $i # 72(%rsp) Vector number jmp early_idt_handler_common UNWIND_HINT_IRET_REGS i = i + 1 .fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc .endr SYM_CODE_END(early_idt_handler_array) ANNOTATE_NOENDBR // early_idt_handler_array[NUM_EXCEPTION_VECTORS] SYM_CODE_START_LOCAL(early_idt_handler_common) UNWIND_HINT_IRET_REGS offset=16 ANNOTATE_UNRET_END /* * The stack is the hardware frame, an error code or zero, and the * vector number. */ cld incl early_recursion_flag(%rip) /* The vector number is currently in the pt_regs->di slot. */ pushq %rsi /* pt_regs->si */ movq 8(%rsp), %rsi /* RSI = vector number */ movq %rdi, 8(%rsp) /* pt_regs->di = RDI */ pushq %rdx /* pt_regs->dx */ pushq %rcx /* pt_regs->cx */ pushq %rax /* pt_regs->ax */ pushq %r8 /* pt_regs->r8 */ pushq %r9 /* pt_regs->r9 */ pushq %r10 /* pt_regs->r10 */ pushq %r11 /* pt_regs->r11 */ pushq %rbx /* pt_regs->bx */ pushq %rbp /* pt_regs->bp */ pushq %r12 /* pt_regs->r12 */ pushq %r13 /* pt_regs->r13 */ pushq %r14 /* pt_regs->r14 */ pushq %r15 /* pt_regs->r15 */ UNWIND_HINT_REGS movq %rsp,%rdi /* RDI = pt_regs; RSI is already trapnr */ call do_early_exception decl early_recursion_flag(%rip) jmp restore_regs_and_return_to_kernel SYM_CODE_END(early_idt_handler_common) #ifdef CONFIG_AMD_MEM_ENCRYPT /* * VC Exception handler used during very early boot. The * early_idt_handler_array can't be used because it returns via the * paravirtualized INTERRUPT_RETURN and pv-ops don't work that early. * * XXX it does, fix this. * * This handler will end up in the .init.text section and not be * available to boot secondary CPUs. */ SYM_CODE_START_NOALIGN(vc_no_ghcb) UNWIND_HINT_IRET_REGS offset=8 ENDBR ANNOTATE_UNRET_END /* Build pt_regs */ PUSH_AND_CLEAR_REGS /* Call C handler */ movq %rsp, %rdi movq ORIG_RAX(%rsp), %rsi call do_vc_no_ghcb /* Unwind pt_regs */ POP_REGS /* Remove Error Code */ addq $8, %rsp /* Pure iret required here - don't use INTERRUPT_RETURN */ iretq SYM_CODE_END(vc_no_ghcb) #endif #define SYM_DATA_START_PAGE_ALIGNED(name) \ SYM_START(name, SYM_L_GLOBAL, .balign PAGE_SIZE) #ifdef CONFIG_PAGE_TABLE_ISOLATION /* * Each PGD needs to be 8k long and 8k aligned. We do not * ever go out to userspace with these, so we do not * strictly *need* the second page, but this allows us to * have a single set_pgd() implementation that does not * need to worry about whether it has 4k or 8k to work * with. * * This ensures PGDs are 8k long: */ #define PTI_USER_PGD_FILL 512 /* This ensures they are 8k-aligned: */ #define SYM_DATA_START_PTI_ALIGNED(name) \ SYM_START(name, SYM_L_GLOBAL, .balign 2 * PAGE_SIZE) #else #define SYM_DATA_START_PTI_ALIGNED(name) \ SYM_DATA_START_PAGE_ALIGNED(name) #define PTI_USER_PGD_FILL 0 #endif /* Automate the creation of 1 to 1 mapping pmd entries */ #define PMDS(START, PERM, COUNT) \ i = 0 ; \ .rept (COUNT) ; \ .quad (START) + (i << PMD_SHIFT) + (PERM) ; \ i = i + 1 ; \ .endr __INITDATA .balign 4 SYM_DATA_START_PTI_ALIGNED(early_top_pgt) .fill 512,8,0 .fill PTI_USER_PGD_FILL,8,0 SYM_DATA_END(early_top_pgt) SYM_DATA_START_PAGE_ALIGNED(early_dynamic_pgts) .fill 512*EARLY_DYNAMIC_PAGE_TABLES,8,0 SYM_DATA_END(early_dynamic_pgts) SYM_DATA(early_recursion_flag, .long 0) .data #if defined(CONFIG_XEN_PV) || defined(CONFIG_PVH) SYM_DATA_START_PTI_ALIGNED(init_top_pgt) .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC .org init_top_pgt + L4_PAGE_OFFSET*8, 0 .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC .org init_top_pgt + L4_START_KERNEL*8, 0 /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */ .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC .fill PTI_USER_PGD_FILL,8,0 SYM_DATA_END(init_top_pgt) SYM_DATA_START_PAGE_ALIGNED(level3_ident_pgt) .quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC .fill 511, 8, 0 SYM_DATA_END(level3_ident_pgt) SYM_DATA_START_PAGE_ALIGNED(level2_ident_pgt) /* * Since I easily can, map the first 1G. * Don't set NX because code runs from these pages. * * Note: This sets _PAGE_GLOBAL despite whether * the CPU supports it or it is enabled. But, * the CPU should ignore the bit. */ PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD) SYM_DATA_END(level2_ident_pgt) #else SYM_DATA_START_PTI_ALIGNED(init_top_pgt) .fill 512,8,0 .fill PTI_USER_PGD_FILL,8,0 SYM_DATA_END(init_top_pgt) #endif #ifdef CONFIG_X86_5LEVEL SYM_DATA_START_PAGE_ALIGNED(level4_kernel_pgt) .fill 511,8,0 .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC SYM_DATA_END(level4_kernel_pgt) #endif SYM_DATA_START_PAGE_ALIGNED(level3_kernel_pgt) .fill L3_START_KERNEL,8,0 /* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */ .quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC .quad level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC SYM_DATA_END(level3_kernel_pgt) SYM_DATA_START_PAGE_ALIGNED(level2_kernel_pgt) /* * Kernel high mapping. * * The kernel code+data+bss must be located below KERNEL_IMAGE_SIZE in * virtual address space, which is 1 GiB if RANDOMIZE_BASE is enabled, * 512 MiB otherwise. * * (NOTE: after that starts the module area, see MODULES_VADDR.) * * This table is eventually used by the kernel during normal runtime. * Care must be taken to clear out undesired bits later, like _PAGE_RW * or _PAGE_GLOBAL in some cases. */ PMDS(0, __PAGE_KERNEL_LARGE_EXEC, KERNEL_IMAGE_SIZE/PMD_SIZE) SYM_DATA_END(level2_kernel_pgt) SYM_DATA_START_PAGE_ALIGNED(level2_fixmap_pgt) .fill (512 - 4 - FIXMAP_PMD_NUM),8,0 pgtno = 0 .rept (FIXMAP_PMD_NUM) .quad level1_fixmap_pgt + (pgtno << PAGE_SHIFT) - __START_KERNEL_map \ + _PAGE_TABLE_NOENC; pgtno = pgtno + 1 .endr /* 6 MB reserved space + a 2MB hole */ .fill 4,8,0 SYM_DATA_END(level2_fixmap_pgt) SYM_DATA_START_PAGE_ALIGNED(level1_fixmap_pgt) .rept (FIXMAP_PMD_NUM) .fill 512,8,0 .endr SYM_DATA_END(level1_fixmap_pgt) #undef PMDS .data .align 16 SYM_DATA(early_gdt_descr, .word GDT_ENTRIES*8-1) SYM_DATA_LOCAL(early_gdt_descr_base, .quad INIT_PER_CPU_VAR(gdt_page)) .align 16 /* This must match the first entry in level2_kernel_pgt */ SYM_DATA(phys_base, .quad 0x0) EXPORT_SYMBOL(phys_base) #include "../../x86/xen/xen-head.S" __PAGE_ALIGNED_BSS SYM_DATA_START_PAGE_ALIGNED(empty_zero_page) .skip PAGE_SIZE SYM_DATA_END(empty_zero_page) EXPORT_SYMBOL(empty_zero_page)