1/* SPDX-License-Identifier: GPL-2.0 */ 2/* 3 * linux/boot/head.S 4 * 5 * Copyright (C) 1991, 1992, 1993 Linus Torvalds 6 */ 7 8/* 9 * head.S contains the 32-bit startup code. 10 * 11 * NOTE!!! Startup happens at absolute address 0x00001000, which is also where 12 * the page directory will exist. The startup code will be overwritten by 13 * the page directory. [According to comments etc elsewhere on a compressed 14 * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC] 15 * 16 * Page 0 is deliberately kept safe, since System Management Mode code in 17 * laptops may need to access the BIOS data stored there. This is also 18 * useful for future device drivers that either access the BIOS via VM86 19 * mode. 20 */ 21 22/* 23 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 24 */ 25 .code32 26 .text 27 28#include <linux/init.h> 29#include <linux/linkage.h> 30#include <asm/segment.h> 31#include <asm/boot.h> 32#include <asm/msr.h> 33#include <asm/processor-flags.h> 34#include <asm/asm-offsets.h> 35#include <asm/bootparam.h> 36#include <asm/desc_defs.h> 37#include <asm/trapnr.h> 38#include "pgtable.h" 39 40/* 41 * Locally defined symbols should be marked hidden: 42 */ 43 .hidden _bss 44 .hidden _ebss 45 .hidden _end 46 47 __HEAD 48 49/* 50 * This macro gives the relative virtual address of X, i.e. the offset of X 51 * from startup_32. This is the same as the link-time virtual address of X, 52 * since startup_32 is at 0, but defining it this way tells the 53 * assembler/linker that we do not want the actual run-time address of X. This 54 * prevents the linker from trying to create unwanted run-time relocation 55 * entries for the reference when the compressed kernel is linked as PIE. 56 * 57 * A reference X(%reg) will result in the link-time VA of X being stored with 58 * the instruction, and a run-time R_X86_64_RELATIVE relocation entry that 59 * adds the 64-bit base address where the kernel is loaded. 60 * 61 * Replacing it with (X-startup_32)(%reg) results in the offset being stored, 62 * and no run-time relocation. 63 * 64 * The macro should be used as a displacement with a base register containing 65 * the run-time address of startup_32 [i.e. rva(X)(%reg)], or as an immediate 66 * [$ rva(X)]. 67 * 68 * This macro can only be used from within the .head.text section, since the 69 * expression requires startup_32 to be in the same section as the code being 70 * assembled. 71 */ 72#define rva(X) ((X) - startup_32) 73 74 .code32 75SYM_FUNC_START(startup_32) 76 /* 77 * 32bit entry is 0 and it is ABI so immutable! 78 * If we come here directly from a bootloader, 79 * kernel(text+data+bss+brk) ramdisk, zero_page, command line 80 * all need to be under the 4G limit. 81 */ 82 cld 83 cli 84 85/* 86 * Calculate the delta between where we were compiled to run 87 * at and where we were actually loaded at. This can only be done 88 * with a short local call on x86. Nothing else will tell us what 89 * address we are running at. The reserved chunk of the real-mode 90 * data at 0x1e4 (defined as a scratch field) are used as the stack 91 * for this calculation. Only 4 bytes are needed. 92 */ 93 leal (BP_scratch+4)(%esi), %esp 94 call 1f 951: popl %ebp 96 subl $ rva(1b), %ebp 97 98 /* Load new GDT with the 64bit segments using 32bit descriptor */ 99 leal rva(gdt)(%ebp), %eax 100 movl %eax, 2(%eax) 101 lgdt (%eax) 102 103 /* Load segment registers with our descriptors */ 104 movl $__BOOT_DS, %eax 105 movl %eax, %ds 106 movl %eax, %es 107 movl %eax, %fs 108 movl %eax, %gs 109 movl %eax, %ss 110 111 /* Setup a stack and load CS from current GDT */ 112 leal rva(boot_stack_end)(%ebp), %esp 113 114 pushl $__KERNEL32_CS 115 leal rva(1f)(%ebp), %eax 116 pushl %eax 117 lretl 1181: 119 120 /* Setup Exception handling for SEV-ES */ 121 call startup32_load_idt 122 123 /* Make sure cpu supports long mode. */ 124 call verify_cpu 125 testl %eax, %eax 126 jnz .Lno_longmode 127 128/* 129 * Compute the delta between where we were compiled to run at 130 * and where the code will actually run at. 131 * 132 * %ebp contains the address we are loaded at by the boot loader and %ebx 133 * contains the address where we should move the kernel image temporarily 134 * for safe in-place decompression. 135 */ 136 137#ifdef CONFIG_RELOCATABLE 138 movl %ebp, %ebx 139 140#ifdef CONFIG_EFI_STUB 141/* 142 * If we were loaded via the EFI LoadImage service, startup_32 will be at an 143 * offset to the start of the space allocated for the image. efi_pe_entry will 144 * set up image_offset to tell us where the image actually starts, so that we 145 * can use the full available buffer. 146 * image_offset = startup_32 - image_base 147 * Otherwise image_offset will be zero and has no effect on the calculations. 148 */ 149 subl rva(image_offset)(%ebp), %ebx 150#endif 151 152 movl BP_kernel_alignment(%esi), %eax 153 decl %eax 154 addl %eax, %ebx 155 notl %eax 156 andl %eax, %ebx 157 cmpl $LOAD_PHYSICAL_ADDR, %ebx 158 jae 1f 159#endif 160 movl $LOAD_PHYSICAL_ADDR, %ebx 1611: 162 163 /* Target address to relocate to for decompression */ 164 addl BP_init_size(%esi), %ebx 165 subl $ rva(_end), %ebx 166 167/* 168 * Prepare for entering 64 bit mode 169 */ 170 171 /* Enable PAE mode */ 172 movl %cr4, %eax 173 orl $X86_CR4_PAE, %eax 174 movl %eax, %cr4 175 176 /* 177 * Build early 4G boot pagetable 178 */ 179 /* 180 * If SEV is active then set the encryption mask in the page tables. 181 * This will insure that when the kernel is copied and decompressed 182 * it will be done so encrypted. 183 */ 184 call get_sev_encryption_bit 185 xorl %edx, %edx 186#ifdef CONFIG_AMD_MEM_ENCRYPT 187 testl %eax, %eax 188 jz 1f 189 subl $32, %eax /* Encryption bit is always above bit 31 */ 190 bts %eax, %edx /* Set encryption mask for page tables */ 191 /* 192 * Mark SEV as active in sev_status so that startup32_check_sev_cbit() 193 * will do a check. The sev_status memory will be fully initialized 194 * with the contents of MSR_AMD_SEV_STATUS later in 195 * set_sev_encryption_mask(). For now it is sufficient to know that SEV 196 * is active. 197 */ 198 movl $1, rva(sev_status)(%ebp) 1991: 200#endif 201 202 /* Initialize Page tables to 0 */ 203 leal rva(pgtable)(%ebx), %edi 204 xorl %eax, %eax 205 movl $(BOOT_INIT_PGT_SIZE/4), %ecx 206 rep stosl 207 208 /* Build Level 4 */ 209 leal rva(pgtable + 0)(%ebx), %edi 210 leal 0x1007 (%edi), %eax 211 movl %eax, 0(%edi) 212 addl %edx, 4(%edi) 213 214 /* Build Level 3 */ 215 leal rva(pgtable + 0x1000)(%ebx), %edi 216 leal 0x1007(%edi), %eax 217 movl $4, %ecx 2181: movl %eax, 0x00(%edi) 219 addl %edx, 0x04(%edi) 220 addl $0x00001000, %eax 221 addl $8, %edi 222 decl %ecx 223 jnz 1b 224 225 /* Build Level 2 */ 226 leal rva(pgtable + 0x2000)(%ebx), %edi 227 movl $0x00000183, %eax 228 movl $2048, %ecx 2291: movl %eax, 0(%edi) 230 addl %edx, 4(%edi) 231 addl $0x00200000, %eax 232 addl $8, %edi 233 decl %ecx 234 jnz 1b 235 236 /* Enable the boot page tables */ 237 leal rva(pgtable)(%ebx), %eax 238 movl %eax, %cr3 239 240 /* Enable Long mode in EFER (Extended Feature Enable Register) */ 241 movl $MSR_EFER, %ecx 242 rdmsr 243 btsl $_EFER_LME, %eax 244 wrmsr 245 246 /* After gdt is loaded */ 247 xorl %eax, %eax 248 lldt %ax 249 movl $__BOOT_TSS, %eax 250 ltr %ax 251 252 /* 253 * Setup for the jump to 64bit mode 254 * 255 * When the jump is performed we will be in long mode but 256 * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1 257 * (and in turn EFER.LMA = 1). To jump into 64bit mode we use 258 * the new gdt/idt that has __KERNEL_CS with CS.L = 1. 259 * We place all of the values on our mini stack so lret can 260 * used to perform that far jump. 261 */ 262 leal rva(startup_64)(%ebp), %eax 263#ifdef CONFIG_EFI_MIXED 264 movl rva(efi32_boot_args)(%ebp), %edi 265 testl %edi, %edi 266 jz 1f 267 leal rva(efi64_stub_entry)(%ebp), %eax 268 movl rva(efi32_boot_args+4)(%ebp), %esi 269 movl rva(efi32_boot_args+8)(%ebp), %edx // saved bootparams pointer 270 testl %edx, %edx 271 jnz 1f 272 /* 273 * efi_pe_entry uses MS calling convention, which requires 32 bytes of 274 * shadow space on the stack even if all arguments are passed in 275 * registers. We also need an additional 8 bytes for the space that 276 * would be occupied by the return address, and this also results in 277 * the correct stack alignment for entry. 278 */ 279 subl $40, %esp 280 leal rva(efi_pe_entry)(%ebp), %eax 281 movl %edi, %ecx // MS calling convention 282 movl %esi, %edx 2831: 284#endif 285 /* Check if the C-bit position is correct when SEV is active */ 286 call startup32_check_sev_cbit 287 288 pushl $__KERNEL_CS 289 pushl %eax 290 291 /* Enter paged protected Mode, activating Long Mode */ 292 movl $(X86_CR0_PG | X86_CR0_PE), %eax /* Enable Paging and Protected mode */ 293 movl %eax, %cr0 294 295 /* Jump from 32bit compatibility mode into 64bit mode. */ 296 lret 297SYM_FUNC_END(startup_32) 298 299#ifdef CONFIG_EFI_MIXED 300 .org 0x190 301SYM_FUNC_START(efi32_stub_entry) 302 add $0x4, %esp /* Discard return address */ 303 popl %ecx 304 popl %edx 305 popl %esi 306 307 call 1f 3081: pop %ebp 309 subl $ rva(1b), %ebp 310 311 movl %esi, rva(efi32_boot_args+8)(%ebp) 312SYM_INNER_LABEL(efi32_pe_stub_entry, SYM_L_LOCAL) 313 movl %ecx, rva(efi32_boot_args)(%ebp) 314 movl %edx, rva(efi32_boot_args+4)(%ebp) 315 movb $0, rva(efi_is64)(%ebp) 316 317 /* Save firmware GDTR and code/data selectors */ 318 sgdtl rva(efi32_boot_gdt)(%ebp) 319 movw %cs, rva(efi32_boot_cs)(%ebp) 320 movw %ds, rva(efi32_boot_ds)(%ebp) 321 322 /* Disable paging */ 323 movl %cr0, %eax 324 btrl $X86_CR0_PG_BIT, %eax 325 movl %eax, %cr0 326 327 jmp startup_32 328SYM_FUNC_END(efi32_stub_entry) 329#endif 330 331 .code64 332 .org 0x200 333SYM_CODE_START(startup_64) 334 /* 335 * 64bit entry is 0x200 and it is ABI so immutable! 336 * We come here either from startup_32 or directly from a 337 * 64bit bootloader. 338 * If we come here from a bootloader, kernel(text+data+bss+brk), 339 * ramdisk, zero_page, command line could be above 4G. 340 * We depend on an identity mapped page table being provided 341 * that maps our entire kernel(text+data+bss+brk), zero page 342 * and command line. 343 */ 344 345 cld 346 cli 347 348 /* Setup data segments. */ 349 xorl %eax, %eax 350 movl %eax, %ds 351 movl %eax, %es 352 movl %eax, %ss 353 movl %eax, %fs 354 movl %eax, %gs 355 356 /* 357 * Compute the decompressed kernel start address. It is where 358 * we were loaded at aligned to a 2M boundary. %rbp contains the 359 * decompressed kernel start address. 360 * 361 * If it is a relocatable kernel then decompress and run the kernel 362 * from load address aligned to 2MB addr, otherwise decompress and 363 * run the kernel from LOAD_PHYSICAL_ADDR 364 * 365 * We cannot rely on the calculation done in 32-bit mode, since we 366 * may have been invoked via the 64-bit entry point. 367 */ 368 369 /* Start with the delta to where the kernel will run at. */ 370#ifdef CONFIG_RELOCATABLE 371 leaq startup_32(%rip) /* - $startup_32 */, %rbp 372 373#ifdef CONFIG_EFI_STUB 374/* 375 * If we were loaded via the EFI LoadImage service, startup_32 will be at an 376 * offset to the start of the space allocated for the image. efi_pe_entry will 377 * set up image_offset to tell us where the image actually starts, so that we 378 * can use the full available buffer. 379 * image_offset = startup_32 - image_base 380 * Otherwise image_offset will be zero and has no effect on the calculations. 381 */ 382 movl image_offset(%rip), %eax 383 subq %rax, %rbp 384#endif 385 386 movl BP_kernel_alignment(%rsi), %eax 387 decl %eax 388 addq %rax, %rbp 389 notq %rax 390 andq %rax, %rbp 391 cmpq $LOAD_PHYSICAL_ADDR, %rbp 392 jae 1f 393#endif 394 movq $LOAD_PHYSICAL_ADDR, %rbp 3951: 396 397 /* Target address to relocate to for decompression */ 398 movl BP_init_size(%rsi), %ebx 399 subl $ rva(_end), %ebx 400 addq %rbp, %rbx 401 402 /* Set up the stack */ 403 leaq rva(boot_stack_end)(%rbx), %rsp 404 405 /* 406 * At this point we are in long mode with 4-level paging enabled, 407 * but we might want to enable 5-level paging or vice versa. 408 * 409 * The problem is that we cannot do it directly. Setting or clearing 410 * CR4.LA57 in long mode would trigger #GP. So we need to switch off 411 * long mode and paging first. 412 * 413 * We also need a trampoline in lower memory to switch over from 414 * 4- to 5-level paging for cases when the bootloader puts the kernel 415 * above 4G, but didn't enable 5-level paging for us. 416 * 417 * The same trampoline can be used to switch from 5- to 4-level paging 418 * mode, like when starting 4-level paging kernel via kexec() when 419 * original kernel worked in 5-level paging mode. 420 * 421 * For the trampoline, we need the top page table to reside in lower 422 * memory as we don't have a way to load 64-bit values into CR3 in 423 * 32-bit mode. 424 * 425 * We go though the trampoline even if we don't have to: if we're 426 * already in a desired paging mode. This way the trampoline code gets 427 * tested on every boot. 428 */ 429 430 /* Make sure we have GDT with 32-bit code segment */ 431 leaq gdt64(%rip), %rax 432 addq %rax, 2(%rax) 433 lgdt (%rax) 434 435 /* Reload CS so IRET returns to a CS actually in the GDT */ 436 pushq $__KERNEL_CS 437 leaq .Lon_kernel_cs(%rip), %rax 438 pushq %rax 439 lretq 440 441.Lon_kernel_cs: 442 443 pushq %rsi 444 call load_stage1_idt 445 popq %rsi 446 447 /* 448 * paging_prepare() sets up the trampoline and checks if we need to 449 * enable 5-level paging. 450 * 451 * paging_prepare() returns a two-quadword structure which lands 452 * into RDX:RAX: 453 * - Address of the trampoline is returned in RAX. 454 * - Non zero RDX means trampoline needs to enable 5-level 455 * paging. 456 * 457 * RSI holds real mode data and needs to be preserved across 458 * this function call. 459 */ 460 pushq %rsi 461 movq %rsi, %rdi /* real mode address */ 462 call paging_prepare 463 popq %rsi 464 465 /* Save the trampoline address in RCX */ 466 movq %rax, %rcx 467 468 /* 469 * Load the address of trampoline_return() into RDI. 470 * It will be used by the trampoline to return to the main code. 471 */ 472 leaq trampoline_return(%rip), %rdi 473 474 /* Switch to compatibility mode (CS.L = 0 CS.D = 1) via far return */ 475 pushq $__KERNEL32_CS 476 leaq TRAMPOLINE_32BIT_CODE_OFFSET(%rax), %rax 477 pushq %rax 478 lretq 479trampoline_return: 480 /* Restore the stack, the 32-bit trampoline uses its own stack */ 481 leaq rva(boot_stack_end)(%rbx), %rsp 482 483 /* 484 * cleanup_trampoline() would restore trampoline memory. 485 * 486 * RDI is address of the page table to use instead of page table 487 * in trampoline memory (if required). 488 * 489 * RSI holds real mode data and needs to be preserved across 490 * this function call. 491 */ 492 pushq %rsi 493 leaq rva(top_pgtable)(%rbx), %rdi 494 call cleanup_trampoline 495 popq %rsi 496 497 /* Zero EFLAGS */ 498 pushq $0 499 popfq 500 501/* 502 * Copy the compressed kernel to the end of our buffer 503 * where decompression in place becomes safe. 504 */ 505 pushq %rsi 506 leaq (_bss-8)(%rip), %rsi 507 leaq rva(_bss-8)(%rbx), %rdi 508 movl $(_bss - startup_32), %ecx 509 shrl $3, %ecx 510 std 511 rep movsq 512 cld 513 popq %rsi 514 515 /* 516 * The GDT may get overwritten either during the copy we just did or 517 * during extract_kernel below. To avoid any issues, repoint the GDTR 518 * to the new copy of the GDT. 519 */ 520 leaq rva(gdt64)(%rbx), %rax 521 leaq rva(gdt)(%rbx), %rdx 522 movq %rdx, 2(%rax) 523 lgdt (%rax) 524 525/* 526 * Jump to the relocated address. 527 */ 528 leaq rva(.Lrelocated)(%rbx), %rax 529 jmp *%rax 530SYM_CODE_END(startup_64) 531 532#ifdef CONFIG_EFI_STUB 533 .org 0x390 534SYM_FUNC_START(efi64_stub_entry) 535SYM_FUNC_START_ALIAS(efi_stub_entry) 536 and $~0xf, %rsp /* realign the stack */ 537 movq %rdx, %rbx /* save boot_params pointer */ 538 call efi_main 539 movq %rbx,%rsi 540 leaq rva(startup_64)(%rax), %rax 541 jmp *%rax 542SYM_FUNC_END(efi64_stub_entry) 543SYM_FUNC_END_ALIAS(efi_stub_entry) 544#endif 545 546 .text 547SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) 548 549/* 550 * Clear BSS (stack is currently empty) 551 */ 552 xorl %eax, %eax 553 leaq _bss(%rip), %rdi 554 leaq _ebss(%rip), %rcx 555 subq %rdi, %rcx 556 shrq $3, %rcx 557 rep stosq 558 559/* 560 * If running as an SEV guest, the encryption mask is required in the 561 * page-table setup code below. When the guest also has SEV-ES enabled 562 * set_sev_encryption_mask() will cause #VC exceptions, but the stage2 563 * handler can't map its GHCB because the page-table is not set up yet. 564 * So set up the encryption mask here while still on the stage1 #VC 565 * handler. Then load stage2 IDT and switch to the kernel's own 566 * page-table. 567 */ 568 pushq %rsi 569 call set_sev_encryption_mask 570 call load_stage2_idt 571 572 /* Pass boot_params to initialize_identity_maps() */ 573 movq (%rsp), %rdi 574 call initialize_identity_maps 575 popq %rsi 576 577/* 578 * Do the extraction, and jump to the new kernel.. 579 */ 580 pushq %rsi /* Save the real mode argument */ 581 movq %rsi, %rdi /* real mode address */ 582 leaq boot_heap(%rip), %rsi /* malloc area for uncompression */ 583 leaq input_data(%rip), %rdx /* input_data */ 584 movl input_len(%rip), %ecx /* input_len */ 585 movq %rbp, %r8 /* output target address */ 586 movl output_len(%rip), %r9d /* decompressed length, end of relocs */ 587 call extract_kernel /* returns kernel location in %rax */ 588 popq %rsi 589 590/* 591 * Jump to the decompressed kernel. 592 */ 593 jmp *%rax 594SYM_FUNC_END(.Lrelocated) 595 596 .code32 597/* 598 * This is the 32-bit trampoline that will be copied over to low memory. 599 * 600 * RDI contains the return address (might be above 4G). 601 * ECX contains the base address of the trampoline memory. 602 * Non zero RDX means trampoline needs to enable 5-level paging. 603 */ 604SYM_CODE_START(trampoline_32bit_src) 605 /* Set up data and stack segments */ 606 movl $__KERNEL_DS, %eax 607 movl %eax, %ds 608 movl %eax, %ss 609 610 /* Set up new stack */ 611 leal TRAMPOLINE_32BIT_STACK_END(%ecx), %esp 612 613 /* Disable paging */ 614 movl %cr0, %eax 615 btrl $X86_CR0_PG_BIT, %eax 616 movl %eax, %cr0 617 618 /* Check what paging mode we want to be in after the trampoline */ 619 testl %edx, %edx 620 jz 1f 621 622 /* We want 5-level paging: don't touch CR3 if it already points to 5-level page tables */ 623 movl %cr4, %eax 624 testl $X86_CR4_LA57, %eax 625 jnz 3f 626 jmp 2f 6271: 628 /* We want 4-level paging: don't touch CR3 if it already points to 4-level page tables */ 629 movl %cr4, %eax 630 testl $X86_CR4_LA57, %eax 631 jz 3f 6322: 633 /* Point CR3 to the trampoline's new top level page table */ 634 leal TRAMPOLINE_32BIT_PGTABLE_OFFSET(%ecx), %eax 635 movl %eax, %cr3 6363: 637 /* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */ 638 pushl %ecx 639 pushl %edx 640 movl $MSR_EFER, %ecx 641 rdmsr 642 btsl $_EFER_LME, %eax 643 wrmsr 644 popl %edx 645 popl %ecx 646 647 /* Enable PAE and LA57 (if required) paging modes */ 648 movl $X86_CR4_PAE, %eax 649 testl %edx, %edx 650 jz 1f 651 orl $X86_CR4_LA57, %eax 6521: 653 movl %eax, %cr4 654 655 /* Calculate address of paging_enabled() once we are executing in the trampoline */ 656 leal .Lpaging_enabled - trampoline_32bit_src + TRAMPOLINE_32BIT_CODE_OFFSET(%ecx), %eax 657 658 /* Prepare the stack for far return to Long Mode */ 659 pushl $__KERNEL_CS 660 pushl %eax 661 662 /* Enable paging again */ 663 movl $(X86_CR0_PG | X86_CR0_PE), %eax 664 movl %eax, %cr0 665 666 lret 667SYM_CODE_END(trampoline_32bit_src) 668 669 .code64 670SYM_FUNC_START_LOCAL_NOALIGN(.Lpaging_enabled) 671 /* Return from the trampoline */ 672 jmp *%rdi 673SYM_FUNC_END(.Lpaging_enabled) 674 675 /* 676 * The trampoline code has a size limit. 677 * Make sure we fail to compile if the trampoline code grows 678 * beyond TRAMPOLINE_32BIT_CODE_SIZE bytes. 679 */ 680 .org trampoline_32bit_src + TRAMPOLINE_32BIT_CODE_SIZE 681 682 .code32 683SYM_FUNC_START_LOCAL_NOALIGN(.Lno_longmode) 684 /* This isn't an x86-64 CPU, so hang intentionally, we cannot continue */ 6851: 686 hlt 687 jmp 1b 688SYM_FUNC_END(.Lno_longmode) 689 690#include "../../kernel/verify_cpu.S" 691 692 .data 693SYM_DATA_START_LOCAL(gdt64) 694 .word gdt_end - gdt - 1 695 .quad gdt - gdt64 696SYM_DATA_END(gdt64) 697 .balign 8 698SYM_DATA_START_LOCAL(gdt) 699 .word gdt_end - gdt - 1 700 .long 0 701 .word 0 702 .quad 0x00cf9a000000ffff /* __KERNEL32_CS */ 703 .quad 0x00af9a000000ffff /* __KERNEL_CS */ 704 .quad 0x00cf92000000ffff /* __KERNEL_DS */ 705 .quad 0x0080890000000000 /* TS descriptor */ 706 .quad 0x0000000000000000 /* TS continued */ 707SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end) 708 709SYM_DATA_START(boot_idt_desc) 710 .word boot_idt_end - boot_idt - 1 711 .quad 0 712SYM_DATA_END(boot_idt_desc) 713 .balign 8 714SYM_DATA_START(boot_idt) 715 .rept BOOT_IDT_ENTRIES 716 .quad 0 717 .quad 0 718 .endr 719SYM_DATA_END_LABEL(boot_idt, SYM_L_GLOBAL, boot_idt_end) 720 721#ifdef CONFIG_AMD_MEM_ENCRYPT 722SYM_DATA_START(boot32_idt_desc) 723 .word boot32_idt_end - boot32_idt - 1 724 .long 0 725SYM_DATA_END(boot32_idt_desc) 726 .balign 8 727SYM_DATA_START(boot32_idt) 728 .rept 32 729 .quad 0 730 .endr 731SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLOBAL, boot32_idt_end) 732#endif 733 734#ifdef CONFIG_EFI_STUB 735SYM_DATA(image_offset, .long 0) 736#endif 737#ifdef CONFIG_EFI_MIXED 738SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0) 739SYM_DATA(efi_is64, .byte 1) 740 741#define ST32_boottime 60 // offsetof(efi_system_table_32_t, boottime) 742#define BS32_handle_protocol 88 // offsetof(efi_boot_services_32_t, handle_protocol) 743#define LI32_image_base 32 // offsetof(efi_loaded_image_32_t, image_base) 744 745 __HEAD 746 .code32 747SYM_FUNC_START(efi32_pe_entry) 748/* 749 * efi_status_t efi32_pe_entry(efi_handle_t image_handle, 750 * efi_system_table_32_t *sys_table) 751 */ 752 753 pushl %ebp 754 movl %esp, %ebp 755 pushl %eax // dummy push to allocate loaded_image 756 757 pushl %ebx // save callee-save registers 758 pushl %edi 759 760 call verify_cpu // check for long mode support 761 testl %eax, %eax 762 movl $0x80000003, %eax // EFI_UNSUPPORTED 763 jnz 2f 764 765 call 1f 7661: pop %ebx 767 subl $ rva(1b), %ebx 768 769 /* Get the loaded image protocol pointer from the image handle */ 770 leal -4(%ebp), %eax 771 pushl %eax // &loaded_image 772 leal rva(loaded_image_proto)(%ebx), %eax 773 pushl %eax // pass the GUID address 774 pushl 8(%ebp) // pass the image handle 775 776 /* 777 * Note the alignment of the stack frame. 778 * sys_table 779 * handle <-- 16-byte aligned on entry by ABI 780 * return address 781 * frame pointer 782 * loaded_image <-- local variable 783 * saved %ebx <-- 16-byte aligned here 784 * saved %edi 785 * &loaded_image 786 * &loaded_image_proto 787 * handle <-- 16-byte aligned for call to handle_protocol 788 */ 789 790 movl 12(%ebp), %eax // sys_table 791 movl ST32_boottime(%eax), %eax // sys_table->boottime 792 call *BS32_handle_protocol(%eax) // sys_table->boottime->handle_protocol 793 addl $12, %esp // restore argument space 794 testl %eax, %eax 795 jnz 2f 796 797 movl 8(%ebp), %ecx // image_handle 798 movl 12(%ebp), %edx // sys_table 799 movl -4(%ebp), %esi // loaded_image 800 movl LI32_image_base(%esi), %esi // loaded_image->image_base 801 movl %ebx, %ebp // startup_32 for efi32_pe_stub_entry 802 /* 803 * We need to set the image_offset variable here since startup_32() will 804 * use it before we get to the 64-bit efi_pe_entry() in C code. 805 */ 806 subl %esi, %ebx 807 movl %ebx, rva(image_offset)(%ebp) // save image_offset 808 jmp efi32_pe_stub_entry 809 8102: popl %edi // restore callee-save registers 811 popl %ebx 812 leave 813 ret 814SYM_FUNC_END(efi32_pe_entry) 815 816 .section ".rodata" 817 /* EFI loaded image protocol GUID */ 818 .balign 4 819SYM_DATA_START_LOCAL(loaded_image_proto) 820 .long 0x5b1b31a1 821 .word 0x9562, 0x11d2 822 .byte 0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b 823SYM_DATA_END(loaded_image_proto) 824#endif 825 826#ifdef CONFIG_AMD_MEM_ENCRYPT 827 __HEAD 828 .code32 829/* 830 * Write an IDT entry into boot32_idt 831 * 832 * Parameters: 833 * 834 * %eax: Handler address 835 * %edx: Vector number 836 * 837 * Physical offset is expected in %ebp 838 */ 839SYM_FUNC_START(startup32_set_idt_entry) 840 push %ebx 841 push %ecx 842 843 /* IDT entry address to %ebx */ 844 leal rva(boot32_idt)(%ebp), %ebx 845 shl $3, %edx 846 addl %edx, %ebx 847 848 /* Build IDT entry, lower 4 bytes */ 849 movl %eax, %edx 850 andl $0x0000ffff, %edx # Target code segment offset [15:0] 851 movl $__KERNEL32_CS, %ecx # Target code segment selector 852 shl $16, %ecx 853 orl %ecx, %edx 854 855 /* Store lower 4 bytes to IDT */ 856 movl %edx, (%ebx) 857 858 /* Build IDT entry, upper 4 bytes */ 859 movl %eax, %edx 860 andl $0xffff0000, %edx # Target code segment offset [31:16] 861 orl $0x00008e00, %edx # Present, Type 32-bit Interrupt Gate 862 863 /* Store upper 4 bytes to IDT */ 864 movl %edx, 4(%ebx) 865 866 pop %ecx 867 pop %ebx 868 ret 869SYM_FUNC_END(startup32_set_idt_entry) 870#endif 871 872SYM_FUNC_START(startup32_load_idt) 873#ifdef CONFIG_AMD_MEM_ENCRYPT 874 /* #VC handler */ 875 leal rva(startup32_vc_handler)(%ebp), %eax 876 movl $X86_TRAP_VC, %edx 877 call startup32_set_idt_entry 878 879 /* Load IDT */ 880 leal rva(boot32_idt)(%ebp), %eax 881 movl %eax, rva(boot32_idt_desc+2)(%ebp) 882 lidt rva(boot32_idt_desc)(%ebp) 883#endif 884 ret 885SYM_FUNC_END(startup32_load_idt) 886 887/* 888 * Check for the correct C-bit position when the startup_32 boot-path is used. 889 * 890 * The check makes use of the fact that all memory is encrypted when paging is 891 * disabled. The function creates 64 bits of random data using the RDRAND 892 * instruction. RDRAND is mandatory for SEV guests, so always available. If the 893 * hypervisor violates that the kernel will crash right here. 894 * 895 * The 64 bits of random data are stored to a memory location and at the same 896 * time kept in the %eax and %ebx registers. Since encryption is always active 897 * when paging is off the random data will be stored encrypted in main memory. 898 * 899 * Then paging is enabled. When the C-bit position is correct all memory is 900 * still mapped encrypted and comparing the register values with memory will 901 * succeed. An incorrect C-bit position will map all memory unencrypted, so that 902 * the compare will use the encrypted random data and fail. 903 */ 904SYM_FUNC_START(startup32_check_sev_cbit) 905#ifdef CONFIG_AMD_MEM_ENCRYPT 906 pushl %eax 907 pushl %ebx 908 pushl %ecx 909 pushl %edx 910 911 /* Check for non-zero sev_status */ 912 movl rva(sev_status)(%ebp), %eax 913 testl %eax, %eax 914 jz 4f 915 916 /* 917 * Get two 32-bit random values - Don't bail out if RDRAND fails 918 * because it is better to prevent forward progress if no random value 919 * can be gathered. 920 */ 9211: rdrand %eax 922 jnc 1b 9232: rdrand %ebx 924 jnc 2b 925 926 /* Store to memory and keep it in the registers */ 927 movl %eax, rva(sev_check_data)(%ebp) 928 movl %ebx, rva(sev_check_data+4)(%ebp) 929 930 /* Enable paging to see if encryption is active */ 931 movl %cr0, %edx /* Backup %cr0 in %edx */ 932 movl $(X86_CR0_PG | X86_CR0_PE), %ecx /* Enable Paging and Protected mode */ 933 movl %ecx, %cr0 934 935 cmpl %eax, rva(sev_check_data)(%ebp) 936 jne 3f 937 cmpl %ebx, rva(sev_check_data+4)(%ebp) 938 jne 3f 939 940 movl %edx, %cr0 /* Restore previous %cr0 */ 941 942 jmp 4f 943 9443: /* Check failed - hlt the machine */ 945 hlt 946 jmp 3b 947 9484: 949 popl %edx 950 popl %ecx 951 popl %ebx 952 popl %eax 953#endif 954 ret 955SYM_FUNC_END(startup32_check_sev_cbit) 956 957/* 958 * Stack and heap for uncompression 959 */ 960 .bss 961 .balign 4 962SYM_DATA_LOCAL(boot_heap, .fill BOOT_HEAP_SIZE, 1, 0) 963 964SYM_DATA_START_LOCAL(boot_stack) 965 .fill BOOT_STACK_SIZE, 1, 0 966 .balign 16 967SYM_DATA_END_LABEL(boot_stack, SYM_L_LOCAL, boot_stack_end) 968 969/* 970 * Space for page tables (not in .bss so not zeroed) 971 */ 972 .section ".pgtable","aw",@nobits 973 .balign 4096 974SYM_DATA_LOCAL(pgtable, .fill BOOT_PGT_SIZE, 1, 0) 975 976/* 977 * The page table is going to be used instead of page table in the trampoline 978 * memory. 979 */ 980SYM_DATA_LOCAL(top_pgtable, .fill PAGE_SIZE, 1, 0) 981