linux/arch/x86/kernel/machine_kexec_64.c
Tom Lendacky 4e237903f9 x86/mm, kexec: Fix memory corruption with SME on successive kexecs
After issuing successive kexecs it was found that the SHA hash failed
verification when booting the kexec'd kernel.  When SME is enabled, the
change from using pages that were marked encrypted to now being marked as
not encrypted (through new identify mapped page tables) results in memory
corruption if there are any cache entries for the previously encrypted
pages. This is because separate cache entries can exist for the same
physical location but tagged both with and without the encryption bit.

To prevent this, issue a wbinvd if SME is active before copying the pages
from the source location to the destination location to clear any possible
cache entry conflicts.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: <kexec@lists.infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/e7fb8610af3a93e8f8ae6f214cd9249adc0df2b4.1501186516.git.thomas.lendacky@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-07-30 12:09:12 +02:00

626 lines
15 KiB
C

/*
* handle transition of Linux booting another kernel
* Copyright (C) 2002-2005 Eric Biederman <ebiederm@xmission.com>
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/
#define pr_fmt(fmt) "kexec: " fmt
#include <linux/mm.h>
#include <linux/kexec.h>
#include <linux/string.h>
#include <linux/gfp.h>
#include <linux/reboot.h>
#include <linux/numa.h>
#include <linux/ftrace.h>
#include <linux/io.h>
#include <linux/suspend.h>
#include <linux/vmalloc.h>
#include <asm/init.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/io_apic.h>
#include <asm/debugreg.h>
#include <asm/kexec-bzimage64.h>
#include <asm/setup.h>
#include <asm/set_memory.h>
#ifdef CONFIG_KEXEC_FILE
static struct kexec_file_ops *kexec_file_loaders[] = {
&kexec_bzImage64_ops,
};
#endif
static void free_transition_pgtable(struct kimage *image)
{
free_page((unsigned long)image->arch.p4d);
free_page((unsigned long)image->arch.pud);
free_page((unsigned long)image->arch.pmd);
free_page((unsigned long)image->arch.pte);
}
static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
{
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
unsigned long vaddr, paddr;
int result = -ENOMEM;
vaddr = (unsigned long)relocate_kernel;
paddr = __pa(page_address(image->control_code_page)+PAGE_SIZE);
pgd += pgd_index(vaddr);
if (!pgd_present(*pgd)) {
p4d = (p4d_t *)get_zeroed_page(GFP_KERNEL);
if (!p4d)
goto err;
image->arch.p4d = p4d;
set_pgd(pgd, __pgd(__pa(p4d) | _KERNPG_TABLE));
}
p4d = p4d_offset(pgd, vaddr);
if (!p4d_present(*p4d)) {
pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
if (!pud)
goto err;
image->arch.pud = pud;
set_p4d(p4d, __p4d(__pa(pud) | _KERNPG_TABLE));
}
pud = pud_offset(p4d, vaddr);
if (!pud_present(*pud)) {
pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
if (!pmd)
goto err;
image->arch.pmd = pmd;
set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
}
pmd = pmd_offset(pud, vaddr);
if (!pmd_present(*pmd)) {
pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
if (!pte)
goto err;
image->arch.pte = pte;
set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
}
pte = pte_offset_kernel(pmd, vaddr);
set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC_NOENC));
return 0;
err:
free_transition_pgtable(image);
return result;
}
static void *alloc_pgt_page(void *data)
{
struct kimage *image = (struct kimage *)data;
struct page *page;
void *p = NULL;
page = kimage_alloc_control_pages(image, 0);
if (page) {
p = page_address(page);
clear_page(p);
}
return p;
}
static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
{
struct x86_mapping_info info = {
.alloc_pgt_page = alloc_pgt_page,
.context = image,
.page_flag = __PAGE_KERNEL_LARGE_EXEC,
.kernpg_flag = _KERNPG_TABLE_NOENC,
};
unsigned long mstart, mend;
pgd_t *level4p;
int result;
int i;
level4p = (pgd_t *)__va(start_pgtable);
clear_page(level4p);
if (direct_gbpages)
info.direct_gbpages = true;
for (i = 0; i < nr_pfn_mapped; i++) {
mstart = pfn_mapped[i].start << PAGE_SHIFT;
mend = pfn_mapped[i].end << PAGE_SHIFT;
result = kernel_ident_mapping_init(&info,
level4p, mstart, mend);
if (result)
return result;
}
/*
* segments's mem ranges could be outside 0 ~ max_pfn,
* for example when jump back to original kernel from kexeced kernel.
* or first kernel is booted with user mem map, and second kernel
* could be loaded out of that range.
*/
for (i = 0; i < image->nr_segments; i++) {
mstart = image->segment[i].mem;
mend = mstart + image->segment[i].memsz;
result = kernel_ident_mapping_init(&info,
level4p, mstart, mend);
if (result)
return result;
}
return init_transition_pgtable(image, level4p);
}
static void set_idt(void *newidt, u16 limit)
{
struct desc_ptr curidt;
/* x86-64 supports unaliged loads & stores */
curidt.size = limit;
curidt.address = (unsigned long)newidt;
__asm__ __volatile__ (
"lidtq %0\n"
: : "m" (curidt)
);
};
static void set_gdt(void *newgdt, u16 limit)
{
struct desc_ptr curgdt;
/* x86-64 supports unaligned loads & stores */
curgdt.size = limit;
curgdt.address = (unsigned long)newgdt;
__asm__ __volatile__ (
"lgdtq %0\n"
: : "m" (curgdt)
);
};
static void load_segments(void)
{
__asm__ __volatile__ (
"\tmovl %0,%%ds\n"
"\tmovl %0,%%es\n"
"\tmovl %0,%%ss\n"
"\tmovl %0,%%fs\n"
"\tmovl %0,%%gs\n"
: : "a" (__KERNEL_DS) : "memory"
);
}
#ifdef CONFIG_KEXEC_FILE
/* Update purgatory as needed after various image segments have been prepared */
static int arch_update_purgatory(struct kimage *image)
{
int ret = 0;
if (!image->file_mode)
return 0;
/* Setup copying of backup region */
if (image->type == KEXEC_TYPE_CRASH) {
ret = kexec_purgatory_get_set_symbol(image,
"purgatory_backup_dest",
&image->arch.backup_load_addr,
sizeof(image->arch.backup_load_addr), 0);
if (ret)
return ret;
ret = kexec_purgatory_get_set_symbol(image,
"purgatory_backup_src",
&image->arch.backup_src_start,
sizeof(image->arch.backup_src_start), 0);
if (ret)
return ret;
ret = kexec_purgatory_get_set_symbol(image,
"purgatory_backup_sz",
&image->arch.backup_src_sz,
sizeof(image->arch.backup_src_sz), 0);
if (ret)
return ret;
}
return ret;
}
#else /* !CONFIG_KEXEC_FILE */
static inline int arch_update_purgatory(struct kimage *image)
{
return 0;
}
#endif /* CONFIG_KEXEC_FILE */
int machine_kexec_prepare(struct kimage *image)
{
unsigned long start_pgtable;
int result;
/* Calculate the offsets */
start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
/* Setup the identity mapped 64bit page table */
result = init_pgtable(image, start_pgtable);
if (result)
return result;
/* update purgatory as needed */
result = arch_update_purgatory(image);
if (result)
return result;
return 0;
}
void machine_kexec_cleanup(struct kimage *image)
{
free_transition_pgtable(image);
}
/*
* Do not allocate memory (or fail in any way) in machine_kexec().
* We are past the point of no return, committed to rebooting now.
*/
void machine_kexec(struct kimage *image)
{
unsigned long page_list[PAGES_NR];
void *control_page;
int save_ftrace_enabled;
#ifdef CONFIG_KEXEC_JUMP
if (image->preserve_context)
save_processor_state();
#endif
save_ftrace_enabled = __ftrace_enabled_save();
/* Interrupts aren't acceptable while we reboot */
local_irq_disable();
hw_breakpoint_disable();
if (image->preserve_context) {
#ifdef CONFIG_X86_IO_APIC
/*
* We need to put APICs in legacy mode so that we can
* get timer interrupts in second kernel. kexec/kdump
* paths already have calls to disable_IO_APIC() in
* one form or other. kexec jump path also need
* one.
*/
disable_IO_APIC();
#endif
}
control_page = page_address(image->control_code_page) + PAGE_SIZE;
memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);
page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page);
page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;
page_list[PA_TABLE_PAGE] =
(unsigned long)__pa(page_address(image->control_code_page));
if (image->type == KEXEC_TYPE_DEFAULT)
page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)
<< PAGE_SHIFT);
/*
* The segment registers are funny things, they have both a
* visible and an invisible part. Whenever the visible part is
* set to a specific selector, the invisible part is loaded
* with from a table in memory. At no other time is the
* descriptor table in memory accessed.
*
* I take advantage of this here by force loading the
* segments, before I zap the gdt with an invalid value.
*/
load_segments();
/*
* The gdt & idt are now invalid.
* If you want to load them you must set up your own idt & gdt.
*/
set_gdt(phys_to_virt(0), 0);
set_idt(phys_to_virt(0), 0);
/* now call it */
image->start = relocate_kernel((unsigned long)image->head,
(unsigned long)page_list,
image->start,
image->preserve_context,
sme_active());
#ifdef CONFIG_KEXEC_JUMP
if (image->preserve_context)
restore_processor_state();
#endif
__ftrace_enabled_restore(save_ftrace_enabled);
}
void arch_crash_save_vmcoreinfo(void)
{
VMCOREINFO_NUMBER(phys_base);
VMCOREINFO_SYMBOL(init_top_pgt);
#ifdef CONFIG_NUMA
VMCOREINFO_SYMBOL(node_data);
VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
#endif
vmcoreinfo_append_str("KERNELOFFSET=%lx\n",
kaslr_offset());
VMCOREINFO_NUMBER(KERNEL_IMAGE_SIZE);
}
/* arch-dependent functionality related to kexec file-based syscall */
#ifdef CONFIG_KEXEC_FILE
int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
unsigned long buf_len)
{
int i, ret = -ENOEXEC;
struct kexec_file_ops *fops;
for (i = 0; i < ARRAY_SIZE(kexec_file_loaders); i++) {
fops = kexec_file_loaders[i];
if (!fops || !fops->probe)
continue;
ret = fops->probe(buf, buf_len);
if (!ret) {
image->fops = fops;
return ret;
}
}
return ret;
}
void *arch_kexec_kernel_image_load(struct kimage *image)
{
vfree(image->arch.elf_headers);
image->arch.elf_headers = NULL;
if (!image->fops || !image->fops->load)
return ERR_PTR(-ENOEXEC);
return image->fops->load(image, image->kernel_buf,
image->kernel_buf_len, image->initrd_buf,
image->initrd_buf_len, image->cmdline_buf,
image->cmdline_buf_len);
}
int arch_kimage_file_post_load_cleanup(struct kimage *image)
{
if (!image->fops || !image->fops->cleanup)
return 0;
return image->fops->cleanup(image->image_loader_data);
}
#ifdef CONFIG_KEXEC_VERIFY_SIG
int arch_kexec_kernel_verify_sig(struct kimage *image, void *kernel,
unsigned long kernel_len)
{
if (!image->fops || !image->fops->verify_sig) {
pr_debug("kernel loader does not support signature verification.");
return -EKEYREJECTED;
}
return image->fops->verify_sig(kernel, kernel_len);
}
#endif
/*
* Apply purgatory relocations.
*
* ehdr: Pointer to elf headers
* sechdrs: Pointer to section headers.
* relsec: section index of SHT_RELA section.
*
* TODO: Some of the code belongs to generic code. Move that in kexec.c.
*/
int arch_kexec_apply_relocations_add(const Elf64_Ehdr *ehdr,
Elf64_Shdr *sechdrs, unsigned int relsec)
{
unsigned int i;
Elf64_Rela *rel;
Elf64_Sym *sym;
void *location;
Elf64_Shdr *section, *symtabsec;
unsigned long address, sec_base, value;
const char *strtab, *name, *shstrtab;
/*
* ->sh_offset has been modified to keep the pointer to section
* contents in memory
*/
rel = (void *)sechdrs[relsec].sh_offset;
/* Section to which relocations apply */
section = &sechdrs[sechdrs[relsec].sh_info];
pr_debug("Applying relocate section %u to %u\n", relsec,
sechdrs[relsec].sh_info);
/* Associated symbol table */
symtabsec = &sechdrs[sechdrs[relsec].sh_link];
/* String table */
if (symtabsec->sh_link >= ehdr->e_shnum) {
/* Invalid strtab section number */
pr_err("Invalid string table section index %d\n",
symtabsec->sh_link);
return -ENOEXEC;
}
strtab = (char *)sechdrs[symtabsec->sh_link].sh_offset;
/* section header string table */
shstrtab = (char *)sechdrs[ehdr->e_shstrndx].sh_offset;
for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
/*
* rel[i].r_offset contains byte offset from beginning
* of section to the storage unit affected.
*
* This is location to update (->sh_offset). This is temporary
* buffer where section is currently loaded. This will finally
* be loaded to a different address later, pointed to by
* ->sh_addr. kexec takes care of moving it
* (kexec_load_segment()).
*/
location = (void *)(section->sh_offset + rel[i].r_offset);
/* Final address of the location */
address = section->sh_addr + rel[i].r_offset;
/*
* rel[i].r_info contains information about symbol table index
* w.r.t which relocation must be made and type of relocation
* to apply. ELF64_R_SYM() and ELF64_R_TYPE() macros get
* these respectively.
*/
sym = (Elf64_Sym *)symtabsec->sh_offset +
ELF64_R_SYM(rel[i].r_info);
if (sym->st_name)
name = strtab + sym->st_name;
else
name = shstrtab + sechdrs[sym->st_shndx].sh_name;
pr_debug("Symbol: %s info: %02x shndx: %02x value=%llx size: %llx\n",
name, sym->st_info, sym->st_shndx, sym->st_value,
sym->st_size);
if (sym->st_shndx == SHN_UNDEF) {
pr_err("Undefined symbol: %s\n", name);
return -ENOEXEC;
}
if (sym->st_shndx == SHN_COMMON) {
pr_err("symbol '%s' in common section\n", name);
return -ENOEXEC;
}
if (sym->st_shndx == SHN_ABS)
sec_base = 0;
else if (sym->st_shndx >= ehdr->e_shnum) {
pr_err("Invalid section %d for symbol %s\n",
sym->st_shndx, name);
return -ENOEXEC;
} else
sec_base = sechdrs[sym->st_shndx].sh_addr;
value = sym->st_value;
value += sec_base;
value += rel[i].r_addend;
switch (ELF64_R_TYPE(rel[i].r_info)) {
case R_X86_64_NONE:
break;
case R_X86_64_64:
*(u64 *)location = value;
break;
case R_X86_64_32:
*(u32 *)location = value;
if (value != *(u32 *)location)
goto overflow;
break;
case R_X86_64_32S:
*(s32 *)location = value;
if ((s64)value != *(s32 *)location)
goto overflow;
break;
case R_X86_64_PC32:
value -= (u64)address;
*(u32 *)location = value;
break;
default:
pr_err("Unknown rela relocation: %llu\n",
ELF64_R_TYPE(rel[i].r_info));
return -ENOEXEC;
}
}
return 0;
overflow:
pr_err("Overflow in relocation type %d value 0x%lx\n",
(int)ELF64_R_TYPE(rel[i].r_info), value);
return -ENOEXEC;
}
#endif /* CONFIG_KEXEC_FILE */
static int
kexec_mark_range(unsigned long start, unsigned long end, bool protect)
{
struct page *page;
unsigned int nr_pages;
/*
* For physical range: [start, end]. We must skip the unassigned
* crashk resource with zero-valued "end" member.
*/
if (!end || start > end)
return 0;
page = pfn_to_page(start >> PAGE_SHIFT);
nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1;
if (protect)
return set_pages_ro(page, nr_pages);
else
return set_pages_rw(page, nr_pages);
}
static void kexec_mark_crashkres(bool protect)
{
unsigned long control;
kexec_mark_range(crashk_low_res.start, crashk_low_res.end, protect);
/* Don't touch the control code page used in crash_kexec().*/
control = PFN_PHYS(page_to_pfn(kexec_crash_image->control_code_page));
/* Control code page is located in the 2nd page. */
kexec_mark_range(crashk_res.start, control + PAGE_SIZE - 1, protect);
control += KEXEC_CONTROL_PAGE_SIZE;
kexec_mark_range(control, crashk_res.end, protect);
}
void arch_kexec_protect_crashkres(void)
{
kexec_mark_crashkres(true);
}
void arch_kexec_unprotect_crashkres(void)
{
kexec_mark_crashkres(false);
}
int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, gfp_t gfp)
{
/*
* If SME is active we need to be sure that kexec pages are
* not encrypted because when we boot to the new kernel the
* pages won't be accessed encrypted (initially).
*/
return set_memory_decrypted((unsigned long)vaddr, pages);
}
void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages)
{
/*
* If SME is active we need to reset the pages back to being
* an encrypted mapping before freeing them.
*/
set_memory_encrypted((unsigned long)vaddr, pages);
}