* This function will switch the EFI runtime services to virtual mode.
* Essentially, we look through the EFI memmap and map every region that
* has the runtime attribute bit set in its memory descriptor into the
- * efi_pgd page table.
+ * ->trampoline_pgd page table using a top-down VA allocation scheme.
*
* The old method which used to update that memory descriptor with the
* virtual address obtained from ioremap() is still supported when the
*
* The new method does a pagetable switch in a preemption-safe manner
* so that we're in a different address space when calling a runtime
- * function. For function arguments passing we do copy the PUDs of the
- * kernel page table into efi_pgd prior to each call.
+ * function. For function arguments passing we do copy the PGDs of the
+ * kernel page table into ->trampoline_pgd prior to each call.
*
* Specially for kexec boot, efi runtime maps in previous kernel should
* be passed in via setup_data. In that case runtime ranges will be mapped
efi.systab = NULL;
- if (efi_alloc_page_tables()) {
- pr_err("Failed to allocate EFI page tables\n");
- clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
- return;
- }
-
efi_merge_regions();
new_memmap = efi_map_regions(&count, &pg_shift);
if (!new_memmap) {
efi_runtime_mkexec();
/*
- * We mapped the descriptor array into the EFI pagetable above
- * but we're not unmapping it here because if we're running in
- * EFI mixed mode we need all of memory to be accessible when
- * we pass parameters to the EFI runtime services in the
- * thunking code.
+ * We mapped the descriptor array into the EFI pagetable above but we're
+ * not unmapping it here. Here's why:
+ *
+ * We're copying select PGDs from the kernel page table to the EFI page
+ * table and when we do so and make changes to those PGDs like unmapping
+ * stuff from them, those changes appear in the kernel page table and we
+ * go boom.
+ *
+ * From setup_real_mode():
+ *
+ * ...
+ * trampoline_pgd[0] = init_level4_pgt[pgd_index(__PAGE_OFFSET)].pgd;
+ *
+ * In this particular case, our allocation is in PGD 0 of the EFI page
+ * table but we've copied that PGD from PGD[272] of the EFI page table:
+ *
+ * pgd_index(__PAGE_OFFSET = 0xffff880000000000) = 272
+ *
+ * where the direct memory mapping in kernel space is.
+ *
+ * new_memmap's VA comes from that direct mapping and thus clearing it,
+ * it would get cleared in the kernel page table too.
*
* efi_cleanup_page_tables(__pa(new_memmap), 1 << pg_shift);
*/
#include <asm/fixmap.h>
#include <asm/realmode.h>
#include <asm/time.h>
-#include <asm/pgalloc.h>
/*
* We allocate runtime services regions bottom-up, starting from -4G, i.e.
early_code_mapping_set_exec(0);
}
-static pgd_t *efi_pgd;
-
-/*
- * We need our own copy of the higher levels of the page tables
- * because we want to avoid inserting EFI region mappings (EFI_VA_END
- * to EFI_VA_START) into the standard kernel page tables. Everything
- * else can be shared, see efi_sync_low_kernel_mappings().
- */
-int __init efi_alloc_page_tables(void)
-{
- pgd_t *pgd;
- pud_t *pud;
- gfp_t gfp_mask;
-
- if (efi_enabled(EFI_OLD_MEMMAP))
- return 0;
-
- gfp_mask = GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO;
- efi_pgd = (pgd_t *)__get_free_page(gfp_mask);
- if (!efi_pgd)
- return -ENOMEM;
-
- pgd = efi_pgd + pgd_index(EFI_VA_END);
-
- pud = pud_alloc_one(NULL, 0);
- if (!pud) {
- free_page((unsigned long)efi_pgd);
- return -ENOMEM;
- }
-
- pgd_populate(NULL, pgd, pud);
-
- return 0;
-}
-
/*
* Add low kernel mappings for passing arguments to EFI functions.
*/
void efi_sync_low_kernel_mappings(void)
{
- unsigned num_entries;
- pgd_t *pgd_k, *pgd_efi;
- pud_t *pud_k, *pud_efi;
+ unsigned num_pgds;
+ pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
if (efi_enabled(EFI_OLD_MEMMAP))
return;
- /*
- * We can share all PGD entries apart from the one entry that
- * covers the EFI runtime mapping space.
- *
- * Make sure the EFI runtime region mappings are guaranteed to
- * only span a single PGD entry and that the entry also maps
- * other important kernel regions.
- */
- BUILD_BUG_ON(pgd_index(EFI_VA_END) != pgd_index(MODULES_END));
- BUILD_BUG_ON((EFI_VA_START & PGDIR_MASK) !=
- (EFI_VA_END & PGDIR_MASK));
-
- pgd_efi = efi_pgd + pgd_index(PAGE_OFFSET);
- pgd_k = pgd_offset_k(PAGE_OFFSET);
-
- num_entries = pgd_index(EFI_VA_END) - pgd_index(PAGE_OFFSET);
- memcpy(pgd_efi, pgd_k, sizeof(pgd_t) * num_entries);
+ num_pgds = pgd_index(MODULES_END - 1) - pgd_index(PAGE_OFFSET);
- /*
- * We share all the PUD entries apart from those that map the
- * EFI regions. Copy around them.
- */
- BUILD_BUG_ON((EFI_VA_START & ~PUD_MASK) != 0);
- BUILD_BUG_ON((EFI_VA_END & ~PUD_MASK) != 0);
-
- pgd_efi = efi_pgd + pgd_index(EFI_VA_END);
- pud_efi = pud_offset(pgd_efi, 0);
-
- pgd_k = pgd_offset_k(EFI_VA_END);
- pud_k = pud_offset(pgd_k, 0);
-
- num_entries = pud_index(EFI_VA_END);
- memcpy(pud_efi, pud_k, sizeof(pud_t) * num_entries);
-
- pud_efi = pud_offset(pgd_efi, EFI_VA_START);
- pud_k = pud_offset(pgd_k, EFI_VA_START);
-
- num_entries = PTRS_PER_PUD - pud_index(EFI_VA_START);
- memcpy(pud_efi, pud_k, sizeof(pud_t) * num_entries);
+ memcpy(pgd + pgd_index(PAGE_OFFSET),
+ init_mm.pgd + pgd_index(PAGE_OFFSET),
+ sizeof(pgd_t) * num_pgds);
}
int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
if (efi_enabled(EFI_OLD_MEMMAP))
return 0;
- efi_scratch.efi_pgt = (pgd_t *)__pa(efi_pgd);
- pgd = efi_pgd;
+ efi_scratch.efi_pgt = (pgd_t *)(unsigned long)real_mode_header->trampoline_pgd;
+ pgd = __va(efi_scratch.efi_pgt);
/*
* It can happen that the physical address of new_memmap lands in memory
void __init efi_cleanup_page_tables(unsigned long pa_memmap, unsigned num_pages)
{
- kernel_unmap_pages_in_pgd(efi_pgd, pa_memmap, num_pages);
+ pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
+
+ kernel_unmap_pages_in_pgd(pgd, pa_memmap, num_pages);
}
static void __init __map_region(efi_memory_desc_t *md, u64 va)
{
+ pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
unsigned long flags = 0;
unsigned long pfn;
- pgd_t *pgd = efi_pgd;
if (!(md->attribute & EFI_MEMORY_WB))
flags |= _PAGE_PCD;
void __init efi_dump_pagetable(void)
{
#ifdef CONFIG_EFI_PGT_DUMP
- ptdump_walk_pgd_level(NULL, efi_pgd);
+ pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
+
+ ptdump_walk_pgd_level(NULL, pgd);
#endif
}
projects / thirdparty / kernel / stable.git / commitdiff
