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riscv: Sync efi page table's kernel mappings before switching 

The EFI page table is initially created as a copy of the kernel page table.
With VMAP_STACK enabled, kernel stacks are allocated in the vmalloc area:
if the stack is allocated in a new PGD (one that was not present at the
moment of the efi page table creation or not synced in a previous vmalloc
fault), the kernel will take a trap when switching to the efi page table
when the vmalloc kernel stack is accessed, resulting in a kernel panic.

Fix that by updating the efi kernel mappings before switching to the efi
page table.

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Fixes: b91540d52a ("RISC-V: Add EFI runtime services")
Tested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20221121133303.1782246-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Alexandre Ghiti 2022-11-21 14:33:03 +01:00 committed by Palmer Dabbelt
parent 1d6b5ed41f
commit 3f105a7427
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
2 changed files with 13 additions and 4 deletions
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6
arch/riscv/include/asm/efi.h
View File

@ -10,6 +10,7 @@
#include <asm/mmu_context.h>
#include <asm/ptrace.h>
#include <asm/tlbflush.h>
#include <asm/pgalloc.h>
#ifdef CONFIG_EFI
extern void efi_init(void);
@ -20,7 +21,10 @@ extern void efi_init(void);
int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
#define arch_efi_call_virt_setup() efi_virtmap_load()
#define arch_efi_call_virt_setup() ({ \
sync_kernel_mappings(efi_mm.pgd); \
efi_virtmap_load(); \
})
#define arch_efi_call_virt_teardown() efi_virtmap_unload()
#define ARCH_EFI_IRQ_FLAGS_MASK (SR_IE | SR_SPIE)

11
arch/riscv/include/asm/pgalloc.h
View File

@ -127,6 +127,13 @@ static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d)
#define __p4d_free_tlb(tlb, p4d, addr) p4d_free((tlb)->mm, p4d)
#endif /* __PAGETABLE_PMD_FOLDED */
static inline void sync_kernel_mappings(pgd_t *pgd)
{
memcpy(pgd + USER_PTRS_PER_PGD,
init_mm.pgd + USER_PTRS_PER_PGD,
(PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
}
static inline pgd_t *pgd_alloc(struct mm_struct *mm)
{
pgd_t *pgd;
@ -135,9 +142,7 @@ static inline pgd_t *pgd_alloc(struct mm_struct *mm)
if (likely(pgd != NULL)) {
memset(pgd, 0, USER_PTRS_PER_PGD * sizeof(pgd_t));
/* Copy kernel mappings */
memcpy(pgd + USER_PTRS_PER_PGD,
init_mm.pgd + USER_PTRS_PER_PGD,
(PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
sync_kernel_mappings(pgd);
}
return pgd;
}