Unverified Commit 3f105a74 authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Palmer Dabbelt
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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: default avatarAlexandre Ghiti <alexghiti@rivosinc.com>
Fixes: b91540d5 ("RISC-V: Add EFI runtime services")
Tested-by: default avatarEmil Renner Berthing <emil.renner.berthing@canonical.com>
Reviewed-by: default avatarAtish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20221121133303.1782246-1-alexghiti@rivosinc.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 1d6b5ed4

arch/riscv/include/asm/efi.h

+5 −1
Original line number Diff line number Diff line
@@ -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)

arch/riscv/include/asm/pgalloc.h

+8 −3
Original line number Diff line number Diff line
@@ -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;

}