From: Will Deacon will.deacon@arm.com
The exception entry trampoline needs to be mapped at the same virtual address in both the trampoline page table (which maps nothing else) and also the kernel page table, so that we can swizzle TTBR1_EL1 on exceptions from and return to EL0.
This patch maps the trampoline at a fixed virtual address in the fixmap area of the kernel virtual address space, which allows the kernel proper to be randomized with respect to the trampoline when KASLR is enabled.
Reviewed-by: Mark Rutland mark.rutland@arm.com Tested-by: Laura Abbott labbott@redhat.com Tested-by: Shanker Donthineni shankerd@codeaurora.org Signed-off-by: Will Deacon will.deacon@arm.com (cherry picked from commit 51a0048beb449682d632d0af52a515adb9f9882e) Signed-off-by: Alex Shi alex.shi@linaro.org --- arch/arm64/include/asm/fixmap.h | 5 +++++ arch/arm64/include/asm/pgtable.h | 1 + arch/arm64/kernel/asm-offsets.c | 6 +++++- arch/arm64/mm/mmu.c | 24 ++++++++++++++++++++++++ 4 files changed, 35 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h index caf86be..7b1d88c 100644 --- a/arch/arm64/include/asm/fixmap.h +++ b/arch/arm64/include/asm/fixmap.h @@ -51,6 +51,11 @@ enum fixed_addresses {
FIX_EARLYCON_MEM_BASE, FIX_TEXT_POKE0, + +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 + FIX_ENTRY_TRAMP_TEXT, +#define TRAMP_VALIAS (__fix_to_virt(FIX_ENTRY_TRAMP_TEXT)) +#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ __end_of_permanent_fixed_addresses,
/* diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 7acd3c5..3a30a39 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -692,6 +692,7 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
extern pgd_t swapper_pg_dir[PTRS_PER_PGD]; extern pgd_t idmap_pg_dir[PTRS_PER_PGD]; +extern pgd_t tramp_pg_dir[PTRS_PER_PGD];
/* * Encode and decode a swap entry: diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index c58ddf8..5f4bf3c 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -24,6 +24,7 @@ #include <linux/kvm_host.h> #include <linux/suspend.h> #include <asm/cpufeature.h> +#include <asm/fixmap.h> #include <asm/thread_info.h> #include <asm/memory.h> #include <asm/smp_plat.h> @@ -144,11 +145,14 @@ int main(void) DEFINE(ARM_SMCCC_RES_X2_OFFS, offsetof(struct arm_smccc_res, a2)); DEFINE(ARM_SMCCC_QUIRK_ID_OFFS, offsetof(struct arm_smccc_quirk, id)); DEFINE(ARM_SMCCC_QUIRK_STATE_OFFS, offsetof(struct arm_smccc_quirk, state)); - BLANK(); DEFINE(HIBERN_PBE_ORIG, offsetof(struct pbe, orig_address)); DEFINE(HIBERN_PBE_ADDR, offsetof(struct pbe, address)); DEFINE(HIBERN_PBE_NEXT, offsetof(struct pbe, next)); DEFINE(ARM64_FTR_SYSVAL, offsetof(struct arm64_ftr_reg, sys_val)); + BLANK(); +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 + DEFINE(TRAMP_VALIAS, TRAMP_VALIAS); +#endif return 0; } diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 05615a3..f6211c7 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -419,6 +419,30 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end, vm_area_add_early(vma); }
+ +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 +static int __init map_entry_trampoline(void) +{ + extern char __entry_tramp_text_start[]; + + pgprot_t prot = rodata_enabled ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC; + phys_addr_t pa_start = __pa_symbol(__entry_tramp_text_start); + + /* The trampoline is always mapped and can therefore be global */ + pgprot_val(prot) &= ~PTE_NG; + + /* Map only the text into the trampoline page table */ + memset(tramp_pg_dir, 0, PGD_SIZE); + __create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS, PAGE_SIZE, + prot, pgd_pgtable_alloc, 0); + + /* ...as well as the kernel page table */ + __set_fixmap(FIX_ENTRY_TRAMP_TEXT, pa_start, prot); + return 0; +} +core_initcall(map_entry_trampoline); +#endif + /* * Create fine-grained mappings for the kernel. */