| Message ID | 1512059986-21325-12-git-send-email-will.deacon@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Will, On Thu, Nov 30, 2017 at 04:39:39PM +0000, Will Deacon wrote: > diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h > index 4052ec39e8db..8119b49be98d 100644 > --- a/arch/arm64/include/asm/fixmap.h > +++ b/arch/arm64/include/asm/fixmap.h > @@ -58,6 +58,10 @@ enum fixed_addresses { > FIX_APEI_GHES_NMI, > #endif /* CONFIG_ACPI_APEI_GHES */ > > +#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, Defining TRAMP_VALIAS here is a little surprising, especially given we reuse the name in asm-offsets: > + DEFINE(TRAMP_VALIAS, TRAMP_VALIAS); Can't we have asm-offsets do: DEFINE(TRAMP_VALIAS, __fix_to_virt(FIX_ENTRY_TRAMP_TEXT)); ... and rely on the asm-offsets TRAMP_VALIAS definition everywhere? [...] > +#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((char *)tramp_pg_dir, 0, PGD_SIZE); The (char *) cast can go; memset() takes a void pointer and we don't do similar casts for other memset instances. > + __create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS, PAGE_SIZE, > + prot, pgd_pgtable_alloc, 0); > + > + /* ...as well as the kernel page table */ This might be clearer as: /* map the text in the kernel page table, too */ Otherwise, this looks good to me. Thanks, Mark.
diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h index 4052ec39e8db..8119b49be98d 100644 --- a/arch/arm64/include/asm/fixmap.h +++ b/arch/arm64/include/asm/fixmap.h @@ -58,6 +58,10 @@ enum fixed_addresses { FIX_APEI_GHES_NMI, #endif /* CONFIG_ACPI_APEI_GHES */ +#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 c9530b5b5ca8..c8f56b2ca414 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -681,6 +681,7 @@ 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 71bf088f1e4b..af247d10252f 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> @@ -148,11 +149,14 @@ 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 267d2b79d52d..c2622525c4d6 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -525,6 +525,29 @@ static int __init parse_rodata(char *arg) } early_param("rodata", parse_rodata); +#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((char *)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. */
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. Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm64/include/asm/fixmap.h | 4 ++++ arch/arm64/include/asm/pgtable.h | 1 + arch/arm64/kernel/asm-offsets.c | 6 +++++- arch/arm64/mm/mmu.c | 23 +++++++++++++++++++++++ 4 files changed, 33 insertions(+), 1 deletion(-)