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0adbdfde8c
update_saved_ttbr0 mandates that mm->pgd is not swapper, since swapper
contains kernel mappings and should never be installed into ttbr0. However,
this means that callers must avoid passing the init_mm to update_saved_ttbr0
which in turn can cause the saved ttbr0 value to be out-of-date in the context
of the idle thread. For example, EFI runtime services may leave the saved ttbr0
pointing at the EFI page table, and kernel threads may end up with stale
references to freed page tables.
This patch changes update_saved_ttbr0 so that the init_mm points the saved
ttbr0 value to the empty zero page, which always exists and never contains
valid translations. EFI and switch can then call into update_saved_ttbr0
unconditionally.
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Cc: <stable@vger.kernel.org>
Fixes: 39bc88e5e3 ("arm64: Disable TTBR0_EL1 during normal kernel execution")
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
146 lines
4.4 KiB
C
146 lines
4.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_EFI_H
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#define _ASM_EFI_H
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#include <asm/boot.h>
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#include <asm/cpufeature.h>
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#include <asm/fpsimd.h>
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#include <asm/io.h>
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#include <asm/memory.h>
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#include <asm/mmu_context.h>
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#include <asm/neon.h>
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#include <asm/ptrace.h>
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#include <asm/tlbflush.h>
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#ifdef CONFIG_EFI
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extern void efi_init(void);
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#else
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#define efi_init()
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#endif
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int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
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int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
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#define arch_efi_call_virt_setup() \
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({ \
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efi_virtmap_load(); \
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__efi_fpsimd_begin(); \
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})
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#define arch_efi_call_virt(p, f, args...) \
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({ \
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efi_##f##_t *__f; \
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__f = p->f; \
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__f(args); \
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})
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#define arch_efi_call_virt_teardown() \
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({ \
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__efi_fpsimd_end(); \
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efi_virtmap_unload(); \
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})
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#define ARCH_EFI_IRQ_FLAGS_MASK (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)
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/* arch specific definitions used by the stub code */
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/*
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* AArch64 requires the DTB to be 8-byte aligned in the first 512MiB from
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* start of kernel and may not cross a 2MiB boundary. We set alignment to
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* 2MiB so we know it won't cross a 2MiB boundary.
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*/
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#define EFI_FDT_ALIGN SZ_2M /* used by allocate_new_fdt_and_exit_boot() */
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/*
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* In some configurations (e.g. VMAP_STACK && 64K pages), stacks built into the
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* kernel need greater alignment than we require the segments to be padded to.
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*/
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#define EFI_KIMG_ALIGN \
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(SEGMENT_ALIGN > THREAD_ALIGN ? SEGMENT_ALIGN : THREAD_ALIGN)
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/* on arm64, the FDT may be located anywhere in system RAM */
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static inline unsigned long efi_get_max_fdt_addr(unsigned long dram_base)
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{
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return ULONG_MAX;
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}
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/*
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* On arm64, we have to ensure that the initrd ends up in the linear region,
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* which is a 1 GB aligned region of size '1UL << (VA_BITS - 1)' that is
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* guaranteed to cover the kernel Image.
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*
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* Since the EFI stub is part of the kernel Image, we can relax the
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* usual requirements in Documentation/arm64/booting.txt, which still
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* apply to other bootloaders, and are required for some kernel
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* configurations.
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*/
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static inline unsigned long efi_get_max_initrd_addr(unsigned long dram_base,
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unsigned long image_addr)
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{
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return (image_addr & ~(SZ_1G - 1UL)) + (1UL << (VA_BITS - 1));
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}
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#define efi_call_early(f, ...) sys_table_arg->boottime->f(__VA_ARGS__)
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#define __efi_call_early(f, ...) f(__VA_ARGS__)
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#define efi_call_runtime(f, ...) sys_table_arg->runtime->f(__VA_ARGS__)
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#define efi_is_64bit() (true)
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#define efi_call_proto(protocol, f, instance, ...) \
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((protocol##_t *)instance)->f(instance, ##__VA_ARGS__)
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#define alloc_screen_info(x...) &screen_info
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#define free_screen_info(x...)
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/* redeclare as 'hidden' so the compiler will generate relative references */
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extern struct screen_info screen_info __attribute__((__visibility__("hidden")));
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static inline void efifb_setup_from_dmi(struct screen_info *si, const char *opt)
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{
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}
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#define EFI_ALLOC_ALIGN SZ_64K
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/*
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* On ARM systems, virtually remapped UEFI runtime services are set up in two
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* distinct stages:
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* - The stub retrieves the final version of the memory map from UEFI, populates
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* the virt_addr fields and calls the SetVirtualAddressMap() [SVAM] runtime
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* service to communicate the new mapping to the firmware (Note that the new
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* mapping is not live at this time)
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* - During an early initcall(), the EFI system table is permanently remapped
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* and the virtual remapping of the UEFI Runtime Services regions is loaded
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* into a private set of page tables. If this all succeeds, the Runtime
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* Services are enabled and the EFI_RUNTIME_SERVICES bit set.
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*/
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static inline void efi_set_pgd(struct mm_struct *mm)
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{
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__switch_mm(mm);
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if (system_uses_ttbr0_pan()) {
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if (mm != current->active_mm) {
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/*
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* Update the current thread's saved ttbr0 since it is
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* restored as part of a return from exception. Set
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* the hardware TTBR0_EL1 using cpu_switch_mm()
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* directly to enable potential errata workarounds.
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*/
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update_saved_ttbr0(current, mm);
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cpu_switch_mm(mm->pgd, mm);
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} else {
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/*
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* Defer the switch to the current thread's TTBR0_EL1
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* until uaccess_enable(). Restore the current
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* thread's saved ttbr0 corresponding to its active_mm
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*/
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cpu_set_reserved_ttbr0();
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update_saved_ttbr0(current, current->active_mm);
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}
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}
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}
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void efi_virtmap_load(void);
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void efi_virtmap_unload(void);
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#endif /* _ASM_EFI_H */
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