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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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130c93fd10
init_mm isn't a normal mm: it has swapper_pg_dir as its pgd (which
contains kernel mappings) and is used as the active_mm for the idle
thread.
When restoring the pgd after an EFI call, we write current->active_mm
into TTBR0. If the current task is actually the idle thread (e.g. when
initialising the EFI RTC before entering userspace), then the TLB can
erroneously populate itself with junk global entries as a result of
speculative table walks.
When we do eventually return to userspace, the task can end up hitting
these junk mappings leading to lockups, corruption or crashes.
This patch fixes the problem in the same way as the CPU suspend code by
ensuring that we never switch to the init_mm in efi_set_pgd and instead
point TTBR0 at the zero page. A check is also added to cpu_switch_mm to
BUG if we get passed swapper_pg_dir.
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Fixes: f3cdfd239d ("arm64/efi: move SetVirtualAddressMap() to UEFI stub")
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
60 lines
1.7 KiB
C
60 lines
1.7 KiB
C
/*
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* Based on arch/arm/include/asm/proc-fns.h
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*
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* Copyright (C) 1997-1999 Russell King
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* Copyright (C) 2000 Deep Blue Solutions Ltd
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* Copyright (C) 2012 ARM Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __ASM_PROCFNS_H
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#define __ASM_PROCFNS_H
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#ifdef __KERNEL__
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#ifndef __ASSEMBLY__
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#include <asm/page.h>
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struct mm_struct;
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struct cpu_suspend_ctx;
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extern void cpu_cache_off(void);
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extern void cpu_do_idle(void);
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extern void cpu_do_switch_mm(unsigned long pgd_phys, struct mm_struct *mm);
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extern void cpu_reset(unsigned long addr) __attribute__((noreturn));
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void cpu_soft_restart(phys_addr_t cpu_reset,
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unsigned long addr) __attribute__((noreturn));
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extern void cpu_do_suspend(struct cpu_suspend_ctx *ptr);
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extern u64 cpu_do_resume(phys_addr_t ptr, u64 idmap_ttbr);
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#include <asm/memory.h>
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#define cpu_switch_mm(pgd,mm) \
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do { \
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BUG_ON(pgd == swapper_pg_dir); \
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cpu_do_switch_mm(virt_to_phys(pgd),mm); \
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} while (0)
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#define cpu_get_pgd() \
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({ \
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unsigned long pg; \
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asm("mrs %0, ttbr0_el1\n" \
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: "=r" (pg)); \
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pg &= ~0xffff000000003ffful; \
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(pgd_t *)phys_to_virt(pg); \
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})
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#endif /* __ASSEMBLY__ */
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#endif /* __KERNEL__ */
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#endif /* __ASM_PROCFNS_H */
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