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2e17430858
When pointer masking is enabled for userspace, the kernel can accept tagged pointers as arguments to some system calls. Allow this by untagging the pointers in access_ok() and the uaccess routines. The uaccess routines must peform untagging in software because U-mode and S-mode have entirely separate pointer masking configurations. In fact, hardware may not even implement pointer masking for S-mode. Since the number of tag bits is variable, untagged_addr_remote() needs to know what PMLEN to use for the remote mm. Therefore, the pointer masking mode must be the same for all threads sharing an mm. Enforce this with a lock flag in the mm context, as x86 does for LAM. The flag gets reset in init_new_context() during fork(), as the new mm is no longer multithreaded. Reviewed-by: Charlie Jenkins <charlie@rivosinc.com> Tested-by: Charlie Jenkins <charlie@rivosinc.com> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Link: https://lore.kernel.org/r/20241016202814.4061541-6-samuel.holland@sifive.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
53 lines
1.2 KiB
C
53 lines
1.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2012 Regents of the University of California
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* Copyright (C) 2017 SiFive
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*/
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#ifndef _ASM_RISCV_MMU_CONTEXT_H
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#define _ASM_RISCV_MMU_CONTEXT_H
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#include <linux/mm_types.h>
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#include <asm-generic/mm_hooks.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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void switch_mm(struct mm_struct *prev, struct mm_struct *next,
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struct task_struct *task);
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#define activate_mm activate_mm
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static inline void activate_mm(struct mm_struct *prev,
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struct mm_struct *next)
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{
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#ifdef CONFIG_RISCV_ISA_SUPM
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next->context.pmlen = 0;
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#endif
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switch_mm(prev, next, NULL);
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}
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#define init_new_context init_new_context
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static inline int init_new_context(struct task_struct *tsk,
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struct mm_struct *mm)
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{
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#ifdef CONFIG_MMU
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atomic_long_set(&mm->context.id, 0);
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#endif
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if (IS_ENABLED(CONFIG_RISCV_ISA_SUPM))
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clear_bit(MM_CONTEXT_LOCK_PMLEN, &mm->context.flags);
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return 0;
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}
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DECLARE_STATIC_KEY_FALSE(use_asid_allocator);
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#ifdef CONFIG_RISCV_ISA_SUPM
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#define mm_untag_mask mm_untag_mask
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static inline unsigned long mm_untag_mask(struct mm_struct *mm)
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{
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return -1UL >> mm->context.pmlen;
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}
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#endif
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#include <asm-generic/mmu_context.h>
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#endif /* _ASM_RISCV_MMU_CONTEXT_H */
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