149 lines
4.4 KiB
C
149 lines
4.4 KiB
C
/*
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* Copyright (c) 2017 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/kernel.h>
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#include <zephyr/sys/speculation.h>
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#include <zephyr/syscall_handler.h>
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#include <kernel_arch_func.h>
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#include <ksched.h>
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#include <x86_mmu.h>
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#ifndef CONFIG_X86_KPTI
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/* Update the to the incoming thread's page table, and update the location of
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* the privilege elevation stack.
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*
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* May be called ONLY during context switch. Hot code path!
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*
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* Nothing to do here if KPTI is enabled. We are in supervisor mode, so the
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* active page tables are the kernel's page tables. If the incoming thread is
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* in user mode we are going to switch CR3 to the domain-specific tables when
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* we go through z_x86_trampoline_to_user.
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*
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* We don't need to update the privilege mode initial stack pointer either,
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* privilege elevation always lands on the trampoline stack and the irq/syscall
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* code has to manually transition off of it to the appropriate stack after
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* switching page tables.
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*/
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__pinned_func
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void z_x86_swap_update_page_tables(struct k_thread *incoming)
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{
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#ifndef CONFIG_X86_64
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/* Set initial stack pointer when elevating privileges from Ring 3
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* to Ring 0.
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*/
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_main_tss.esp0 = (uintptr_t)incoming->arch.psp;
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#endif
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#ifdef CONFIG_X86_COMMON_PAGE_TABLE
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z_x86_swap_update_common_page_table(incoming);
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#else
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/* Check first that we actually need to do this, since setting
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* CR3 involves an expensive full TLB flush.
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*/
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uintptr_t ptables_phys = incoming->arch.ptables;
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__ASSERT(ptables_phys != 0, "NULL page tables for thread %p\n",
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incoming);
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if (ptables_phys != z_x86_cr3_get()) {
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z_x86_cr3_set(ptables_phys);
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}
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#endif /* CONFIG_X86_COMMON_PAGE_TABLE */
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}
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#endif /* CONFIG_X86_KPTI */
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/* Preparation steps needed for all threads if user mode is turned on.
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*
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* Returns the initial entry point to swap into.
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*/
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void *z_x86_userspace_prepare_thread(struct k_thread *thread)
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{
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void *initial_entry;
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struct z_x86_thread_stack_header *header =
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(struct z_x86_thread_stack_header *)thread->stack_obj;
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thread->arch.psp =
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header->privilege_stack + sizeof(header->privilege_stack);
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#ifndef CONFIG_X86_COMMON_PAGE_TABLE
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/* Important this gets cleared, so that arch_mem_domain_* APIs
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* can distinguish between new threads, and threads migrating
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* between domains
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*/
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thread->arch.ptables = (uintptr_t)NULL;
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#endif /* CONFIG_X86_COMMON_PAGE_TABLE */
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if ((thread->base.user_options & K_USER) != 0U) {
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initial_entry = arch_user_mode_enter;
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} else {
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initial_entry = z_thread_entry;
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}
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return initial_entry;
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}
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FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
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void *p1, void *p2, void *p3)
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{
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size_t stack_end;
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/* Transition will reset stack pointer to initial, discarding
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* any old context since this is a one-way operation
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*/
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stack_end = Z_STACK_PTR_ALIGN(_current->stack_info.start +
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_current->stack_info.size -
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_current->stack_info.delta);
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#ifdef CONFIG_X86_64
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/* x86_64 SysV ABI requires 16 byte stack alignment, which
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* means that on entry to a C function (which follows a CALL
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* that pushes 8 bytes) the stack must be MISALIGNED by
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* exactly 8 bytes.
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*/
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stack_end -= 8;
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#endif
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#if defined(CONFIG_DEMAND_PAGING) && \
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!defined(CONFIG_LINKER_GENERIC_SECTIONS_PRESENT_AT_BOOT)
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/* If generic section is not present at boot,
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* the thread stack may not be in physical memory.
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* Unconditionally page in the stack instead of
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* relying on page fault to speed up a little bit
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* on starting the thread.
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*
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* Note that this also needs to page in the reserved
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* portion of the stack (which is usually the page just
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* before the beginning of stack in
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* _current->stack_info.start.
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*/
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uintptr_t stack_start;
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size_t stack_size;
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uintptr_t stack_aligned_start;
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size_t stack_aligned_size;
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stack_start = POINTER_TO_UINT(_current->stack_obj);
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stack_size = Z_THREAD_STACK_SIZE_ADJUST(_current->stack_info.size);
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#if defined(CONFIG_HW_STACK_PROTECTION)
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/* With hardware stack protection, the first page of stack
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* is a guard page. So need to skip it.
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*/
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stack_start += CONFIG_MMU_PAGE_SIZE;
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stack_size -= CONFIG_MMU_PAGE_SIZE;
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#endif
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(void)k_mem_region_align(&stack_aligned_start, &stack_aligned_size,
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stack_start, stack_size,
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CONFIG_MMU_PAGE_SIZE);
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k_mem_page_in(UINT_TO_POINTER(stack_aligned_start),
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stack_aligned_size);
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#endif
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z_x86_userspace_enter(user_entry, p1, p2, p3, stack_end,
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_current->stack_info.start);
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CODE_UNREACHABLE;
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}
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