131 lines
3.9 KiB
C
131 lines
3.9 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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#ifndef ZEPHYR_INCLUDE_SYSCALL_H_
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#define ZEPHYR_INCLUDE_SYSCALL_H_
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#include <zephyr/syscall_list.h>
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#include <zephyr/arch/syscall.h>
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#include <stdbool.h>
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#ifndef _ASMLANGUAGE
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#include <zephyr/types.h>
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#include <zephyr/linker/sections.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* System Call Declaration macros
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*
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* These macros are used in public header files to declare system calls.
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* They generate inline functions which have different implementations
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* depending on the current compilation context:
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*
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* - Kernel-only code, or CONFIG_USERSPACE disabled, these inlines will
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* directly call the implementation
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* - User-only code, these inlines will marshal parameters and elevate
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* privileges
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* - Mixed or indeterminate code, these inlines will do a runtime check
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* to determine what course of action is needed.
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*
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* All system calls require a verifier function and an implementation
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* function. These must follow a naming convention. For a system call
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* named k_foo():
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*
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* - The handler function will be named z_vrfy_k_foo(). Handler
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* functions have the same type signature as the wrapped call,
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* verify arguments passed up from userspace, and call the
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* implementation function. See documentation for that typedef for
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* more information. - The implementation function will be named
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* z_impl_k_foo(). This is the actual implementation of the system
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* call.
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*/
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/**
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* @typedef _k_syscall_handler_t
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* @brief System call handler function type
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*
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* These are kernel-side skeleton functions for system calls. They are
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* necessary to sanitize the arguments passed into the system call:
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*
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* - Any kernel object or device pointers are validated with _SYSCALL_IS_OBJ()
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* - Any memory buffers passed in are checked to ensure that the calling thread
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* actually has access to them
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* - Many kernel calls do no sanity checking of parameters other than
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* assertions. The handler must check all of these conditions using
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* _SYSCALL_ASSERT()
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* - If the system call has more than 6 arguments, then arg6 will be a pointer
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* to some struct containing arguments 6+. The struct itself needs to be
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* validated like any other buffer passed in from userspace, and its members
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* individually validated (if necessary) and then passed to the real
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* implementation like normal arguments
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*
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* Even if the system call implementation has no return value, these always
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* return something, even 0, to prevent register leakage to userspace.
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*
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* Once everything has been validated, the real implementation will be executed.
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*
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* @param arg1 system call argument 1
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* @param arg2 system call argument 2
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* @param arg3 system call argument 3
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* @param arg4 system call argument 4
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* @param arg5 system call argument 5
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* @param arg6 system call argument 6
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* @param ssf System call stack frame pointer. Used to generate kernel oops
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* via _arch_syscall_oops_at(). Contents are arch-specific.
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* @return system call return value, or 0 if the system call implementation
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* return void
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*
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*/
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typedef uintptr_t (*_k_syscall_handler_t)(uintptr_t arg1, uintptr_t arg2,
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uintptr_t arg3, uintptr_t arg4,
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uintptr_t arg5, uintptr_t arg6,
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void *ssf);
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/* True if a syscall function must trap to the kernel, usually a
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* compile-time decision.
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*/
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static ALWAYS_INLINE bool z_syscall_trap(void)
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{
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bool ret = false;
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#ifdef CONFIG_USERSPACE
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#if defined(__ZEPHYR_SUPERVISOR__)
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ret = false;
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#elif defined(__ZEPHYR_USER__)
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ret = true;
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#else
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ret = arch_is_user_context();
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#endif
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#endif
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return ret;
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}
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/**
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* Indicate whether the CPU is currently in user mode
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*
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* @return true if the CPU is currently running with user permissions
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*/
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__pinned_func
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static inline bool k_is_user_context(void)
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{
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#ifdef CONFIG_USERSPACE
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return arch_is_user_context();
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#else
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return false;
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#endif
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}
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#ifdef __cplusplus
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}
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#endif
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#endif /* _ASMLANGUAGE */
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#endif
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