Zephyr API Documentation 4.0.0-rc2
A Scalable Open Source RTOS
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exc_handle.h
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1/*
2 * Copyright (c) 2018 Intel Corporation.
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7#ifndef ZEPHYR_INCLUDE_EXC_HANDLE_H_
8#define ZEPHYR_INCLUDE_EXC_HANDLE_H_
9
10/*
11 * This is used by some architectures to define code ranges which may
12 * perform operations that could generate a CPU exception that should not
13 * be fatal. Instead, the exception should return but set the program
14 * counter to a 'fixup' memory address which will gracefully error out.
15 *
16 * For example, in the case where user mode passes in a C string via
17 * system call, the length of that string needs to be measured. A specially
18 * written assembly language version of strlen (arch_user_string_len)
19 * defines start and end symbols where the memory in the string is examined;
20 * if this generates a fault, jumping to the fixup symbol within the same
21 * function will return an error result to the caller.
22 *
23 * To ensure precise control of the state of registers and the stack pointer,
24 * these functions need to be written in assembly.
25 *
26 * The arch-specific fault handling code will define an array of these
27 * z_exc_handle structures and return from the exception with the PC updated
28 * to the fixup address if a match is found.
29 */
30
31struct z_exc_handle {
32 void *start;
33 void *end;
34 void *fixup;
35};
36
37#define Z_EXC_HANDLE(name) \
38 { name ## _fault_start, name ## _fault_end, name ## _fixup }
39
40#define Z_EXC_DECLARE(name) \
41 void name ## _fault_start(void); \
42 void name ## _fault_end(void); \
43 void name ## _fixup(void)
44
45#endif /* ZEPHYR_INCLUDE_EXC_HANDLE_H_ */