d3ffeb40a7
In order to turn longjmp context-switch safe, it's necessary to disable interrupts before modifying windowbase and windowstart. Otherwise, after a context switch, windowstart and windowbase would be different, leading to a wrongly set windowstart bit due to longjmp writing it based on the windowbase before the context switch. This corrupts the registers at the next window overflow reaching that wrongly set bit. *Background:* This PR is related to an issue first observed on ESP-IDF https://github.com/espressif/esp-idf/issues/5229 and it was, then, checked on NuttX using a test application. *The test application:* To check if the problem affects ESP32, ESP32-S2 and ESP32-S3 on NuttX, it was created an application based on: https://en.cppreference.com/w/c/program/longjmp The application creates 16 tasks (`#define NUMBER_OF_TASKS 16`) that implements the following daemon: ``` static int setjmp_longjmp_daemon(int argc, char *argv[]) { for (int i = 0; i < NUMBER_OF_TASKS * 2; i++) { jmp_buf env; volatile int count = 0; if (setjmp(env) != UINT16_MAX) { foo(&env, ++count); } } sem_post(&g_sem); return EXIT_SUCCESS; } ``` The main function also initializes a semaphore to avoid application exiting before tasks return successfully: ``` sem_init(&g_sem, 0, -NUMBER_OF_TASKS); ``` Finally, the round-robin interval was lowered to 1ms to raise the chances of the longjmp being interrupted by a context switch (`CONFIG_RR_INTERVAL=1). This setup was able to reproduce the problem prior to this patch being applied. |
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| libc | ||
| libdsp | ||
| libnx | ||
| libxx | ||
| README.txt | ||
README ====== This directory holds NuttX libraries. Libraries in NuttX are very special creatures. They have these properties: 1. They can be shared by both application logic and logic within the OS when using the FLAT build. 2. But in PROTECTED and KERNEL modes, they must be built differently: The copies used by applications and the OS cannot be the same. Rather, separate versions of libraries must be built for the kernel and for applications. 3. When used by the OS, some special care must be taken to assure that the OS logic does not disrupt the user's errno value and that the OS does not create inappropriate cancellation points. For example, sem_wait() is both a cancellation point and modifies the errno value. So within the FLAT build and without kernel version for the PROTECTED and KERNEL builds, the special internal OS interface nxsem_wait() must be used. Within libraries, the macro _SEM_WAIT() (as defined in include/nuttx/semaphore.h) is used instead. The definition of this macro accounts for the different usage environments. NOTE: The libraries under libs/ build differently from other NuttX components: There are no build-related files in the libs/ directory; it is simply a container for other well-known, individual library directories. The upper level Makefile logic is aware of the libraries within the libs/ container. The only real function of the libs/ directory is to prevent the top-level directory from becoming cluttered with individual libraries.