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https://github.com/cirosantilli/linux-kernel-module-cheat.git
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36940cb322
Move benchmark this repo out of conversation, there is plenty of action there! Move kernel module sections and buildroot sections out of conversation. Document the instruction count between baseline Buildroot and our monstrosity. Put ./count-boot-instructions in a separate script. Link to MIPS graphics QEMU question. Link to VFIO QEMU question.
140 lines
4.0 KiB
C
140 lines
4.0 KiB
C
/*
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TODO get working. Currently I don't understand the behaviour.
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TODO how to ACK interrupts? How to ensure that every interrupt gets handled separately?
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TODO write to registers. Currently using /dev/mem and lspci.
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Handle interrupts from userland and print a message to stdout.
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- Userland driver
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- https://stackoverflow.com/questions/15286772/userspace-vs-kernel-space-driver
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- https://01.org/linuxgraphics/gfx-docs/drm/driver-api/uio-howto.html
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- https://stackoverflow.com/questions/7986260/linux-interrupt-handling-in-user-space
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- https://yurovsky.github.io/2014/10/10/linux-uio-gpio-interrupt/
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- https://github.com/bmartini/zynq-axis/blob/65a3a448fda1f0ea4977adfba899eb487201853d/dev/axis.c
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- https://yurovsky.github.io/2014/10/10/linux-uio-gpio-interrupt/
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- http://nairobi-embedded.org/uio_example.html that website has QEMU examples for everything as usual. The example has a kernel-side which creates the memory mappings and is used by the user.
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- https://stackoverflow.com/questions/49309162/interfacing-with-qemu-edu-device-via-userspace-i-o-uio-linux-driver
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Userland driver stability questions:
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- https://stackoverflow.com/questions/8030758/getting-kernel-version-from-linux-kernel-module-at-runtime/45430233#45430233
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- https://stackoverflow.com/questions/37098482/how-to-build-a-linux-kernel-module-so-that-it-is-compatible-with-all-kernel-rele/45429681#45429681
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- https://liquidat.wordpress.com/2007/07/21/linux-kernel-2623-to-have-stable-userspace-driver-api/
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VFIO looks like the newer UIO replacement, but there are no examples out there anywhere:
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- https://stackoverflow.com/questions/49309162/interfacing-with-qemu-edu-device-via-userspace-i-o-uio-linux-driver
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*/
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#if 1
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/* Adapted from: https://yurovsky.github.io/2014/10/10/linux-uio-gpio-interrupt */
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#define _XOPEN_SOURCE 700
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#include <fcntl.h> /* open */
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h> /* write */
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#include <assert.h>
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#include <sys/mman.h>
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int main(int argc, char **argv)
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{
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char *dev = "/dev/uio0";
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if (argc > 1) {
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dev = argv[1];
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exit(EXIT_FAILURE);
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}
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int fd = open(dev, O_RDWR);
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if (fd < 0) {
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perror("open");
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exit(EXIT_FAILURE);
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}
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/* TODO not supported by this kernel module? */
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/*int *addr = mmap(NULL, sysconf(_SC_PAGE_SIZE), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);*/
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/*if (addr == MAP_FAILED) {*/
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/*perror("mmap");*/
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/*assert(0);*/
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/*}*/
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/**addr = 0x12345678;*/
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while (1) {
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uint32_t info = 1;
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size_t nb = write(fd, &info, sizeof(info));
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if (nb < sizeof(info)) {
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perror("write");
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close(fd);
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exit(EXIT_FAILURE);
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}
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nb = read(fd, &info, sizeof(info));
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if (nb == sizeof(info)) {
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printf(__FILE__ " read = %u\n", info);
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}
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}
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}
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#else
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/* Ripped from the kernel docs. */
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#define _XOPEN_SOURCE 700
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <unistd.h>
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int main()
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{
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int uiofd;
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int configfd;
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int err;
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int i;
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unsigned icount;
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unsigned char command_high;
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uiofd = open("/dev/uio0", O_RDONLY);
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if (uiofd < 0) {
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perror("uio open:");
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return errno;
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}
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configfd = open("/sys/class/uio/uio0/device/config", O_RDWR);
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if (configfd < 0) {
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perror("config open:");
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return errno;
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}
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err = pread(configfd, &command_high, 1, 5);
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if (err != 1) {
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perror("command config read:");
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return errno;
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}
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command_high &= ~0x4;
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for(i = 0;; ++i) {
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fprintf(stderr, "Interrupts: %d\n", icount);
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err = pwrite(configfd, &command_high, 1, 5);
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if (err != 1) {
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perror("config write:");
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break;
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}
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err = read(uiofd, &icount, 4);
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if (err != 4) {
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perror("uio read:");
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break;
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}
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}
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return errno;
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}
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#endif
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