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102 lines
2.0 KiB
102 lines
2.0 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Copyright (c) 2021, Microsoft Corporation. |
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* |
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* Authors: |
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* Beau Belgrave <[email protected]> |
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*/ |
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#include <errno.h> |
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#include <sys/ioctl.h> |
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#include <sys/mman.h> |
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#include <fcntl.h> |
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#include <stdio.h> |
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#include <unistd.h> |
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#include <asm/bitsperlong.h> |
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#include <endian.h> |
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#include <linux/user_events.h> |
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#if __BITS_PER_LONG == 64 |
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#define endian_swap(x) htole64(x) |
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#else |
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#define endian_swap(x) htole32(x) |
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#endif |
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/* Assumes debugfs is mounted */ |
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const char *data_file = "/sys/kernel/debug/tracing/user_events_data"; |
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const char *status_file = "/sys/kernel/debug/tracing/user_events_status"; |
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static int event_status(long **status) |
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{ |
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int fd = open(status_file, O_RDONLY); |
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*status = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ, |
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MAP_SHARED, fd, 0); |
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close(fd); |
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if (*status == MAP_FAILED) |
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return -1; |
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return 0; |
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} |
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static int event_reg(int fd, const char *command, long *index, long *mask, |
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int *write) |
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{ |
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struct user_reg reg = {0}; |
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reg.size = sizeof(reg); |
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reg.name_args = (__u64)command; |
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if (ioctl(fd, DIAG_IOCSREG, ®) == -1) |
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return -1; |
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*index = reg.status_bit / __BITS_PER_LONG; |
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*mask = endian_swap(1L << (reg.status_bit % __BITS_PER_LONG)); |
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*write = reg.write_index; |
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return 0; |
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} |
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int main(int argc, char **argv) |
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{ |
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int data_fd, write; |
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long index, mask; |
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long *status_page; |
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struct iovec io[2]; |
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__u32 count = 0; |
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if (event_status(&status_page) == -1) |
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return errno; |
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data_fd = open(data_file, O_RDWR); |
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if (event_reg(data_fd, "test u32 count", &index, &mask, &write) == -1) |
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return errno; |
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/* Setup iovec */ |
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io[0].iov_base = &write; |
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io[0].iov_len = sizeof(write); |
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io[1].iov_base = &count; |
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io[1].iov_len = sizeof(count); |
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ask: |
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printf("Press enter to check status...\n"); |
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getchar(); |
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/* Check if anyone is listening */ |
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if (status_page[index] & mask) { |
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/* Yep, trace out our data */ |
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writev(data_fd, (const struct iovec *)io, 2); |
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/* Increase the count */ |
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count++; |
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printf("Something was attached, wrote data\n"); |
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} |
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goto ask; |
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return 0; |
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}
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