mirror of https://gitee.com/openkylin/linux.git
311 lines
9.0 KiB
C
311 lines
9.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Augment the raw_syscalls tracepoints with the contents of the pointer arguments.
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*
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* Test it with:
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*
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* perf trace -e tools/perf/examples/bpf/augmented_raw_syscalls.c cat /etc/passwd > /dev/null
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*
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* This exactly matches what is marshalled into the raw_syscall:sys_enter
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* payload expected by the 'perf trace' beautifiers.
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*
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* For now it just uses the existing tracepoint augmentation code in 'perf
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* trace', in the next csets we'll hook up these with the sys_enter/sys_exit
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* code that will combine entry/exit in a strace like way.
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*/
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#include <unistd.h>
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#include <linux/limits.h>
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#include <pid_filter.h>
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/* bpf-output associated map */
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bpf_map(__augmented_syscalls__, PERF_EVENT_ARRAY, int, u32, __NR_CPUS__);
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struct syscall {
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bool enabled;
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};
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bpf_map(syscalls, ARRAY, int, struct syscall, 512);
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struct syscall_enter_args {
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unsigned long long common_tp_fields;
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long syscall_nr;
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unsigned long args[6];
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};
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struct syscall_exit_args {
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unsigned long long common_tp_fields;
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long syscall_nr;
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long ret;
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};
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struct augmented_filename {
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unsigned int size;
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int reserved;
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char value[PATH_MAX];
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};
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/* syscalls where the first arg is a string */
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#define SYS_OPEN 2
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#define SYS_STAT 4
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#define SYS_LSTAT 6
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#define SYS_ACCESS 21
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#define SYS_EXECVE 59
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#define SYS_TRUNCATE 76
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#define SYS_CHDIR 80
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#define SYS_RENAME 82
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#define SYS_MKDIR 83
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#define SYS_RMDIR 84
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#define SYS_CREAT 85
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#define SYS_LINK 86
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#define SYS_UNLINK 87
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#define SYS_SYMLINK 88
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#define SYS_READLINK 89
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#define SYS_CHMOD 90
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#define SYS_CHOWN 92
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#define SYS_LCHOWN 94
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#define SYS_MKNOD 133
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#define SYS_STATFS 137
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#define SYS_PIVOT_ROOT 155
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#define SYS_CHROOT 161
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#define SYS_ACCT 163
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#define SYS_SWAPON 167
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#define SYS_SWAPOFF 168
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#define SYS_DELETE_MODULE 176
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#define SYS_SETXATTR 188
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#define SYS_LSETXATTR 189
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#define SYS_GETXATTR 191
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#define SYS_LGETXATTR 192
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#define SYS_LISTXATTR 194
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#define SYS_LLISTXATTR 195
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#define SYS_REMOVEXATTR 197
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#define SYS_LREMOVEXATTR 198
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#define SYS_MQ_OPEN 240
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#define SYS_MQ_UNLINK 241
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#define SYS_ADD_KEY 248
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#define SYS_REQUEST_KEY 249
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#define SYS_SYMLINKAT 266
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#define SYS_MEMFD_CREATE 319
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/* syscalls where the first arg is a string */
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#define SYS_PWRITE64 18
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#define SYS_EXECVE 59
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#define SYS_RENAME 82
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#define SYS_QUOTACTL 179
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#define SYS_FSETXATTR 190
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#define SYS_FGETXATTR 193
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#define SYS_FREMOVEXATTR 199
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#define SYS_MQ_TIMEDSEND 242
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#define SYS_REQUEST_KEY 249
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#define SYS_INOTIFY_ADD_WATCH 254
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#define SYS_OPENAT 257
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#define SYS_MKDIRAT 258
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#define SYS_MKNODAT 259
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#define SYS_FCHOWNAT 260
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#define SYS_FUTIMESAT 261
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#define SYS_NEWFSTATAT 262
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#define SYS_UNLINKAT 263
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#define SYS_RENAMEAT 264
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#define SYS_LINKAT 265
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#define SYS_READLINKAT 267
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#define SYS_FCHMODAT 268
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#define SYS_FACCESSAT 269
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#define SYS_UTIMENSAT 280
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#define SYS_NAME_TO_HANDLE_AT 303
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#define SYS_FINIT_MODULE 313
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#define SYS_RENAMEAT2 316
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#define SYS_EXECVEAT 322
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#define SYS_STATX 332
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pid_filter(pids_filtered);
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struct augmented_args_filename {
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struct syscall_enter_args args;
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struct augmented_filename filename;
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};
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bpf_map(augmented_filename_map, PERCPU_ARRAY, int, struct augmented_args_filename, 1);
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SEC("raw_syscalls:sys_enter")
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int sys_enter(struct syscall_enter_args *args)
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{
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struct augmented_args_filename *augmented_args;
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unsigned int len = sizeof(*augmented_args);
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const void *filename_arg = NULL;
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struct syscall *syscall;
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int key = 0;
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augmented_args = bpf_map_lookup_elem(&augmented_filename_map, &key);
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if (augmented_args == NULL)
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return 1;
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if (pid_filter__has(&pids_filtered, getpid()))
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return 0;
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probe_read(&augmented_args->args, sizeof(augmented_args->args), args);
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syscall = bpf_map_lookup_elem(&syscalls, &augmented_args->args.syscall_nr);
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if (syscall == NULL || !syscall->enabled)
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return 0;
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/*
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* Yonghong and Edward Cree sayz:
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*
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* https://www.spinics.net/lists/netdev/msg531645.html
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*
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* >> R0=inv(id=0) R1=inv2 R6=ctx(id=0,off=0,imm=0) R7=inv64 R10=fp0,call_-1
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* >> 10: (bf) r1 = r6
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* >> 11: (07) r1 += 16
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* >> 12: (05) goto pc+2
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* >> 15: (79) r3 = *(u64 *)(r1 +0)
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* >> dereference of modified ctx ptr R1 off=16 disallowed
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* > Aha, we at least got a different error message this time.
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* > And indeed llvm has done that optimisation, rather than the more obvious
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* > 11: r3 = *(u64 *)(r1 +16)
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* > because it wants to have lots of reads share a single insn. You may be able
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* > to defeat that optimisation by adding compiler barriers, idk. Maybe someone
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* > with llvm knowledge can figure out how to stop it (ideally, llvm would know
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* > when it's generating for bpf backend and not do that). -O0? ¯\_(ツ)_/¯
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*
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* The optimization mostly likes below:
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*
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* br1:
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* ...
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* r1 += 16
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* goto merge
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* br2:
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* ...
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* r1 += 20
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* goto merge
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* merge:
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* *(u64 *)(r1 + 0)
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*
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* The compiler tries to merge common loads. There is no easy way to
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* stop this compiler optimization without turning off a lot of other
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* optimizations. The easiest way is to add barriers:
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*
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* __asm__ __volatile__("": : :"memory")
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*
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* after the ctx memory access to prevent their down stream merging.
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*/
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/*
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* This table of what args are strings will be provided by userspace,
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* in the syscalls map, i.e. we will already have to do the lookup to
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* see if this specific syscall is filtered, so we can as well get more
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* info about what syscall args are strings or pointers, and how many
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* bytes to copy, per arg, etc.
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*
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* For now hard code it, till we have all the basic mechanisms in place
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* to automate everything and make the kernel part be completely driven
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* by information obtained in userspace for each kernel version and
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* processor architecture, making the kernel part the same no matter what
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* kernel version or processor architecture it runs on.
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*/
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switch (augmented_args->args.syscall_nr) {
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case SYS_ACCT:
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case SYS_ADD_KEY:
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case SYS_CHDIR:
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case SYS_CHMOD:
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case SYS_CHOWN:
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case SYS_CHROOT:
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case SYS_CREAT:
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case SYS_DELETE_MODULE:
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case SYS_EXECVE:
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case SYS_GETXATTR:
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case SYS_LCHOWN:
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case SYS_LGETXATTR:
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case SYS_LINK:
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case SYS_LISTXATTR:
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case SYS_LLISTXATTR:
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case SYS_LREMOVEXATTR:
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case SYS_LSETXATTR:
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case SYS_LSTAT:
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case SYS_MEMFD_CREATE:
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case SYS_MKDIR:
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case SYS_MKNOD:
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case SYS_MQ_OPEN:
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case SYS_MQ_UNLINK:
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case SYS_PIVOT_ROOT:
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case SYS_READLINK:
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case SYS_REMOVEXATTR:
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case SYS_RENAME:
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case SYS_REQUEST_KEY:
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case SYS_RMDIR:
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case SYS_SETXATTR:
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case SYS_STAT:
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case SYS_STATFS:
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case SYS_SWAPOFF:
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case SYS_SWAPON:
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case SYS_SYMLINK:
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case SYS_SYMLINKAT:
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case SYS_TRUNCATE:
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case SYS_UNLINK:
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case SYS_ACCESS:
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case SYS_OPEN: filename_arg = (const void *)args->args[0];
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__asm__ __volatile__("": : :"memory");
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break;
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case SYS_EXECVEAT:
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case SYS_FACCESSAT:
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case SYS_FCHMODAT:
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case SYS_FCHOWNAT:
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case SYS_FGETXATTR:
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case SYS_FINIT_MODULE:
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case SYS_FREMOVEXATTR:
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case SYS_FSETXATTR:
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case SYS_FUTIMESAT:
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case SYS_INOTIFY_ADD_WATCH:
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case SYS_LINKAT:
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case SYS_MKDIRAT:
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case SYS_MKNODAT:
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case SYS_MQ_TIMEDSEND:
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case SYS_NAME_TO_HANDLE_AT:
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case SYS_NEWFSTATAT:
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case SYS_PWRITE64:
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case SYS_QUOTACTL:
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case SYS_READLINKAT:
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case SYS_RENAMEAT:
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case SYS_RENAMEAT2:
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case SYS_STATX:
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case SYS_UNLINKAT:
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case SYS_UTIMENSAT:
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case SYS_OPENAT: filename_arg = (const void *)args->args[1];
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break;
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}
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if (filename_arg != NULL) {
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augmented_args->filename.reserved = 0;
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augmented_args->filename.size = probe_read_str(&augmented_args->filename.value,
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sizeof(augmented_args->filename.value),
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filename_arg);
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if (augmented_args->filename.size < sizeof(augmented_args->filename.value)) {
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len -= sizeof(augmented_args->filename.value) - augmented_args->filename.size;
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len &= sizeof(augmented_args->filename.value) - 1;
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}
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} else {
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len = sizeof(augmented_args->args);
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}
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/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */
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return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, augmented_args, len);
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}
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SEC("raw_syscalls:sys_exit")
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int sys_exit(struct syscall_exit_args *args)
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{
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struct syscall_exit_args exit_args;
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struct syscall *syscall;
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if (pid_filter__has(&pids_filtered, getpid()))
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return 0;
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probe_read(&exit_args, sizeof(exit_args), args);
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syscall = bpf_map_lookup_elem(&syscalls, &exit_args.syscall_nr);
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if (syscall == NULL || !syscall->enabled)
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return 0;
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return 1;
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}
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license(GPL);
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