1 files changed, 19 insertions, 13 deletions

diff --git a/etc/templates/syscalls.txt b/etc/templates/syscalls.txt
index 0775f60ff..827b075e5 100644
--- a/etc/templates/syscalls.txt
+++ b/etc/templates/syscalls.txt
@@ -33,7 +33,7 @@ Definition of groups
 @clock=adjtimex,clock_adjtime,clock_settime,settimeofday,stime
 @cpu-emulation=modify_ldt,subpage_prot,switch_endian,vm86,vm86old
 @debug=lookup_dcookie,perf_event_open,process_vm_writev,rtas,s390_runtime_instr,sys_debug_setcontext
-@default=@clock,@cpu-emulation,@debug,@module,@mount,@obsolete,@raw-io,@reboot,@swap,open_by_handle_at,name_to_handle_at,ioprio_set,ni_syscall,syslog,fanotify_init,kcmp,add_key,request_key,mbind,migrate_pages,move_pages,keyctl,io_setup,io_destroy,io_getevents,io_submit,io_cancel,remap_file_pages,set_mempolicyvmsplice,userfaultfd,acct,bpf,nfsservctl,setdomainname,sethostname,vhangup
+@default=@clock,@cpu-emulation,@debug,@module,@mount,@obsolete,@raw-io,@reboot,@swap,open_by_handle_at,name_to_handle_at,ioprio_set,ni_syscall,syslog,fanotify_init,add_key,request_key,mbind,migrate_pages,move_pages,keyctl,io_setup,io_destroy,io_getevents,io_submit,io_cancel,remap_file_pages,set_mempolicyvmsplice,userfaultfd,acct,bpf,nfsservctl,setdomainname,sethostname,vhangup
 @default-nodebuggers=@default,ptrace,personality,process_vm_readv
 @default-keep=execveat,execve,prctl
 @file-system=access,chdir,chmod,close,creat,faccessat,faccessat2,fallocate,fchdir,fchmod,fchmodat,fcntl,fcntl64,fgetxattr,flistxattr,fremovexattr,fsetxattr,fstat,fstat64,fstatat64,fstatfs,fstatfs64,ftruncate,ftruncate64,futimesat,getcwd,getdents,getdents64,getxattr,inotify_add_watch,inotify_init,inotify_init1,inotify_rm_watch,lgetxattr,link,linkat,listxattr,llistxattr,lremovexattr,lsetxattr,lstat,lstat64,mkdir,mkdirat,mknod,mknodat,mmap,mmap2,munmap,newfstatat,oldfstat,oldlstat,oldstat,open,openat,readlink,readlinkat,removexattr,rename,renameat,renameat2,rmdir,setxattr,stat,stat64,statfs,statfs64,statx,symlink,symlinkat,truncate,truncate64,unlink,unlinkat,utime,utimensat,utimes
@@ -89,18 +89,24 @@ Inheritance of groups
 What to do if seccomp breaks a program
 --------------------------------------
 
+Start `journalctl --grep=SECCOMP --follow` in a terminal and run
+`firejail --seccomp-error-action=log /path/to/program` in a second terminal.
+Now switch back to the first terminal (where `journalctl` is running) and look
+for the numbers of the blocked syscall(s) (`syscall=<NUMBER>`). As soon as you
+have found them, you can stop `journalctl` (^C) and execute
+`firejail --debug-syscalls | grep NUMBER` to get the name of the syscall.
+In the particular case that it is a 32bit syscall on a 64bit system, use `firejail --debug-syscalls32 | grep NUMBER`.
+Now you can add a seccomp exception using `seccomp !NAME`.
+
+If the blocked syscall is ptrace, consider to add allow-debuggers to the profile.
+
 ```
-$ journalctl --grep=syscall --follow
-<...> audit[…]: SECCOMP <...> syscall=161 <...>
-$ firejail --debug-syscalls | grep 161
-161 - chroot
+term1$ journalctl --grep=SECCOMP --follow
+term2$ firejail --seccomp-error-action=log /usr/bin/signal-desktop
+term1$ (journalctl --grep=SECCOMP --follow)
+audit[1234]: SECCOMP ... comm="signal-desktop" exe="/usr/bin/signal-desktop" sig=31 arch=c000003e syscall=161 ...
+^C
+term1$ firejail --debug-syscalls | grep "^161[[:space:]]"
+161     - chroot
 ```
 Profile: `seccomp -> seccomp !chroot`
-
-Start `journalctl --grep=syscall --follow` in a terminal, then start the broken
-program. Now you see one or more long lines containing `syscall=NUMBER` somewhere.
-Stop journalctl (^C) and execute `firejail --debug-syscalls | grep NUMBER`. You
-will see something like `NUMBER  - NAME`, because you now know the name of the
-syscall, you can add an exception to seccomp by putting `!NAME` to seccomp.
-
-If the blocked syscall is ptrace, consider to add allow-debuggers to the profile.