Programming notes

Select Fastest Apt Server on Debian

sudo apt install netselect-apt -y
sudo netselect-apt -a arm64
sudo mv sources.list /etc/apt/sources.list
sudo apt update && sudo apt full-upgrade -y --fix-missing && sudo apt autoremove -y

Setting up rsync script to copy programming folder from server

Install rsync, sshpass, and dialog.

sudo apt install rsync sshpass dialog -y

Copy and run the rsync.sh bash script to copy the programming folder contents from the NAS server.

scp <username>@<nas_ip>:~/rsync.sh . && . ~/rsync.sh

Choose the default selection, Option 1. The script will time out after a few seconds.

Libraries to install for development

Some packages may not be installed, type 'gcc --version', if not recignised, install the following packages:-

sudo apt install build-essential gdb dpkg-dev -y

curl library for c and c++

sudo apt install libcurl4-openssl-dev -y && sudo apt install libcurl4-gnutls-dev -y

To use the librarary, add -lcurl to the end of gcc, as in the following example:-

gcc url_test.c -o url_test -lcurl

Debuging code using GDB

To allow gdb scripts to run within the programming folder, type

mkdir -p ~/.config/gdb/
echo "add-auto-load-safe-path ~/programming/" > ~/.config/gdb/gdbinit

Setting locale on Debian

Check your locale

locale

If it needs changing to GB (WSL2 defaults to US), edit the locale language file

sudo nano /etc/default/locale

and change the locales

LANG=en_GB.UTF-8
LC_ALL=en_GB.UTF-8

Save the file then issue the following commands:-

sudo locale-gen en_GB en_GB.UTF-8
sudo dpkg-reconfigure locales

Allow a sudoer root privaliges without using a password on Debian

This is not neccasary on a Raspberry Pi, as it is already implemented.

sudo nano /etc/sudoers.d/010_user-nopasswd

and add the line

<username> ALL=(ALL) NOPASSWD:ALL

Usefull external links

• HTML Unicode UTF-8 Box Drawings
• Linux System Call Table
• ANSI Escape Sequences cheatsheet · GitHub

Usefull apps for development

sudo apt install -y net-tools

Using JSON in c (cJSON)

Go to this website for latest cJSON repository and instructions.

Copy cJSON.c and cJSON.h from the repository to the code folder, add '#include "cJSON.h"' to your code, and add cJSON.c to the gcc compilation.

Setting console text on putty in Windows

Compiling c code with assembly dump (example)

gcc -g -Wa,-adln -O3 test.c -o test > test.s

Cross-compiling

ARM 32bit

sudo apt install gcc gcc-arm-linux-gnueabihf binutils-arm-linux-gnueabihf make -y

arm-linux-gnueabihf-gcc

compiled with the following options for Raspberry Pi Zero compatibility

-mfloat-abi=hard -mtls-dialect=gnu -marm -mlibarch=armv6+fp -march=armv6+fp

ARM 64bit

sudo apt install gcc-aarch64-linux-gnu binutils-aarch64-linux-gnu make -y

aarch64-linux-gnu-gcc

x86-64

sudo apt install gcc-multilib-x86-64-linux-gnu -y

x86_64-linux-gnu-gcc

Here is a sample script to put in .gdbinit in the same folder as Makefile to automate gdb.

file ./bin/debug/temp_aarch64
set pagination off
define hook-next
  refresh
end
tui new-layout hsrc -horizontal {src 2 asm 2 cmd 1 status 1} 2 regs 1
layout hsrc
break main
focus cmd
run

Using strace

strace is a diagnostic and debugging utility for Linux.

Here are a few examples of commands:-

sudo apt install strace
strace -c ~/programming/c/OpenWeather/bin/arm64/debug/weathermk
strace -e trace=connect -o trace.txt ~/programming/c/OpenWeather/bin/arm64/debug/weathermk
strace -e trace=network curl http://example.com

arch64 assembly: Syscall: basic input/output macros

example 1:

openat #AT_FDCWD, x12, "file.txt", O_RDONLY	// Open file in current working directory, x12 <- fd
read x12, x13, #2048, x14			// Read file, x12=fd, x13=buffer,max 2048b, x14<-bytes read
write #1, x13, x14				// Write to stdout, x13=buffer, x14=size
close x13					// Close file

To generate a list of #define directives for all the macros

touch foo.h; cpp -dM foo.h

        #ifdef __aarch64__
                printf("Hello %d", __aarch64__);
        #endif

.equ STDOUT_FILENO, 1
.equ AT_FDCWD, -100		// syscall openat current directory

// from file: "/usr/aarch64-linux-gnu/include/asm/unistd_64.h"

.equ SYS_io_setup, 0
.equ SYS_io_destroy, 1
.equ SYS_io_submit, 2
.equ SYS_io_cancel, 3
.equ SYS_io_getevents, 4
.equ SYS_setxattr, 5
.equ SYS_lsetxattr, 6
.equ SYS_fsetxattr, 7
.equ SYS_getxattr, 8
.equ SYS_lgetxattr, 9
.equ SYS_fgetxattr, 10
.equ SYS_listxattr, 11
.equ SYS_llistxattr, 12
.equ SYS_flistxattr, 13
.equ SYS_removexattr, 14
.equ SYS_lremovexattr, 15
.equ SYS_fremovexattr, 16
.equ SYS_getcwd, 17
.equ SYS_lookup_dcookie, 18
.equ SYS_eventfd2, 19
.equ SYS_epoll_create1, 20
.equ SYS_epoll_ctl, 21
.equ SYS_epoll_pwait, 22
.equ SYS_dup, 23
.equ SYS_dup3, 24
.equ SYS_fcntl, 25
.equ SYS_inotify_init1, 26
.equ SYS_inotify_add_watch, 27
.equ SYS_inotify_rm_watch, 28
.equ SYS_ioctl, 29
.equ SYS_ioprio_set, 30
.equ SYS_ioprio_get, 31
.equ SYS_flock, 32
.equ SYS_mknodat, 33
.equ SYS_mkdirat, 34
.equ SYS_unlinkat, 35
.equ SYS_symlinkat, 36
.equ SYS_linkat, 37
.equ SYS_renameat, 38
.equ SYS_umount2, 39
.equ SYS_mount, 40
.equ SYS_pivot_root, 41
.equ SYS_nfsservctl, 42
.equ SYS_statfs, 43
.equ SYS_fstatfs, 44
.equ SYS_truncate, 45
.equ SYS_ftruncate, 46
.equ SYS_fallocate, 47
.equ SYS_faccessat, 48
.equ SYS_chdir, 49
.equ SYS_fchdir, 50
.equ SYS_chroot, 51
.equ SYS_fchmod, 52
.equ SYS_fchmodat, 53
.equ SYS_fchownat, 54
.equ SYS_fchown, 55
.equ SYS_openat, 56
.equ SYS_close, 57
.equ SYS_vhangup, 58
.equ SYS_pipe2, 59
.equ SYS_quotactl, 60
.equ SYS_getdents64, 61
.equ SYS_lseek, 62
.equ SYS_read, 63
.equ SYS_write, 64
.equ SYS_readv, 65
.equ SYS_writev, 66
.equ SYS_pread64, 67
.equ SYS_pwrite64, 68
.equ SYS_preadv, 69
.equ SYS_pwritev, 70
.equ SYS_sendfile, 71
.equ SYS_pselect6, 72
.equ SYS_ppoll, 73
.equ SYS_signalfd4, 74
.equ SYS_vmsplice, 75
.equ SYS_splice, 76
.equ SYS_tee, 77
.equ SYS_readlinkat, 78
.equ SYS_newfstatat, 79
.equ SYS_fstat, 80
.equ SYS_sync, 81
.equ SYS_fsync, 82
.equ SYS_fdatasync, 83
.equ SYS_sync_file_range, 84
.equ SYS_timerfd_create, 85
.equ SYS_timerfd_settime, 86
.equ SYS_timerfd_gettime, 87
.equ SYS_utimensat, 88
.equ SYS_acct, 89
.equ SYS_capget, 90
.equ SYS_capset, 91
.equ SYS_personality, 92
.equ SYS_exit, 93
.equ SYS_exit_group, 94
.equ SYS_waitid, 95
.equ SYS_set_tid_address, 96
.equ SYS_unshare, 97
.equ SYS_futex, 98
.equ SYS_set_robust_list, 99
.equ SYS_get_robust_list, 100
.equ SYS_nanosleep, 101
.equ SYS_getitimer, 102
.equ SYS_setitimer, 103
.equ SYS_kexec_load, 104
.equ SYS_init_module, 105
.equ SYS_delete_module, 106
.equ SYS_timer_create, 107
.equ SYS_timer_gettime, 108
.equ SYS_timer_getoverrun, 109
.equ SYS_timer_settime, 110
.equ SYS_timer_delete, 111
.equ SYS_clock_settime, 112
.equ SYS_clock_gettime, 113
.equ SYS_clock_getres, 114
.equ SYS_clock_nanosleep, 115
.equ SYS_syslog, 116
.equ SYS_ptrace, 117
.equ SYS_sched_setparam, 118
.equ SYS_sched_setscheduler, 119
.equ SYS_sched_getscheduler, 120
.equ SYS_sched_getparam, 121
.equ SYS_sched_setaffinity, 122
.equ SYS_sched_getaffinity, 123
.equ SYS_sched_yield, 124
.equ SYS_sched_get_priority_max, 125
.equ SYS_sched_get_priority_min, 126
.equ SYS_sched_rr_get_interval, 127
.equ SYS_restart_syscall, 128
.equ SYS_kill, 129
.equ SYS_tkill, 130
.equ SYS_tgkill, 131
.equ SYS_sigaltstack, 132
.equ SYS_rt_sigsuspend, 133
.equ SYS_rt_sigaction, 134
.equ SYS_rt_sigprocmask, 135
.equ SYS_rt_sigpending, 136
.equ SYS_rt_sigtimedwait, 137
.equ SYS_rt_sigqueueinfo, 138
.equ SYS_rt_sigreturn, 139
.equ SYS_setpriority, 140
.equ SYS_getpriority, 141
.equ SYS_reboot, 142
.equ SYS_setregid, 143
.equ SYS_setgid, 144
.equ SYS_setreuid, 145
.equ SYS_setuid, 146
.equ SYS_setresuid, 147
.equ SYS_getresuid, 148
.equ SYS_setresgid, 149
.equ SYS_getresgid, 150
.equ SYS_setfsuid, 151
.equ SYS_setfsgid, 152
.equ SYS_times, 153
.equ SYS_setpgid, 154
.equ SYS_getpgid, 155
.equ SYS_getsid, 156
.equ SYS_setsid, 157
.equ SYS_getgroups, 158
.equ SYS_setgroups, 159
.equ SYS_uname, 160
.equ SYS_sethostname, 161
.equ SYS_setdomainname, 162
.equ SYS_getrlimit, 163
.equ SYS_setrlimit, 164
.equ SYS_getrusage, 165
.equ SYS_umask, 166
.equ SYS_prctl, 167
.equ SYS_getcpu, 168
.equ SYS_gettimeofday, 169
.equ SYS_settimeofday, 170
.equ SYS_adjtimex, 171
.equ SYS_getpid, 172
.equ SYS_getppid, 173
.equ SYS_getuid, 174
.equ SYS_geteuid, 175
.equ SYS_getgid, 176
.equ SYS_getegid, 177
.equ SYS_gettid, 178
.equ SYS_sysinfo, 179
.equ SYS_mq_open, 180
.equ SYS_mq_unlink, 181
.equ SYS_mq_timedsend, 182
.equ SYS_mq_timedreceive, 183
.equ SYS_mq_notify, 184
.equ SYS_mq_getsetattr, 185
.equ SYS_msgget, 186
.equ SYS_msgctl, 187
.equ SYS_msgrcv, 188
.equ SYS_msgsnd, 189
.equ SYS_semget, 190
.equ SYS_semctl, 191
.equ SYS_semtimedop, 192
.equ SYS_semop, 193
.equ SYS_shmget, 194
.equ SYS_shmctl, 195
.equ SYS_shmat, 196
.equ SYS_shmdt, 197
.equ SYS_socket, 198
.equ SYS_socketpair, 199
.equ SYS_bind, 200
.equ SYS_listen, 201
.equ SYS_accept, 202
.equ SYS_connect, 203
.equ SYS_getsockname, 204
.equ SYS_getpeername, 205
.equ SYS_sendto, 206
.equ SYS_recvfrom, 207
.equ SYS_setsockopt, 208
.equ SYS_getsockopt, 209
.equ SYS_shutdown, 210
.equ SYS_sendmsg, 211
.equ SYS_recvmsg, 212
.equ SYS_readahead, 213
.equ SYS_brk, 214
.equ SYS_munmap, 215
.equ SYS_mremap, 216
.equ SYS_add_key, 217
.equ SYS_request_key, 218
.equ SYS_keyctl, 219
.equ SYS_clone, 220
.equ SYS_execve, 221
.equ SYS_mmap, 222
.equ SYS_fadvise64, 223
.equ SYS_swapon, 224
.equ SYS_swapoff, 225
.equ SYS_mprotect, 226
.equ SYS_msync, 227
.equ SYS_mlock, 228
.equ SYS_munlock, 229
.equ SYS_mlockall, 230
.equ SYS_munlockall, 231
.equ SYS_mincore, 232
.equ SYS_madvise, 233
.equ SYS_remap_file_pages, 234
.equ SYS_mbind, 235
.equ SYS_get_mempolicy, 236
.equ SYS_set_mempolicy, 237
.equ SYS_migrate_pages, 238
.equ SYS_move_pages, 239
.equ SYS_rt_tgsigqueueinfo, 240
.equ SYS_perf_event_open, 241
.equ SYS_accept4, 242
.equ SYS_recvmmsg, 243
.equ SYS_wait4, 260
.equ SYS_prlimit64, 261
.equ SYS_fanotify_init, 262
.equ SYS_fanotify_mark, 263
.equ SYS_name_to_handle_at, 264
.equ SYS_open_by_handle_at, 265
.equ SYS_clock_adjtime, 266
.equ SYS_syncfs, 267
.equ SYS_setns, 268
.equ SYS_sendmmsg, 269
.equ SYS_process_vm_readv, 270
.equ SYS_process_vm_writev, 271
.equ SYS_kcmp, 272
.equ SYS_finit_module, 273
.equ SYS_sched_setattr, 274
.equ SYS_sched_getattr, 275
.equ SYS_renameat2, 276
.equ SYS_seccomp, 277
.equ SYS_getrandom, 278
.equ SYS_memfd_create, 279
.equ SYS_bpf, 280
.equ SYS_execveat, 281
.equ SYS_userfaultfd, 282
.equ SYS_membarrier, 283
.equ SYS_mlock2, 284
.equ SYS_copy_file_range, 285
.equ SYS_preadv2, 286
.equ SYS_pwritev2, 287
.equ SYS_pkey_mprotect, 288
.equ SYS_pkey_alloc, 289
.equ SYS_pkey_free, 290
.equ SYS_statx, 291
.equ SYS_io_pgetevents, 292
.equ SYS_rseq, 293
.equ SYS_kexec_file_load, 294
.equ SYS_pidfd_send_signal, 424
.equ SYS_io_uring_setup, 425
.equ SYS_io_uring_enter, 426
.equ SYS_io_uring_register, 427
.equ SYS_open_tree, 428
.equ SYS_move_mount, 429
.equ SYS_fsopen, 430
.equ SYS_fsconfig, 431
.equ SYS_fsmount, 432
.equ SYS_fspick, 433
.equ SYS_pidfd_open, 434
.equ SYS_clone3, 435
.equ SYS_close_range, 436
.equ SYS_openat2, 437
.equ SYS_pidfd_getfd, 438
.equ SYS_faccessat2, 439
.equ SYS_process_madvise, 440
.equ SYS_epoll_pwait2, 441
.equ SYS_mount_setattr, 442
.equ SYS_quotactl_fd, 443
.equ SYS_landlock_create_ruleset, 444
.equ SYS_landlock_add_rule, 445
.equ SYS_landlock_restrict_self, 446
.equ SYS_memfd_secret, 447
.equ SYS_process_mrelease, 448
.equ SYS_futex_waitv, 449
.equ SYS_set_mempolicy_home_node, 450
.equ SYS_cachestat, 451
.equ SYS_fchmodat2, 452
.equ SYS_map_shadow_stack, 453
.equ SYS_futex_wake, 454
.equ SYS_futex_wait, 455
.equ SYS_futex_requeue, 456
.equ SYS_statmount, 457
.equ SYS_listmount, 458
.equ SYS_lsm_get_self_attr, 459
.equ SYS_lsm_set_self_attr, 460
.equ SYS_lsm_list_modules, 461
.equ SYS_mseal, 462

.equ O_RDONLY,	00
.equ O_WRONLY,	01
.equ O_RDWR,	02
.equ O_CREAT,	00100	 
.equ O_TRUNC,	01000	 
.equ O_APPEND,	02000

.equ S_IRWXU,	00700 // user has read, write, and execute permission
.equ S_IRUSR,	00400 // user has read permission
.equ S_IWUSR,	00200 // user has write permission
.equ S_IXUSR,	00100 // user has execute permission
.equ S_IRWXG,	00070 // group has read, write, and execute permission
.equ S_IRGRP,	00040 // group has read permission
.equ S_IWGRP,	00020 // group has write permission
.equ S_IXGRP,	00010 // group has execute permission
.equ S_IRWXO,	00007 // others have read, write, and execute permission
.equ S_IROTH,	00004 // others have read permission
.equ S_IWOTH,	00002 // others have write permission
.equ S_IXOTH,	00001 // others have execute permission

.macro SYSCALL number
	mov  x8, #\number 
	svc #0  //invokes syscall
.endm

.macro openat dfd, fd, filename, flags, mode=0
	.pushsection .data
	str\@:	.asciz "\filename"
	.popsection
	mov	x0, \dfd
	ldr	x1, =str\@
	mov	x2, #\flags
	mov	x3, #\mode
	SYSCALL SYS_openat
	mov	\fd, x0
.endm

.macro read fd, buffer, maxsize, sizeread
	mov     x0, \fd
	mov     x1, \buffer
	mov     x2, \maxsize
	SYSCALL SYS_read
	mov	\sizeread, x0
.endm

.macro write fd, buffer, size
	mov	x0, \fd
	mov	x1, \buffer
	mov	x2, \size
	SYSCALL SYS_write
.endm

.macro close fd
	mov	x0, \fd
	SYSCALL SYS_close
.endm

.macro exit value
	mov	x0, #\value
	SYSCALL SYS_exit
.endm

.macro print string, fd=#STDOUT_FILENO
	.pushsection .data
	str\@:	.ascii  "\string"
	len\@=	.-str\@
	.popsection
	mov	x0, \fd
	ldr	x1, =str\@
	mov	x2, #len\@
	SYSCALL SYS_write
.endm