我使用stdout系统调用以汇编语言写sys_write，如果在写入期间发生错误然后正常退出，我想打印错误消息。
我只能使用errno和perror退出但无法打印错误消息。如果syscall失败，如何处理错误的任何建议。我想根据发生的错误类型打印错误消息。
我在 Ubuntu 14.04 ，我正在使用 nasm 来编译我的汇编代码。
目前我只做这个：
test rax,rax ; Lets make sure the file descriptor is valid
js skipWrite ;
答案 0 :(得分：7)
perror和errno仅在您与libc（-lc）关联时才可用。
A＆＃34;裸体＆＃34; syscall（没有库支持）通常会在失败的情况下返回＆＃34;标准错误代码的否定＆＃34; （man syscall(2)）即可。使用简单的NEG，您将获得错误的正数。
可以在Linux源文件include/asm-generic/errno-base.h和include/asm-generic/errno.h中找到错误编号。
可能的错误在手册页中描述，例如： man open(2)。可以找出特定系统调用的名称（带有一点想象力）here。 strace关于已知工作的程序可能会有所帮助。
我写了一个示例，展示如何使用错误消息构建一个＆＃34; Pascal＆＃34; -strings列表以及如何遍历该列表：
DEFAULT rel
GLOBAL _start
SECTION .data
non_existing_file db "bielefeld.txt",0
SECTION .text
_start:
push rbp
mov rbp, rsp
and rsp, -16 ; Align 16
mov rdi, non_existing_file ; Pointer to null-terminated filename
xor rsi, rsi ; RD_ONLY
mov rax, 2 ; sys_open
syscall ; Call Linux
; if no errorcode (EAX > -1 || EAX < -133) exit (and close)
cmp eax, -1
jg .done
cmp eax, -133
jl .done
neg rax ; Get positive error number: RAX = Abs (RAX)
mov rdi, rax ; Argument for my_perror
call my_perror ; Output error message
.done:
leave
xor edi, edi ; Return 0
mov eax, 60 ; sys_exit
syscall
;==================== my_perror ====================
SECTION .text
my_perror: ; ARG: RDI=errno
push rbp
mov rbp, rsp
sub rsp, 16 ; Aligning 16 though only one byte is needed
; No processing if wrong number
test edi, edi
jz .done
cmp edi, 133
ja .done
; Walk through the err_txt-list
xor edx,edx
mov rsi, err_txt
.L1:
lea rsi, [rsi+rdx]
mov dl, [rsi] ; Length of string
add rsi, 1 ; Pointer to string
sub edi, 1
jnz .L1
mov edi, 1 ; stdout
mov eax, 1 ; sys_write
syscall ; call Linux
mov byte [rsp], 0x0A ; Linefeed
mov rsi, rsp
mov edx, 1
mov edi, 1 ; stdout
mov eax, 1 ; sys_write
syscall ; call Linux
.done:
leave
ret
SECTION .data
%MACRO DATA_ERR 1
%strlen len %1
db len, %1
%ENDMACRO
err_txt:
; /usr/src/linux-source-3.2/include/asm-generic/errno-base.h
DATA_ERR "Operation not permitted" ; EPERM 1
DATA_ERR "No such file or directory" ; ENOENT 2
DATA_ERR "No such process" ; ESRCH 3
DATA_ERR "Interrupted system call" ; EINTR 4
DATA_ERR "I/O error" ; EIO 5
DATA_ERR "No such device or address" ; ENXIO 6
DATA_ERR "Argument list too long" ; E2BIG 7
DATA_ERR "Exec format error" ; ENOEXEC 8
DATA_ERR "Bad file number" ; EBADF 9
DATA_ERR "No child processes" ; ECHILD 10
DATA_ERR "Try again" ; EAGAIN 11
DATA_ERR "Out of memory" ; ENOMEM 12
DATA_ERR "Permission denied" ; EACCES 13
DATA_ERR "Bad address" ; EFAULT 14
DATA_ERR "Block device required" ; ENOTBLK 15
DATA_ERR "Device or resource busy" ; EBUSY 16
DATA_ERR "File exists" ; EEXIST 17
DATA_ERR "Cross-device link" ; EXDEV 18
DATA_ERR "No such device" ; ENODEV 19
DATA_ERR "Not a directory" ; ENOTDIR 20
DATA_ERR "Is a directory" ; EISDIR 21
DATA_ERR "Invalid argument" ; EINVAL 22
DATA_ERR "File table overflow" ; ENFILE 23
DATA_ERR "Too many open files" ; EMFILE 24
DATA_ERR "Not a typewriter" ; ENOTTY 25
DATA_ERR "Text file busy" ; ETXTBSY 26
DATA_ERR "File too large" ; EFBIG 27
DATA_ERR "No space left on device" ; ENOSPC 28
DATA_ERR "Illegal seek" ; ESPIPE 29
DATA_ERR "Read-only file system" ; EROFS 30
DATA_ERR "Too many links" ; EMLINK 31
DATA_ERR "Broken pipe" ; EPIPE 32
DATA_ERR "Math argument out of domain of func" ; EDOM 33
DATA_ERR "Math result not representable" ; ERANGE 34
DATA_ERR "Resource deadlock would occur" ; EDEADLK 35
; /usr/src/linux-source-3.2/include/asm-generic/errno.h
DATA_ERR "File name too long" ; ENAMETOOLONG 36
DATA_ERR "No record locks available" ; ENOLCK 37
DATA_ERR "Function not implemented" ; ENOSYS 38
DATA_ERR "Directory not empty" ; ENOTEMPTY 39
DATA_ERR "Too many symbolic links encountered" ; ELOOP 40
DATA_ERR "Operation would block" ; EWOULDBLOCK EAGAIN
DATA_ERR "No message of desired type" ; ENOMSG 42
DATA_ERR "Identifier removed" ; EIDRM 43
DATA_ERR "Channel number out of range" ; ECHRNG 44
DATA_ERR "Level 2 not synchronized" ; EL2NSYNC 45
DATA_ERR "Level 3 halted" ; EL3HLT 46
DATA_ERR "Level 3 reset" ; EL3RST 47
DATA_ERR "Link number out of range" ; ELNRNG 48
DATA_ERR "Protocol driver not attached" ; EUNATCH 49
DATA_ERR "No CSI structure available" ; ENOCSI 50
DATA_ERR "Level 2 halted" ; EL2HLT 51
DATA_ERR "Invalid exchange" ; EBADE 52
DATA_ERR "Invalid request descriptor" ; EBADR 53
DATA_ERR "Exchange full" ; EXFULL 54
DATA_ERR "No anode" ; ENOANO 55
DATA_ERR "Invalid request code" ; EBADRQC 56
DATA_ERR "Invalid slot" ; EBADSLT 57
DATA_ERR "Resource deadlock would occur" ; EDEADLOCK EDEADLK
DATA_ERR "Bad font file format" ; EBFONT 59
DATA_ERR "Device not a stream" ; ENOSTR 60
DATA_ERR "No data available" ; ENODATA 61
DATA_ERR "Timer expired" ; ETIME 62
DATA_ERR "Out of streams resources" ; ENOSR 63
DATA_ERR "Machine is not on the network" ; ENONET 64
DATA_ERR "Package not installed" ; ENOPKG 65
DATA_ERR "Object is remote" ; EREMOTE 66
DATA_ERR "Link has been severed" ; ENOLINK 67
DATA_ERR "Advertise error" ; EADV 68
DATA_ERR "Srmount error" ; ESRMNT 69
DATA_ERR "Communication error on send" ; ECOMM 70
DATA_ERR "Protocol error" ; EPROTO 71
DATA_ERR "Multihop attempted" ; EMULTIHOP 72
DATA_ERR "RFS specific error" ; EDOTDOT 73
DATA_ERR "Not a data message" ; EBADMSG 74
DATA_ERR "Value too large for defined data type" ; EOVERFLOW 75
DATA_ERR "Name not unique on network" ; ENOTUNIQ 76
DATA_ERR "File descriptor in bad state" ; EBADFD 77
DATA_ERR "Remote address changed" ; EREMCHG 78
DATA_ERR "Can not access a needed shared library" ; ELIBACC 79
DATA_ERR "Accessing a corrupted shared library" ; ELIBBAD 80
DATA_ERR ".lib section in a.out corrupted" ; ELIBSCN 81
DATA_ERR "Attempting to link in too many shared libraries" ; ELIBMAX 82
DATA_ERR "Cannot exec a shared library directly" ; ELIBEXEC 83
DATA_ERR "Illegal byte sequence" ; EILSEQ 84
DATA_ERR "Interrupted system call should be restarted" ; ERESTART 85
DATA_ERR "Streams pipe error" ; ESTRPIPE 86
DATA_ERR "Too many users" ; EUSERS 87
DATA_ERR "Socket operation on non-socket" ; ENOTSOCK 88
DATA_ERR "Destination address required" ; EDESTADDRREQ 89
DATA_ERR "Message too long" ; EMSGSIZE 90
DATA_ERR "Protocol wrong type for socket" ; EPROTOTYPE 91
DATA_ERR "Protocol not available" ; ENOPROTOOPT 92
DATA_ERR "Protocol not supported" ; EPROTONOSUPPORT 93
DATA_ERR "Socket type not supported" ; ESOCKTNOSUPPORT 94
DATA_ERR "Operation not supported on transport endpoint" ; EOPNOTSUPP 95
DATA_ERR "Protocol family not supported" ; EPFNOSUPPORT 96
DATA_ERR "Address family not supported by protocol" ; EAFNOSUPPORT 97
DATA_ERR "Address already in use" ; EADDRINUSE 98
DATA_ERR "Cannot assign requested address" ; EADDRNOTAVAIL 99
DATA_ERR "Network is down" ; ENETDOWN 100
DATA_ERR "Network is unreachable" ; ENETUNREACH 101
DATA_ERR "Network dropped connection because of reset" ; ENETRESET 102
DATA_ERR "Software caused connection abort" ; ECONNABORTED 103
DATA_ERR "Connection reset by peer" ; ECONNRESET 104
DATA_ERR "No buffer space available" ; ENOBUFS 105
DATA_ERR "Transport endpoint is already connected" ; EISCONN 106
DATA_ERR "Transport endpoint is not connected" ; ENOTCONN 107
DATA_ERR "Cannot send after transport endpoint shutdown" ; ESHUTDOWN 108
DATA_ERR "Too many references: cannot splice" ; ETOOMANYREFS 109
DATA_ERR "Connection timed out" ; ETIMEDOUT 110
DATA_ERR "Connection refused" ; ECONNREFUSED 111
DATA_ERR "Host is down" ; EHOSTDOWN 112
DATA_ERR "No route to host" ; EHOSTUNREACH 113
DATA_ERR "Operation already in progress" ; EALREADY 114
DATA_ERR "Operation now in progress" ; EINPROGRESS 115
DATA_ERR "Stale NFS file handle" ; ESTALE 116
DATA_ERR "Structure needs cleaning" ; EUCLEAN 117
DATA_ERR "Not a XENIX named type file" ; ENOTNAM 118
DATA_ERR "No XENIX semaphores available" ; ENAVAIL 119
DATA_ERR "Is a named type file" ; EISNAM 120
DATA_ERR "Remote I/O error" ; EREMOTEIO 121
DATA_ERR "Quota exceeded" ; EDQUOT 122
DATA_ERR "No medium found" ; ENOMEDIUM 123
DATA_ERR "Wrong medium type" ; EMEDIUMTYPE 124
DATA_ERR "Operation Canceled" ; ECANCELED 125
DATA_ERR "Required key not available" ; ENOKEY 126
DATA_ERR "Key has expired" ; EKEYEXPIRED 127
DATA_ERR "Key has been revoked" ; EKEYREVOKED 128
DATA_ERR "Key was rejected by service" ; EKEYREJECTED 129
DATA_ERR "Owner died" ; EOWNERDEAD 130
DATA_ERR "State not recoverable" ; ENOTRECOVERABLE 131
DATA_ERR "Operation not possible due to RF-kill" ; ERFKILL 132
DATA_ERR "Memory page has hardware error" ; EHWPOISON 133
答案 1 :(得分：2)
Linux上的系统调用接口将错误返回为小的负数 - 在-1 .. -4095范围内的任何返回值（在％rax中）都是错误返回码。
因此，在写入系统调用之后，当您检查%rax的值以查看写入的字节数时，如果值为负，则发生错误，负值为错误代码。< / p>