.\" Copyright (c) 1980, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" %%%LICENSE_START(BSD_4_CLAUSE_UCB) .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" %%%LICENSE_END .\" .\" @(#)syscall.2 8.1 (Berkeley) 6/16/93 .\" .\" .\" 2002-03-20 Christoph Hellwig .\" - adopted for Linux .\" 2015-01-17, Kees Cook .\" Added mips and arm64. .\" .\"******************************************************************* .\" .\" This file was generated with po4a. Translate the source file. .\" .\"******************************************************************* .\" .\" Japanese Version Copyright (c) 2002 Yuichi SATO .\" all rights reserved. .\" Translated Tue Aug 6 03:43:25 JST 2002 .\" by Yuichi SATO .\" Updated 2013-05-06, Akihiro MOTOKI .\" Updated 2013-07-24, Akihiro MOTOKI .\" .TH SYSCALL 2 2020\-06\-09 Linux "Linux Programmer's Manual" .SH 名前 syscall \- 間接システムコール .SH 書式 .nf \fB#include \fP \fB#include \fP/* SYS_xxx の定義用 */ .PP \fBlong syscall(long \fP\fInumber\fP\fB, ...);\fP .fi .PP .RS -4 glibc 向けの機能検査マクロの要件 (\fBfeature_test_macros\fP(7) 参照): .RE \fBsyscall\fP(): .PD 0 .ad l .RS 4 .TP 4 glibc 2.19 以降: _DEFAULT_SOURCE .TP glibc 2.19 より前: _BSD_SOURCE || _SVID_SOURCE .RE .ad .PD .SH 説明 \fBsyscall\fP() は、システムコールを起動する小さなライブラリ関数で、 \fInumber\fP で指定されたアセンブリ言語インターフェースのシステムコールを、指定された引数をつけて実行する。 \fBsyscall\fP() が役に立つのは、例えば C ライブラリにラッパー関数が存在しないシステムコールを呼び出したい場合である。 .PP \fBsyscall\fP() は、システムコールを行う前に CPU レジスターを保存し、システムコールから返った際にレジスターを復元し、システムコールが返したエラーを \fBerrno\fP(3) に格納する。 .PP システムコールのシンボル定数は、ヘッダーファイル \fI\fP に書かれている。 .SH 返り値 返り値は呼び出されたシステムコールによって定義される。 一般に、返り値 0 は成功を表す。 \-1 はエラーを表し、エラー番号は \fIerrno\fP に入れられる。 .SH 注意 \fBsyscall\fP() は 4BSD で最初に登場した。 .SS アーキテクチャー固有の要件 各アーキテクチャーの ABI には、 システムコールの引数のカーネルへの渡し方に関する独自の要件がある。 (ほとんどのシステムコールのように) glibc ラッパー関数があるシステムコールでは、 glibc が詳細を処理し、アーキテクチャーに応じた方法で引数が適切なレジスターにコピーされる。 しかし、 システムコールを呼び出すのに \fBsyscall\fP() を使う場合には、 呼び出し側でアーキテクチャー依存の詳細を処理しなければならない場合がある。 これはいくつかの 32 ビットアーキテクチャーでは非常によくあることだ。 .PP For example, on the ARM architecture Embedded ABI (EABI), a 64\-bit value (e.g., \fIlong long\fP) must be aligned to an even register pair. Thus, using \fBsyscall\fP() instead of the wrapper provided by glibc, the \fBreadahead\fP(2) system call would be invoked as follows on the ARM architecture with the EABI in little endian mode: .PP .in +4n .EX syscall(SYS_readahead, fd, 0, (unsigned int) (offset & 0xFFFFFFFF), (unsigned int) (offset >> 32), count); .EE .in .PP Since the offset argument is 64 bits, and the first argument (\fIfd\fP) is passed in \fIr0\fP, the caller must manually split and align the 64\-bit value so that it is passed in the \fIr2\fP/\fIr3\fP register pair. That means inserting a dummy value into \fIr1\fP (the second argument of 0). Care also must be taken so that the split follows endian conventions (according to the C ABI for the platform). .PP .\" Mike Frysinger: this issue ends up forcing MIPS .\" O32 to take 7 arguments to syscall() Similar issues can occur on MIPS with the O32 ABI, on PowerPC and parisc with the 32\-bit ABI, and on Xtensa. .PP .\" See arch/parisc/kernel/sys_parisc.c. Note that while the parisc C ABI also uses aligned register pairs, it uses a shim layer to hide the issue from user space. .PP 次のシステムコールに影響がある: \fBfadvise64_64\fP(2), \fBftruncate64\fP(2), \fBposix_fadvise\fP(2), \fBpread64\fP(2), \fBpwrite64\fP(2), \fBreadahead\fP(2), \fBsync_file_range\fP(2), \fBtruncate64\fP(2) .PP .\" You need to look up the syscalls directly in the kernel source to see if .\" they should be in this list. For example, look at fs/read_write.c and .\" the function signatures that do: .\" ..., unsigned long, pos_l, unsigned long, pos_h, ... .\" If they use off_t, then they most likely do not belong in this list. This does not affect syscalls that manually split and assemble 64\-bit values such as \fB_llseek\fP(2), \fBpreadv\fP(2), \fBpreadv2\fP(2), \fBpwritev\fP(2), and \fBpwritev2\fP(2). Welcome to the wonderful world of historical baggage. .SS アーキテクチャー毎の呼び出し規約 各アーキテクチャーには、それぞれ独自のシステムコール起動方法とカーネルへの引数の渡し方がある。 各種のアーキテクチャーの詳細を以下の 2 つの表にまとめる。 .PP The first table lists the instruction used to transition to kernel mode (which might not be the fastest or best way to transition to the kernel, so you might have to refer to \fBvdso\fP(7)), the register used to indicate the system call number, the register(s) used to return the system call result, and the register used to signal an error. .if t \{\ .ft CW \} .TS l2 l2 l2 l2 l1 l2 l. Arch/ABI Instruction System Ret Ret Error 備考 call # val val2 _ alpha callsys v0 v0 a4 a3 1, 6 arc trap0 r8 r0 \- \- arm/OABI swi NR \- r0 \- \- 2 arm/EABI swi 0x0 r7 r0 r1 \- arm64 svc #0 w8 x0 x1 \- blackfin excpt 0x0 P0 R0 \- \- i386 int $0x80 eax eax edx \- ia64 break 0x100000 r15 r8 r9 r10 1, 6 m68k trap #0 d0 d0 \- \- microblaze brki r14,8 r12 r3 \- \- mips syscall v0 v0 v1 a3 1, 6 nios2 trap r2 r2 \- r7 parisc ble 0x100(%sr2, %r0) r20 r28 \- \- powerpc sc r0 r3 \- r0 1 powerpc64 sc r0 r3 \- cr0.SO 1 riscv ecall a7 a0 a1 \- s390 svc 0 r1 r2 r3 \- 3 s390x svc 0 r1 r2 r3 \- 3 superh trap #0x17 r3 r0 r1 \- 4, 6 sparc/32 t 0x10 g1 o0 o1 psr/csr 1, 6 sparc/64 t 0x6d g1 o0 o1 psr/csr 1, 6 tile swint1 R10 R00 \- R01 1 x86\-64 syscall rax rax rdx \- 5 x32 syscall rax rax rdx \- 5 xtensa syscall a2 a2 \- \- .TE .PP Notes: .IP [1] 4 On a few architectures, a register is used as a boolean (0 indicating no error, and \-1 indicating an error) to signal that the system call failed. The actual error value is still contained in the return register. On sparc, the carry bit (\fIcsr\fP) in the processor status register (\fIpsr\fP) is used instead of a full register. On powerpc64, the summary overflow bit (\fISO\fP) in field 0 of the condition register (\fIcr0\fP) is used. .IP [2] \fINR\fP is the system call number. .IP [3] s390 と s390x では、 \fINR\fP (システムコール番号) が 256 未満の場合 \fIsvc\ NR\fP で NR が直接渡される場合がある。 .IP [4] On SuperH, the trap number controls the maximum number of arguments passed. A \fItrap\ #0x10\fP can be used with only 0\-argument system calls, a \fItrap\ #0x11\fP can be used with 0\- or 1\-argument system calls, and so on up to \fItrap #0x17\fP for 7\-argument system calls. .IP [5] The x32 ABI shares syscall table with x86\-64 ABI, but there are some nuances: .RS .IP \(bu 3 In order to indicate that a system call is called under the x32 ABI, an additional bit, \fB__X32_SYSCALL_BIT\fP, is bitwise\-ORed with the system call number. The ABI used by a process affects some process behaviors, including signal handling or system call restarting. .IP \(bu Since x32 has different sizes for \fIlong\fP and pointer types, layouts of some (but not all; \fIstruct timeval\fP or \fIstruct rlimit\fP are 64\-bit, for example) structures are different. In order to handle this, additional system calls are added to the system call table, starting from number 512 (without the \fB__X32_SYSCALL_BIT\fP). For example, \fB__NR_readv\fP is defined as 19 for the x86\-64 ABI and as \fI__X32_SYSCALL_BIT\fP | \fB515\fP for the x32 ABI. Most of these additional system calls are actually identical to the system calls used for providing i386 compat. There are some notable exceptions, however, such as \fBpreadv2\fP(2), which uses \fIstruct iovec\fP entities with 4\-byte pointers and sizes ("compat_iovec" in kernel terms), but passes an 8\-byte \fIpos\fP argument in a single register and not two, as is done in every other ABI. .RE .IP [6] Some architectures (namely, Alpha, IA\-64, MIPS, SuperH, sparc/32, and sparc/64) use an additional register ("Retval2" in the above table) to pass back a second return value from the \fBpipe\fP(2) system call; Alpha uses this technique in the architecture\-specific \fBgetxpid\fP(2), \fBgetxuid\fP(2), and \fBgetxgid\fP(2) system calls as well. Other architectures do not use the second return value register in the system call interface, even if it is defined in the System V ABI. .if t \{\ .in .ft P \} .PP 2 つ目の表は、システムコールの引数を渡すのに使用されるレジスターの一覧である。 .if t \{\ .ft CW \} .TS l l2 l2 l2 l2 l2 l2 l2 l. Arch/ABI arg1 arg2 arg3 arg4 arg5 arg6 arg7 備考 _ alpha a0 a1 a2 a3 a4 a5 \- arc r0 r1 r2 r3 r4 r5 \- arm/OABI r0 r1 r2 r3 r4 r5 r6 arm/EABI r0 r1 r2 r3 r4 r5 r6 arm64 x0 x1 x2 x3 x4 x5 \- blackfin R0 R1 R2 R3 R4 R5 \- i386 ebx ecx edx esi edi ebp \- ia64 out0 out1 out2 out3 out4 out5 \- m68k d1 d2 d3 d4 d5 a0 \- microblaze r5 r6 r7 r8 r9 r10 \- mips/o32 a0 a1 a2 a3 \- \- \- 1 mips/n32,64 a0 a1 a2 a3 a4 a5 \- nios2 r4 r5 r6 r7 r8 r9 \- parisc r26 r25 r24 r23 r22 r21 \- powerpc r3 r4 r5 r6 r7 r8 r9 powerpc64 r3 r4 r5 r6 r7 r8 \- riscv a0 a1 a2 a3 a4 a5 \- s390 r2 r3 r4 r5 r6 r7 \- s390x r2 r3 r4 r5 r6 r7 \- superh r4 r5 r6 r7 r0 r1 r2 sparc/32 o0 o1 o2 o3 o4 o5 \- sparc/64 o0 o1 o2 o3 o4 o5 \- tile R00 R01 R02 R03 R04 R05 \- x86\-64 rdi rsi rdx r10 r8 r9 \- x32 rdi rsi rdx r10 r8 r9 \- xtensa a6 a3 a4 a5 a8 a9 \- .TE .PP Notes: .IP [1] 4 mips/o32 のシステムコールの規約では、 ユーザースタックに引数を 5 個から 8 個渡す。 .if t \{\ .in .ft P \} .PP これらの表にはすべての呼び出し規約が記載されているわけではない点に注意すること \(em アーキテクチャーによっては、ここに記載されていない他のレジスターが見境なく上書きされる場合もある。 .SH 例 .EX #define _GNU_SOURCE #include #include #include #include int main(int argc, char *argv[]) { pid_t tid; tid = syscall(SYS_gettid); syscall(SYS_tgkill, getpid(), tid, SIGHUP); } .EE .SH 関連項目 \fB_syscall\fP(2), \fBintro\fP(2), \fBsyscalls\fP(2), \fBerrno\fP(3), \fBvdso\fP(7) .SH この文書について この man ページは Linux \fIman\-pages\fP プロジェクトのリリース 5.10 の一部である。プロジェクトの説明とバグ報告に関する情報は \%https://www.kernel.org/doc/man\-pages/ に書かれている。