ARM系统调用的接口是什么?它在Linux内核中的哪里定义?

问题描述 投票:0回答:6

我读过有关 Linux 中的系统调用的内容,并且到处都给出了有关 x86 架构的描述(

0x80
中断和
SYSENTER
)。但我无法追踪 ARM 架构中系统调用的文件和进程。有谁可以帮忙吗?

我所了解的相关文件有:

arch/arm/kernel/calls.S

arch/arm/kernel/entry-common.S(需要解释)

linux linux-kernel arm system-calls
6个回答
26
投票

比你问的更通用的答案。

在 Linux 上,

man syscall (2)
是了解如何在各种体系结构中进行系统调用的良好开端。

从该手册页复制:

Architecture calling conventions
    Every architecture has its own way of invoking and passing arguments
    to the kernel.  The details for various architectures are listed in
    the two tables below.

    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 vdso(7)), the register used to
    indicate the system call number, the register used to return the sys‐
    tem call result, and the register used to signal an error.

    arch/ABI    instruction           syscall #  retval  error    Notes
    ────────────────────────────────────────────────────────────────────
    alpha       callsys               v0         a0      a3       [1]
    arc         trap0                 r8         r0      -
    arm/OABI    swi NR                -          a1      -        [2]
    arm/EABI    swi 0x0               r7         r0      -
    arm64       svc #0                x8         x0      -
    blackfin    excpt 0x0             P0         R0      -
    i386        int $0x80             eax        eax     -
    ia64        break 0x100000        r15        r8      r10      [1]
    m68k        trap #0               d0         d0      -
    microblaze  brki r14,8            r12        r3      -
    mips        syscall               v0         v0      a3       [1]
    nios2       trap                  r2         r2      r7
    parisc      ble 0x100(%sr2, %r0)  r20        r28     -
    powerpc     sc                    r0         r3      r0       [1]
    riscv       scall                 a7         a0      -
    s390        svc 0                 r1         r2      -        [3]
    s390x       svc 0                 r1         r2      -        [3]
    superh      trap #0x17            r3         r0      -        [4]
    sparc/32    t 0x10                g1         o0      psr/csr  [1]
    sparc/64    t 0x6d                g1         o0      psr/csr  [1]
    tile        swint1                R10        R00     R01      [1]
    x86-64      syscall               rax        rax     -        [5]
    x32         syscall               rax        rax     -        [5]
    xtensa      syscall               a2         a2      -

    Notes:

        [1] 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
            (csr) in the processor status register (psr) is used instead
            of a full register.

        [2] NR is the system call number.

        [3] For s390 and s390x, NR (the system call number) may be passed
            directly with svc NR if it is less than 256.

        [4] On SuperH, the trap number controls the maximum number of
            arguments passed.  A trap #0x10 can be used with only 0-argu‐
            ment system calls, a trap #0x11 can be used with 0- or
            1-argument system calls, and so on up to trap #0x17 for
            7-argument system calls.

        [5] The x32 ABI uses the same instruction as the x86-64 ABI and
            is used on the same processors.  To differentiate between
            them, the bit mask __X32_SYSCALL_BIT is bitwise-ORed into the
            system call number for system calls under the x32 ABI.  Both
            system call tables are available though, so setting the bit
            is not a hard requirement.

    The second table shows the registers used to pass the system call
    arguments.

    arch/ABI      arg1  arg2  arg3  arg4  arg5  arg6  arg7  Notes
    ──────────────────────────────────────────────────────────────
    alpha         a0    a1    a2    a3    a4    a5    -
    arc           r0    r1    r2    r3    r4    r5    -
    arm/OABI      a1    a2    a3    a4    v1    v2    v3
    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
    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    -

    Notes:

        [1] The mips/o32 system call convention passes arguments 5
            through 8 on the user stack.

    Note that these tables don't cover the entire calling convention—some
    architectures may indiscriminately clobber other registers not listed
    here.

所以这取决于系统使用OABI还是EABI。

所以在 EABI 中你使用

r7
来传递系统调用号, 使用
r0-r6
传递参数, 使用
SWI 0
进行系统调用, 期待
r0
的结果。

在 OABI 中,一切都是一样的,除了您使用

SWI <number>
进行系统调用。


17
投票

在 ARM 世界中,您通过

software interrupt
(以前称为 SWI)执行
supervisor call / svc
(向内核发出信号的机制)。

ARM 汇编 (UAL) 语法如下所示:

SVC{<c>}{<q>} {#}<imm>

(在Linux中你需要传递#0)

您应该从其他项目中作弊,例如 bionicuClibc


4
投票

如果您正在查找 Linux 系统中的系统调用号,请查看 w3challs.

该站点有助于找出使用了哪个系统调用号和哪些寄存器 用于传递参数。它支持下面列出的许多架构:


编辑:提交https://w3challs.com/forum/general/dev/bugs#04以跟踪不正确的错误。


3
投票

n900中hello world的反汇编显示

svc #0

http://brnz.org/hbr/?m=201102


0
投票

布防系统呼叫号码

v4.19 在

arch/arm/tools/syscall.tbl
定义了它们: https://github.com/torvalds/linux/blob/v4.19/arch/arm/tools/syscall.tbl

摘录:

0   common  restart_syscall     sys_restart_syscall
1   common  exit            sys_exit
2   common  fork            sys_fork
3   common  read            sys_read
4   common  write           sys_write
5   common  open            sys_open
6   common  close           sys_close

我已经测试过,

exit
write
在 QEMU 用户模式下的 这个 Linux 程序集 hello world 上有这些确切的数字。

arm64 系统调用号

aarch64 采用了新的机制,参见:https://reverseengineering.stackexchange.com/questions/16917/arm64-syscalls-table/18834#18834


0
投票

Linux 系统调用号在 C 包含文件中定义:

/usr/include/asm-generic/unistd.h

在此文件中,有如下定义语句:

/* fs/read_write.c */
#define __NR_write 64

/* kernel/exit.c */
#define __NR_exit 93

这定义了符号

__NR_write
代表用于 write Linux 系统调用的幻数 64 和用于退出的 93。


摘自使用 64 位 ARM 汇编语言进行编程:用于 Raspberry Pi 和移动设备的单板计算机开发 |第 7 章:Linux 操作系统服务 - 调用约定 - Linux 系统调用号

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