1#include <machine/asm.h> 2 3/* 4 * Emulate the Linux system call interface. The system call number is set in 5 * %rax, and %rdi, %rsi, %rdx, %r10, %r8, %r9 have the 6 system call 6 * arguments. errno is returned as a negative value, but we use it more as a 7 * flag something went wrong rather than using its value. 8 * 9 * Note: For system calls, we use %r10 instead of %rcx for the 4th argument. 10 * See section A.2.1 for the Linux calling conventions of the ABI spec 11 * https://web.archive.org/web/20160801075146/http://www.x86-64.org/documentation/abi.pdf 12 * In addition to the below, %r11 and %rcx are destroyed, negative 13 * values are ERRNO for %rax between -1 and -4095 otherwise the system 14 * call is successful. Unlike other Unix systems, carry isn't used to 15 * signal an error in the system call. We expose the raw system call 16 * result, rather than do the POSIX converion to -1 and setting errno. 17 */ 18ENTRY(host_syscall) 19 movq %rdi, %rax /* SYS_ number in %rax */ 20 movq %rsi, %rdi /* arg2 -> 1 */ 21 movq %rdx, %rsi /* arg3 -> 2 */ 22 movq %rcx, %rdx /* arg4 -> 3 */ 23 movq %r8, %r10 /* arg5 -> 4 */ 24 movq %r9, %r8 /* arg6 -> 5 */ 25 movq 8(%rsp),%r9 /* arg7 -> 6 from stack. */ 26 syscall 27 ret 28/* Note: We're exposing the raw return value to the caller */ 29END(host_syscall) 30