ref: e22c4b573a6d0d71a8781ef655a7249f8b1921a4
dir: /lib/sys/syscall+plan9-x64.s/
/* Ugly: Kernel is caller-save, Myrddin is callee-save. We need to preserve registers before entering the kernel. However, we also need SP to point to the start of the arguments. Luckily, the kernel doesn't touch our stack, and we have 256 bytes of gap if we get a note. */ TEXT sys$syscall+0(SB),1,$0 MOVQ R11,-16(SP) MOVQ R12,-24(SP) MOVQ R13,-32(SP) MOVQ R14,-40(SP) MOVQ R15,-48(SP) MOVQ BP,-56(SP) MOVQ 8(SP),RARG ADDQ $8,SP MOVQ DI, RARG SYSCALL SUBQ $8,SP MOVQ -16(SP),R11 MOVQ -24(SP),R12 MOVQ -32(SP),R13 MOVQ -40(SP),R14 MOVQ -48(SP),R15 MOVQ -56(SP),BP RET