libk  Diff

Differences From Artifact [856b7532d5]:

• File mod/kcore/syscall.fn.x86.lin.64.s — part of check-in [e42b590b45] at 2019-08-24 23:02:13 on branch trunk — stop attempting to auto-detect system constants during build process, and maintain os/arch-specific tables instead (user: lexi, size: 2474) [annotate] [blame] [check-ins using]

To Artifact [3fa83c18de]:

• File mod/kcore/syscall.fn.x86.lin.64.s — part of check-in [481509e134] at 2019-10-21 04:28:46 on branch trunk — don't clobber callee-saved registers (user: lexi, size: 2716) [annotate] [blame] [check-ins using]

    31     31   	; locals: rbx = s64* result
    32     32   	;         r12 = u64* errno
    33     33   	; arg 0 = s64* result
    34     34   	; arg 1 = errno ptr
    35     35   	; arg 2 = syscall num
    36     36   	; arg 3 = valency
    37     37   	; arg 4 = args ptr
           38  +
           39  +	; we use two registers that are supposed
           40  +	; to be callee-saved, so we need to
           41  +	; push them to the stack and then pop
           42  +	; them back off just before the fn rets.
           43  +	push rbx
           44  +	push r12
    38     45   
    39     46   	; store the locals in registers that
    40     47   	; are guaranteed not to be clobbered,
    41     48   	; saving us some cycles pushing to
    42     49   	; and popping back from the stack
    43     50   	mov rbx, ccall.reg.0
    44     51   	mov r12, ccall.reg.1
................................................................................
    82     89   	js .error ; jump if sign flag set
    83     90   	
    84     91   	; move our return values into place and
    85     92   	; return to the caller (which should
    86     93   	; always be k_platform_syscall, btw)
    87     94   	mov       [rbx], sys.reg.ret
    88     95   	mov qword [r12], 0 ; no error
    89         -	ret
           96  +	jmp .return
    90     97   
    91     98   	; an error was returned - we need to set
    92     99   	; the errno to its positive equivalent,
    93    100   	; and store -1 in the return variable
    94    101   	.error: neg sys.reg.ret
    95    102   	        mov qword [rbx], -1
    96    103   			mov       [r12], sys.reg.ret
    97         -			ret
          104  +			jmp .return
          105  +
          106  +	.return: pop r12
          107  +	         pop rbx
          108  +			 ret