From 6e1eeeebfb453fa7c871869c19375ce60fbd7413 Mon Sep 17 00:00:00 2001 From: Kartik Agaram Date: Sat, 27 Jul 2019 16:01:55 -0700 Subject: 5485 - promote SubX to top-level --- html/050_write.subx.html | 120 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) create mode 100644 html/050_write.subx.html (limited to 'html/050_write.subx.html') diff --git a/html/050_write.subx.html b/html/050_write.subx.html new file mode 100644 index 00000000..5205e615 --- /dev/null +++ b/html/050_write.subx.html @@ -0,0 +1,120 @@ + + + + +Mu - subx/050_write.subx + + + + + + + + + + +https://github.com/akkartik/mu/blob/master/subx/050_write.subx +
+ 1 # _write: write to a file descriptor (fd)
+ 2 
+ 3 == code
+ 4 #   instruction                     effective address                                                   register    displacement    immediate
+ 5 # . op          subop               mod             rm32          base        index         scale       r32
+ 6 # . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
+ 7 
+ 8 Entry:  # just exit; can't test _write just yet
+ 9     # . syscall(exit, 0)
+10     bb/copy-to-EBX  0/imm32
+11     b8/copy-to-EAX  1/imm32/exit
+12     cd/syscall  0x80/imm8
+13 
+14 _write:  # fd : int, s : (address array byte) -> <void>
+15     # . prolog
+16     55/push-EBP
+17     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
+18     # . save registers
+19     50/push-EAX
+20     51/push-ECX
+21     52/push-EDX
+22     53/push-EBX
+23     # syscall(write, fd, (data) s+4, (size) *s)
+24     # . fd : EBX
+25     8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           3/r32/EBX   8/disp8         .                 # copy *(EBP+8) to EBX
+26     # . data : ECX = s+4
+27     8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           1/r32/ECX   0xc/disp8       .                 # copy *(EBP+12) to ECX
+28     81          0/subop/add         3/mod/direct    1/rm32/ECX    .           .             .           .           .               4/imm32           # add to ECX
+29     # . size : EDX = *s
+30     8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           2/r32/EDX   0xc/disp8       .                 # copy *(EBP+12) to EDX
+31     8b/copy                         0/mod/indirect  2/rm32/EDX    .           .             .           2/r32/EDX   .               .                 # copy *EDX to EDX
+32     # . syscall
+33     b8/copy-to-EAX  4/imm32/write
+34     cd/syscall  0x80/imm8
+35     # if (EAX < 0) abort
+36     3d/compare-EAX-with  0/imm32
+37     0f 8c/jump-if-lesser  $_write:abort/disp32
+38 $_write:end:
+39     # . restore registers
+40     5b/pop-to-EBX
+41     5a/pop-to-EDX
+42     59/pop-to-ECX
+43     58/pop-to-EAX
+44     # . epilog
+45     89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
+46     5d/pop-to-EBP
+47     c3/return
+48 
+49 $_write:abort:
+50     # can't write a message here for risk of an infinite loop, so we'll use a special exit code instead
+51     # . syscall(exit, 255)
+52     bb/copy-to-EBX  0xff/imm32
+53     b8/copy-to-EAX  1/imm32/exit
+54     cd/syscall  0x80/imm8
+55     # never gets here
+56 
+57 # . . vim:nowrap:textwidth=0
+
+ + + -- cgit 1.4.1-2-gfad0