From 4254408a385f90ffe212e85a7b405054f4e73f5e Mon Sep 17 00:00:00 2001 From: Kartik Agaram Date: Sat, 23 Jan 2021 11:14:07 -0800 Subject: 7549 --- html/baremetal/313index-bounds-check.subx.html | 73 +++++++++++++++++++++----- 1 file changed, 60 insertions(+), 13 deletions(-) (limited to 'html/baremetal/313index-bounds-check.subx.html') diff --git a/html/baremetal/313index-bounds-check.subx.html b/html/baremetal/313index-bounds-check.subx.html index 2dc4cfc4..48ea8b01 100644 --- a/html/baremetal/313index-bounds-check.subx.html +++ b/html/baremetal/313index-bounds-check.subx.html @@ -54,19 +54,66 @@ if ('onhashchange' in window) { https://github.com/akkartik/mu/blob/main/baremetal/313index-bounds-check.subx

- 1 # TODO: bring this back
- 2 
- 3 == code
- 4 
- 5 __check-mu-array-bounds:  # index: int, elem-size: int, arr-size: int, function-name: (addr array byte), array-name: (addr array byte)
- 6     # . prologue
- 7     55/push-ebp
- 8     89/<- %ebp 4/r32/esp
- 9 $__check-mu-array-bounds:end:
-10     # . epilogue
-11     89/<- %esp 5/r32/ebp
-12     5d/pop-to-ebp
-13     c3/return
+ 1 # Helper to check an array's bounds, and to abort if they're violated.
+ 2 # Really only intended to be called from code generated by mu.subx.
+ 3 
+ 4 == code
+ 5 
+ 6 __check-mu-array-bounds:  # index: int, elem-size: int, arr-size: int, function-name: (addr array byte), array-name: (addr array byte)
+ 7     # . prologue
+ 8     55/push-ebp
+ 9     89/<- %ebp 4/r32/esp
+10     # . save registers
+11     50/push-eax
+12     51/push-ecx
+13     52/push-edx
+14     # . not bothering saving ebx; it's only clobbered if we're going to abort
+15     # ecx = arr-size
+16     8b/-> *(ebp+0x10) 1/r32/ecx
+17     # var overflow/edx: int = 0
+18     ba/copy-to-edx 0/imm32
+19     # var offset/eax: int = index * elem-size
+20     8b/-> *(ebp+8) 0/r32/eax
+21     f7 4/subop/multiply-eax-with *(ebp+0xc)
+22     # check for overflow
+23     81 7/subop/compare %edx 0/imm32
+24     0f 85/jump-if-!= __check-mu-array-bounds:overflow/disp32
+25     # check bounds
+26     39/compare %eax 1/r32/ecx
+27     0f 82/jump-if-unsigned< $__check-mu-array-bounds:end/disp32  # negative index should always abort
+28     # abort if necessary
+29     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "fn " 3)  # 3=cyan
+30     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+0x14) 3)  # 3=cyan
+31     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 ": offset " 3)  # 3=cyan
+32     (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %eax 3)  # 3=cyan
+33     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 " is too large for array '" 3)  # 3=cyan
+34     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+0x18) 3)  # 3=cyan
+35     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "'" 3)  # 3=cyan
+36     {
+37       eb/jump loop/disp8
+38     }
+39     # never gets here
+40 $__check-mu-array-bounds:end:
+41     # . restore registers
+42     5a/pop-to-edx
+43     59/pop-to-ecx
+44     58/pop-to-eax
+45     # . epilogue
+46     89/<- %esp 5/r32/ebp
+47     5d/pop-to-ebp
+48     c3/return
+49 
+50 __check-mu-array-bounds:overflow:
+51     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "fn " 3)  # 3=cyan
+52     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+0x14) 3)  # 3=cyan
+53     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 ": offset to array '" 3)  # 3=cyan
+54     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "offset to array overflowed 32 bits" 3)  # 3=cyan
+55     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+0x18) 3)  # 3=cyan
+56     (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "' overflowed 32 bits" 3)  # 3=cyan
+57     {
+58       eb/jump loop/disp8
+59     }
+60     # never gets here

-- cgit 1.4.1-2-gfad0