6153 - switch 'main' to use Mu strings

At the SubX level we have to put up with null-terminated kernel strings
for commandline args. But so far we haven't done much with them. Rather
than try to support them we'll just convert them transparently to standard
length-prefixed strings.

In the process I realized that it's not quite right to treat the combination
of argc and argv as an array of kernel strings. Argc counts the number
of elements, whereas the length of an array is usually denominated in bytes.

1 files changed, 32 insertions, 0 deletions

diff --git a/069allocate.subx b/069allocate.subx
index 48ba9413..503d151f 100644
--- a/069allocate.subx
+++ b/069allocate.subx
@@ -234,4 +234,36 @@ $allocate-region:abort:
     cd/syscall  0x80/imm8
     # never gets here
 
+# Claim the next 'n+4' bytes of memory and initialize the first 4 to n.
+# Abort if there isn't enough memory in 'ad'.
+allocate-array:  # ad: (addr allocation-descriptor), n: int -> result/eax: (addr _)
+    # . prologue
+    55/push-ebp
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+    # . save registers
+    51/push-ecx
+    52/push-edx
+    # ecx = n
+    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           1/r32/ecx   0xc/disp8       .                 # copy *(ebp+0xc) to ecx
+    # var size/edx: int = n+4
+    8d/copy-address                 1/mod/*+disp8   1/rm32/ecx    .           .             .           2/r32/edx   4/disp8         .                 # copy ecx+4 to edx
+    # result = allocate(ad, size)
+    # . . push args
+    52/push-edx
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
+    # . . call
+    e8/call  allocate/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # *result = n
+    89/copy                         0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # copy ecx to *eax
+$allocate-array:end:
+    # . restore registers
+    5a/pop-to-edx
+    59/pop-to-ecx
+    # . epilogue
+    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
+    5d/pop-to-ebp
+    c3/return
+
 # . . vim:nowrap:textwidth=0