diff options
Diffstat (limited to 'lib/malloc/x386-alloca.s')
| -rw-r--r-- | lib/malloc/x386-alloca.s | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/lib/malloc/x386-alloca.s b/lib/malloc/x386-alloca.s new file mode 100644 index 0000000..112d33c --- /dev/null +++ b/lib/malloc/x386-alloca.s @@ -0,0 +1,63 @@ +;; alloca386.s 1.2 +;; GNU-compatible stack allocation function for Xenix/386. +;; Written by Chip Salzenberg at ComDev. +;; Last modified 90/01/11 +;;> Is your alloca clearly better than the one in i386-alloca.s? I haven't +;;> looked at either. +;; +;;They're different because Xenix/386 has a different assembler. SCO +;;Xenix has the Microsoft C compiler and the Microsoft macro assembler, +;;called "masm". MASM's assembler syntax is quite different from AT&T's +;;in all sorts of ways. Xenix people can't use the AT&T version. +;;-- +;;Chip Salzenberg at ComDev/TCT <chip@tct.uucp>, <uunet!ateng!tct!chip> + + TITLE $alloca386 + + .386 +DGROUP GROUP CONST, _BSS, _DATA +_DATA SEGMENT DWORD USE32 PUBLIC 'DATA' +_DATA ENDS +_BSS SEGMENT DWORD USE32 PUBLIC 'BSS' +_BSS ENDS +CONST SEGMENT DWORD USE32 PUBLIC 'CONST' +CONST ENDS +_TEXT SEGMENT DWORD USE32 PUBLIC 'CODE' + ASSUME CS: _TEXT, DS: DGROUP, SS: DGROUP, ES: DGROUP + + PUBLIC _alloca +_alloca PROC NEAR + +; Get argument. + pop edx ; edx -> return address + pop eax ; eax = amount to allocate + +; Validate allocation amount. + add eax,3 + and eax,not 3 + cmp eax,0 + jg aa_size_ok + mov eax,4 +aa_size_ok: + +; Allocate stack space. + mov ecx,esp ; ecx -> old stack pointer + sub esp,eax ; perform allocation + mov eax,esp ; eax -> new stack pointer + +; Copy the three saved register variables from old stack top to new stack top. +; They may not be there. So we waste twelve bytes. Big fat hairy deal. + push DWORD PTR 8[ecx] + push DWORD PTR 4[ecx] + push DWORD PTR 0[ecx] + +; Push something so the caller can pop it off. + push eax + +; Return to caller. + jmp edx + +_alloca ENDP + +_TEXT ENDS + END |