brt@pyuxvv.UUCP (B Reytblat) (03/20/84)
$$$$$$$$$ <- bribe to the line-eater
This is a rather long submission consisting of questions, theories
and examples:
1. I'm running C programs in a STAND-ALONE environment.
Problem:
How does one bind an INITIALIZED variable to a specific
address? What I want to do is some thing like this:
struct FOO{ ... } name;
(struct FOO *)0x80 = &name
Needless to say, cc barfs on the 0x80 part.
2. I have attempted to do this by splitting the program in two
source files:
file1:
extern struct FOO name;
struct FOO *p_name = &name;
file2:
static struct FOO name;
extern struct FOO *p_name;
and then binding the .data section of file1 to the address in
question using an allocation tool similar to ld(1). As you can see,
p_name must be accessible inside file2. Also, in physical memory,
p_name is surrounded by other things, so I can't put name and p_name
into the same source file (or else they will go into the same
.data section, and end up in contiguous memory locations.)
Unfortunately, that didn't work either. It seems (and this is pure
speculation based on a few hours of hacking different versions of
this) that cc(1) understands (&name) to be a compile-time constant
rather than a reference to a variable. I haven't looked at the
code to see if this is really true (and if I did, I wouldn't know
where to look :-).
3. I'm sure some of you have run into this sort of thing before.
Am I completely off base? What have I missed? Are there any
"nice" solutions to the original problem of bindidng an
initialized variable explicitly? Or is this another one
of those things that C cannot do?
Thanks for help in advance,
B.Reytblat
...!pyuxvv!brt
(201)-981-2044 (office)
"... I'm a hacker,
she's a hacker,
he's a hacker,
Wouldn't you like to be a hacker too?
Be a hacker,
Try a little hackin'
Be a hacker,
Try a little hackin' ..."gnu@sun.uucp (John Gilmore) (03/21/84)
You can't assign an absolute address to a piece of text or data that
comes out of the C compiler. You can make an absolute address look
like a struct (or other variable), then do a structure assignment
at runtime to initialize it if you want. For example:
#define DISKCTLR (*(struct diskregs *)0xFFF304)
struct diskregs diskinit = {...};
DISKCTLR = diskinit;
DISKCTLR.command = DISK_RESET;
...
Note that in the structure assignment, you can't control the ordering
of the storage references, so if it's an I/O device (not real memory),
you're probably better off doing it by hand. Most devices are finicky
about what registers you write in what order anyway.brt@pyuxvv.UUCP (B Reytblat) (03/23/84)
^ | comon, eat that blank line, punk. make my day. Thanks to all who answered my question. The responses seem to fall into two categories: ************************************************************************ 1. Initialization takes place at RUN-time, i.e. AFTER the program has started executing: ------------------------------------------------------------------------ What's wrong with: struct FOO {...} name, **addr; **addr = (struct FOO **)0x80; *addr = &name; I think that this gives the effect that you want, that is, storing the address of name at location 0x80. Tony Hansen pegasus!hansen ------------------------------------------------------------------------ I might have misunderstood, but won't this do what you want? struct FOO { int x; } ; struct FOO *xp = (struct FOO *)0x80; main(){ struct FOO name; xp = &name; } {harpo,houxm,ihnp4}!pyuxss!aaw Aaron Werman ------------------------------------------------------------------------ Try struct a { int a_x; }; main () { ((struct a *)100)->a_x = 10; } which produces the following assembler output: .file "a.c" .data .text .align 4 .globl _main _main: .word .R1 jbr .L13 .L14: movl $10,100 /* this is the actual access */ ret#0 .set .R1,0x0 .L13: jbr .L14 .data Of course, you ought to parameterise it: #define DEV_ADDR 100 #define DEV_REGS (struct a *) DEV_ADDR then use DEV_REGS->a_x = /* whatever */ John Hutchinson hou5g!jrh AGS Computers at AT&T ISL, Holmdel. ************************************************************************ 2. The initialization takes place at COMPILE-time. AND the initialized pointer is bound to an address outside the .data section of the program. Unfortunately, as the submission below indicates, IT CAN'T BE DONE in C : From: gnu@sun.uucp (John Gilmore) Subject: Re: help! (much shorter) You can't assign an absolute address to a piece of text or data that comes out of the C compiler. You can make an absolute address look like a struct (or other variable), then do a structure assignment at runtime to initialize it if you want. For example: #define DISKCTLR (*(struct diskregs *)0xFFF304) struct diskregs diskinit = {...}; DISKCTLR = diskinit; DISKCTLR.command = DISK_RESET; ... Note that in the structure assignment, you can't control the ordering of the storage references, so if it's an I/O device (not real memory), you're probably better off doing it by hand. Most devices are finicky about what registers you write in what order anyway. ********************************************************************** Solution, you might ask? I've settled on the two file approach: file1: ....................................... extern struct FOO name; struct FOO *p_name = &name; ....................................... file2: ....................................... extern struct *p_name; struct FOO {...} name = {@@@}; other code. references to both name & p_name. ....................................... and then bind the .data section of file1 to the absolute address at LINK-EDIT-time. Thanks to all, B.Reytblat ...!pyuxvv!brt (201)-981-2044 (office)
sllu@ucla-cs.UUCP (10/31/85)
"..., line 341: compiler error: parameter stack overflow" I encountered the above error while compiling (cc) SPICE3.0 on a SUN station. Has anyone encountered similar problem? If yes how did you solve it? Has anyone successfully installed SPICE3.0 on a SUN workstation? Thanks in advance. Shih-Lien Lu // UCLA Computer Science Department // +1 213-825-2266 3689 Boelter Hall // Los Angeles, California 90024 // USA ARPA: sllu@UCLA-CS.ARPA -or- sllu@CS.UCLA.EDU UUCP: ...!(ihnp4,ucbvax)!ucla-cs!sllu -- Shih-Lien Lu // UCLA Computer Science Department // +1 213-825-2266 3680 Boelter Hall // Los Angeles, California 90024 // USA ARPA: sllu@UCLA-CS.ARPA -or- sllu@CS.UCLA.EDU UUCP: ...!(ihnp4,ucbvax)!ucla-cs!sllu
DPHARP01%ULKYVX.BITNET@wiscvm.ARPA (02/22/86)
I am looking for an implementation of either the DES or RSA encryption algorithims written in C. Any flavor of C will do, although VAX C would be nice if I had a choice. Any help on where I might look, etc. would be greatly appreciated. David Harpe University of Louisville BITNET: DPHARP01@ULKYVX Phone: (502) 588-6303