[parisc-linux] mcontext registers on parisc64 (was Re: subo -> overflow_trap (12) -> What to do?)

[Christophe Rhodes <csr21@cam.ac.uk>]

[-- Attachment #1: Type: text/plain, Size: 1828 bytes --]

On Sat, Aug 17, 2002 at 06:05:45PM -0400, Carlos O'Donell wrote:
> Talking with Christophe Rhodes who is porting some Common Lisp code[1]
> to parisc-linux and he has some old-ish code from HPUX (circa 1994)
> that does some interesting things :)

Firstly, thanks to this, my code seems to work on a parisc-1.1 machine
that I have available.  However, I'm having trouble getting it to run on
a parisc64 kernel...

As you may have gathered, the Common Lisp compiler in question depends
quite heavily on signal handling, and in particular SA_SIGINFO
sigaction-style handling. This seems to work fine in 32-bit mode, but
not in 64-bits; in particular, there seem to be some 32/64-bit
confusions going on...

I've attached a test program to (try to) demonstrate the problem; it's
complicated a bit by Debian bug #157374 (basically, incompatibility
between <sys/ucontext.h> and what the kernel actually delivers) but I
hope that what it's doing is clear enough... if I'm doing something
wrong, please let me know.

Inspecting the sigcontext that I get on a parisc64 machine gives
register contents looking a bit like
    [...]
    0xffffffff, 0xdeadbeef, 0x0, 0xf00d, 0x0, 0xfaf00380, 0x0, 0x2097a, 0x0, 
    0xfaf001a4, 0x0, 0x2096a, 0x0, 0x1, 0x0, 0x20972, 0x0, 0x1, 0x0, 0x0, 0x0, 
    [...]

and the alternation of data, 0/-1 is what leads me to believe that
64-bit quantities are being delivered; userland only seems to know about
32-bits, though.

Please don't hesitate to get back to me with comments and/or criticisms,

Cheers,

Christophe
-- 
Jesus College, Cambridge, CB5 8BL                           +44 1223 510 299
http://www-jcsu.jesus.cam.ac.uk/~csr21/                  (defun pling-dollar 
(str schar arg) (first (last +))) (make-dispatch-macro-character #\! t)
(set-dispatch-macro-character #\! #\$ #'pling-dollar)

[-- Attachment #2: test.c --]
[-- Type: text/x-csrc, Size: 707 bytes --]

#include <stdio.h>
#include <sys/ucontext.h>
#include <signal.h>
/* c.f. Debian Bug#157374 */
#include <asm/sigcontext.h>

void sigsegv_handler(int signal, siginfo_t *info, void *context) {
  fprintf(stderr, "si_addr: %p (should probably be 0x0 [aka \"(nil)\"]\n",info->si_addr);
  fprintf(stderr, "%r1    : 0x%08x (should probably be 0xdeadbeef)\n",
	  ((struct sigcontext *) &(((ucontext_t *) context)->uc_mcontext))->sc_gr[1]);
  exit(0);
}

int main () {
  int *foo;
  struct sigaction sa;
  
  sa.sa_sigaction = sigsegv_handler;
  sa.sa_flags = SA_SIGINFO | SA_RESTART;
  sigaction(SIGSEGV, &sa, NULL);
  
  asm("ldil L%0xdeadbeef,%r1");
  asm("ldo R%0xdeadbeef(%r1),%r1");
  foo = NULL;
  *foo = 3;
}