Date: Thu, 29 Jun 2000 20:28:50 -0700 (PDT) From: John Polstra <jdp@polstra.com> To: hackers@freebsd.org Subject: Please run this test on an 80386 Message-ID: <XFMail.000629202850.jdp@polstra.com>
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I am making some changes to FreeBSD's dynamic linker which require
the ability to find out whether the CPU running the program supports
the cmpxchg instruction. This instruction was introduced with
the 80486; it did not exist on the 80386. The attached program
attempts to determine whether the cmpxchg instruction is supported.
Unfortunately, I don't have an 80386 to test it on. I would
appreciate it if somebody with FreeBSD running on an 80386 would
compile the program, run it, and send me the output. To compile it,
just type:
cc -o sigill sigill.c
and then run it with
./sigill
On an 80386 it should print out
This CPU does not support the cmpxchg instruction
Thanks in advance!
John
--
John Polstra jdp@polstra.com
John D. Polstra & Co., Inc. Seattle, Washington USA
"Disappointment is a good sign of basic intelligence." -- Chögyam Trungpa
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#include <err.h>
#include <setjmp.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#ifdef TEST
#define cmpxchgl(old, new, m) ({ \
__asm volatile (".byte 0x0f; .byte 0x0f"); \
0; })
#else
#define cmpxchgl(old, new, m) ({ \
unsigned int __eax; \
__asm volatile ("lock; cmpxchgl %2, %0" \
: "=m"(m), "=a"(__eax) \
: "r"(new), "0"(m), "1"(old) \
: "cc"); \
(__eax); })
#endif
static jmp_buf sigill_env;
static void
sigill(int sig)
{
longjmp(sigill_env, 1);
}
static int
cpu_supports_cmpxchg(void)
{
struct sigaction act, oact;
int result = 1;
int lock = 0;
memset(&act, 0, sizeof act);
act.sa_handler = sigill;
sigemptyset(&act.sa_mask);
act.sa_flags = 0;
if (sigaction(SIGILL, &act, &oact) == -1)
err(1, "sigaction failed");
if (setjmp(sigill_env) == 0)
cmpxchgl(0, 1, lock);
else
result = 0;
if (sigaction(SIGILL, &oact, NULL) == -1)
err(1, "sigaction failed");
return result;
}
int
main(int argc, char *argv[])
{
if (cpu_supports_cmpxchg())
printf("This CPU supports the cmpxchg instruction\n");
else
printf("This CPU does not support the cmpxchg instruction\n");
return 0;
}
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