[sanitizer] remove PS_STRINGS fallback on FreeBSD

[emaste]

Summary

The PS_STRINGS constant can easily be incorrect with mismatched kernel/userland - e.g. when building i386 sanitizers on FreeBSD/amd64 with -m32. The kern.ps_strings sysctl exists on all supported versions of FreeBSD and is the supported way to get the environment and argument strings, so we never use the PS_STRINGS fallback. Just remove it.

[davide]

This is reasonable to me. Filipe, what do you think?

[emaste]

I'm hoping to eventually move PS_STRINGS to be for the FreeBSD kernel only, and have started removing uses from the FreeBSD base system: https://svnweb.freebsd.org/changeset/base/297888

[filcab]

This seems to be in line with the rest of your commits in FreeBSD's base system, so LGTM.

[filcab]

Well, there's another point of view. Do we care about keeping the
PS_STRINGS for FreeBSD < 11? (Possibly <10.4 or <10.3)

Thank you,

Filipe

[emaste]

In D19027#401005, @filcab wrote:

Well, there's another point of view. Do we care about keeping the
PS_STRINGS for FreeBSD < 11? (Possibly <10.4 or <10.3)

No, there's no need. I made a mistake in my FreeBSD commit message when I said kern.ps_strings is available in any FreeBSD release supported within the last decade -- it's actually much longer.

kern.ps_strings was actually introduced in r14235 over 20 years ago: https://svnweb.freebsd.org/changeset/base/14235
And in 1998 it was understood that "applications should use the kern.ps_strings sysctl instead of PS_STRINGS": https://svnweb.freebsd.org/changeset/base/41871

compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc

#if !SANITIZER_GO
     static const int kMaxArgv = 2000, kMaxEnvp = 2000;
     ReadNullSepFileToArray("/proc/self/cmdline", argv, kMaxArgv);
     ReadNullSepFileToArray("/proc/self/environ", envp, kMaxEnvp);
   }
 #endif
 #else
   // On FreeBSD, retrieving the argument and environment arrays is done via the
   // kern.ps_strings sysctl, which returns a pointer to a structure containing
-  // this information.  If the sysctl is not available, a "hardcoded" address,
-  // PS_STRINGS, must be used instead.  See also <sys/exec.h>.
+  // this information. See also <sys/exec.h>.
   ps_strings *pss;
   size_t sz = sizeof(pss);
-  if (sysctlbyname("kern.ps_strings", &pss, &sz, NULL, 0) == -1)
-    pss = (ps_strings*)PS_STRINGS;
+  if (sysctlbyname("kern.ps_strings", &pss, &sz, NULL, 0) == -1) {
+    Printf("sysctl kern.ps_strings failed\n");
+    Die();
+  }
   *argv = pss->ps_argvstr;
   *envp = pss->ps_envstr;
 #endif
 }
 
 char **GetArgv() {
   char **argv, **envp;
   GetArgsAndEnv(&argv, &envp);