Patchwork Fix signals reported for faults on Solaris

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Submitter Rainer Orth
Date Sept. 4, 2019, 9 a.m.
Message ID <yddtv9sfnb3.fsf@CeBiTec.Uni-Bielefeld.DE>
Download mbox | patch
Permalink /patch/34384/
State New
Headers show

Comments

Rainer Orth - Sept. 4, 2019, 9 a.m.
It's been a long-standing nuisance that gdb reported unaligned accesses
on Solaris/SPARC as SIGSEGV, contrary to the shells and truss which
correctly report SIGBUS instead.

I could trace this down to the fault handling code in procfs.c
(procfs_target::wait): when pr_why is set to PR_FAULTED, the current
code sets the signal based on the fault number.  For one, the code gets
this wrong for FLTACCESS (the unaligned access case) where it uses
SIGSEGV.  What's worse, it's completely unnecessary to make up the
signal number inside gdb.  Instead, it should just take what procfs
reports to avoid mismatches, which is what this patch does.  I've
completely removed the explicit handling of the various fault codes: for
one, the list has already been incomplete, lacking FLTCPCOVF which
existed since at least Solaris 8.  Besides, there's no reason to error
out on unknown fault codes: either the fault causes a signal which can
then be reported from procfs, or it doesn't (as for FLTPAGE) and no
reporting is necessary.

Tested on sparcv9-sun-solaris2.11 and x86_64-pc-solaris2.11.  Also
spot-checked manually for a couple of cases (unaligned access, division
by 0, NULL pointer dereference).

I thought about adding a testcase, but that's going to be difficult
because both the existance of faults (as in the unaligned access case
which only happens on SPARC) or the mapping from fault to signal is
target and OS specific.

Thus, unless someone objects, I'm going to install the patch in a day or
two.

	Rainer

Patch

# HG changeset patch
# Parent  0dae8fb1c51501778a95bad44ddbc511c49b50fb
Fix signals reported for faults on Solaris

diff --git a/gdb/procfs.c b/gdb/procfs.c
--- a/gdb/procfs.c
+++ b/gdb/procfs.c
@@ -2476,40 +2476,12 @@  wait_again:
 		wstat = (what << 8) | 0177;
 		break;
 	      case PR_FAULTED:
-		switch (what) {
-		case FLTWATCH:
-		  wstat = (SIGTRAP << 8) | 0177;
-		  break;
-		  /* FIXME: use si_signo where possible.  */
-		case FLTPRIV:
-		case FLTILL:
-		  wstat = (SIGILL << 8) | 0177;
-		  break;
-		case FLTBPT:
-		case FLTTRACE:
-		  wstat = (SIGTRAP << 8) | 0177;
-		  break;
-		case FLTSTACK:
-		case FLTACCESS:
-		case FLTBOUNDS:
-		  wstat = (SIGSEGV << 8) | 0177;
-		  break;
-		case FLTIOVF:
-		case FLTIZDIV:
-		case FLTFPE:
-		  wstat = (SIGFPE << 8) | 0177;
-		  break;
-		case FLTPAGE:	/* Recoverable page fault */
-		default:	/* FIXME: use si_signo if possible for
-				   fault.  */
-		  retval = ptid_t (-1);
-		  printf_filtered ("procfs:%d -- ", __LINE__);
-		  printf_filtered (_("child stopped for unknown reason:\n"));
-		  proc_prettyprint_why (why, what, 1);
-		  error (_("... giving up..."));
-		  break;
+		{
+		  int signo = pi->prstatus.pr_lwp.pr_info.si_signo;
+		  if (signo != 0)
+		    wstat = (signo << 8) | 0177;
 		}
-		break;	/* case PR_FAULTED: */
+		break;
 	      default:	/* switch (why) unmatched */
 		printf_filtered ("procfs:%d -- ", __LINE__);
 		printf_filtered (_("child stopped for unknown reason:\n"));