From f9e233c9c465dd4fdbfda4839c45fb624723b604 Mon Sep 17 00:00:00 2001
From: Kevin Buettner <kevinb@redhat.com>
Date: Tue, 16 Jun 2020 11:39:22 -0700
Subject: [PATCH] Add test for accessing read-only mmapped data in a core file

This test passes when run using a GDB with my corefile patches.  When
run against a GDB without my patches, I see the following failures,
the first of which is due to the test added by this commit:

FAIL: gdb.base/corefile.exp: accessing read-only mmapped data in core file (mapping address not found in core file)
FAIL: gdb.base/corefile.exp: accessing anonymous, unwritten-to mmap data

gdb/testsuite/ChangeLog:

	* gdb.base/corefile.exp: Add test "accessing read-only mmapped
	data in core file".
	* gdb.base/coremaker.c (buf2ro): New global.
	(mmapdata): Add a read-only mmap mapping.
---
 gdb/testsuite/ChangeLog             |  7 +++++++
 gdb/testsuite/gdb.base/corefile.exp | 18 +++++++++++++++++-
 gdb/testsuite/gdb.base/coremaker.c  | 14 ++++++++++++--
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 57e63f5216c..5ed9969d187 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2020-07-22  Kevin Buettner  <kevinb@redhat.com>
+
+	* gdb.base/corefile.exp: Add test "accessing read-only mmapped
+	data in core file".
+	* gdb.base/coremaker.c (buf2ro): New global.
+	(mmapdata): Add a read-only mmap mapping.
+
 2020-07-22  Kevin Buettner  <kevinb@redhat.com>
 
 	PR corefiles/25631
diff --git a/gdb/testsuite/gdb.base/corefile.exp b/gdb/testsuite/gdb.base/corefile.exp
index eaabe6c0f8c..8abf62b51f1 100644
--- a/gdb/testsuite/gdb.base/corefile.exp
+++ b/gdb/testsuite/gdb.base/corefile.exp
@@ -34,7 +34,10 @@ if {[build_executable $testfile.exp $testfile $srcfile debug] == -1} {
     return -1
 }
 
-set corefile [core_find $binfile {coremmap.data}]
+# Do not delete coremap.data when calling core_find.  This file is
+# required for GDB to find mmap'd data in the "accessing read-only
+# mmapped data in core file" test.
+set corefile [core_find $binfile {}]
 if {$corefile == ""} {
     return 0
 }
@@ -175,6 +178,19 @@ gdb_test_multiple "x/8bd buf2" "$test" {
     }
 }
 
+set test "accessing read-only mmapped data in core file"
+gdb_test_multiple "x/8bd buf2ro" "$test" {
+    -re ".*:.*0.*1.*2.*3.*4.*5.*6.*7.*$gdb_prompt $" {
+	pass "$test"
+    }
+    -re "0x\[f\]*:.*Cannot access memory at address 0x\[f\]*.*$gdb_prompt $" {
+	fail "$test (mapping failed at runtime)"
+    }
+    -re "0x.*:.*Cannot access memory at address 0x.*$gdb_prompt $" {
+	fail "$test (mapping address not found in core file)"
+    }
+}
+
 # Test ability to read anonymous and, more importantly, unwritten-to
 # mmap'd data.
 
diff --git a/gdb/testsuite/gdb.base/coremaker.c b/gdb/testsuite/gdb.base/coremaker.c
index 0981b21738f..3fc13e92875 100644
--- a/gdb/testsuite/gdb.base/coremaker.c
+++ b/gdb/testsuite/gdb.base/coremaker.c
@@ -38,6 +38,7 @@
 
 char *buf1;
 char *buf2;
+char *buf2ro;
 char *buf3;
 
 int coremaker_data = 1;	/* In Data section */
@@ -90,16 +91,25 @@ mmapdata ()
       return;
     }
 
+  /* Map in another copy, read-only.  We won't write to this copy so it
+     will likely not end up in the core file.  */
+  buf2ro = (char *) mmap (0, MAPSIZE, PROT_READ, MAP_PRIVATE, fd, 0);
+  if (buf2ro == (char *) -1)
+    {
+      perror ("mmap failed");
+      return;
+    }
+
   /* Verify that the original data and the mapped data are identical.
      If not, we'd rather fail now than when trying to access the mapped
      data from the core file. */
 
   for (j = 0; j < MAPSIZE; ++j)
     {
-      if (buf1[j] != buf2[j])
+      if (buf1[j] != buf2[j] || buf1[j] != buf2ro[j])
 	{
 	  fprintf (stderr, "mapped data is incorrect");
-	  buf2 = (char *) -1;
+	  buf2 = buf2ro = (char *) -1;
 	  return;
 	}
     }
-- 
2.30.2