From: Aaron Merey <amerey@redhat.com>
Date: Tue, 16 Jul 2024 16:25:57 +0000 (-0400)
Subject: libdwP.h: Add locking to __libdw_dieabbrev
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ac0e88d8b4243dc78d8c7fbd48b2ca53a0820f93;p=thirdparty%2Felfutils.git

libdwP.h: Add locking to __libdw_dieabbrev

        * libdw/libdwP.h (__libdw_dieabbrev): Add locking.
        (struct Dwarf): Add dwarf_lock.
        (struct Dwarf_CU): Add abbrev_lock, split_lock.

Signed-off-by: Heather S. McIntyre <hsm2@rice.edu>
Signed-off-by: Aaron Merey <amerey@redhat.com>
Signed-off-by: Mark Wielaard <mark@klomp.org>

v2 changes:
This replaces patch "libdw: Add locking around __libdw_dieabbrev for
dwarf_hasattr".  Mark suggested that we remove lazy abbrev reading
in order to simplify the locking of __libdw_dieabbrev.  This is
a fair bit of work so for now lets just put a write lock around all
of __libdw_dieabbrev.  The removal of lazy reading of abbrev will be
done in a future patch.
---

diff --git a/libdw/dwarf_formref_die.c b/libdw/dwarf_formref_die.c
index 48ba8194..f8a51970 100644
--- a/libdw/dwarf_formref_die.c
+++ b/libdw/dwarf_formref_die.c
@@ -92,7 +92,9 @@ dwarf_formref_die (Dwarf_Attribute *attr, Dwarf_Die *result)
 	  bool scan_debug_types = false;
 	  do
 	    {
+        rwlock_wrlock(attr->cu->dbg->dwarf_lock);
 	      cu = __libdw_intern_next_unit (attr->cu->dbg, scan_debug_types);
+        rwlock_unlock(attr->cu->dbg->dwarf_lock);
 	      if (cu == NULL)
 		{
 		  if (scan_debug_types == false)
diff --git a/libdw/dwarf_setalt.c b/libdw/dwarf_setalt.c
index dc9b61cb..f7d70d9d 100644
--- a/libdw/dwarf_setalt.c
+++ b/libdw/dwarf_setalt.c
@@ -35,6 +35,8 @@
 void
 dwarf_setalt (Dwarf *main, Dwarf *alt)
 {
+  rwlock_wrlock(main->dwarf_lock);
+
   if (main->alt_fd != -1)
     {
       INTUSE(dwarf_end) (main->alt_dwarf);
@@ -43,5 +45,7 @@ dwarf_setalt (Dwarf *main, Dwarf *alt)
     }
 
   main->alt_dwarf = alt;
+
+  rwlock_unlock(main->dwarf_lock);
 }
 INTDEF (dwarf_setalt)
diff --git a/libdw/libdwP.h b/libdw/libdwP.h
index a4f26b82..9dce10e5 100644
--- a/libdw/libdwP.h
+++ b/libdw/libdwP.h
@@ -804,15 +804,28 @@ static inline Dwarf_Abbrev *
 __nonnull_attribute__ (1)
 __libdw_dieabbrev (Dwarf_Die *die, const unsigned char **readp)
 {
+  if (unlikely (die->cu == NULL))
+    {
+      die->abbrev = DWARF_END_ABBREV;
+      return DWARF_END_ABBREV;
+    }
+
+  rwlock_wrlock (die->cu->abbrev_lock);
+
   /* Do we need to get the abbreviation, or need to read after the code?  */
   if (die->abbrev == NULL || readp != NULL)
     {
       /* Get the abbreviation code.  */
       unsigned int code;
       const unsigned char *addr = die->addr;
-      if (unlikely (die->cu == NULL
-		    || addr >= (const unsigned char *) die->cu->endp))
-	return die->abbrev = DWARF_END_ABBREV;
+
+      if (addr >= (const unsigned char *) die->cu->endp)
+	{
+	  die->abbrev = DWARF_END_ABBREV;
+	  rwlock_unlock (die->cu->abbrev_lock);
+	  return DWARF_END_ABBREV;
+	}
+
       get_uleb128 (code, addr, die->cu->endp);
       if (readp != NULL)
 	*readp = addr;
@@ -821,7 +834,9 @@ __libdw_dieabbrev (Dwarf_Die *die, const unsigned char **readp)
       if (die->abbrev == NULL)
 	die->abbrev = __libdw_findabbrev (die->cu, code);
     }
-  return die->abbrev;
+
+  rwlock_unlock (die->cu->abbrev_lock);
+  return (Dwarf_Abbrev *) die->abbrev;
 }
 
 /* Helper functions for form handling.  */