svn commit: r360979 - head/lib/librtld_db

[Mark Johnston]

Author: markj
Date: Tue May 12 17:00:47 2020
New Revision: 360979
URL: https://svnweb.freebsd.org/changeset/base/360979

Log:
  librtld_db: Fix shlib mapping offsets.
  
  kve_offset gives the offset into the backing file, which is not what we
  want since different segments may map the same page.  Use the base of
  the mapping to determine the offset exported by librtld_db instead.
  
  PR:		244732
  Reported by:	Jenkins, Nicolò Mazzucato <nicomazz97 at gmail.com>
  MFC after:	2 weeks
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/lib/librtld_db/rtld_db.c

Modified: head/lib/librtld_db/rtld_db.c
==============================================================================
--- head/lib/librtld_db/rtld_db.c	Tue May 12 17:00:23 2020	(r360978)
+++ head/lib/librtld_db/rtld_db.c	Tue May 12 17:00:47 2020	(r360979)
@@ -160,9 +160,12 @@ rd_err_e
 rd_loadobj_iter(rd_agent_t *rdap, rl_iter_f *cb, void *clnt_data)
 {
 	struct kinfo_vmentry *kves, *kve;
+	const char *path;
+	uint64_t fileid;
 	rd_loadobj_t rdl;
 	rd_err_e ret;
-	int cnt, i, lastvn;
+	uintptr_t base;
+	int cnt, i;
 
 	DPRINTF("%s\n", __func__);
 
@@ -171,27 +174,38 @@ rd_loadobj_iter(rd_agent_t *rdap, rl_iter_f *cb, void 
 		return (RD_ERR);
 	}
 
+	base = 0;
+	fileid = 0;
+	path = NULL;
 	ret = RD_OK;
-	lastvn = 0;
 	for (i = 0; i < cnt; i++) {
-		kve = kves + i;
-		if (kve->kve_type == KVME_TYPE_VNODE)
-			lastvn = i;
+		kve = &kves[i];
+		/*
+		 * Cache the base offset of the file mapping.  The kve_offset
+		 * field gives the file offset of a particular mapping into the
+		 * file, but we want the mapping offset relative to the base
+		 * mapping.
+		 */
+		if (kve->kve_type == KVME_TYPE_VNODE &&
+		    kve->kve_vn_fileid != fileid) {
+			base = kve->kve_start;
+			fileid = kve->kve_vn_fileid;
+			path = kve->kve_path;
+		}
 		memset(&rdl, 0, sizeof(rdl));
 		/*
 		 * Map the kinfo_vmentry struct to the rd_loadobj structure.
 		 */
 		rdl.rdl_saddr = kve->kve_start;
 		rdl.rdl_eaddr = kve->kve_end;
-		rdl.rdl_offset = kve->kve_offset;
+		rdl.rdl_offset = kve->kve_start - base;
 		if (kve->kve_protection & KVME_PROT_READ)
 			rdl.rdl_prot |= RD_RDL_R;
 		if (kve->kve_protection & KVME_PROT_WRITE)
 			rdl.rdl_prot |= RD_RDL_W;
 		if (kve->kve_protection & KVME_PROT_EXEC)
 			rdl.rdl_prot |= RD_RDL_X;
-		strlcpy(rdl.rdl_path, kves[lastvn].kve_path,
-		    sizeof(rdl.rdl_path));
+		strlcpy(rdl.rdl_path, path, sizeof(rdl.rdl_path));
 		if ((*cb)(&rdl, clnt_data) != 0) {
 			ret = RD_ERR;
 			break;