git: 105fd928b0b5 - main - libctf: Improve check for duplicate SOU definitions in ctf_add_type()

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=105fd928b0b5b35ab529e5f6914788dc49582901

commit 105fd928b0b5b35ab529e5f6914788dc49582901
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2021-10-04 16:28:22 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2021-10-04 16:28:22 +0000

    libctf: Improve check for duplicate SOU definitions in ctf_add_type()
    
    When copying a struct or union from one CTF container to another,
    ctf_add_type() checks whether it matches an existing type in the
    destination container.  It does so by looking for a type with the same
    name and kind as the new type, and if one exists, it iterates over all
    members of the source type and checks whether a member with matching
    name and offset exists in the matched destination type.  This can
    produce false positives, for example because member types are not
    compared, but this is not expected to arise in practice.  If the match
    fails, ctf_add_type() returns an error.
    
    The procedure used for member comparison breaks down in the face of
    anonymous struct and union members.  ctf_member_iter() visits each
    member in the source definition and looks up the corresponding member in
    the desination definition by name using ctf_member_info(), but this
    function will descend into anonymous members and thus fail to match.
    Fix the problem by introducing a custom comparison routine which does
    not assume member names are unique.  This should also be faster for
    types with many members; in the previous scheme, membcmp() would perform
    a linear scan of the desination type's members to perform a lookup by
    name.  The new routine steps through the members of both types in a
    single loop.
    
    PR:             258763
    MFC after:      2 weeks
    Sponsored by:   The FreeBSD Foundation
---
 cddl/contrib/opensolaris/common/ctf/ctf_create.c | 100 +++++++++++++++++------
 1 file changed, 73 insertions(+), 27 deletions(-)

diff --git a/cddl/contrib/opensolaris/common/ctf/ctf_create.c b/cddl/contrib/opensolaris/common/ctf/ctf_create.c
index ae4cc7f31176..3a080e71baa0 100644
--- a/cddl/contrib/opensolaris/common/ctf/ctf_create.c
+++ b/cddl/contrib/opensolaris/common/ctf/ctf_create.c
@@ -1196,17 +1196,6 @@ enumadd(const char *name, int value, void *arg)
 	    name, value) == CTF_ERR);
 }
 
-/*ARGSUSED*/
-static int
-membcmp(const char *name, ctf_id_t type, ulong_t offset, void *arg)
-{
-	ctf_bundle_t *ctb = arg;
-	ctf_membinfo_t ctm;
-
-	return (ctf_member_info(ctb->ctb_file, ctb->ctb_type,
-	    name, &ctm) == CTF_ERR || ctm.ctm_offset != offset);
-}
-
 static int
 membadd(const char *name, ctf_id_t type, ulong_t offset, void *arg)
 {
@@ -1240,6 +1229,71 @@ membadd(const char *name, ctf_id_t type, ulong_t offset, void *arg)
 	return (0);
 }
 
+static long
+soucmp(ctf_file_t *src_fp, ctf_id_t src_type, ctf_file_t *dst_fp,
+    ctf_id_t dst_type)
+{
+	const struct ctf_type *src_tp, *dst_tp;
+	const char *src_name, *dst_name;
+	ssize_t src_sz, dst_sz, src_inc, dst_inc;
+	uint_t kind, n;
+
+	if ((src_type = ctf_type_resolve(src_fp, src_type)) == CTF_ERR)
+		return (CTF_ERR);
+	if ((dst_type = ctf_type_resolve(dst_fp, dst_type)) == CTF_ERR)
+		return (CTF_ERR);
+
+	if ((src_tp = ctf_lookup_by_id(&src_fp, src_type)) == NULL)
+		return (CTF_ERR);
+	if ((dst_tp = ctf_lookup_by_id(&dst_fp, dst_type)) == NULL)
+		return (CTF_ERR);
+
+	if ((kind = LCTF_INFO_KIND(src_fp, src_tp->ctt_info)) !=
+	    LCTF_INFO_KIND(dst_fp, dst_tp->ctt_info))
+		return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
+	if (kind != CTF_K_STRUCT && kind != CTF_K_UNION)
+		return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
+	if ((n = LCTF_INFO_VLEN(src_fp, src_tp->ctt_info)) !=
+	    LCTF_INFO_VLEN(dst_fp, dst_tp->ctt_info))
+		return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
+
+	(void) ctf_get_ctt_size(src_fp, src_tp, &src_sz, &src_inc);
+	(void) ctf_get_ctt_size(dst_fp, dst_tp, &dst_sz, &dst_inc);
+	if (src_sz != dst_sz || src_inc != dst_inc)
+		return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
+
+	if (src_sz < CTF_LSTRUCT_THRESH) {
+		const ctf_member_t *src_mp, *dst_mp;
+
+		src_mp = (const ctf_member_t *)((uintptr_t)src_tp + src_inc);
+		dst_mp = (const ctf_member_t *)((uintptr_t)dst_tp + dst_inc);
+		for (; n != 0; n--, src_mp++, dst_mp++) {
+			if (src_mp->ctm_offset != dst_mp->ctm_offset)
+				return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
+			src_name = ctf_strptr(src_fp, src_mp->ctm_name);
+			dst_name = ctf_strptr(dst_fp, dst_mp->ctm_name);
+			if (strcmp(src_name, dst_name) != 0)
+				return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
+		}
+	} else {
+		const ctf_lmember_t *src_mp, *dst_mp;
+
+		src_mp = (const ctf_lmember_t *)((uintptr_t)src_tp + src_inc);
+		dst_mp = (const ctf_lmember_t *)((uintptr_t)dst_tp + dst_inc);
+		for (; n != 0; n--, src_mp++, dst_mp++) {
+			if (src_mp->ctlm_offsethi != dst_mp->ctlm_offsethi ||
+			    src_mp->ctlm_offsetlo != dst_mp->ctlm_offsetlo)
+				return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
+			src_name = ctf_strptr(src_fp, src_mp->ctlm_name);
+			dst_name = ctf_strptr(dst_fp, dst_mp->ctlm_name);
+			if (strcmp(src_name, dst_name) != 0)
+				return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
+		}
+	}
+
+	return (0);
+}
+
 /*
  * The ctf_add_type routine is used to copy a type from a source CTF container
  * to a dynamic destination container.  This routine operates recursively by
@@ -1460,23 +1514,15 @@ ctf_add_type(ctf_file_t *dst_fp, ctf_file_t *src_fp, ctf_id_t src_type)
 		ctf_dmdef_t *dmd;
 		int errs = 0;
 
-		/*
-		 * Technically to match a struct or union we need to check both
-		 * ways (src members vs. dst, dst members vs. src) but we make
-		 * this more optimal by only checking src vs. dst and comparing
-		 * the total size of the structure (which we must do anyway)
-		 * which covers the possibility of dst members not in src.
-		 * This optimization can be defeated for unions, but is so
-		 * pathological as to render it irrelevant for our purposes.
-		 */
 		if (dst_type != CTF_ERR && dst_kind != CTF_K_FORWARD) {
-			if (ctf_type_size(src_fp, src_type) !=
-			    ctf_type_size(dst_fp, dst_type))
-				return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
-
-			if (ctf_member_iter(src_fp, src_type, membcmp, &dst))
-				return (ctf_set_errno(dst_fp, ECTF_CONFLICT));
-
+			/*
+			 * Compare the sizes and fields of the two types.
+			 * The field comparisons only check the names and
+			 * offsets, so this is not perfect but is good enough
+			 * for scenarios that we care about.
+			 */
+			if (soucmp(src_fp, src_type, dst_fp, dst_type) != 0)
+				return (CTF_ERR); /* errno is set for us */
 			break;
 		}