From 35e1f2fc7324fd7d656f55395f87646b1f558105 Mon Sep 17 00:00:00 2001
From: Denys Vlasenko <dvlasenk@redhat.com>
Date: Sun, 7 May 2023 17:43:27 +0200
Subject: [PATCH] modalias.prov: speed up, explain  and make more correct
 combining code

The time to run on tests/* data decreased from 34.517s to 30.201s.

Do not allow combining of any glob meta characters, either in first
or second line.

The code is still buggy, it may attempt to combine
    modalias(abc[def]123)
    modalias(abc[dXf]123)
into
    modalias(abc[d[eX]f]123)
(presumably there won't be any such cases in real modules, but still).

Eliminate "| head -n1" - do it with bash string ops.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
---
 modalias.prov | 60 ++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 40 insertions(+), 20 deletions(-)

diff --git a/modalias.prov b/modalias.prov
index f362fd3..525e1df 100755
--- a/modalias.prov
+++ b/modalias.prov
@@ -51,7 +51,7 @@ print_modaliases() {
 # replace with
 # modalias(pci:v0000168Cd0000002[3479]sv*sd*bc*sc*i*)
 combine_modaliases() {
-    local unused_len tag class variants="" pos="" n
+    local unused_len tag class variants="" pos="" n end xc
 
     # Due to set -e, we can exit with exitcode 1 on read EOF
     # and this makes our caller think we failed. "|| return 0" prevents this:
@@ -59,26 +59,44 @@ combine_modaliases() {
 
     # For each line after the first...
     while IFS=' ' read unused_len tag; do
-	# For each char in prev line...
-	for ((n=0; n<${#class}; n++)); do
-	    # If aaaNbbb = aaaMbbb and N isn't "*"
-	    # and N's position is the same as last time...
-	    if [ "*" != "${class:n:1}" -a \
-		 "${class:0:n}" = "${tag:0:n}" -a \
-		 "${class:n+1}" = "${tag:n+1}" ] &&
-	       [ -z "$pos" -o "$n" = "$pos" ]; then
-		# Add M (and maybe N) to $variants, go to next line
-		variants="${variants:-${class:n:1}}${tag:n:1}"
-		pos=$n
+	if [ -z "$pos" ]; then
+	    # 2nd line: after "modalias(" prefix, for each char in prev line...
+	    n=9
+	    end=${#class}
+	else
+	    # 3rd+ lines: only check the char at the same position
+	    n=$pos
+	    end=$((pos + 1))
+	fi
+	# Search for aaaNbbb,aaaMbbb line pair, where N and M chars differ.
+	# sort -u guarantees there are no identical line pairs.
+	# We assume that lines will not differ only in " = version" suffix.
+	for ((; n < $end; n++)); do
+	    if [ "${class:0:n}" != "${tag:0:n}" ]; then
+		# the prefixes already aren't the same: break
+		n=$end
 		break
 	    fi
+	    # If suffixes differ, go to next char
+	    [ x"${class:n+1}" != x"${tag:n+1}" ] && continue
+	    # aaaNbbb = aaaMbbb. If N and M aren't special...
+	    xc=x"${class:n:1}"
+	    [ x"[" = "$xc" -o x"]" = "$xc" ] && continue
+	    [ x"?" = "$xc" -o x"*" = "$xc" ] && continue
+	    xc=x"${tag:n:1}"
+	    [ x"[" = "$xc" -o x"]" = "$xc" ] && continue
+	    [ x"?" = "$xc" -o x"*" = "$xc" ] && continue
+	    # Add M (and maybe N) to $variants, go to next line
+	    variants="${variants:-${class:n:1}}${tag:n:1}"
+	    pos=$n
+	    break
 	done
-	if [ $n -eq ${#class} ]; then
-	    # This line is not mergeable, print collected merged line
-	    # and reset the state
+	if [ $n -eq $end ]; then
+	    # This line is not mergeable with the previous one(s),
+	    # print collected merged line and reset the state
 	    print_modaliases "$class" "$variants" "$pos"
-	    variants=
-	    pos=
+	    variants=""
+	    pos=""
 	    class=$tag
 	fi
     done
@@ -87,10 +105,12 @@ combine_modaliases() {
 }
 
 for module in $(grep -E '/lib/modules/.+\.ko(\.gz|\.bz2|\.xz|\.zst)?$') "$@"; do
-    # | head -n1 because some modules have *two* version tags. *cough*b44*cough*
-    modver=$(/sbin/modinfo -F version "$module"| head -n1)
+    modver=$(/sbin/modinfo -F version "$module")
+    # delete possible extra lines because some modules have *two* version tags. *cough*b44*cough*
+    modver=${modver%%$'\n'*}    # using $'' bashism, avoid running "head -n1" process
+    # replace any strange chars with underscores.
     modver=${modver//[^0-9a-zA-Z._]/_}
-    # only add version tag if it has a version
+    # only add version tag if it indeed has a version
     [ -z "$modver" ] || modver=" = $modver"
 
     /sbin/modinfo -F alias "$module" \