Read ldcache at construction instead of on each locate call

This change udpates the ldcache locator to read the ldcache at construction
and use these contents to perform future lookups against. Each of the cache
entries are resolved and lookups return the resolved target.

Assuming a symlink chain: libcuda.so -> libcuda.so.1 -> libcuda.so.VERSION, this
means that libcuda.so.VERION will be returned for any of the following inputs:
libcuda.so, libcuda.so.1, libcudal.so.*.

Signed-off-by: Evan Lezar <[email protected]>

Author: elezar

internal/ldcache/ldcache.go

@@ -22,15 +22,12 @@ import (
 	"bytes"
 	"encoding/binary"
 	"errors"
-	"fmt"
 	"os"
 	"path/filepath"
-	"strings"
 	"syscall"
 	"unsafe"
 
 	"github.com/NVIDIA/nvidia-container-toolkit/internal/logger"
-	"github.com/NVIDIA/nvidia-container-toolkit/internal/lookup/symlinks"
 )
 
 const ldcachePath = "/etc/ld.so.cache"
@@ -82,10 +79,9 @@ type entry2 struct {
 
 // LDCache represents the interface for performing lookups into the LDCache
 //
-//go:generate moq -out ldcache_mock.go . LDCache
+//go:generate moq -rm -out ldcache_mock.go . LDCache
 type LDCache interface {
 	List() ([]string, []string)
-	Lookup(...string) ([]string, []string)
 }
 
 type ldcache struct {
@@ -105,14 +101,7 @@ func New(logger logger.Interface, root string) (LDCache, error) {
 
 	logger.Debugf("Opening ld.conf at %v", path)
 	f, err := os.Open(path)
-	if os.IsNotExist(err) {
-		logger.Warningf("Could not find ld.so.cache at %v; creating empty cache", path)
-		e := &empty{
-			logger: logger,
-			path:   path,
-		}
-		return e, nil
-	} else if err != nil {
+	if err != nil {
 		return nil, err
 	}
 	defer f.Close()
@@ -196,7 +185,7 @@ type entry struct {
 }
 
 // getEntries returns the entires of the ldcache in a go-friendly struct.
-func (c *ldcache) getEntries(selected func(string) bool) []entry {
+func (c *ldcache) getEntries() []entry {
 	var entries []entry
 	for _, e := range c.entries {
 		bits := 0
@@ -223,9 +212,6 @@ func (c *ldcache) getEntries(selected func(string) bool) []entry {
 			c.logger.Debugf("Skipping invalid lib")
 			continue
 		}
-		if !selected(lib) {
-			continue
-		}
 		value := bytesToString(c.libs[e.Value:])
 		if value == "" {
 			c.logger.Debugf("Skipping invalid value for lib %v", lib)
@@ -236,51 +222,19 @@ func (c *ldcache) getEntries(selected func(string) bool) []entry {
 			bits:    bits,
 			value:   value,
 		}
-
 		entries = append(entries, e)
 	}
-
 	return entries
 }
 
 // List creates a list of libraries in the ldcache.
 // The 32-bit and 64-bit libraries are returned separately.
 func (c *ldcache) List() ([]string, []string) {
-	all := func(s string) bool { return true }
-
-	return c.resolveSelected(all)
-}
-
-// Lookup searches the ldcache for the specified prefixes.
-// The 32-bit and 64-bit libraries matching the prefixes are returned.
-func (c *ldcache) Lookup(libPrefixes ...string) ([]string, []string) {
-	c.logger.Debugf("Looking up %v in cache", libPrefixes)
-
-	// We define a functor to check whether a given library name matches any of the prefixes
-	matchesAnyPrefix := func(s string) bool {
-		for _, p := range libPrefixes {
-			if strings.HasPrefix(s, p) {
-				return true
-			}
-		}
-		return false
-	}
-
-	return c.resolveSelected(matchesAnyPrefix)
-}
-
-// resolveSelected process the entries in the LDCach based on the supplied filter and returns the resolved paths.
-// The paths are separated by bittage.
-func (c *ldcache) resolveSelected(selected func(string) bool) ([]string, []string) {
 	paths := make(map[int][]string)
 	processed := make(map[string]bool)
 
-	for _, e := range c.getEntries(selected) {
-		path, err := c.resolve(e.value)
-		if err != nil {
-			c.logger.Debugf("Could not resolve entry: %v", err)
-			continue
-		}
+	for _, e := range c.getEntries() {
+		path := filepath.Join(c.root, e.value)
 		if processed[path] {
 			continue
 		}
@@ -291,29 +245,6 @@ func (c *ldcache) resolveSelected(selected func(string) bool) ([]string, []strin
 	return paths[32], paths[64]
 }
 
-// resolve resolves the specified ldcache entry based on the value being processed.
-// The input is the name of the entry in the cache.
-func (c *ldcache) resolve(target string) (string, error) {
-	name := filepath.Join(c.root, target)
-
-	c.logger.Debugf("checking %v", name)
-
-	link, err := symlinks.Resolve(name)
-	if err != nil {
-		return "", fmt.Errorf("failed to resolve symlink: %v", err)
-	}
-	if link == name {
-		return name, nil
-	}
-
-	// We return absolute paths for all targets
-	if !filepath.IsAbs(link) || strings.HasPrefix(link, ".") {
-		link = filepath.Join(filepath.Dir(target), link)
-	}
-
-	return c.resolve(link)
-}
-
 // bytesToString converts a byte slice to a string.
 // This assumes that the byte slice is null-terminated
 func bytesToString(value []byte) string {

internal/ldcache/ldcache_mock.go

@@ -0,0 +1,118 @@
+/**
+# Copyright 2024 NVIDIA CORPORATION
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package lookup
+
+import (
+	"fmt"
+	"path/filepath"
+	"slices"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/ldcache"
+)
+
+type ldcacheLocator struct {
+	*builder
+	resolvesTo map[string]string
+}
+
+var _ Locator = (*ldcacheLocator)(nil)
+
+func NewLdcacheLocator(opts ...Option) Locator {
+	b := newBuilder(opts...)
+
+	cache, err := ldcache.New(b.logger, b.root)
+	if err != nil {
+		b.logger.Warningf("Failed to load ldcache: %v", err)
+		if b.isOptional {
+			return &null{}
+		}
+		return &notFound{}
+	}
+
+	chain := NewSymlinkChainLocator(WithOptional(true))
+
+	resolvesTo := make(map[string]string)
+	_, libs64 := cache.List()
+	for _, library := range libs64 {
+		if _, processed := resolvesTo[library]; processed {
+			continue
+		}
+		candidates, err := chain.Locate(library)
+		if err != nil {
+			b.logger.Errorf("error processing library %s from ldcache: %v", library, err)
+			continue
+		}
+
+		if len(candidates) == 0 {
+			resolvesTo[library] = library
+			continue
+		}
+
+		// candidates represents a symlink chain.
+		// The first element represents the start of the chain and the last
+		// element the final target.
+		target := candidates[len(candidates)-1]
+		for _, candidate := range candidates {
+			resolvesTo[candidate] = target
+		}
+	}
+
+	return &ldcacheLocator{
+		builder:    b,
+		resolvesTo: resolvesTo,
+	}
+}
+
+// Locate finds the specified libraryname.
+// If the input is a library name, the ldcache is searched otherwise the
+// provided path is resolved as a symlink.
+func (l ldcacheLocator) Locate(libname string) ([]string, error) {
+	var matcher func(string, string) bool
+
+	if filepath.IsAbs(libname) {
+		matcher = func(p string, c string) bool {
+			m, _ := filepath.Match(filepath.Join(l.root, p), c)
+			return m
+		}
+	} else {
+		matcher = func(p string, c string) bool {
+			m, _ := filepath.Match(p, filepath.Base(c))
+			return m
+		}
+	}
+
+	var matches []string
+	seen := make(map[string]bool)
+	for name, target := range l.resolvesTo {
+		if !matcher(libname, name) {
+			continue
+		}
+		if seen[target] {
+			continue
+		}
+		seen[target] = true
+		matches = append(matches, target)
+	}
+
+	slices.Sort(matches)
+
+	if len(matches) == 0 && !l.isOptional {
+		return nil, fmt.Errorf("%s: %w", libname, ErrNotFound)
+	}
+
+	return matches, nil
+}

internal/lookup/ldcache.go

@@ -28,22 +28,40 @@ func TestLDCacheLookup(t *testing.T) {
 			expectedError: ErrNotFound,
 		},
 		{
-			rootFs:   "rootfs-1",
-			inputs:   []string{"libcuda.so.1", "libcuda.so.*", "libcuda.so.*.*", "libcuda.so.999.88.77"},
+			rootFs: "rootfs-1",
+			inputs: []string{
+				"libcuda.so.1",
+				"libcuda.so.*",
+				"libcuda.so.*.*",
+				"libcuda.so.999.88.77",
+				"/lib/x86_64-linux-gnu/libcuda.so.1",
+				"/lib/x86_64-linux-gnu/libcuda.so.*",
+				"/lib/x86_64-linux-gnu/libcuda.so.*.*",
+				"/lib/x86_64-linux-gnu/libcuda.so.999.88.77",
+			},
 			expected: "/lib/x86_64-linux-gnu/libcuda.so.999.88.77",
 		},
 		{
-			rootFs:   "rootfs-2",
-			inputs:   []string{"libcuda.so.1", "libcuda.so.*", "libcuda.so.*.*", "libcuda.so.999.88.77"},
+			rootFs: "rootfs-2",
+			inputs: []string{
+				"libcuda.so.1",
+				"libcuda.so.*",
+				"libcuda.so.*.*",
+				"libcuda.so.999.88.77",
+				"/var/lib/nvidia/lib64/libcuda.so.1",
+				"/var/lib/nvidia/lib64/libcuda.so.*",
+				"/var/lib/nvidia/lib64/libcuda.so.*.*",
+				"/var/lib/nvidia/lib64/libcuda.so.999.88.77",
+			},
 			expected: "/var/lib/nvidia/lib64/libcuda.so.999.88.77",
 		},
 	}
 
 	for _, tc := range testCases {
 		for _, input := range tc.inputs {
-			t.Run(tc.rootFs+input, func(t *testing.T) {
+			t.Run(tc.rootFs+" "+input, func(t *testing.T) {
 				rootfs := filepath.Join(moduleRoot, "testdata", "lookup", tc.rootFs)
-				l := newLdcacheLocator(
+				l := NewLdcacheLocator(
 					WithLogger(logger),
 					WithRoot(rootfs),
 				)