Merge "libstore: Create platform LocalStore subclasses" into main

12 files changed, 268 insertions, 119 deletions

diff --git a/src/libstore/gc-store.hh b/src/libstore/gc-store.hh
index ab1059fb1..88c997247 100644
--- a/src/libstore/gc-store.hh
+++ b/src/libstore/gc-store.hh
@@ -7,7 +7,14 @@
 namespace nix {
 
 
+/**
+ * Garbage-collector roots, referring to a store path
+ */
 typedef std::unordered_map<StorePath, std::unordered_set<std::string>> Roots;
+/**
+ * Possible garbage collector roots, referring to any path
+ */
+typedef std::unordered_map<Path, std::unordered_set<std::string>> UncheckedRoots;
 
 
 struct GCOptions
diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 20519c1a2..535bbd251 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -321,105 +321,8 @@ Roots LocalStore::findRoots(bool censor)
     return roots;
 }
 
-typedef std::unordered_map<Path, std::unordered_set<std::string>> UncheckedRoots;
-
-static void readProcLink(const std::string & file, UncheckedRoots & roots)
-{
-    constexpr auto bufsiz = PATH_MAX;
-    char buf[bufsiz];
-    auto res = readlink(file.c_str(), buf, bufsiz);
-    if (res == -1) {
-        if (errno == ENOENT || errno == EACCES || errno == ESRCH)
-            return;
-        throw SysError("reading symlink");
-    }
-    if (res == bufsiz) {
-        throw Error("overly long symlink starting with '%1%'", std::string_view(buf, bufsiz));
-    }
-    if (res > 0 && buf[0] == '/')
-        roots[std::string(static_cast<char *>(buf), res)]
-            .emplace(file);
-}
-
-static std::string quoteRegexChars(const std::string & raw)
-{
-    static auto specialRegex = std::regex(R"([.^$\\*+?()\[\]{}|])");
-    return std::regex_replace(raw, specialRegex, R"(\$&)");
-}
-
-#if __linux__
-static void readFileRoots(const char * path, UncheckedRoots & roots)
+void LocalStore::findPlatformRoots(UncheckedRoots & unchecked)
 {
-    try {
-        roots[readFile(path)].emplace(path);
-    } catch (SysError & e) {
-        if (e.errNo != ENOENT && e.errNo != EACCES)
-            throw;
-    }
-}
-#endif
-
-void LocalStore::findRuntimeRoots(Roots & roots, bool censor)
-{
-    UncheckedRoots unchecked;
-
-    auto procDir = AutoCloseDir{opendir("/proc")};
-    if (procDir) {
-        struct dirent * ent;
-        auto digitsRegex = std::regex(R"(^\d+$)");
-        auto mapRegex = std::regex(R"(^\s*\S+\s+\S+\s+\S+\s+\S+\s+\S+\s+(/\S+)\s*$)");
-        auto storePathRegex = std::regex(quoteRegexChars(storeDir) + R"(/[0-9a-z]+[0-9a-zA-Z\+\-\._\?=]*)");
-        while (errno = 0, ent = readdir(procDir.get())) {
-            checkInterrupt();
-            if (std::regex_match(ent->d_name, digitsRegex)) {
-                try {
-                    readProcLink(fmt("/proc/%s/exe" ,ent->d_name), unchecked);
-                    readProcLink(fmt("/proc/%s/cwd", ent->d_name), unchecked);
-
-                    auto fdStr = fmt("/proc/%s/fd", ent->d_name);
-                    auto fdDir = AutoCloseDir(opendir(fdStr.c_str()));
-                    if (!fdDir) {
-                        if (errno == ENOENT || errno == EACCES)
-                            continue;
-                        throw SysError("opening %1%", fdStr);
-                    }
-                    struct dirent * fd_ent;
-                    while (errno = 0, fd_ent = readdir(fdDir.get())) {
-                        if (fd_ent->d_name[0] != '.')
-                            readProcLink(fmt("%s/%s", fdStr, fd_ent->d_name), unchecked);
-                    }
-                    if (errno) {
-                        if (errno == ESRCH)
-                            continue;
-                        throw SysError("iterating /proc/%1%/fd", ent->d_name);
-                    }
-                    fdDir.reset();
-
-                    auto mapFile = fmt("/proc/%s/maps", ent->d_name);
-                    auto mapLines = tokenizeString<std::vector<std::string>>(readFile(mapFile), "\n");
-                    for (const auto & line : mapLines) {
-                        auto match = std::smatch{};
-                        if (std::regex_match(line, match, mapRegex))
-                            unchecked[match[1]].emplace(mapFile);
-                    }
-
-                    auto envFile = fmt("/proc/%s/environ", ent->d_name);
-                    auto envString = readFile(envFile);
-                    auto env_end = std::sregex_iterator{};
-                    for (auto i = std::sregex_iterator{envString.begin(), envString.end(), storePathRegex}; i != env_end; ++i)
-                        unchecked[i->str()].emplace(envFile);
-                } catch (SysError & e) {
-                    if (errno == ENOENT || errno == EACCES || errno == ESRCH)
-                        continue;
-                    throw;
-                }
-            }
-        }
-        if (errno)
-            throw SysError("iterating /proc");
-    }
-
-#if !defined(__linux__)
     // lsof is really slow on OS X. This actually causes the gc-concurrent.sh test to fail.
     // See: https://github.com/NixOS/nix/issues/3011
     // Because of this we disable lsof when running the tests.
@@ -437,13 +340,13 @@ void LocalStore::findRuntimeRoots(Roots & roots, bool censor)
             /* lsof not installed, lsof failed */
         }
     }
-#endif
+}
+
+void LocalStore::findRuntimeRoots(Roots & roots, bool censor)
+{
+    UncheckedRoots unchecked;
 
-#if __linux__
-    readFileRoots("/proc/sys/kernel/modprobe", unchecked);
-    readFileRoots("/proc/sys/kernel/fbsplash", unchecked);
-    readFileRoots("/proc/sys/kernel/poweroff_cmd", unchecked);
-#endif
+    findPlatformRoots(unchecked);
 
     for (auto & [target, links] : unchecked) {
         if (!isInStore(target)) continue;
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index f252b449c..2f59b3591 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -1940,6 +1940,4 @@ std::optional<std::string> LocalStore::getVersion()
     return nixVersion;
 }
 
-static RegisterStoreImplementation<LocalStore, LocalStoreConfig> regLocalStore;
-
 }  // namespace nix
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index fe26a0f27..b8d1f02ab 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -127,26 +127,35 @@ private:
 
     const PublicKeys & getPublicKeys();
 
-public:
-
-    /**
-     * Hack for build-remote.cc.
-     */
-    PathSet locksHeld;
+protected:
 
     /**
      * Initialise the local store, upgrading the schema if
      * necessary.
+     * Protected so that users don't accidentally create a LocalStore
+     * instead of a platform's subclass.
      */
     LocalStore(const Params & params);
     LocalStore(std::string scheme, std::string path, const Params & params);
 
-    ~LocalStore();
+public:
+
+    /**
+     * Hack for build-remote.cc.
+     */
+    PathSet locksHeld;
+
+    virtual ~LocalStore();
 
     static std::set<std::string> uriSchemes()
     { return {}; }
 
     /**
+     * Create a LocalStore, possibly a platform-specific subclass
+     */
+    static std::shared_ptr<LocalStore> makeLocalStore(const Params & params);
+
+    /**
      * Implementations of abstract store API methods.
      */
 
@@ -330,6 +339,12 @@ private:
 
     void findRootsNoTemp(Roots & roots, bool censor);
 
+    /**
+     * Find possible garbage collector roots in a platform-specific manner,
+     * e.g. by looking in `/proc` or using `lsof`
+     */
+    virtual void findPlatformRoots(UncheckedRoots & unchecked);
+
     void findRuntimeRoots(Roots & roots, bool censor);
 
     std::pair<Path, AutoCloseFD> createTempDirInStore();
diff --git a/src/libstore/local.mk b/src/libstore/local.mk
index 68ccdc409..6bd73965d 100644
--- a/src/libstore/local.mk
+++ b/src/libstore/local.mk
@@ -5,6 +5,11 @@ libstore_NAME = libnixstore
 libstore_DIR := $(d)
 
 libstore_SOURCES := $(wildcard $(d)/*.cc $(d)/builtins/*.cc $(d)/build/*.cc)
+ifdef HOST_LINUX
+libstore_SOURCES += $(d)/platform/linux.cc
+else
+libstore_SOURCES += $(d)/platform/fallback.cc
+endif
 
 libstore_LIBS = libutil
 
diff --git a/src/libstore/meson.build b/src/libstore/meson.build
index a6d7e6d56..94471dc29 100644
--- a/src/libstore/meson.build
+++ b/src/libstore/meson.build
@@ -66,6 +66,7 @@ libstore_sources = files(
   'path-with-outputs.cc',
   'path.cc',
   'pathlocks.cc',
+  'platform.cc',
   'profiles.cc',
   'realisation.cc',
   'remote-fs-accessor.cc',
@@ -158,6 +159,14 @@ libstore_headers = files(
   'worker-protocol.hh',
 )
 
+if host_machine.system() == 'linux'
+  libstore_sources += files('platform/linux.cc')
+  libstore_headers += files('platform/linux.hh')
+else
+  libstore_sources += files('platform/fallback.cc')
+  libstore_headers += files('platform/fallback.hh')
+endif
+
 # These variables (aside from LSOF) are created pseudo-dynamically, near the beginning of
 # the top-level meson.build. Aside from prefix itself, each of these was
 # made into an absolute path by joining it with prefix, unless it was already
diff --git a/src/libstore/platform.cc b/src/libstore/platform.cc
new file mode 100644
index 000000000..9c389ef55
--- /dev/null
+++ b/src/libstore/platform.cc
@@ -0,0 +1,18 @@
+#include "local-store.hh"
+
+#if __linux__
+#include "platform/linux.hh"
+#else
+#include "platform/fallback.hh"
+#endif
+
+namespace nix {
+std::shared_ptr<LocalStore> LocalStore::makeLocalStore(const Params & params)
+{
+#if __linux__
+    return std::shared_ptr<LocalStore>(new LinuxLocalStore(params));
+#else
+    return std::shared_ptr<LocalStore>(new FallbackLocalStore(params));
+#endif
+}
+}
diff --git a/src/libstore/platform/fallback.cc b/src/libstore/platform/fallback.cc
new file mode 100644
index 000000000..5a01d64c8
--- /dev/null
+++ b/src/libstore/platform/fallback.cc
@@ -0,0 +1,5 @@
+#include "platform/fallback.hh"
+
+namespace nix {
+static RegisterStoreImplementation<FallbackLocalStore, LocalStoreConfig> regLocalStore;
+}
diff --git a/src/libstore/platform/fallback.hh b/src/libstore/platform/fallback.hh
new file mode 100644
index 000000000..fd27edbe6
--- /dev/null
+++ b/src/libstore/platform/fallback.hh
@@ -0,0 +1,31 @@
+#pragma once
+///@file
+
+#include "local-store.hh"
+
+namespace nix {
+
+/**
+ * Fallback platform implementation of LocalStore
+ * Exists so we can make LocalStore constructor protected
+ */
+class FallbackLocalStore : public LocalStore
+{
+public:
+    FallbackLocalStore(const Params & params)
+        : StoreConfig(params)
+        , LocalFSStoreConfig(params)
+        , LocalStoreConfig(params)
+        , Store(params)
+        , LocalFSStore(params)
+        , LocalStore(params)
+    {
+    }
+    FallbackLocalStore(const std::string scheme, std::string path, const Params & params)
+        : FallbackLocalStore(params)
+    {
+        throw UnimplementedError("FallbackLocalStore");
+    }
+};
+
+}
diff --git a/src/libstore/platform/linux.cc b/src/libstore/platform/linux.cc
new file mode 100644
index 000000000..9be3e47da
--- /dev/null
+++ b/src/libstore/platform/linux.cc
@@ -0,0 +1,123 @@
+#include "gc-store.hh"
+#include "signals.hh"
+#include "platform/linux.hh"
+
+#include <regex>
+
+namespace nix {
+static RegisterStoreImplementation<LinuxLocalStore, LocalStoreConfig> regLocalStore;
+
+static void readProcLink(const std::string & file, UncheckedRoots & roots)
+{
+    constexpr auto bufsiz = PATH_MAX;
+    char buf[bufsiz];
+    auto res = readlink(file.c_str(), buf, bufsiz);
+    if (res == -1) {
+        if (errno == ENOENT || errno == EACCES || errno == ESRCH) {
+            return;
+        }
+        throw SysError("reading symlink");
+    }
+    if (res == bufsiz) {
+        throw Error("overly long symlink starting with '%1%'", std::string_view(buf, bufsiz));
+    }
+    if (res > 0 && buf[0] == '/') {
+        roots[std::string(static_cast<char *>(buf), res)].emplace(file);
+    }
+}
+
+static std::string quoteRegexChars(const std::string & raw)
+{
+    static auto specialRegex = std::regex(R"([.^$\\*+?()\[\]{}|])");
+    return std::regex_replace(raw, specialRegex, R"(\$&)");
+}
+
+static void readFileRoots(const char * path, UncheckedRoots & roots)
+{
+    try {
+        roots[readFile(path)].emplace(path);
+    } catch (SysError & e) {
+        if (e.errNo != ENOENT && e.errNo != EACCES) {
+            throw;
+        }
+    }
+}
+
+void LinuxLocalStore::findPlatformRoots(UncheckedRoots & unchecked)
+{
+    auto procDir = AutoCloseDir{opendir("/proc")};
+    if (procDir) {
+        struct dirent * ent;
+        auto digitsRegex = std::regex(R"(^\d+$)");
+        auto mapRegex = std::regex(R"(^\s*\S+\s+\S+\s+\S+\s+\S+\s+\S+\s+(/\S+)\s*$)");
+        auto storePathRegex =
+            std::regex(quoteRegexChars(storeDir) + R"(/[0-9a-z]+[0-9a-zA-Z\+\-\._\?=]*)");
+        while (errno = 0, ent = readdir(procDir.get())) {
+            checkInterrupt();
+            if (std::regex_match(ent->d_name, digitsRegex)) {
+                try {
+                    readProcLink(fmt("/proc/%s/exe", ent->d_name), unchecked);
+                    readProcLink(fmt("/proc/%s/cwd", ent->d_name), unchecked);
+
+                    auto fdStr = fmt("/proc/%s/fd", ent->d_name);
+                    auto fdDir = AutoCloseDir(opendir(fdStr.c_str()));
+                    if (!fdDir) {
+                        if (errno == ENOENT || errno == EACCES) {
+                            continue;
+                        }
+                        throw SysError("opening %1%", fdStr);
+                    }
+                    struct dirent * fd_ent;
+                    while (errno = 0, fd_ent = readdir(fdDir.get())) {
+                        if (fd_ent->d_name[0] != '.') {
+                            readProcLink(fmt("%s/%s", fdStr, fd_ent->d_name), unchecked);
+                        }
+                    }
+                    if (errno) {
+                        if (errno == ESRCH) {
+                            continue;
+                        }
+                        throw SysError("iterating /proc/%1%/fd", ent->d_name);
+                    }
+                    fdDir.reset();
+
+                    auto mapFile = fmt("/proc/%s/maps", ent->d_name);
+                    auto mapLines =
+                        tokenizeString<std::vector<std::string>>(readFile(mapFile), "\n");
+                    for (const auto & line : mapLines) {
+                        auto match = std::smatch{};
+                        if (std::regex_match(line, match, mapRegex)) {
+                            unchecked[match[1]].emplace(mapFile);
+                        }
+                    }
+
+                    auto envFile = fmt("/proc/%s/environ", ent->d_name);
+                    auto envString = readFile(envFile);
+                    auto env_end = std::sregex_iterator{};
+                    for (auto i =
+                             std::sregex_iterator{
+                                 envString.begin(), envString.end(), storePathRegex
+                             };
+                         i != env_end;
+                         ++i)
+                    {
+                        unchecked[i->str()].emplace(envFile);
+                    }
+                } catch (SysError & e) {
+                    if (errno == ENOENT || errno == EACCES || errno == ESRCH) {
+                        continue;
+                    }
+                    throw;
+                }
+            }
+        }
+        if (errno) {
+            throw SysError("iterating /proc");
+        }
+    }
+
+    readFileRoots("/proc/sys/kernel/modprobe", unchecked);
+    readFileRoots("/proc/sys/kernel/fbsplash", unchecked);
+    readFileRoots("/proc/sys/kernel/poweroff_cmd", unchecked);
+}
+}
diff --git a/src/libstore/platform/linux.hh b/src/libstore/platform/linux.hh
new file mode 100644
index 000000000..8b97e17c5
--- /dev/null
+++ b/src/libstore/platform/linux.hh
@@ -0,0 +1,35 @@
+#pragma once
+///@file
+
+#include "gc-store.hh"
+#include "local-store.hh"
+
+namespace nix {
+
+/**
+ * Linux-specific implementation of LocalStore
+ */
+class LinuxLocalStore : public LocalStore
+{
+public:
+    LinuxLocalStore(const Params & params)
+        : StoreConfig(params)
+        , LocalFSStoreConfig(params)
+        , LocalStoreConfig(params)
+        , Store(params)
+        , LocalFSStore(params)
+        , LocalStore(params)
+    {
+    }
+    LinuxLocalStore(const std::string scheme, std::string path, const Params & params)
+        : LinuxLocalStore(params)
+    {
+        throw UnimplementedError("LinuxLocalStore");
+    }
+
+private:
+
+    void findPlatformRoots(UncheckedRoots & unchecked) override;
+};
+
+}
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 94202d46e..69e89263b 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -1426,7 +1426,7 @@ std::shared_ptr<Store> openFromNonUri(const std::string & uri, const Store::Para
     if (uri == "" || uri == "auto") {
         auto stateDir = getOr(params, "state", settings.nixStateDir);
         if (access(stateDir.c_str(), R_OK | W_OK) == 0)
-            return std::make_shared<LocalStore>(params);
+            return LocalStore::makeLocalStore(params);
         else if (pathExists(settings.nixDaemonSocketFile))
             return std::make_shared<UDSRemoteStore>(params);
         #if __linux__
@@ -1444,26 +1444,26 @@ std::shared_ptr<Store> openFromNonUri(const std::string & uri, const Store::Para
                 try {
                     createDirs(chrootStore);
                 } catch (Error & e) {
-                    return std::make_shared<LocalStore>(params);
+                    return LocalStore::makeLocalStore(params);
                 }
                 warn("'%s' does not exist, so Nix will use '%s' as a chroot store", stateDir, chrootStore);
             } else
                 debug("'%s' does not exist, so Nix will use '%s' as a chroot store", stateDir, chrootStore);
             Store::Params params2;
             params2["root"] = chrootStore;
-            return std::make_shared<LocalStore>(params2);
+            return LocalStore::makeLocalStore(params);
         }
         #endif
         else
-            return std::make_shared<LocalStore>(params);
+            return LocalStore::makeLocalStore(params);
     } else if (uri == "daemon") {
         return std::make_shared<UDSRemoteStore>(params);
     } else if (uri == "local") {
-        return std::make_shared<LocalStore>(params);
+        return LocalStore::makeLocalStore(params);
     } else if (isNonUriPath(uri)) {
         Store::Params params2 = params;
         params2["root"] = absPath(uri);
-        return std::make_shared<LocalStore>(params2);
+        return LocalStore::makeLocalStore(params2);
     } else {
         return nullptr;
     }