libstore: add capnp build request parameter struct to builders

there's nothing in here yet, we'll add that piece by piece.

Change-Id: Ib276d9e8281bb08013197db0f2bbfd8eec76b5ce

lix/libstore/build/local-derivation-goal.cc

@@ -33,7 +33,9 @@
 #include "lix/libutil/thread-name.hh"
 #include "lix/libstore/platform/linux.hh"
 #include "lix/libstore/path-tree.hh"
+#include "request.capnp.h"
 
+#include <capnp/message.h>
 #include <cstddef>
 #include <dirent.h>
 #include <exception>
@@ -921,8 +923,14 @@ try {
         builder = drv->builder;
     }
 
+    capnp::MallocMessageBuilder requestBuilder;
+
+    auto request = requestBuilder.initRoot<build::Request>();
+
+    fillBuilderConfig(request);
+
     /* Fork a child to build the package. */
-    pg = ProcessGroup{startChild(builder, envStrs, args, std::move(builderOut))};
+    pg = ProcessGroup{startChild(request.asReader(), builder, envStrs, args, std::move(builderOut))};
 
     /* Check if setting up the build environment failed. */
     std::vector<std::string> msgs;
@@ -956,7 +964,11 @@ try {
 }
 
 Pid LocalDerivationGoal::startChild(
-    const Path & builder, const Strings & envStrs, const Strings & args, AutoCloseFD logPTY
+    build::Request::Reader request,
+    const Path & builder,
+    const Strings & envStrs,
+    const Strings & args,
+    AutoCloseFD logPTY
 )
 {
     return startProcess([&]() {
@@ -964,7 +976,7 @@ Pid LocalDerivationGoal::startChild(
             throw SysError("failed to redirect build output to log file");
         }
         closeOnExec(STDERR_FILENO, false);
-        runChild(builder, envStrs, args);
+        runChild(request, builder, envStrs, args);
     });
 }
 
@@ -1245,7 +1257,9 @@ static void closeExtraFDs()
     }
 }
 
-void LocalDerivationGoal::runChild(const Path & builder, const Strings & envStrs, const Strings & args)
+void LocalDerivationGoal::runChild(
+    build::Request::Reader request, const Path & builder, const Strings & envStrs, const Strings & args
+)
 {
     /* Warning: in the child we should absolutely not make any SQLite
        calls! */
@@ -1286,7 +1300,7 @@ void LocalDerivationGoal::runChild(const Path & builder, const Strings & envStrs
             throw SysError("cannot dup null device into stdin");
         }
 
-        const bool setUser = prepareChildSetup();
+        const bool setUser = prepareChildSetup(request);
 
         if (sys::chdir(tmpDirInSandbox) == -1) {
             throw SysError("changing into '%1%'", tmpDir);
@@ -1328,7 +1342,7 @@ void LocalDerivationGoal::runChild(const Path & builder, const Strings & envStrs
                 throw SysError("setuid failed");
         }
 
-        finishChildSetup();
+        finishChildSetup(request);
 
         /* Indicate that we managed to set up the build environment. */
         writeFull(STDERR_FILENO, std::string("\2\n"));
@@ -1336,7 +1350,7 @@ void LocalDerivationGoal::runChild(const Path & builder, const Strings & envStrs
         sendException = false;
 
         /* Execute the program.  This should not return. */
-        execBuilder(builder, args, envStrs);
+        execBuilder(request, builder, args, envStrs);
 
         throw SysError("executing '%1%'", drv->builder);
 
@@ -1352,7 +1366,9 @@ void LocalDerivationGoal::runChild(const Path & builder, const Strings & envStrs
     }
 }
 
-void LocalDerivationGoal::execBuilder(std::string builder, Strings args, Strings envStrs)
+void LocalDerivationGoal::execBuilder(
+    build::Request::Reader request, std::string builder, Strings args, Strings envStrs
+)
 {
     sys::execve(builder, args, envStrs);
 }

lix/libstore/build/local-derivation-goal.hh

@@ -2,6 +2,7 @@
 ///@file
 
 #include "lix/libstore/build/derivation-goal.hh"
+#include "lix/libstore/build/request.capnp.h"
 #include "lix/libstore/local-store.hh"
 #include "lix/libutil/error.hh"
 #include "lix/libutil/processes.hh"
@@ -209,7 +210,9 @@ struct LocalDerivationGoal : public DerivationGoal
     /**
      * Run the builder's process.
      */
-    void runChild(const Path & builder, const Strings & envStrs, const Strings & args);
+    void runChild(
+        build::Request::Reader request, const Path & builder, const Strings & envStrs, const Strings & args
+    );
 
     /**
      * Check that the derivation outputs all exist and register them
@@ -291,12 +294,19 @@ protected:
      * Create a new process that runs `openSlave` and `runChild`
      * On some platforms this process is created with sandboxing flags.
      */
-    virtual Pid
-    startChild(const Path & builder, const Strings & envStrs, const Strings & args, AutoCloseFD logPTY);
+    virtual Pid startChild(
+        build::Request::Reader request,
+        const Path & builder,
+        const Strings & envStrs,
+        const Strings & args,
+        AutoCloseFD logPTY
+    );
 
     kj::Promise<Result<WorkResult>> handleRawChild() noexcept;
     kj::Promise<Result<std::optional<WorkResult>>> handleRawChildStream() noexcept;
 
+    virtual void fillBuilderConfig(build::Request::Builder request) {}
+
     /**
      * Prepare the sandbox. Currently only used on linux to build the sandbox namespace,
      * write configuration files inside it, and to set up networking with pasta enabled.
@@ -304,7 +314,7 @@ protected:
      * `false` if this step has changed our credentials to the build user/group already.
      */
     [[nodiscard]]
-    virtual bool prepareChildSetup()
+    virtual bool prepareChildSetup(build::Request::Reader request)
     {
         return true;
     }
@@ -312,7 +322,7 @@ protected:
     /**
      * Finish sandbox setup and prepare for actually executing the builder processes.
      */
-    virtual void finishChildSetup() {}
+    virtual void finishChildSetup(build::Request::Reader request) {}
 
     /**
      * Create a special accessor that can access paths that were built within the sandbox's
@@ -327,7 +337,8 @@ protected:
      * Execute the builder, replacing the current process.
      * Generally this means an `execve` call.
      */
-    virtual void execBuilder(std::string builder, Strings args, Strings envStrs);
+    virtual void
+    execBuilder(build::Request::Reader request, std::string builder, Strings args, Strings envStrs);
 
     /**
      * Whether derivation can be built on current platform with `uid-range` feature

lix/libstore/build/meson.build

@@ -1,21 +1,26 @@
-libstore_rpc += custom_target(
-  command : [
-    capnpc_wrapper,
-    '--language=c++',
-    '--src-prefix=@CURRENT_SOURCE_DIR@',
-    '--outdir=@OUTDIR@',
-    '--depfile=@DEPFILE@',
-    '-I@SOURCE_ROOT@',
-    '@INPUT@',
-  ],
-  input : files(
-    # keep-sorted start
-    'hook-instance.capnp',
-    # keep-sorted end
-  ),
-  output : [
-    '@PLAINNAME@.h',
-    '@PLAINNAME@.c++',
-  ],
-  depfile : '@PLAINNAME@.d',
+build_capnp_files = files(
+  # keep-sorted start
+  'hook-instance.capnp',
+  'request.capnp',
+  # keep-sorted end
 )
+
+foreach infile : build_capnp_files
+  libstore_rpc += custom_target(
+    command : [
+      capnpc_wrapper,
+      '--language=c++',
+      '--src-prefix=@CURRENT_SOURCE_DIR@',
+      '--outdir=@OUTDIR@',
+      '--depfile=@DEPFILE@',
+      '-I@SOURCE_ROOT@',
+      '@INPUT@',
+    ],
+    input : infile,
+    output : [
+      '@PLAINNAME@.h',
+      '@PLAINNAME@.c++',
+    ],
+    depfile : '@PLAINNAME@.d',
+  )
+endforeach

lix/libstore/build/request.capnp

@@ -0,0 +1,7 @@
+@0xa7f090bdc7816f8f;
+
+using Cxx = import "/capnp/c++.capnp";
+$Cxx.namespace("nix::build");
+
+struct Request {
+}

lix/libstore/platform/darwin.cc

@@ -371,7 +371,7 @@ void DarwinLocalDerivationGoal::prepareSandbox()
     debug("Generated sandbox profile: %1%", sandboxProfile);
 }
 
-void DarwinLocalDerivationGoal::finishChildSetup()
+void DarwinLocalDerivationGoal::finishChildSetup(build::Request::Reader request)
 {
     bool allowLocalNetworking = parsedDrv->getBoolAttr("__darwinAllowLocalNetworking");
 
@@ -405,7 +405,9 @@ void DarwinLocalDerivationGoal::finishChildSetup()
     }
 }
 
-void DarwinLocalDerivationGoal::execBuilder(std::string builder, Strings args, Strings envStrs)
+void DarwinLocalDerivationGoal::execBuilder(
+    build::Request::Reader request, std::string builder, Strings args, Strings envStrs
+)
 {
     posix_spawnattr_t attrp;
 

lix/libstore/platform/darwin.hh

@@ -44,12 +44,13 @@ private:
      */
     void prepareSandbox() override;
 
-    void finishChildSetup() override;
+    void finishChildSetup(build::Request::Reader request) override;
 
     /**
      * Set process flags to enter or leave rosetta, then execute the builder
      */
-    void execBuilder(std::string builder, Strings args, Strings envStrs) override;
+    void
+    execBuilder(build::Request::Reader request, std::string builder, Strings args, Strings envStrs) override;
 
     /**
      * Whether we need to rewrite output hashes.

lix/libstore/platform/linux.cc

@@ -1267,7 +1267,7 @@ static void bindPath(const Path & source, const Path & target, bool optional = f
     }
 }
 
-bool LinuxLocalDerivationGoal::prepareChildSetup()
+bool LinuxLocalDerivationGoal::prepareChildSetup(build::Request::Reader request)
 {
     // Set the NO_NEW_PRIVS prctl flag.
     // This both makes loading seccomp filters work for unprivileged users,
@@ -1551,7 +1551,7 @@ bool LinuxLocalDerivationGoal::prepareChildSetup()
     return false;
 }
 
-void LinuxLocalDerivationGoal::finishChildSetup()
+void LinuxLocalDerivationGoal::finishChildSetup(build::Request::Reader request)
 {
     if (prctl(PR_SET_PDEATHSIG, SIGKILL) == -1) {
         throw SysError("setting death signal");
@@ -1562,12 +1562,16 @@ void LinuxLocalDerivationGoal::finishChildSetup()
 }
 
 Pid LinuxLocalDerivationGoal::startChild(
-    const Path & builder, const Strings & envStrs, const Strings & args, AutoCloseFD logPTY
+    build::Request::Reader request,
+    const Path & builder,
+    const Strings & envStrs,
+    const Strings & args,
+    AutoCloseFD logPTY
 )
 {
     // If we're not sandboxing no need to faff about, use the fallback
     if (!useChroot) {
-        return LocalDerivationGoal::startChild(builder, envStrs, args, std::move(logPTY));
+        return LocalDerivationGoal::startChild(request, builder, envStrs, args, std::move(logPTY));
     }
     /* Set up private namespaces for the build:
 
@@ -1737,7 +1741,7 @@ Pid LinuxLocalDerivationGoal::startChild(
         options.cloneFlags =
             CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_PARENT | SIGCHLD;
 
-        return startProcess([&]() { runChild(builder, envStrs, args); }, options);
+        return startProcess([&]() { runChild(request, builder, envStrs, args); }, options);
     });
 }
 

lix/libstore/platform/linux.hh

@@ -81,7 +81,11 @@ private:
      * create /etc/passwd and /etc/group based on discovered uid/gid
      */
     Pid startChild(
-        const Path & builder, const Strings & envStrs, const Strings & args, AutoCloseFD logPTY
+        build::Request::Reader request,
+        const Path & builder,
+        const Strings & envStrs,
+        const Strings & args,
+        AutoCloseFD logPTY
     ) override;
 
     /**
@@ -94,9 +98,9 @@ private:
         return true;
     }
 
-    bool prepareChildSetup() override;
+    bool prepareChildSetup(build::Request::Reader request) override;
 
-    void finishChildSetup() override;
+    void finishChildSetup(build::Request::Reader request) override;
 
     std::string rewriteResolvConf(std::string fromHost);
 

meson.build

@@ -293,6 +293,7 @@ configdata.set('HAVE_BOEHMGC', boehm.found().to_int())
 
 boost = dependency('boost', required : true, include_type : 'system')
 kj = dependency('kj-async', required : true, include_type : 'system')
+capnp = dependency('capnp', required : true, include_type : 'system')
 capnp_rpc = dependency('capnp-rpc', required : true, include_type : 'system')
 
 # cpuid only makes sense on x86_64