all: add support for custom linker

Add this as an option to syz-ci and syz-build tools.
Otherwise we cannot use clang + ld.lld for kernel builds.

6 files changed, 22 insertions, 13 deletions

diff --git a/pkg/build/build.go b/pkg/build/build.go
index cabb8046e..4baed2b95 100644
--- a/pkg/build/build.go
+++ b/pkg/build/build.go
@@ -28,6 +28,7 @@ type Params struct {
 	KernelDir    string
 	OutputDir    string
 	Compiler     string
+	Linker       string
 	Ccache       string
 	UserspaceDir string
 	CmdlineFile  string
@@ -47,13 +48,14 @@ type ImageDetails struct {
 // If CmdlineFile is not empty, contents of the file are appended to the kernel command line.
 // If SysctlFile is not empty, contents of the file are appended to the image /etc/sysctl.conf.
 // Output is stored in OutputDir and includes (everything except for image is optional):
-//  - image: the image
-//  - key: ssh key for the image
-//  - kernel: kernel for injected boot
-//  - initrd: initrd for injected boot
-//  - kernel.config: actual kernel config used during build
-//  - obj/: directory with kernel object files (this should match KernelObject
-//    specified in sys/targets, e.g. vmlinux for linux)
+//   - image: the image
+//   - key: ssh key for the image
+//   - kernel: kernel for injected boot
+//   - initrd: initrd for injected boot
+//   - kernel.config: actual kernel config used during build
+//   - obj/: directory with kernel object files (this should match KernelObject
+//     specified in sys/targets, e.g. vmlinux for linux)
+//
 // The returned structure contains a kernel ID that will be the same for kernels
 // with the same runtime behavior, and different for kernels with different runtime
 // behavior. Binary equal builds, or builds that differ only in e.g. debug info,
diff --git a/pkg/build/linux.go b/pkg/build/linux.go
index be9a38377..9fae48fc6 100644
--- a/pkg/build/linux.go
+++ b/pkg/build/linux.go
@@ -148,9 +148,9 @@ func (linux) writeFile(file string, data []byte) error {
 	return osutil.SandboxChown(file)
 }
 
-func runMakeImpl(arch, compiler, ccache, kernelDir string, addArgs ...string) error {
+func runMakeImpl(arch, compiler, linker, ccache, kernelDir string, addArgs ...string) error {
 	target := targets.Get(targets.Linux, arch)
-	args := LinuxMakeArgs(target, compiler, ccache, "")
+	args := LinuxMakeArgs(target, compiler, linker, ccache, "")
 	args = append(args, addArgs...)
 	cmd := osutil.Command("make", args...)
 	if err := osutil.Sandbox(cmd, true, true); err != nil {
@@ -175,10 +175,10 @@ func runMakeImpl(arch, compiler, ccache, kernelDir string, addArgs ...string) er
 }
 
 func runMake(params Params, addArgs ...string) error {
-	return runMakeImpl(params.TargetArch, params.Compiler, params.Ccache, params.KernelDir, addArgs...)
+	return runMakeImpl(params.TargetArch, params.Compiler, params.Linker, params.Ccache, params.KernelDir, addArgs...)
 }
 
-func LinuxMakeArgs(target *targets.Target, compiler, ccache, buildDir string) []string {
+func LinuxMakeArgs(target *targets.Target, compiler, linker, ccache, buildDir string) []string {
 	args := []string{
 		"-j", fmt.Sprint(runtime.NumCPU()),
 		"ARCH=" + target.KernelArch,
@@ -189,7 +189,7 @@ func LinuxMakeArgs(target *targets.Target, compiler, ccache, buildDir string) []
 	if compiler == "" {
 		compiler = target.KernelCompiler
 		if target.KernelLinker != "" {
-			args = append(args, "LD="+target.KernelLinker)
+			linker = target.KernelLinker
 		}
 	}
 	if compiler != "" {
@@ -198,6 +198,9 @@ func LinuxMakeArgs(target *targets.Target, compiler, ccache, buildDir string) []
 		}
 		args = append(args, "CC="+compiler)
 	}
+	if linker != "" {
+		args = append(args, "LD="+linker)
+	}
 	if buildDir != "" {
 		args = append(args, "O="+buildDir)
 	}
diff --git a/sys/syz-extract/linux.go b/sys/syz-extract/linux.go
index 10284d221..086c2d64b 100644
--- a/sys/syz-extract/linux.go
+++ b/sys/syz-extract/linux.go
@@ -79,7 +79,7 @@ func (*linux) prepareArch(arch *Arch) error {
 		return nil
 	}
 	kernelDir := arch.sourceDir
-	makeArgs := build.LinuxMakeArgs(arch.target, "", "", arch.buildDir)
+	makeArgs := build.LinuxMakeArgs(arch.target, "", "", "", arch.buildDir)
 	out, err := osutil.RunCmd(time.Hour, kernelDir, "make", append(makeArgs, "defconfig")...)
 	if err != nil {
 		return fmt.Errorf("make defconfig failed: %v\n%s", err, out)
diff --git a/syz-ci/manager.go b/syz-ci/manager.go
index 0f449268e..cbd6a469f 100644
--- a/syz-ci/manager.go
+++ b/syz-ci/manager.go
@@ -321,6 +321,7 @@ func (mgr *Manager) build(kernelCommit *vcs.Commit) error {
 		KernelDir:    mgr.kernelDir,
 		OutputDir:    tmpDir,
 		Compiler:     mgr.mgrcfg.Compiler,
+		Linker:       mgr.mgrcfg.Linker,
 		Ccache:       mgr.mgrcfg.Ccache,
 		UserspaceDir: mgr.mgrcfg.Userspace,
 		CmdlineFile:  mgr.mgrcfg.KernelCmdline,
diff --git a/syz-ci/syz-ci.go b/syz-ci/syz-ci.go
index 4abbe21c0..790a29f86 100644
--- a/syz-ci/syz-ci.go
+++ b/syz-ci/syz-ci.go
@@ -158,6 +158,7 @@ type ManagerConfig struct {
 	// explicit plumbing for every os/compiler combination.
 	CompilerType string `json:"compiler_type"` // Defaults to "gcc"
 	Compiler     string `json:"compiler"`
+	Linker       string `json:"linker"`
 	Ccache       string `json:"ccache"`
 	Userspace    string `json:"userspace"`
 	KernelConfig string `json:"kernel_config"`
diff --git a/tools/syz-build/build.go b/tools/syz-build/build.go
index ec7e76eb5..20461bb7f 100644
--- a/tools/syz-build/build.go
+++ b/tools/syz-build/build.go
@@ -22,6 +22,7 @@ var (
 	flagVM            = flag.String("vm", "gce", "VM type to build")
 	flagKernelSrc     = flag.String("kernel_src", "", "path to kernel checkout")
 	flagCompiler      = flag.String("compiler", "", "non-defult compiler")
+	flagLinker        = flag.String("linker", "", "non-default linker")
 	flagKernelConfig  = flag.String("config", "", "kernel config file")
 	flagKernelSysctl  = flag.String("sysctl", "", "kernel sysctl file")
 	flagKernelCmdline = flag.String("cmdline", "", "kernel cmdline file")
@@ -46,6 +47,7 @@ func main() {
 		KernelDir:    *flagKernelSrc,
 		OutputDir:    ".",
 		Compiler:     *flagCompiler,
+		Linker:       *flagLinker,
 		Ccache:       "",
 		UserspaceDir: *flagUserspace,
 		CmdlineFile:  *flagKernelCmdline,