pkg/vcs: move linuxAlterConfigs() to separate file

The new linux_configs.go file will contain routines that manage
Linux-related configs.

1 files changed, 88 insertions, 0 deletions

diff --git a/pkg/vcs/linux_configs.go b/pkg/vcs/linux_configs.go
new file mode 100644
index 000000000..b54fed8fa
--- /dev/null
+++ b/pkg/vcs/linux_configs.go
@@ -0,0 +1,88 @@
+// Copyright 2023 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package vcs
+
+import "github.com/google/syzkaller/pkg/kconfig"
+
+// setLinuxTagConfigs() disables Linux kernel configurations depending on the Linux kernel version,
+// which is determined by the git tags reachable from HEAD.
+// The problem is that Linux kernel is regularly broken w.r.t syzbot configs, especially on older versions.
+func setLinuxTagConfigs(cf *kconfig.ConfigFile, tags map[string]bool) {
+	const disableAlways = "disable-always"
+	// If tags is nil, disable only configs marked as disableAlways.
+	checkTag := func(tag string) bool {
+		return tags != nil && !tags[tag] ||
+			tags == nil && tag == disableAlways
+	}
+	disable := map[string]string{
+		// 5.2 has CONFIG_SECURITY_TOMOYO_INSECURE_BUILTIN_SETTING which allows to test tomoyo better.
+		// This config also enables CONFIG_SECURITY_TOMOYO_OMIT_USERSPACE_LOADER
+		// but we need it disabled to boot older kernels.
+		"SECURITY_TOMOYO_OMIT_USERSPACE_LOADER": "v5.2",
+		// Kernel is boot broken before 4.15 due to double-free in vudc_probe:
+		// https://lkml.org/lkml/2018/9/7/648
+		// Fixed by e28fd56ad5273be67d0fae5bedc7e1680e729952.
+		"USBIP_VUDC": "v4.15",
+		// CONFIG_CAN causes:
+		// all runs: crashed: INFO: trying to register non-static key in can_notifier
+		// for v4.11..v4.12 and v4.12..v4.13 ranges.
+		// Fixed by 74b7b490886852582d986a33443c2ffa50970169.
+		"CAN": "v4.13",
+		// Setup of network devices is broken before v4.12 with a "WARNING in hsr_get_node".
+		// Fixed by 675c8da049fd6556eb2d6cdd745fe812752f07a8.
+		"HSR": "v4.12",
+		// Setup of network devices is broken before v4.12 with a "WARNING: ODEBUG bug in __sk_destruct"
+		// coming from smc_release.
+		"SMC": "v4.12",
+		// Kernel is boot broken before 4.10 with a lockdep warning in vhci_hcd_probe.
+		"USBIP_VHCI_HCD": "v4.10",
+		"BT_HCIVHCI":     "v4.10",
+		// Setup of network devices is broken before v4.7 with a deadlock involving team.
+		"NET_TEAM": "v4.7",
+		// Setup of network devices is broken before v4.5 with a warning in batadv_tvlv_container_remove.
+		"BATMAN_ADV": "v4.5",
+		// UBSAN is broken in multiple ways before v5.3, see:
+		// https://github.com/google/syzkaller/issues/1523#issuecomment-696514105
+		"UBSAN": "v5.3",
+		// First, we disable coverage in pkg/bisect because it fails machine testing starting from 4.7.
+		// Second, at 6689da155bdcd17abfe4d3a8b1e245d9ed4b5f2c CONFIG_KCOV selects CONFIG_GCC_PLUGIN_SANCOV
+		// (why?), which is build broken for hundreds of revisions.
+		"KCOV": disableAlways,
+		// This helps to produce stable binaries in presence of kernel tag changes.
+		"LOCALVERSION_AUTO": disableAlways,
+		// BTF fails lots of builds with:
+		// pahole version v1.9 is too old, need at least v1.13
+		// Failed to generate BTF for vmlinux. Try to disable CONFIG_DEBUG_INFO_BTF.
+		"DEBUG_INFO_BTF": disableAlways,
+		// This config only adds debug output. It should not be enabled at all,
+		// but it was accidentially enabled on some instances for some periods of time,
+		// and kernel is boot-broken for prolonged ranges of commits with deadlock
+		// which makes bisections take weeks.
+		"DEBUG_KOBJECT": disableAlways,
+		// This config is causing problems to kernel signature calculation as new initramfs is generated
+		// as a part of every build. Due to this init.data section containing this generated initramfs
+		// is differing between builds causing signture being random number.
+		"BLK_DEV_INITRD": disableAlways,
+	}
+	for cfg, tag := range disable {
+		if checkTag(tag) {
+			cf.Unset(cfg)
+		}
+	}
+	alter := []struct {
+		From string
+		To   string
+		Tag  string
+	}{
+		// Even though ORC unwinder was introduced a long time ago, it might have been broken for
+		// some time. 5.4 is chosen as a version tag, where ORC unwinder seems to work properly.
+		{"UNWINDER_ORC", "UNWINDER_FRAME_POINTER", "v5.4"},
+	}
+	for _, a := range alter {
+		if checkTag(a.Tag) {
+			cf.Unset(a.From)
+			cf.Set(a.To, kconfig.Yes)
+		}
+	}
+}