kbuild: Show marked Kconfig fragments in "help"

Currently the Kconfig fragments in kernel/configs and arch/*/configs
that aren't used internally aren't discoverable through "make help",
which consists of hard-coded lists of config fragments. Instead, list
all the fragment targets that have a "# Help: " comment prefix so the
targets can be generated dynamically.

Add logic to the Makefile to search for and display the fragment and
comment. Add comments to fragments that are intended to be direct targets.

Signed-off-by: Kees Cook <keescook@chromium.org>
Co-developed-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

20 files changed, 34 insertions, 9 deletions

diff --git a/Makefile b/Makefile
index e21bf66af6fd3b..23cd62a5ff0595 100644
--- a/Makefile
+++ b/Makefile
@@ -1552,7 +1552,6 @@ help:
 	@echo  '  mrproper	  - Remove all generated files + config + various backup files'
 	@echo  '  distclean	  - mrproper + remove editor backup and patch files'
 	@echo  ''
-	@echo  'Configuration targets:'
 	@$(MAKE) -f $(srctree)/scripts/kconfig/Makefile help
 	@echo  ''
 	@echo  'Other generic targets:'
diff --git a/arch/arm/configs/dram_0x00000000.config b/arch/arm/configs/dram_0x00000000.config
index db96dcb420cebe..8803a0f58343c8 100644
--- a/arch/arm/configs/dram_0x00000000.config
+++ b/arch/arm/configs/dram_0x00000000.config
@@ -1 +1,2 @@
+# Help: DRAM base at 0x00000000
 CONFIG_DRAM_BASE=0x00000000
diff --git a/arch/arm/configs/dram_0xc0000000.config b/arch/arm/configs/dram_0xc0000000.config
index 343d5333d973d5..aab8f864686b52 100644
--- a/arch/arm/configs/dram_0xc0000000.config
+++ b/arch/arm/configs/dram_0xc0000000.config
@@ -1 +1,2 @@
+# Help: DRAM base at 0xc0000000
 CONFIG_DRAM_BASE=0xc0000000
diff --git a/arch/arm/configs/dram_0xd0000000.config b/arch/arm/configs/dram_0xd0000000.config
index 61ba7045f8a139..4aabce4ea3d465 100644
--- a/arch/arm/configs/dram_0xd0000000.config
+++ b/arch/arm/configs/dram_0xd0000000.config
@@ -1 +1,2 @@
+# Help: DRAM base at 0xd0000000
 CONFIG_DRAM_BASE=0xd0000000
diff --git a/arch/arm/configs/lpae.config b/arch/arm/configs/lpae.config
index a6d6f7ab3c01a1..1ab94da8345d32 100644
--- a/arch/arm/configs/lpae.config
+++ b/arch/arm/configs/lpae.config
@@ -1,2 +1,3 @@
+# Help: Enable Large Physical Address Extension mode
 CONFIG_ARM_LPAE=y
 CONFIG_VMSPLIT_2G=y
diff --git a/arch/arm64/configs/virt.config b/arch/arm64/configs/virt.config
index 6865d54e68f888..c47c36f8f67b7c 100644
--- a/arch/arm64/configs/virt.config
+++ b/arch/arm64/configs/virt.config
@@ -1,3 +1,4 @@
+# Help: Virtualization guest
 #
 # Base options for platforms
 #
diff --git a/arch/powerpc/configs/disable-werror.config b/arch/powerpc/configs/disable-werror.config
index 6ea12a12432c9d..7776b91da37f13 100644
--- a/arch/powerpc/configs/disable-werror.config
+++ b/arch/powerpc/configs/disable-werror.config
@@ -1 +1,2 @@
+# Help: Disable -Werror
 CONFIG_PPC_DISABLE_WERROR=y
diff --git a/arch/powerpc/configs/security.config b/arch/powerpc/configs/security.config
index 1c91a35c6a733a..0d54e29e2cdfc6 100644
--- a/arch/powerpc/configs/security.config
+++ b/arch/powerpc/configs/security.config
@@ -1,3 +1,5 @@
+# Help: Common security options for PowerPC builds
+
 # This is the equivalent of booting with lockdown=integrity
 CONFIG_SECURITY=y
 CONFIG_SECURITYFS=y
@@ -12,4 +14,4 @@ CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
 
 # UBSAN bounds checking is very cheap and good for hardening
 CONFIG_UBSAN=y
-# CONFIG_UBSAN_MISC is not set
\ No newline at end of file
+# CONFIG_UBSAN_MISC is not set
diff --git a/arch/riscv/configs/32-bit.config b/arch/riscv/configs/32-bit.config
index f6af0f708df4a6..16ee163847b447 100644
--- a/arch/riscv/configs/32-bit.config
+++ b/arch/riscv/configs/32-bit.config
@@ -1,3 +1,4 @@
+# Help: Build a 32-bit image
 CONFIG_ARCH_RV32I=y
 CONFIG_32BIT=y
 # CONFIG_PORTABLE is not set
diff --git a/arch/riscv/configs/64-bit.config b/arch/riscv/configs/64-bit.config
index 313edc554d84cc..d872a2d533f20e 100644
--- a/arch/riscv/configs/64-bit.config
+++ b/arch/riscv/configs/64-bit.config
@@ -1,2 +1,3 @@
+# Help: Build a 64-bit image
 CONFIG_ARCH_RV64I=y
 CONFIG_64BIT=y
diff --git a/arch/s390/configs/btf.config b/arch/s390/configs/btf.config
index 39227b4511aff8..eb7f84f5925cf3 100644
--- a/arch/s390/configs/btf.config
+++ b/arch/s390/configs/btf.config
@@ -1 +1,2 @@
+# Help: Enable BTF debug info
 CONFIG_DEBUG_INFO_BTF=y
diff --git a/arch/s390/configs/kasan.config b/arch/s390/configs/kasan.config
index 700a8b25c3ffc0..84c2b551e9927b 100644
--- a/arch/s390/configs/kasan.config
+++ b/arch/s390/configs/kasan.config
@@ -1,3 +1,4 @@
+# Help: Enable KASan for debugging
 CONFIG_KASAN=y
 CONFIG_KASAN_INLINE=y
 CONFIG_KASAN_VMALLOC=y
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index fdc2e3abd6152f..c4b2a8a19fc831 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -335,9 +335,5 @@ define archhelp
   echo  '			  bzdisk/fdimage*/hdimage/isoimage also accept:'
   echo  '			  FDARGS="..."  arguments for the booted kernel'
   echo  '			  FDINITRD=file initrd for the booted kernel'
-  echo  ''
-  echo  '  kvm_guest.config	- Enable Kconfig items for running this kernel as a KVM guest'
-  echo  '  xen.config		- Enable Kconfig items for running this kernel as a Xen guest'
-  echo  '  x86_debug.config	- Enable tip tree debugging options for testing'
 
 endef
diff --git a/kernel/configs/debug.config b/kernel/configs/debug.config
index e8db8d93866177..4722b998a32453 100644
--- a/kernel/configs/debug.config
+++ b/kernel/configs/debug.config
@@ -1,3 +1,5 @@
+# Help: Debugging for CI systems and finding regressions
+#
 # The config is based on running daily CI for enterprise Linux distros to
 # seek regressions on linux-next builds on different bare-metal and virtual
 # platforms. It can be used for example,
diff --git a/kernel/configs/kvm_guest.config b/kernel/configs/kvm_guest.config
index 208481d9109030..d0877063d925cd 100644
--- a/kernel/configs/kvm_guest.config
+++ b/kernel/configs/kvm_guest.config
@@ -1,3 +1,4 @@
+# Help: Bootable as a KVM guest
 CONFIG_NET=y
 CONFIG_NET_CORE=y
 CONFIG_NETDEVICES=y
diff --git a/kernel/configs/nopm.config b/kernel/configs/nopm.config
index 81ff078635769e..ebfdc3d8aa9add 100644
--- a/kernel/configs/nopm.config
+++ b/kernel/configs/nopm.config
@@ -1,3 +1,5 @@
+# Help: Disable Power Management
+
 CONFIG_PM=n
 CONFIG_SUSPEND=n
 CONFIG_HIBERNATION=n
diff --git a/kernel/configs/rust.config b/kernel/configs/rust.config
index 38a7c5362c9cf1..2c6e001a728497 100644
--- a/kernel/configs/rust.config
+++ b/kernel/configs/rust.config
@@ -1 +1,2 @@
+# Help: Enable Rust
 CONFIG_RUST=y
diff --git a/kernel/configs/x86_debug.config b/kernel/configs/x86_debug.config
index 6fac5b405334e1..35f48671b8d5c2 100644
--- a/kernel/configs/x86_debug.config
+++ b/kernel/configs/x86_debug.config
@@ -1,3 +1,4 @@
+# Help: Debugging options for tip tree testing
 CONFIG_X86_DEBUG_FPU=y
 CONFIG_LOCK_STAT=y
 CONFIG_DEBUG_VM=y
diff --git a/kernel/configs/xen.config b/kernel/configs/xen.config
index 436f806aa1ed0d..6878b9a49be8d4 100644
--- a/kernel/configs/xen.config
+++ b/kernel/configs/xen.config
@@ -1,3 +1,5 @@
+# Help: Bootable as a Xen guest
+#
 # global stuff - these enable us to allow some
 # of the not so generic stuff below for xen
 CONFIG_PARAVIRT=y
diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index af1c96198f4919..4eee155121a8b3 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -93,11 +93,13 @@ endif
 %_defconfig: $(obj)/conf
 	$(Q)$< $(silent) --defconfig=arch/$(SRCARCH)/configs/$@ $(Kconfig)
 
-configfiles=$(wildcard $(srctree)/kernel/configs/$@ $(srctree)/arch/$(SRCARCH)/configs/$@)
+configfiles = $(wildcard $(srctree)/kernel/configs/$(1) $(srctree)/arch/$(SRCARCH)/configs/$(1))
+all-config-fragments = $(call configfiles,*.config)
+config-fragments = $(call configfiles,$@)
 
 %.config: $(obj)/conf
-	$(if $(call configfiles),, $(error No configuration exists for this target on this architecture))
-	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/kconfig/merge_config.sh -m .config $(configfiles)
+	$(if $(config-fragments),, $(error $@ fragment does not exists on this architecture))
+	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/kconfig/merge_config.sh -m .config $(config-fragments)
 	$(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
 
 PHONY += tinyconfig
@@ -115,6 +117,7 @@ clean-files += tests/.cache
 
 # Help text used by make help
 help:
+	@echo  'Configuration targets:'
 	@echo  '  config	  - Update current config utilising a line-oriented program'
 	@echo  '  nconfig         - Update current config utilising a ncurses menu based program'
 	@echo  '  menuconfig	  - Update current config utilising a menu based program'
@@ -141,6 +144,12 @@ help:
 	@echo  '                    default value without prompting'
 	@echo  '  tinyconfig	  - Configure the tiniest possible kernel'
 	@echo  '  testconfig	  - Run Kconfig unit tests (requires python3 and pytest)'
+	@echo  ''
+	@echo  'Configuration topic targets:'
+	@$(foreach f, $(all-config-fragments), \
+		if help=$$(grep -m1 '^# Help: ' $(f)); then \
+			printf '  %-25s - %s\n' '$(notdir $(f))' "$${help#*: }"; \
+		fi;)
 
 # ===========================================================================
 # object files used by all kconfig flavours