autoconf: Pretend `CONFIG_MODULES` is always on

- Unconditionally inject `CONFIG_MODULES` make variable
  and `#define CONFIG_MODULES` to Kbuild in `ZFS_LINUX_COMPILE`
  autoconf function to emulate loadable kernel modules support.
  This allows OpenZFS to perform Linux checks despite
  `CONFIG_MODULES=n` in the actual Linux config.

- Add `ZFS_AC_KERNEL_CONFIG_MODULES` check which encompasses
  the logic from `ZFS_AC_KERNEL_TEST_MODULE` with additional
  diagnostic messages to the user

- Removed `ZFS_AC_KERNEL_TEST_MODULE` as it merely duplicates
  every check in `ZFS_AC_KERNEL_CONFIG_DEFINED`

- Moved `ZFS_AC_MODULE_SYMVERS` after `ZFS_AC_KERNEL_CONFIG_DEFINED`
  so the user has a chance to see the proper diagnostic from the
  steps before.

A workaround for Linux's

```
commit 3e3005df73b535cb849cf4ec8075d6aa3c460f68
Author: Masahiro Yamada <masahiroy@kernel.org>
Date:   Wed Mar 31 22:38:03 2021 +0900

kbuild: unify modules(_install) for in-tree and external modules

If you attempt to build or install modules ('make modules(_install)'
with CONFIG_MODULES disabled, you will get a clear error message, but
nothing for external module builds.

Factor out the modules and modules_install rules into the common part,
so you will get the same error message when you try to build external
modules with CONFIG_MODULES=n.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
```

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: szubersk <szuberskidamian@gmail.com>
Closes #10832
Closes #13361

diff --git a/config/kernel-config-defined.m4 b/config/kernel-config-defined.m4
index d9f053400a678b214b6e4d045c64cb852c6eac1e..54837d7283410d1511cd71052e0632734b1d98dd 100644 (file)
--- a/config/kernel-config-defined.m4
+++ b/config/kernel-config-defined.m4
@@ -19,6 +19,7 @@ AC_DEFUN([ZFS_AC_KERNEL_CONFIG_DEFINED], [
                ])
        ])
 
+       ZFS_AC_KERNEL_SRC_CONFIG_MODULES
        ZFS_AC_KERNEL_SRC_CONFIG_BLOCK
        ZFS_AC_KERNEL_SRC_CONFIG_DEBUG_LOCK_ALLOC
        ZFS_AC_KERNEL_SRC_CONFIG_TRIM_UNUSED_KSYMS
@@ -29,6 +30,7 @@ AC_DEFUN([ZFS_AC_KERNEL_CONFIG_DEFINED], [
        ZFS_LINUX_TEST_COMPILE_ALL([config])
        AC_MSG_RESULT([done])
 
+       ZFS_AC_KERNEL_CONFIG_MODULES
        ZFS_AC_KERNEL_CONFIG_BLOCK
        ZFS_AC_KERNEL_CONFIG_DEBUG_LOCK_ALLOC
        ZFS_AC_KERNEL_CONFIG_TRIM_UNUSED_KSYMS
@@ -99,6 +101,61 @@ AC_DEFUN([ZFS_AC_KERNEL_CONFIG_DEBUG_LOCK_ALLOC], [
        ])
 ])
 
+dnl #
+dnl # Check CONFIG_MODULES
+dnl #
+dnl # Verify the kernel has CONFIG_MODULES support enabled.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_CONFIG_MODULES], [
+       ZFS_LINUX_TEST_SRC([config_modules], [
+               #if !defined(CONFIG_MODULES)
+               #error CONFIG_MODULES not defined
+               #endif
+       ],[])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_CONFIG_MODULES], [
+       AC_MSG_CHECKING([whether CONFIG_MODULES is defined])
+       AS_IF([test "x$enable_linux_builtin" != xyes], [
+               ZFS_LINUX_TEST_RESULT([config_modules], [
+                       AC_MSG_RESULT([yes])
+               ],[
+                       AC_MSG_RESULT([no])
+                       AC_MSG_ERROR([
+               *** This kernel does not include the required loadable module
+               *** support!
+               ***
+               *** To build OpenZFS as a loadable Linux kernel module
+               *** enable loadable module support by setting
+               *** `CONFIG_MODULES=y` in the kernel configuration and run
+               *** `make modules_prepare` in the Linux source tree.
+               ***
+               *** If you don't intend to enable loadable kernel module
+               *** support, please compile OpenZFS as a Linux kernel built-in.
+               ***
+               *** Prepare the Linux source tree by running `make prepare`,
+               *** use the OpenZFS `--enable-linux-builtin` configure option,
+               *** copy the OpenZFS sources into the Linux source tree using
+               *** `./copy-builtin <linux source directory>`,
+               *** set `CONFIG_ZFS=y` in the kernel configuration and compile
+               *** kernel as usual.
+                       ])
+               ])
+       ], [
+               ZFS_LINUX_TRY_COMPILE([], [], [
+                       AC_MSG_RESULT([not needed])
+               ],[
+                       AC_MSG_RESULT([error])
+                       AC_MSG_ERROR([
+               *** This kernel is unable to compile object files.
+               ***
+               *** Please make sure you prepared the Linux source tree
+               *** by running `make prepare` there.
+                       ])
+               ])
+       ])
+])
+
 dnl #
 dnl # Check CONFIG_TRIM_UNUSED_KSYMS
 dnl #

diff --git a/config/kernel.m4 b/config/kernel.m4
index 7cf181beb3b113b618073ef2374c635bc655e04e..2a552431ad43fd3ee24b45be98354aaba75a2da9 100644 (file)
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -8,8 +8,8 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
                ZFS_AC_QAT
 
                dnl # Sanity checks for module building and CONFIG_* defines
-               ZFS_AC_KERNEL_TEST_MODULE
                ZFS_AC_KERNEL_CONFIG_DEFINED
+               ZFS_AC_MODULE_SYMVERS
 
                dnl # Sequential ZFS_LINUX_TRY_COMPILE tests
                ZFS_AC_KERNEL_FPU_HEADER
@@ -445,8 +445,6 @@ AC_DEFUN([ZFS_AC_KERNEL], [
        AC_SUBST(LINUX)
        AC_SUBST(LINUX_OBJ)
        AC_SUBST(LINUX_VERSION)
-
-       ZFS_AC_MODULE_SYMVERS
 ])
 
 dnl #
@@ -541,27 +539,6 @@ AC_DEFUN([ZFS_AC_QAT], [
        ])
 ])
 
-dnl #
-dnl # Basic toolchain sanity check.
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_TEST_MODULE], [
-       AC_MSG_CHECKING([whether modules can be built])
-       ZFS_LINUX_TRY_COMPILE([], [], [
-               AC_MSG_RESULT([yes])
-       ],[
-               AC_MSG_RESULT([no])
-               if test "x$enable_linux_builtin" != xyes; then
-                       AC_MSG_ERROR([
-       *** Unable to build an empty module.
-                       ])
-               else
-                       AC_MSG_ERROR([
-       *** Unable to build an empty module.
-       *** Please run 'make scripts' inside the kernel source tree.])
-               fi
-       ])
-])
-
 dnl #
 dnl # ZFS_LINUX_CONFTEST_H
 dnl #
@@ -664,8 +641,10 @@ AC_DEFUN([ZFS_LINUX_COMPILE], [
                build kernel modules with LLVM/CLANG toolchain])
        AC_TRY_COMMAND([
            KBUILD_MODPOST_NOFINAL="$5" KBUILD_MODPOST_WARN="$6"
-           make modules -k -j$TEST_JOBS ${KERNEL_CC:+CC=$KERNEL_CC} ${KERNEL_LD:+LD=$KERNEL_LD} ${KERNEL_LLVM:+LLVM=$KERNEL_LLVM} -C $LINUX_OBJ $ARCH_UM
-           M=$PWD/$1 >$1/build.log 2>&1])
+           make modules -k -j$TEST_JOBS ${KERNEL_CC:+CC=$KERNEL_CC}
+           ${KERNEL_LD:+LD=$KERNEL_LD} ${KERNEL_LLVM:+LLVM=$KERNEL_LLVM}
+           CONFIG_MODULES=y CFLAGS_MODULE=-DCONFIG_MODULES
+           -C $LINUX_OBJ $ARCH_UM M=$PWD/$1 >$1/build.log 2>&1])
        AS_IF([AC_TRY_COMMAND([$2])], [$3], [$4])
 ])