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Kconfig currently doesn't handle 'm' appearing in a Kconfig file before the modules symbol is defined (the symbol with 'option modules'). The problem is the following code, which runs during parsing: /* change 'm' into 'm' && MODULES */ if (e->left.sym == &symbol_mod) return expr_alloc_and(e, expr_alloc_symbol(modules_sym)); If the modules symbol has not yet been defined, modules_sym is NULL, giving an invalid expression. Here is a test file where both BEFORE_1 and BEFORE_2 trigger a segfault. If the modules symbol is removed, all symbols trigger segfaults. config BEFORE_1 def_tristate y if m if m config BEFORE_2 def_tristate y endif config MODULES def_bool y option modules config AFTER_1 def_tristate y if m if m config AFTER_2 def_tristate y endif Fix the issue by rewriting 'm' in menu_finalize() instead. This function runs after parsing and is the proper place to do it. The following existing code in conf_parse() in zconf.y ensures that the modules symbol exists at that point: if (!modules_sym) modules_sym = sym_find( "n" ); ... menu_finalize(&rootmenu); The following tests were done to ensure no functional changes for configurations that don't reference 'm' before the modules symbol: - zconfdump(stdout) was run with ARCH=x86 and ARCH=arm before and after the change and verified to produce identical output. This function prints all symbols, choices, and menus together with their properties and their dependency expressions. A rewritten 'm' appears as 'm && MODULES'. A small annoyance is that the assert(len != 0) in xfwrite() needs to be disabled in order to use zconfdump(), because it chokes on e.g. 'default ""'. - The Kconfiglib test suite was run to indirectly verify that alldefconfig, allyesconfig, allnoconfig, and all defconfigs in the kernel still generate the same final .config. - Valgrind was used to check for memory errors and (new) memory leaks. Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.