From 859c81750130844590a83eff847c6c55e2340ab1 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 7 May 2020 13:56:01 -0500 Subject: modpost,fixdep: Replace zero-length array with flexible-array The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Signed-off-by: Masahiro Yamada --- scripts/basic/fixdep.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'scripts/basic') diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c index 877ca2c88246..d98540552941 100644 --- a/scripts/basic/fixdep.c +++ b/scripts/basic/fixdep.c @@ -160,7 +160,7 @@ struct item { struct item *next; unsigned int len; unsigned int hash; - char name[0]; + char name[]; }; #define HASHSZ 256 -- cgit v1.2.3 From faabed295cccc2aba2b67f2e7b309f2892d55004 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sat, 1 Aug 2020 21:27:18 +0900 Subject: kbuild: introduce hostprogs-always-y and userprogs-always-y To build host programs, you need to add the program names to 'hostprogs' to use the necessary build rule, but it is not enough to build them because there is no dependency. There are two types of host programs: built as the prerequisite of another (e.g. gen_crc32table in lib/Makefile), or always built when Kbuild visits the Makefile (e.g. genksyms in scripts/genksyms/Makefile). The latter is typical in Makefiles under scripts/, which contains host programs globally used during the kernel build. To build them, you need to add them to both 'hostprogs' and 'always-y'. This commit adds hostprogs-always-y as a shorthand. The same applies to user programs. net/bpfilter/Makefile builds bpfilter_umh on demand, hence always-y is unneeded. In contrast, programs under samples/ are added to both 'userprogs' and 'always-y' so they are always built when Kbuild visits the Makefiles. userprogs-always-y works as a shorthand. Signed-off-by: Masahiro Yamada Acked-by: Miguel Ojeda --- scripts/basic/Makefile | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'scripts/basic') diff --git a/scripts/basic/Makefile b/scripts/basic/Makefile index 290dd27d2809..eeb6a38c5551 100644 --- a/scripts/basic/Makefile +++ b/scripts/basic/Makefile @@ -2,5 +2,4 @@ # # fixdep: used to generate dependency information during build process -hostprogs := fixdep -always-y := $(hostprogs) +hostprogs-always-y += fixdep -- cgit v1.2.3