user/sven/linux.git/scripts/basic/fixdep.c, branch v6.1.67

fixdep: use fflush() and ferror() to ensure successful write to files

2022-03-31T03:03:46Z

Currently, fixdep checks the return value from (v)printf(), but it does not ensure the complete write to the .cmd file. printf() just writes data to the internal buffer, which usually succeeds. (Of course, it may fail for another reason, for example when the file descriptor is closed, but that is another story.) When the buffer (4k?) is full, an actual write occurs, and printf() may really fail. One of typical cases is "No space left on device" when the disk is full. The data remaining in the buffer will be pushed out to the file when the program exits, but we never know if it is successful. One straight-forward fix would be to add the following code at the end of the program. ret = fflush(stdout); if (ret < 0) { /* error handling */ } However, it is tedious to check the return code in all the call sites of printf(), fflush(), fclose(), and whatever can cause actual writes to the end device. Doing that lets the program bail out at the first failure but is usually not worth the effort. Instead, let's check the error status from ferror(). This is 'sticky', so you need to check it just once. You still need to call fflush(). Signed-off-by: Masahiro Yamada Reviewed-by: David Laight Reviewed-by: Nick Desaulniers

kbuild: redo fake deps at include/config/*.h

2021-04-24T20:26:10Z

Make include/config/foo/bar.h fake deps files generation simpler. * delete .h suffix those aren't header files, shorten filenames, * delete tolower() Linux filesystems can deal with both upper and lowercase filenames very well, * put everything in 1 directory Presumably 'mkdir -p' split is from dark times when filesystems handled huge directories badly, disks were round adding to seek times. x86_64 allmodconfig lists 12364 files in include/config. ../obj/include/config/ ├── 104_QUAD_8 ├── 60XX_WDT ├── 64BIT ... ├── ZSWAP_DEFAULT_ON ├── ZSWAP_ZPOOL_DEFAULT └── ZSWAP_ZPOOL_DEFAULT_ZBUD 0 directories, 12364 files Signed-off-by: Alexey Dobriyan Signed-off-by: Masahiro Yamada

modpost,fixdep: Replace zero-length array with flexible-array

2020-05-25T15:03:16Z

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

fixdep: remove redundant null character check

2020-03-02T12:18:19Z

If *q is '\0', the condition (isalnum(*q) || *q == '_') is false anyway. It is redundant to ensure non-zero *q. Signed-off-by: Masahiro Yamada

fixdep: remove unneeded code and comments about *.ver files

2020-03-02T12:18:19Z

This is probably stale code. In old days (~ Linux 2.5.59), Kbuild made genksyms generate include/linux/modules/*.ver files. The currenct Kbuild does not generate *.ver files at all. Signed-off-by: Masahiro Yamada

fixdep: check return value of printf() and putchar()

2019-07-01T01:30:39Z

When there is not enough space on your storage device, the build will fail with 'No space left on device' error message. The reason is obvious from the message, so you will free up some disk space, then you will resume the build. However, sometimes you may still see a mysterious error message: unterminated call to function 'wildcard': missing ')'. If you run out of the disk space, fixdep may end up with generating incomplete .*.cmd files. For example, if the disk-full error occurs while fixdep is running print_dep(), the .*.cmd might be truncated like this: $(wildcard include/config/ When you run 'make' next time, this broken .*.cmd will be included, then Make will terminate parsing since it is a wrong syntax. Once this happens, you need to run 'make clean' or delete the broken .*.cmd file manually. Even if you do not see any error message, the .*.cmd files after any error could be potentially incomplete, and unreliable. You may miss the re-compilation due to missing header dependency. If printf() cannot output the string for disk shortage or whatever reason, it returns a negative value, but currently fixdep does not check it at all. Consequently, fixdep *successfully* generates a broken .*.cmd file. Make never notices that since fixdep exits with 0, which means success. Given the intended usage of fixdep, it must respect the return value of not only malloc(), but also printf() and putchar(). This seems a long-standing issue since the introduction of fixdep. In old days, Kbuild tried to provide an extra safety by letting fixdep output to a temporary file and renaming it after everything is done: scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp;\ rm -f $(depfile); \ mv -f $(dot-target).tmp $(dot-target).cmd) It was no help to avoid the current issue; fixdep successfully created a truncated tmp file, which would be renamed to a .*.cmd file. This problem should be fixed by propagating the error status to the build system because: [1] Since commit 9c2af1c7377a ("kbuild: add .DELETE_ON_ERROR special target"), Make will delete the target automatically on any failure in the recipe. [2] Since commit 392885ee82d3 ("kbuild: let fixdep directly write to .*.cmd files"), .*.cmd file is included only when the corresponding target already exists. Signed-off-by: Masahiro Yamada

kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS

2018-12-01T14:13:14Z

My main motivation of this commit is to clean up scripts/Kbuild.include and scripts/Makefile.build. Currently, CONFIG_TRIM_UNUSED_KSYMS works with a tricky gimmick; possibly exported symbols are detected by letting $(CPP) replace EXPORT_SYMBOL* with a special string '=== __KSYM_*===', which is post-processed by sed, and passed to fixdep. The extra preprocessing is costly, and hacking cmd_and_fixdep is ugly. I came up with a new way to find exported symbols; insert a dummy symbol __ksym_marker_* to each potentially exported symbol. Those dummy symbols are picked up by $(NM), post-processed by sed, then appended to .*.cmd files. I collected the post-process part to a new shell script scripts/gen_ksymdeps.sh for readability. The dummy symbols are put into the .discard.* section so that the linker script rips them off the final vmlinux or modules. A nice side-effect is building with CONFIG_TRIM_UNUSED_KSYMS will be much faster. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Pitre

fixdep: suppress consecutive / from file paths in dependency list files

2018-05-07T12:40:39Z

Underscores in symbol names are translated into slashes for path names. Filesystems treat consecutive slashes as if there was only one, so let's do the same in the dependency list for easier grepping, etc. Signed-off-by: Nicolas Pitre Signed-off-by: Masahiro Yamada

kbuild: move include/config/ksym/* to include/ksym/*

2018-03-25T17:01:23Z

The idea of using fixdep was inspired by Kconfig, but autoksyms belongs to a different group. So, I want to move those touched files under include/config/ksym/ to include/ksym/. The directory include/ksym/ can be removed by 'make clean' because it is meaningless for the external module building. Signed-off-by: Masahiro Yamada Acked-by: Nicolas Pitre

fixdep: do not ignore kconfig.h

2018-03-05T14:48:29Z

kconfig.h was excluded from consideration by fixdep by 6a5be57f0f00 (fixdep: fix extraneous dependencies) to avoid some false positive hits (1) include/config/.h (2) include/config/h.h (3) include/config/foo.h (1) occurred because kconfig.h contains the string CONFIG_ in a comment. However, since dee81e988674 (fixdep: faster CONFIG_ search), we have a check that the part after CONFIG_ is non-empty, so this does not happen anymore (and CONFIG_ appears by itself elsewhere, so that check is worthwhile). (2) comes from the include guard, __LINUX_KCONFIG_H. But with the previous patch, we no longer match that either. That leaves (3), which amounts to one [1] false dependency (aka stat() call done by make), which I think we can live with: We've already had one case [2] where the lack of include/linux/kconfig.h in the .o.cmd file caused a missing rebuild, and while I originally thought we should just put kconfig.h in the dependency list without parsing it for the CONFIG_ pattern, we actually do have some real CONFIG_ symbols mentioned in it, and one can imagine some translation unit that just does '#ifdef __BIG_ENDIAN' but doesn't through some other header actually depend on CONFIG_CPU_BIG_ENDIAN - so changing the target endianness could end up rebuilding the world, minus that small TU. Quoting Linus, ... when missing dependencies cause a missed re-compile, the resulting bugs can be _really_ subtle. [1] well, two, we now also have CONFIG_BOOGER/booger.h - we could change that to FOO if we care [2] https://lkml.org/lkml/2018/2/22/838 Cc: Linus Torvalds Signed-off-by: Rasmus Villemoes Signed-off-by: Masahiro Yamada