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authorMasahiro Yamada <yamada.masahiro@socionext.com>2019-07-17 15:17:57 +0900
committerMasahiro Yamada <yamada.masahiro@socionext.com>2019-07-18 02:19:31 +0900
commitb7dca6dd1e591ad19a9aae716f3898be8063f880 (patch)
tree34d1ad73abe2f2c3a9f359927718e1604cf8ff58 /lib
parent7deb55f57159f9de696ef8d5e93b201a6aba871c (diff)
kbuild: create *.mod with full directory path and remove MODVERDIR
While descending directories, Kbuild produces objects for modules, but do not link final *.ko files; it is done in the modpost. To keep track of modules, Kbuild creates a *.mod file in $(MODVERDIR) for every module it is building. Some post-processing steps read the necessary information from *.mod files. This avoids descending into directories again. This mechanism was introduced in 2003 or so. Later, commit 551559e13af1 ("kbuild: implement modules.order") added modules.order. So, we can simply read it out to know all the modules with directory paths. This is easier than parsing the first line of *.mod files. $(MODVERDIR) has a flat directory structure, that is, *.mod files are named only with base names. This is based on the assumption that the module name is unique across the tree. This assumption is really fragile. Stephen Rothwell reported a race condition caused by a module name conflict: https://lkml.org/lkml/2019/5/13/991 In parallel building, two different threads could write to the same $(MODVERDIR)/*.mod simultaneously. Non-unique module names are the source of all kind of troubles, hence commit 3a48a91901c5 ("kbuild: check uniqueness of module names") introduced a new checker script. However, it is still fragile in the build system point of view because this race happens before scripts/modules-check.sh is invoked. If it happens again, the modpost will emit unclear error messages. To fix this issue completely, create *.mod with full directory path so that two threads never attempt to write to the same file. $(MODVERDIR) is no longer needed. Since modules with directory paths are listed in modules.order, Kbuild is still able to find *.mod files without additional descending. I also killed cmd_secanalysis; scripts/mod/sumversion.c computes MD4 hash for modules with MODULE_VERSION(). When CONFIG_DEBUG_SECTION_MISMATCH=y, it occurs not only in the modpost stage, but also during directory descending, where sumversion.c may parse stale *.mod files. It would emit 'No such file or directory' warning when an object consisting a module is renamed, or when a single-obj module is turned into a multi-obj module or vice versa. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by: Nicolas Pitre <nico@fluxnic.net>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug12
1 files changed, 1 insertions, 11 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 4ac4ca21a30a..cde5675340ba 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -353,23 +353,13 @@ config DEBUG_SECTION_MISMATCH
which results in the code/data being placed in specific sections.
The section mismatch analysis is always performed after a full
kernel build, and enabling this option causes the following
- additional steps to occur:
+ additional step to occur:
- Add the option -fno-inline-functions-called-once to gcc commands.
When inlining a function annotated with __init in a non-init
function, we would lose the section information and thus
the analysis would not catch the illegal reference.
This option tells gcc to inline less (but it does result in
a larger kernel).
- - Run the section mismatch analysis for each module/built-in.a file.
- When we run the section mismatch analysis on vmlinux.o, we
- lose valuable information about where the mismatch was
- introduced.
- Running the analysis for each module/built-in.a file
- tells where the mismatch happens much closer to the
- source. The drawback is that the same mismatch is
- reported at least twice.
- - Enable verbose reporting from modpost in order to help resolve
- the section mismatches that are reported.
config SECTION_MISMATCH_WARN_ONLY
bool "Make section mismatch errors non-fatal"