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gcc-8 warns for every single definition of a system call entry
point, e.g.:
include/linux/compat.h:56:18: error: 'compat_sys_rt_sigprocmask' alias between functions of incompatible types 'long int(int, compat_sigset_t *, compat_sigset_t *, compat_size_t)' {aka 'long int(int, struct <anonymous> *, struct <anonymous> *, unsigned int)'} and 'long int(long int, long int, long int, long int)' [-Werror=attribute-alias]
asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
^~~~~~~~~~
include/linux/compat.h:45:2: note: in expansion of macro 'COMPAT_SYSCALL_DEFINEx'
COMPAT_SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
^~~~~~~~~~~~~~~~~~~~~~
kernel/signal.c:2601:1: note: in expansion of macro 'COMPAT_SYSCALL_DEFINE4'
COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
^~~~~~~~~~~~~~~~~~~~~~
include/linux/compat.h:60:18: note: aliased declaration here
asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
^~~~~~~~~~
The new warning seems reasonable in principle, but it doesn't
help us here, since we rely on the type mismatch to sanitize the
system call arguments. After I reported this as GCC PR82435, a new
-Wno-attribute-alias option was added that could be used to turn the
warning off globally on the command line, but I'd prefer to do it a
little more fine-grained.
Interestingly, turning a warning off and on again inside of
a single macro doesn't always work, in this case I had to add
an extra statement inbetween and decided to copy the __SC_TEST
one from the native syscall to the compat syscall macro. See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83256 for more details
about this.
[paul.burton@mips.com:
- Rebase atop current master.
- Split GCC & version arguments to __diag_ignore() in order to match
changes to the preceding patch.
- Add the comment argument to match the preceding patch.]
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82435
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Tested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Tested-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
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.