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89 lines
3.8 KiB
89 lines
3.8 KiB
6 years ago
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From: Arnd Bergmann <arnd@arndb.de>
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Date: Tue, 19 Jun 2018 13:14:57 -0700
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Subject: [PATCH] disable -Wattribute-alias warning for SYSCALL_DEFINEx()
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gcc-8 warns for every single definition of a system call entry
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point, e.g.:
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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]
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asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
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^~~~~~~~~~
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include/linux/compat.h:45:2: note: in expansion of macro 'COMPAT_SYSCALL_DEFINEx'
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COMPAT_SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
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^~~~~~~~~~~~~~~~~~~~~~
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kernel/signal.c:2601:1: note: in expansion of macro 'COMPAT_SYSCALL_DEFINE4'
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COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
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^~~~~~~~~~~~~~~~~~~~~~
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include/linux/compat.h:60:18: note: aliased declaration here
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asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
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^~~~~~~~~~
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The new warning seems reasonable in principle, but it doesn't
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help us here, since we rely on the type mismatch to sanitize the
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system call arguments. After I reported this as GCC PR82435, a new
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-Wno-attribute-alias option was added that could be used to turn the
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warning off globally on the command line, but I'd prefer to do it a
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little more fine-grained.
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Interestingly, turning a warning off and on again inside of
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a single macro doesn't always work, in this case I had to add
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an extra statement inbetween and decided to copy the __SC_TEST
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one from the native syscall to the compat syscall macro. See
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83256 for more details
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about this.
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[paul.burton@mips.com:
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- Rebase atop current master.
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- Split GCC & version arguments to __diag_ignore() in order to match
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changes to the preceding patch.
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- Add the comment argument to match the preceding patch.]
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Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82435
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Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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Signed-off-by: Paul Burton <paul.burton@mips.com>
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Tested-by: Christophe Leroy <christophe.leroy@c-s.fr>
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Tested-by: Stafford Horne <shorne@gmail.com>
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Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
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---
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--- a/include/linux/compat.h
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+++ b/include/linux/compat.h
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@@ -48,6 +48,9 @@
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COMPAT_SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
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#define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
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+ __diag_push(); \
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+ __diag_ignore(GCC, 8, "-Wattribute-alias", \
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+ "Type aliasing is used to sanitize syscall arguments");\
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asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
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__attribute__((alias(__stringify(compat_SyS##name)))); \
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static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
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@@ -56,6 +59,7 @@
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{ \
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return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__)); \
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} \
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+ __diag_pop(); \
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static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
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#ifndef compat_user_stack_pointer
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--- a/include/linux/syscalls.h
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+++ b/include/linux/syscalls.h
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@@ -208,6 +208,9 @@ static inline int is_syscall_trace_event
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#define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
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#define __SYSCALL_DEFINEx(x, name, ...) \
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+ __diag_push(); \
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+ __diag_ignore(GCC, 8, "-Wattribute-alias", \
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+ "Type aliasing is used to sanitize syscall arguments");\
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asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
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__attribute__((alias(__stringify(SyS##name)))); \
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static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
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@@ -219,6 +222,7 @@ static inline int is_syscall_trace_event
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__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
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return ret; \
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} \
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+ __diag_pop(); \
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static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
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/*
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