152 lines
6.1 KiB
Diff
152 lines
6.1 KiB
Diff
From mboxrd@z Thu Jan 1 00:00:00 1970
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references; bh=2lQNwDLO9/HfsHTvSmLn5csGG1S09yt0LuSYqXeE0y0=;
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From: Stefan Agner <stefan@agner.ch>
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To: gregkh@linuxfoundation.org
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Cc: stable@vger.kernel.org,
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Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
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Martin Sebor <msebor@gcc.gnu.org>,
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Nick Desaulniers <ndesaulniers@google.com>,
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Stefan Agner <stefan@agner.ch>
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Subject: [PATCH BACKPORT 4.19 1/2] Compiler Attributes: add support for __copy (gcc >= 9)
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Date: Tue, 4 Jun 2019 15:24:40 +0200
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Message-Id: <20190604132441.15383-1-stefan@agner.ch>
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List-Post: <mailto:stable@vger.kernel.org>
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From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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[ Upstream commit c0d9782f5b6d7157635ae2fd782a4b27d55a6013 ]
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>From the GCC manual:
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copy
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copy(function)
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The copy attribute applies the set of attributes with which function
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has been declared to the declaration of the function to which
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the attribute is applied. The attribute is designed for libraries
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that define aliases or function resolvers that are expected
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to specify the same set of attributes as their targets. The copy
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attribute can be used with functions, variables, or types. However,
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the kind of symbol to which the attribute is applied (either
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function or variable) must match the kind of symbol to which
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the argument refers. The copy attribute copies only syntactic and
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semantic attributes but not attributes that affect a symbol’s
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linkage or visibility such as alias, visibility, or weak.
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The deprecated attribute is also not copied.
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https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html
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The upcoming GCC 9 release extends the -Wmissing-attributes warnings
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(enabled by -Wall) to C and aliases: it warns when particular function
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attributes are missing in the aliases but not in their target, e.g.:
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void __cold f(void) {}
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void __alias("f") g(void);
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diagnoses:
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warning: 'g' specifies less restrictive attribute than
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its target 'f': 'cold' [-Wmissing-attributes]
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Using __copy(f) we can copy the __cold attribute from f to g:
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void __cold f(void) {}
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void __copy(f) __alias("f") g(void);
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This attribute is most useful to deal with situations where an alias
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is declared but we don't know the exact attributes the target has.
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For instance, in the kernel, the widely used module_init/exit macros
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define the init/cleanup_module aliases, but those cannot be marked
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always as __init/__exit since some modules do not have their
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functions marked as such.
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Cc: <stable@vger.kernel.org> # 4.14+
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Suggested-by: Martin Sebor <msebor@gcc.gnu.org>
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Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
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Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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Signed-off-by: Stefan Agner <stefan@agner.ch>
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---
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include/linux/compiler-gcc.h | 4 ++++
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include/linux/compiler_types.h | 4 ++++
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2 files changed, 8 insertions(+)
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diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
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index a8ff0ca0c321..3ebee1ce6f98 100644
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--- a/include/linux/compiler-gcc.h
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+++ b/include/linux/compiler-gcc.h
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@@ -345,6 +345,10 @@
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#endif /* gcc version >= 40000 specific checks */
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+#if GCC_VERSION >= 90100
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+#define __copy(symbol) __attribute__((__copy__(symbol)))
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+#endif
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+
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#if !defined(__noclone)
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#define __noclone /* not needed */
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#endif
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diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
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index c2ded31a4cec..2b8ed70c4c77 100644
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--- a/include/linux/compiler_types.h
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+++ b/include/linux/compiler_types.h
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@@ -261,6 +261,10 @@ struct ftrace_likely_data {
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#define __visible
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#endif
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+#ifndef __copy
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+# define __copy(symbol)
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+#endif
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+
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#ifndef __nostackprotector
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# define __nostackprotector
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#endif
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--
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2.21.0
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