140 lines
6.4 KiB
Diff
140 lines
6.4 KiB
Diff
From mboxrd@z Thu Jan 1 00:00:00 1970
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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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Jessica Yu <jeyu@kernel.org>, Stefan Agner <stefan@agner.ch>
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Subject: [PATCH BACKPORT 4.19 2/2] include/linux/module.h: copy __init/__exit attrs to init/cleanup_module
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Date: Tue, 4 Jun 2019 15:24:41 +0200
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Message-Id: <20190604132441.15383-2-stefan@agner.ch>
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Archived-At: <https://lore.kernel.org/stable/20190604132441.15383-2-stefan@agner.ch/>
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List-Archive: <https://lore.kernel.org/stable/>
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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 a6e60d84989fa0e91db7f236eda40453b0e44afa ]
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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.
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In particular, it triggers for all the init/cleanup_module
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aliases in the kernel (defined by the module_init/exit macros),
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ending up being very noisy.
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These aliases point to the __init/__exit functions of a module,
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which are defined as __cold (among other attributes). However,
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the aliases themselves do not have the __cold attribute.
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Since the compiler behaves differently when compiling a __cold
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function as well as when compiling paths leading to calls
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to __cold functions, the warning is trying to point out
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the possibly-forgotten attribute in the alias.
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In order to keep the warning enabled, we decided to silence
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this case. Ideally, we would mark the aliases directly
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as __init/__exit. However, there are currently around 132 modules
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in the kernel which are missing __init/__exit in their init/cleanup
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functions (either because they are missing, or for other reasons,
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e.g. the functions being called from somewhere else); and
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a section mismatch is a hard error.
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A conservative alternative was to mark the aliases as __cold only.
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However, since we would like to eventually enforce __init/__exit
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to be always marked, we chose to use the new __copy function
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attribute (introduced by GCC 9 as well to deal with this).
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With it, we copy the attributes used by the target functions
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into the aliases. This way, functions that were not marked
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as __init/__exit won't have their aliases marked either,
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and therefore there won't be a section mismatch.
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Note that the warning would go away marking either the extern
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declaration, the definition, or both. However, we only mark
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the definition of the alias, since we do not want callers
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(which only see the declaration) to be compiled as if the function
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was __cold (and therefore the paths leading to those calls
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would be assumed to be unlikely).
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Cc: <stable@vger.kernel.org> # 4.14+
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Link: https://lore.kernel.org/lkml/20190123173707.GA16603@gmail.com/
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Link: https://lore.kernel.org/lkml/20190206175627.GA20399@gmail.com/
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Suggested-by: Martin Sebor <msebor@gcc.gnu.org>
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Acked-by: Jessica Yu <jeyu@kernel.org>
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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/module.h | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/include/linux/module.h b/include/linux/module.h
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index c71044644979..9915397715fc 100644
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--- a/include/linux/module.h
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+++ b/include/linux/module.h
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@@ -130,13 +130,13 @@ extern void cleanup_module(void);
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#define module_init(initfn) \
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static inline initcall_t __maybe_unused __inittest(void) \
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{ return initfn; } \
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- int init_module(void) __attribute__((alias(#initfn)));
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+ int init_module(void) __copy(initfn) __attribute__((alias(#initfn)));
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/* This is only required if you want to be unloadable. */
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#define module_exit(exitfn) \
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static inline exitcall_t __maybe_unused __exittest(void) \
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{ return exitfn; } \
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- void cleanup_module(void) __attribute__((alias(#exitfn)));
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+ void cleanup_module(void) __copy(exitfn) __attribute__((alias(#exitfn)));
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#endif
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--
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2.21.0
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