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| author | Matthias Maennich <maennich@google.com> | 2019-09-06 12:32:27 +0200 |
|---|---|---|
| committer | Jessica Yu <jeyu@kernel.org> | 2019-09-10 10:30:17 +0200 |
| commit | 8651ec01daedad26290f76beeb4736f9d2da4b87 (patch) | |
| tree | addd8a0c1a51b5000c96218a1b349fde30ff4f29 /include/asm-generic | |
| parent | export: explicitly align struct kernel_symbol (diff) | |
| download | linux-8651ec01daedad26290f76beeb4736f9d2da4b87.tar.xz linux-8651ec01daedad26290f76beeb4736f9d2da4b87.zip | |
module: add support for symbol namespaces.
The EXPORT_SYMBOL_NS() and EXPORT_SYMBOL_NS_GPL() macros can be used to
export a symbol to a specific namespace. There are no _GPL_FUTURE and
_UNUSED variants because these are currently unused, and I'm not sure
they are necessary.
I didn't add EXPORT_SYMBOL_NS() for ASM exports; this patch sets the
namespace of ASM exports to NULL by default. In case of relative
references, it will be relocatable to NULL. If there's a need, this
should be pretty easy to add.
A module that wants to use a symbol exported to a namespace must add a
MODULE_IMPORT_NS() statement to their module code; otherwise, modpost
will complain when building the module, and the kernel module loader
will emit an error and fail when loading the module.
MODULE_IMPORT_NS() adds a modinfo tag 'import_ns' to the module. That
tag can be observed by the modinfo command, modpost and kernel/module.c
at the time of loading the module.
The ELF symbols are renamed to include the namespace with an asm label;
for example, symbol 'usb_stor_suspend' in namespace USB_STORAGE becomes
'usb_stor_suspend.USB_STORAGE'. This allows modpost to do namespace
checking, without having to go through all the effort of parsing ELF and
relocation records just to get to the struct kernel_symbols.
On x86_64 I saw no difference in binary size (compression), but at
runtime this will require a word of memory per export to hold the
namespace. An alternative could be to store namespaced symbols in their
own section and use a separate 'struct namespaced_kernel_symbol' for
that section, at the cost of making the module loader more complex.
Co-developed-by: Martijn Coenen <maco@android.com>
Signed-off-by: Martijn Coenen <maco@android.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/export.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h index 63f54907317b..e2b5d0f569d3 100644 --- a/include/asm-generic/export.h +++ b/include/asm-generic/export.h @@ -17,11 +17,11 @@ .macro __put, val, name #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS - .long \val - ., \name - . + .long \val - ., \name - ., 0 - . #elif defined(CONFIG_64BIT) - .quad \val, \name + .quad \val, \name, 0 #else - .long \val, \name + .long \val, \name, 0 #endif .endm |