https://github.com/torvalds/linux
Revision c0d9782f5b6d7157635ae2fd782a4b27d55a6013 authored by Miguel Ojeda on 08 February 2019, 22:51:05 UTC, committed by Miguel Ojeda on 15 February 2019, 18:52:17 UTC
From the GCC manual:

  copy
  copy(function)

    The copy attribute applies the set of attributes with which function
    has been declared to the declaration of the function to which
    the attribute is applied. The attribute is designed for libraries
    that define aliases or function resolvers that are expected
    to specify the same set of attributes as their targets. The copy
    attribute can be used with functions, variables, or types. However,
    the kind of symbol to which the attribute is applied (either
    function or variable) must match the kind of symbol to which
    the argument refers. The copy attribute copies only syntactic and
    semantic attributes but not attributes that affect a symbol’s
    linkage or visibility such as alias, visibility, or weak.
    The deprecated attribute is also not copied.

  https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html

The upcoming GCC 9 release extends the -Wmissing-attributes warnings
(enabled by -Wall) to C and aliases: it warns when particular function
attributes are missing in the aliases but not in their target, e.g.:

    void __cold f(void) {}
    void __alias("f") g(void);

diagnoses:

    warning: 'g' specifies less restrictive attribute than
    its target 'f': 'cold' [-Wmissing-attributes]

Using __copy(f) we can copy the __cold attribute from f to g:

    void __cold f(void) {}
    void __copy(f) __alias("f") g(void);

This attribute is most useful to deal with situations where an alias
is declared but we don't know the exact attributes the target has.

For instance, in the kernel, the widely used module_init/exit macros
define the init/cleanup_module aliases, but those cannot be marked
always as __init/__exit since some modules do not have their
functions marked as such.

Suggested-by: Martin Sebor <msebor@gcc.gnu.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
1 parent ff98e20
Raw File
Tip revision: c0d9782f5b6d7157635ae2fd782a4b27d55a6013 authored by Miguel Ojeda on 08 February 2019, 22:51:05 UTC
Compiler Attributes: add support for __copy (gcc >= 9)
Tip revision: c0d9782
Kconfig
menuconfig SAMPLES
	bool "Sample kernel code"
	depends on !UML
	help
	  You can build and test sample kernel code here.

if SAMPLES

config SAMPLE_TRACE_EVENTS
	tristate "Build trace_events examples -- loadable modules only"
	depends on EVENT_TRACING && m
	help
	  This build trace event example modules.

config SAMPLE_TRACE_PRINTK
        tristate "Build trace_printk module - tests various trace_printk formats"
	depends on EVENT_TRACING && m
	help
	 This builds a module that calls trace_printk() and can be used to
	 test various trace_printk() calls from a module.

config SAMPLE_KOBJECT
	tristate "Build kobject examples -- loadable modules only"
	depends on m
	help
	  This config option will allow you to build a number of
	  different kobject sample modules showing how to use kobjects,
	  ksets, and ktypes properly.

	  If in doubt, say "N" here.

config SAMPLE_KPROBES
	tristate "Build kprobes examples -- loadable modules only"
	depends on KPROBES && m
	help
	  This build several kprobes example modules.

config SAMPLE_KRETPROBES
	tristate "Build kretprobes example -- loadable modules only"
	default m
	depends on SAMPLE_KPROBES && KRETPROBES

config SAMPLE_HW_BREAKPOINT
	tristate "Build kernel hardware breakpoint examples -- loadable module only"
	depends on HAVE_HW_BREAKPOINT && m
	help
	  This builds kernel hardware breakpoint example modules.

config SAMPLE_KFIFO
	tristate "Build kfifo examples -- loadable modules only"
	depends on m
	help
	  This config option will allow you to build a number of
	  different kfifo sample modules showing how to use the
	  generic kfifo API.

	  If in doubt, say "N" here.

config SAMPLE_KDB
	tristate "Build kdb command example -- loadable modules only"
	depends on KGDB_KDB && m
	help
	  Build an example of how to dynamically add the hello
	  command to the kdb shell.

config SAMPLE_QMI_CLIENT
	tristate "Build qmi client sample -- loadable modules only"
	depends on m
	depends on ARCH_QCOM
	depends on NET
	select QCOM_QMI_HELPERS
	help
	  Build an QMI client sample driver, which demonstrates how to
	  communicate with a remote QRTR service, using QMI encoded messages.

config SAMPLE_RPMSG_CLIENT
	tristate "Build rpmsg client sample -- loadable modules only"
	depends on RPMSG && m
	help
	  Build an rpmsg client sample driver, which demonstrates how
	  to communicate with an AMP-configured remote processor over
	  the rpmsg bus.

config SAMPLE_LIVEPATCH
	tristate "Build live patching samples -- loadable modules only"
	depends on LIVEPATCH && m
	help
	  Build sample live patch demonstrations.

config SAMPLE_CONFIGFS
	tristate "Build configfs patching sample -- loadable modules only"
	depends on CONFIGFS_FS && m
	help
	  Builds a sample configfs interface.

config SAMPLE_CONNECTOR
	tristate "Build connector sample -- loadable modules only"
	depends on CONNECTOR && m
	help
	  When enabled, this builds both a sample kernel module for
	  the connector interface and a user space tool to communicate
	  with it.
	  See also Documentation/connector/connector.txt

config SAMPLE_SECCOMP
	tristate "Build seccomp sample code -- loadable modules only"
	depends on SECCOMP_FILTER && m
	help
	  Build samples of seccomp filters using various methods of
	  BPF filter construction.

config SAMPLE_VFIO_MDEV_MTTY
	tristate "Build VFIO mtty example mediated device sample code -- loadable modules only"
	depends on VFIO_MDEV_DEVICE && m
	help
	  Build a virtual tty sample driver for use as a VFIO
	  mediated device

config SAMPLE_VFIO_MDEV_MDPY
	tristate "Build VFIO mdpy example mediated device sample code -- loadable modules only"
	depends on VFIO_MDEV_DEVICE && m
	help
	  Build a virtual display sample driver for use as a VFIO
	  mediated device.  It is a simple framebuffer and supports
	  the region display interface (VFIO_GFX_PLANE_TYPE_REGION).

config SAMPLE_VFIO_MDEV_MDPY_FB
	tristate "Build VFIO mdpy example guest fbdev driver -- loadable module only"
	depends on FB && m
	select FB_CFB_FILLRECT
	select FB_CFB_COPYAREA
	select FB_CFB_IMAGEBLIT
	help
	  Guest fbdev driver for the virtual display sample driver.

config SAMPLE_VFIO_MDEV_MBOCHS
	tristate "Build VFIO mdpy example mediated device sample code -- loadable modules only"
	depends on VFIO_MDEV_DEVICE && m
	select DMA_SHARED_BUFFER
	help
	  Build a virtual display sample driver for use as a VFIO
	  mediated device.  It supports the region display interface
	  (VFIO_GFX_PLANE_TYPE_DMABUF).
	  Emulate enough of qemu stdvga to make bochs-drm.ko happy.
	  That is basically the vram memory bar and the bochs dispi
	  interface vbe registers in the mmio register bar.
	  Specifically it does *not* include any legacy vga stuff.
	  Device looks a lot like "qemu -device secondary-vga".

config SAMPLE_STATX
	bool "Build example extended-stat using code"
	depends on BROKEN
	help
	  Build example userspace program to use the new extended-stat syscall.

endif # SAMPLES
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