[PATCH v3 0/7] Introduce the initify gcc plugin

[Emese Revfy]

I would like to introduce the initify gcc plugin. The kernel already has
a mechanism to free up code and data memory that is only used during kernel
or module initialization.
This plugin will teach the compiler to find more such code and data that
can be freed after initialization. It reduces memory usage.
The initify gcc plugin can be useful for embedded systems.

Originally it was a CII project supported by the Linux Foundation.

This plugin is the part of grsecurity/PaX.

The plugin supports all gcc versions from 4.5 to 6.0.

I made some changes on top of the PaX version (since March 6.). These are
the important ones:
 * move all local strings to init.rodata.str and exit.rodata.str
   (not just __func__)
 * report all initified strings and functions
   (GCC_PLUGIN_INITIFY_VERBOSE config option)
 * automatically discover init/exit functions and apply the __init or
   __exit attributes on them

You can find more about the changes here:
https://github.com/ephox-gcc-plugins/initify

This patch set is based on next-20160721.

Some statistics about the plugin:

On allyes config (amd64, gcc-6):
* 8412 initified strings
*  167 initified functions

On allmod config (i386, gcc-6):
* 8597 initified strings
*  159 initified functions

On allyes config (amd64, gcc-6):

section         vanilla                 vanilla + initify        change
-----------------------------------------------------------------------
.rodata		21746728 (0x14bd428)	21488680 (0x147e428)	-258048
.init.data	 1338376  (0x146c08)	 1683016  (0x19ae48)	+344640
.text		78270904 (0x4aa51b8)	78228280 (0x4a9ab38)	 -42624
.init.text	 1184725  (0x1213d5)	 1223257  (0x12aa59)	 +38532
.exit.data	     104  (0x000068)	   17760  (0x004560)	 +17656
.exit.text	  174473  (0x02a989)	  175763  (0x02ae93)	  +1290

	FileSiz (vanilla)	FileSiz (vanilla + initify)	 change
------------------------------------------------------------------------
00	102936576 (0x622b000)	102678528 (0x61ec000)		-258048
03	 28680192 (0x1b5a000)	 29081600 (0x1bbc000)		+401408

00     .text .notes __ex_table .rodata __bug_table .pci_fixup .builtin_fw
       .tracedata __ksymtab __ksymtab_gpl __ksymtab_strings __init_rodata
       __param __modver
03     .init.text .altinstr_aux .init.data .x86_cpu_dev.init
       .parainstructions .altinstructions .altinstr_replacement
       .iommu_table .apicdrivers .exit.text .exit.data .smp_locks .bss .brk


On defconfig (amd64, gcc-6):
* 1957 initified strings
*   29 initified functions

On defconfig (amd64, gcc-6):

section         vanilla                 vanilla + initify        change
-----------------------------------------------------------------------
.rodata		2524240 (0x268450)	2462800 (0x259450)	-61440
.init.data	 560256 (0x088c80)	 644000 (0x09d3a0)	+83744
.text		9377367 (0x8f1657)	9373079 (0x8f0597)	 -4288
.init.text	 438586 (0x06b13a)	 441828 (0x06bde4)	 +3242
.exit.data	      0			    832 (0x000340)	  +832
.exit.text	   8857 (0x002299)	    8857 (0x002299)	     0

	FileSiz (vanilla)	FileSiz (vanilla + initify)	 change
------------------------------------------------------------------------
00	13398016 (0xcc7000)	13336576 (0xcb8000)		-61440
03	 2203648 (0x21a000)	 2293760 (0x230000)		+90112

00     .text .notes __ex_table .rodata __bug_table .pci_fixup .builtin_fw
       .tracedata __ksymtab __ksymtab_gpl __ksymtab_strings __init_rodata
       __param __modver
03     .init.text .altinstr_aux .init.data .x86_cpu_dev.init
       .parainstructions .altinstructions .altinstr_replacement
       .iommu_table .apicdrivers .exit.text .exit.data .smp_locks .bss .brk


Emese Revfy (7):
 Move type casts into is_kernel_rodata
 Split up struct warn_args to enable dataflow verification by the initify plugin
 Constify some function parameters
 Add the initify gcc plugin
 Mark functions with the __nocapture attribute
 Mark a few functions with the printf attribute
 Mark functions with the __unverified_nocapture attribute


Changed from v2:
 * Check all uses when walking a use-def chain.
 * Check all uses of initialized local variables and initify them if they
   have only nocapture uses. Previously only uses in call arguments
   determined whether the initializer value could be initified.
 * Handle the format gcc attribute from the plugin too.
 * Verify nocapture parameters of calls. Track uses of these parameters
   and verify that all uses are not captured. Verify only the nocapture
   attribute (The format attribute should be verified too.).
 * Fixed wrong indexing of function arguments.
 * Fixed decl comparison. When comparing two decls the tree codes must be
   the same.
 * Search capture uses of the return value. Use negative nocapture
   attribute parameter on a function argument to verify that the return
   value is not captured.
 * Stop the search for capture uses if there is a cast to integer type.
 * Removed unnecessary duplication hook.
 * Handle cloned functions with a changed argument list.
 * Check visited tree nodes to avoid an infinite loop.
 * Add a new initify plugin option: enable_init_to_exit_moves. Move a
   function to the exit section if it is called by __init and __exit
   functions too.
 * Added plugin option to disable the search of capture uses in nocapture
   functions. We must be able to disable verification of nocapture
   functions because there is a lot of asm code in the str* and mem*
   functions on i386.
 * Added some more nocapture attributes.
 * Added some more printf attributes.
 * Added some unverified_nocapture attributes.
 * Make is_kernel_rodata() nocapture.
 * Added comment for the nocapture attribute from Kees.

Changes from v1:
 * Removed unnecessary nocapture attributes from boot code
   (Reported-by: PaX Team <pageexec@xxxxxxxxxxx>)
 * Removed nocapture attributes from functions that return
   the marked parameter
   (Reported-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>)
 * Added nocapture attribute to strlen()
 * Updated gcc-common.h from PaX
 * Don't forcibly constify initified string types
   this caused the size reduction of the .data section
   (initify_plugin.c)
 * Added the section mismatch problem in the commit message

---
 arch/Kconfig                         |   35 +
 arch/arm/include/asm/string.h        |   10 +-
 arch/arm64/include/asm/string.h      |   25 +-
 arch/powerpc/include/asm/string.h    |   19 +-
 arch/x86/Kconfig                     |    1 +
 arch/x86/include/asm/string_32.h     |   25 +-
 arch/x86/include/asm/string_64.h     |   20 +-
 arch/x86/kernel/hpet.c               |    2 +-
 arch/x86/lib/Makefile                |    4 +
 drivers/acpi/acpica/acutils.h        |    2 +-
 drivers/isdn/hisax/config.c          |   16 +-
 drivers/isdn/hisax/hisax.h           |    4 +-
 drivers/scsi/esas2r/esas2r_log.h     |    4 +-
 fs/char_dev.c                        |    2 +-
 fs/ntfs/debug.h                      |    6 +-
 fs/ocfs2/cluster/masklog.h           |    2 +-
 include/acpi/acpiosxf.h              |    3 +-
 include/acpi/acpixf.h                |    2 +-
 include/asm-generic/bug.h            |   12 +-
 include/asm-generic/vmlinux.lds.h    |    2 +
 include/drm/drmP.h                   |    2 +-
 include/linux/audit.h                |    5 +-
 include/linux/compiler-gcc.h         |   15 +
 include/linux/compiler.h             |    8 +
 include/linux/fs.h                   |    8 +-
 include/linux/printk.h               |    2 +-
 include/linux/ratelimit.h            |    3 +-
 include/linux/string.h               |   75 +-
 kernel/panic.c                       |   32 +-
 lib/bug.c                            |    2 +-
 lib/vsprintf.c                       |    6 +-
 mm/util.c                            |   10 +-
 scripts/Makefile.gcc-plugins         |    9 +
 scripts/gcc-plugins/gcc-common.h     |   41 +
 scripts/gcc-plugins/initify_plugin.c | 1880 ++++++++++++++++++++++++++++++++++
 security/integrity/integrity.h       |    2 +-
 36 files changed, 2146 insertions(+), 150 deletions(-)