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(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
