On 12/16/2016 02:06 PM, Kees Cook wrote: > Hi, > > This is a continuation of Emese Revfy's initify plugin upstreaming. This > is based on her v3, but updated with various fixes from her github tree. > Additionally, I split off the printf attribute fixes and sent those > separately. > > This is 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 7.0. > > 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 v4.9-rc2. > > Some build 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 > > One thing of note is that this plugin triggers false positive warnings > from the modpost section mismatch detector. Further work is needed to > deal with this. > > > Changed from v3: > * Refresh from Emese's latest version. > > 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 > I gave this a spin on arm64 and it seems to boot up and run okay with just the "select HAVE_GCC_PLUGIN_INITIFY_INIT_EXIT if GCC_PLUGINS" added for arm64. The patches could probably use more review but I think it would be good to just fold this in for arm64 for ease of testing. Thanks, Laura -- 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
