On Fri, Dec 16, 2016 at 2:06 PM, Kees Cook <keescook@xxxxxxxxxxxx> 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. FWIW, it still seems to me that these aren't false positives: WARNING: vmlinux.o(.text.unlikely+0x1b1): Section mismatch in reference from the function uncore_pci_exit.part.22() to the function .init.text:uncore_free_pcibus_map() The function uncore_pci_exit.part.22() references the function __init uncore_free_pcibus_map(). This is often because uncore_pci_exit.part.22 lacks a __init annotation or the annotation of uncore_free_pcibus_map is wrong. This is complaining about arch/x86/events/intel/uncore.c: __init intel_uncore_init() calls uncore_pci_exit(). __exit intel_uncore_exit() calls uncore_pci_exit(). uncore_pci_exit() is marked as "both" (which will resolve to __exit). __init intel_uncore_init() calls uncore_free_pcibus_map(). uncore_pci_exit() calls uncore_free_pcibus_map(). uncore_free_pcibus_map() should be marked as "both", but it seems like it ends up marked only __init. When I tried a build that looked only at -D MODULE being set, I got fewer warnings, but the modpost on builtins would still have warnings, but they complained about things in __exit calling __init, which for a builtin is fine: the __exit section will never be called... I think the modular-build checking is better than the Kconfig approach. It just requires that the __exit sections for non-modules get discarded before the modpost runs to complain about it... -Kees -- Kees Cook Nexus Security -- 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
