On Mon, May 5, 2014 at 6:25 PM, tip-bot for Andy Lutomirski <tipbot@xxxxxxxxx> wrote: > Commit-ID: 6f121e548f83674ab4920a4e60afb58d4f61b829 > Gitweb: http://git.kernel.org/tip/6f121e548f83674ab4920a4e60afb58d4f61b829 > Author: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > AuthorDate: Mon, 5 May 2014 12:19:34 -0700 > Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> > CommitDate: Mon, 5 May 2014 13:18:51 -0700 > > x86, vdso: Reimplement vdso.so preparation in build-time C Just a heads up in case it hasn't been mentioned already; the x86 builds in linux-next which IIRC are done as cross compile on a powerpc box are failing as follows: VDSO2C arch/x86/vdso/vdso-image-64.c /bin/sh: line 1: 15995 Segmentation fault arch/x86/vdso/vdso2c arch/x86/vdso/vdso64.so.dbg arch/x86/vdso/vdso-image-64.c make[3]: *** [arch/x86/vdso/vdso-image-64.c] Error 139 http://kisskb.ellerman.id.au/kisskb/buildresult/11265454/ Paul. -- > > Currently, vdso.so files are prepared and analyzed by a combination > of objcopy, nm, some linker script tricks, and some simple ELF > parsers in the kernel. Replace all of that with plain C code that > runs at build time. > > All five vdso images now generate .c files that are compiled and > linked in to the kernel image. > > This should cause only one userspace-visible change: the loaded vDSO > images are stripped more heavily than they used to be. Everything > outside the loadable segment is dropped. In particular, this causes > the section table and section name strings to be missing. This > should be fine: real dynamic loaders don't load or inspect these > tables anyway. The result is roughly equivalent to eu-strip's > --strip-sections option. > > The purpose of this change is to enable the vvar and hpet mappings > to be moved to the page following the vDSO load segment. Currently, > it is possible for the section table to extend into the page after > the load segment, so, if we map it, it risks overlapping the vvar or > hpet page. This happens whenever the load segment is just under a > multiple of PAGE_SIZE. > > The only real subtlety here is that the old code had a C file with > inline assembler that did 'call VDSO32_vsyscall' and a linker script > that defined 'VDSO32_vsyscall = __kernel_vsyscall'. This most > likely worked by accident: the linker script entry defines a symbol > associated with an address as opposed to an alias for the real > dynamic symbol __kernel_vsyscall. That caused ld to relocate the > reference at link time instead of leaving an interposable dynamic > relocation. Since the VDSO32_vsyscall hack is no longer needed, I > now use 'call __kernel_vsyscall', and I added -Bsymbolic to make it > work. vdso2c will generate an error and abort the build if the > resulting image contains any dynamic relocations, so we won't > silently generate bad vdso images. > > (Dynamic relocations are a problem because nothing will even attempt > to relocate the vdso.) > > Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > Link: http://lkml.kernel.org/r/2c4fcf45524162a34d87fdda1eb046b2a5cecee7.1399317206.git.luto@xxxxxxxxxxxxxx > Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> > --- -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
