There is one sensible address: end of address space perhaps minus some small offset. Unlikely to be used by anything specific.
On March 11, 2014 11:09:11 PM PDT, Andy Lutomirski <l...@amacapital.net> wrote: >On Mar 11, 2014 10:02 PM, "H. Peter Anvin" <h...@zytor.com> wrote: >> >> On 03/11/2014 03:15 PM, Andy Lutomirski wrote: >>> >>> The meat of this patch series is in patch 1. Patch 2 is split out >for >>> improved bisectability. >>> >>> Changes from v1: Split into two patches and fixed a comment. >>> >>> Andy Lutomirski (2): >>> x86: Dynamically relocate the compat vdso >>> x86_32: Remove user bit from identity map PDE >>> >>> Documentation/kernel-parameters.txt | 18 +++- >>> arch/x86/Kconfig | 24 +++-- >>> arch/x86/include/asm/elf.h | 4 - >>> arch/x86/include/asm/fixmap.h | 8 -- >>> arch/x86/include/asm/pgtable_types.h | 7 +- >>> arch/x86/include/asm/vdso.h | 5 +- >>> arch/x86/vdso/vdso-layout.lds.S | 2 +- >>> arch/x86/vdso/vdso32-setup.c | 173 >++++++++++++++++------------------- >>> arch/x86/vdso/vdso32/vdso32.lds.S | 2 - >>> 9 files changed, 111 insertions(+), 132 deletions(-) >>> >> >> Why per process? *If* we have compat vdso turned on, can't we just >put it in one place system-wide? > >My machine has ASLR turned on, and the vma really does end up >somewhere different each time. I suspect that most (?) ASLR users >would happily accept the 4k hit to keep ASLR working fully. > >Another downside of trying to have a common address for all processes: >someone needs to figure out what that address is. What happens if an >ELF binary (or interpreter) wants to load something at the chosen >address? > >--Andy -- Sent from my mobile phone. Please pardon brevity and lack of formatting. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
