Messages in this thread | | | Date | Sun, 29 May 2011 21:19:24 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 0/5] x86-64: Remove syscall instructions at fixed addresses |
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* Andy Lutomirski <luto@MIT.EDU> wrote:
> I lied about taking awhile to do this.
Heh :-)
A very nice series btw!
> There are a bunch of syscall instructions in kernel space at fixed > addresses that user code can execute. > > One is a time() fallback. Patch 3/5 removes it. > > Several are data that isn't marked NX. Patch 2/5 makes vvars NX and > 5/5 makes the HPET NX. > > The last one is the gettimeofday fallback. We need that, but it > doesn't have to be a real syscall. Patch 3/5 adds int 0xCC (callable > only from the vsyscall page) that implements the gettimeofday fallback > and nothing else. > > Patch 1/5 is just a dumb but harmless bug fix from the last vdso > series. > > I've only tested this in KVM with a hacked-up initramfs, but Ingo > wanted it for 2.6.40, so here it is. > > Andy Lutomirski (5): > x86-64: Fix alignment of jiffies variable > x86-64: Give vvars their own page > x86-64: Remove kernel.vsyscall64 sysctl > x86-64: Replace vsyscall gettimeofday fallback with int 0xcc > x86-64: Map the HPET NX > > arch/x86/include/asm/fixmap.h | 1 + > arch/x86/include/asm/pgtable_types.h | 6 ++- > arch/x86/include/asm/traps.h | 4 ++ > arch/x86/include/asm/vgtod.h | 1 - > arch/x86/include/asm/vsyscall.h | 6 ++ > arch/x86/include/asm/vvar.h | 24 ++++----- > arch/x86/kernel/entry_64.S | 2 + > arch/x86/kernel/hpet.c | 2 +- > arch/x86/kernel/traps.c | 4 ++ > arch/x86/kernel/vmlinux.lds.S | 27 ++++++---- > arch/x86/kernel/vsyscall_64.c | 86 ++++++++++++++++++--------------- > arch/x86/vdso/vclock_gettime.c | 55 ++++++++------------- > tools/power/x86/turbostat/turbostat | Bin 0 -> 29200 bytes > 13 files changed, 117 insertions(+), 101 deletions(-) > create mode 100755 tools/power/x86/turbostat/turbostat
If no-one finds any review problems with these patches and if you fix the details i pointed out for 3/5 then we can do this for v2.6.40.
I really like this series, it makes full-PIE randomized user-space executables fully safe against known-address syscall instructions. As much as i like crazy speedups, they are probably more relevant to the everyday Linux user than the other patches ;-)
Btw., do you know CONFIG_X86_PTDUMP=y and /debug/kernel_page_tables? You could use that to double check that after your patches all executable (and fixed address) pages are removed [or are harmless].
Thanks,
Ingo
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