Peter Zijlstra
2018-Sep-14 13:09 UTC
[patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support
On Fri, Sep 14, 2018 at 02:56:46PM +0200, Florian Weimer wrote:> On 09/14/2018 02:50 PM, Thomas Gleixner wrote: > > Matt attempted to add CLOCK_TAI support to the VDSO clock_gettime() > > implementation, which extended the clockid switch case and added yet > > another slightly different copy of the same code. > > > > Especially the extended switch case is problematic as the compiler tends to > > generate a jump table which then requires to use retpolines. > > Does vDSO code really have to use retpolines? It's in userspace, after all.Userspace is equally susceptible to spectre-v2. Ideally we'd recompile world with retpoline, but given the amount of inline asm in say things like openssl and similar projects, validating that there are indeed no indirect calls/jumps left is nontrivial. There are currently pending patches to otherwise address user-user spectre-v2 attacks.