Eli, Am 18.03.2016 um 02:41 schrieb Eli Cooper: > Hi Richard, > > On 2016/3/18 6:21, Richard Weinberger wrote: >> Where exactly are the FPU regs restored in the sigregturn case? >> Not sure if I fully understand the error scenario. > > Well, sys_sigreturn() or sys_rt_sigreturn() calls copy_sc_from_user(), > and the latter copies fpstate, which is the saved FPU state before the > signal handler was invoked, from sigframe and restores it. > That is correct: after returning from the signal handler, the process is > in the same FPU state before it was invoked. > > However, userspace() saves the FPU state before a system call and > restores it after. In the sigreturn case, after sys_sigreturn() returns, > which has already made FPU in the right state, userspace() overwrites it > by making it in the state prior to the sigreturn was called (i.e., the > signal handler's state). That leaves the process in question a corrupted > FPU state.
Okay. That's what I thought/feared. I wonder how other architectures handle this case? Ideally I'd like to avoid as much extra code as possible in userspace(). Thanks, //richard ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785231&iu=/4140 _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
