Hello Keno, On 3/16/20 4:21 AM, Keno Fischer wrote: > This subcommand was added a few years ago to support cpuid emulation > on x86 targets, but no changes to the man page appear to have been > made at the time. This commit adds a description for it and the > corresponding getter. > > Signed-off-by: Keno Fischer <keno@xxxxxxxxxxxxxxxxxx> Thanks. Patch applied. Cheers, Michael > --- > man2/arch_prctl.2 | 43 ++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 42 insertions(+), 1 deletion(-) > > diff --git a/man2/arch_prctl.2 b/man2/arch_prctl.2 > index c49f4e0..e40d6bb 100644 > --- a/man2/arch_prctl.2 > +++ b/man2/arch_prctl.2 > @@ -48,7 +48,44 @@ for the "set" operations, or as an > .IR "unsigned long\ *" , > for the "get" operations. > .PP > -Subfunctions for x86-64 are: > +Subfunctions for both x86 and x86-64 are: > +.TP > +.BR ARCH_SET_CPUID " (since Linux 4.12)" > +Enable ( > +.I addr != 0 > +) or disable ( > +.I addr == 0 > +) the > +.I cpuid > +instruction for the current thread. The instruction > +is enabled by default. If disabled, > +any execution of a > +.I cpuid > +instruction will instead generate a > +.B SIGSEGV > +signal. This feature can be used to emulate > +.I cpuid > +results that differ from what the underlying > +hardware would have produced (e.g. in a paravirtualization setting). > +This setting is preserved across > +.BR fork (2) > +and > +.BR clone (2) > +but reset to default (i.e. > +.I cpuid > +enabled) on > +.BR execve (2) > +. > +.TP > +.BR ARCH_GET_CPUID " (since Linux 4.12)" > +Return the setting of the flag manipulated by > +.B ARCH_SET_CPUID > +as the result of the system call (1 for enabled, 0 for disabled). > +.I addr > +is ignored. > + > +.TP > +Subfunctions for x86-64 only are: > .TP > .B ARCH_SET_FS > Set the 64-bit base for the > @@ -96,6 +133,10 @@ is not a valid subcommand. > .B EPERM > .I addr > is outside the process address space. > +.TP > +.B ENODEV > +.B ARCH_SET_CPUID > +was requested, but the underlying hardware does not support CPUID faulting. > .\" .SH AUTHOR > .\" Man page written by Andi Kleen. > .SH CONFORMING TO > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
