On Thu, Nov 19, 2020 at 10:18:15AM +0100, Borislav Petkov wrote: > On Thu, Nov 19, 2020 at 03:20:55PM +0800, Feng Tang wrote: > > I just tried the patch on one Debian 9 and 2 Ubuntus (16.04 & 20.10) with > > different gcc versions, and haven't reproduced it yet. > > That's because you're testing in VMs and they have CPUID(4) which baremetal - > where I am testing - doesn't and I get
That's really odd. I tried on 3 baremetal machines: one Skylake NUC device, one Xeon E5-2699 and one Xeon E5-2680. > parse_line: entry > parse_line: skip comments > parse_line: index/main leaf, func: 0x5588497d7300 > parse_line: sub 0, leafs: (nil) > ^^^^^^ Thanks for the debugging and root causing! > for leafs for index 4 and thus this is a NUL ptr. And leaf 4 is the test > range in cpuid.csv. > > Which brings me to another important point: setup_platform_cpuid() > should not blindly simply look at the two ranges 0 and 0x8000_0000 > but detect whether it is running on baremetal or on a hypervisor and > depending on which, setup the respective ranges. > > For example, guests would need to scan 0x4, in addition to the above. > Centaur CPUs have CPUID in the ranges 0xc0000000 and so on. > > But you don't have to implement all CPUID leafs and ranges - just your > tool should be careful and first detect on what it runs and then scan > the possible ranges. Ok, will check more on this. > And then exit gracefully when it encounters a range which it doesn't > know and not segfault. Yes, it needs to consider more possible errors. > There could be another option which, when set, would go and scan the > *whole* 32-bit CPUID range to find whether there are some CPUID ranges > which are not known. Another option because the scan would potentially > take long time and thus off by default. And so on. > > Here's the patch I've cleaned up and fixed up so far, please continue > with it. Thanks! will go with this version. - Feng > Thx. > > --- > >From 244c34532d1596a0e3603683904497847bb26b1c Mon Sep 17 00:00:00 2001 > From: Feng Tang <feng.t...@intel.com> > Date: Thu, 22 Oct 2020 13:21:23 +0800 > Subject: [PATCH] tools/x86: Add a kcpuid tool to show raw CPU features > MIME-Version: 1.0 > Content-Type: text/plain; charset=UTF-8 > Content-Transfer-Encoding: 8bit > > End users frequently want to know what features their processor > supports, independent of what the kernel supports. > > /proc/cpuinfo is great. It is omnipresent and since it is provided by > the kernel it is always as up to date as the kernel. But, it could be > ambiguous about processor features which can be disabled by the kernel > at boot-time or compile-time. > > There are some user space tools showing more raw features, but they are > not bound with kernel, and go with distros. Many end users are still > using old distros with new kernels (upgraded by themselves), and may > not upgrade the distros only to get a newer tool. > > So here arise the need for a new tool, which > * shows raw CPU features read from the CPUID instruction > * will be easier to update compared to existing userspace > tooling (perhaps distributed like perf) > * inherits "modern" kernel development process, in contrast to some > of the existing userspace CPUID tools which are still being developed > without git and distributed in tarballs from non-https sites. > * Can produce output consistent with /proc/cpuinfo to make comparison > easier. > > The CPUID leaf definitions are kept in an .csv file which allows for > updating only that file to add support for new feature leafs. > > This is based on prototype code from Borislav Petkov > (http://sr71.net/~dave/intel/stupid-cpuid.c). > > [ bp: Massage, add #define _GNU_SOURCE to fix implicit declaration of > function ‘strcasestr' warning. ] > > Originally-from: Borislav Petkov <b...@alien8.de> > Suggested-by: Dave Hansen <dave.han...@intel.com> > Suggested-by: Borislav Petkov <b...@alien8.de> > Signed-off-by: Feng Tang <feng.t...@intel.com> > Signed-off-by: Borislav Petkov <b...@suse.de> > Link: > https://lkml.kernel.org/r/1603344083-100742-1-git-send-email-feng.t...@intel.com > --- > tools/arch/x86/kcpuid/Makefile | 24 ++ > tools/arch/x86/kcpuid/cpuid.csv | 57 +++ > tools/arch/x86/kcpuid/kcpuid.c | 623 ++++++++++++++++++++++++++++++++ > 3 files changed, 704 insertions(+) > create mode 100644 tools/arch/x86/kcpuid/Makefile > create mode 100644 tools/arch/x86/kcpuid/cpuid.csv > create mode 100644 tools/arch/x86/kcpuid/kcpuid.c
