On Tue, Sep 08, 2020 at 10:43:12AM +0530, Anshuman Khandual wrote: > > > On 09/07/2020 05:46 PM, Will Deacon wrote: > > On Mon, Aug 17, 2020 at 05:34:23PM +0530, Anshuman Khandual wrote: > >> HWCAP name arrays (hwcap_str, compat_hwcap_str, compat_hwcap2_str) that are > >> scanned for /proc/cpuinfo are detached from their bit definitions making it > >> vulnerable and difficult to correlate. It is also bit problematic because > >> during /proc/cpuinfo dump these arrays get traversed sequentially assuming > >> they reflect and match actual HWCAP bit sequence, to test various features > >> for a given CPU. This redefines name arrays per their HWCAP bit definitions > >> . It also warns after detecting any feature which is not expected on arm64. > >> > >> Cc: Catalin Marinas <catalin.mari...@arm.com> > >> Cc: Will Deacon <w...@kernel.org> > >> Cc: Mark Brown <broo...@kernel.org> > >> Cc: Dave Martin <dave.mar...@arm.com> > >> Cc: Ard Biesheuvel <a...@kernel.org> > >> Cc: Mark Rutland <mark.rutl...@arm.com> > >> Cc: Suzuki K Poulose <suzuki.poul...@arm.com> > >> Cc: linux-arm-ker...@lists.infradead.org > >> Cc: linux-kernel@vger.kernel.org > >> Signed-off-by: Anshuman Khandual <anshuman.khand...@arm.com> > >> --- > >> This applies on 5.9-rc1 > >> > >> Mark, since the patch has changed I have dropped your Acked-by: tag. Are > >> you > >> happy to give a new one ? > >> > >> Changes in V3: > >> > >> - Moved name arrays to (arch/arm64/kernel/cpuinfo.c) to prevent a build > >> warning > >> - Replaced string values with NULL for all compat features not possible on > >> arm64 > >> - Changed compat_hwcap_str[] iteration on size as some NULL values are > >> expected > >> - Warn once after detecting any feature on arm64 that is not expected > >> > >> Changes in V2: (https://patchwork.kernel.org/patch/11533755/) > >> > >> - Defined COMPAT_KERNEL_HWCAP[2] and updated the name arrays per Mark > >> - Updated the commit message as required > >> > >> Changes in V1: (https://patchwork.kernel.org/patch/11532945/) > >> > >> arch/arm64/include/asm/hwcap.h | 9 +++ > >> arch/arm64/kernel/cpuinfo.c | 172 > >> ++++++++++++++++++++++------------------- > >> 2 files changed, 100 insertions(+), 81 deletions(-) > > > > [...] > > > >> + [KERNEL_HWCAP_FP] = "fp", > >> + [KERNEL_HWCAP_ASIMD] = "asimd", > >> + [KERNEL_HWCAP_EVTSTRM] = "evtstrm", > >> + [KERNEL_HWCAP_AES] = "aes", > > > > It would be nice if the cap and the string were generated by the same > > macro, along the lines of: > > > > #define KERNEL_HWCAP(c) [KERNEL_HWCAP_##c] = #c, > > > > Does making the constants mixed case break anything, or is it just really > > churny to do? > > Currently all existing HWCAP feature strings are lower case, above change > will make them into upper case instead. I could not find a method to force > convert #c into lower case constant strings in the macro definition. Would > not changing the HWCAP string case here, break user interface ?
Yes, we can't change the user-visible strings, but what's wrong with having e.g. KERNEL_HWCAP_fp instead of KERNEL_HWCAP_FP? Will
