Messages in this thread | | | Date | Wed, 27 May 2020 08:53:04 +0100 | From | Will Deacon <> | Subject | Re: [PATCH V2] arm64/cpufeature: Add get_arm64_ftr_reg_nowarn() |
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On Wed, May 27, 2020 at 07:56:30AM +0530, Anshuman Khandual wrote: > > > On 05/27/2020 01:16 AM, Will Deacon wrote: > > On Tue, May 26, 2020 at 04:01:35PM +0100, Catalin Marinas wrote: > >> On Tue, May 26, 2020 at 07:09:13PM +0530, Anshuman Khandual wrote: > >>> @@ -632,8 +654,6 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) > >>> const struct arm64_ftr_bits *ftrp; > >>> struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg); > >>> > >>> - BUG_ON(!reg); > >>> - > >>> for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) { > >>> u64 ftr_mask = arm64_ftr_mask(ftrp); > >>> s64 ftr_new = arm64_ftr_value(ftrp, new); > >>> @@ -762,7 +782,6 @@ static int check_update_ftr_reg(u32 sys_id, int cpu, u64 val, u64 boot) > >>> { > >>> struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id); > >>> > >>> - BUG_ON(!regp); > >>> update_cpu_ftr_reg(regp, val); > >>> if ((boot & regp->strict_mask) == (val & regp->strict_mask)) > >>> return 0; > >>> @@ -776,9 +795,6 @@ static void relax_cpu_ftr_reg(u32 sys_id, int field) > >>> const struct arm64_ftr_bits *ftrp; > >>> struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id); > >>> > >>> - if (WARN_ON(!regp)) > >>> - return; > >> > >> I think Will wanted an early return in all these functions not just > >> removing the BUG_ON(). I'll let him clarify. > > > > Yes, the callers need to check the pointer and return early. > > Sure, will do. But for check_update_ftr_reg(), a feature register search > failure should be treated as a success (0) or a failure (1). What should > it return ? Seems bit tricky, as there are good reasons to go either way.
We're unable to check it so return 0, otherwise we'll randomly taint the kernel and print a weird message.
Will
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