Re: [PATCH v7 1/3] riscv: Avoid unaligned access when relocating modules

[Andreas Schwab]

On Okt 31 2023, Emil Renner Berthing wrote:

>> +static int riscv_insn_rmw(void *location, u32 keep, u32 set)
>> +{
>> +	u16 *parcel = location;
>> +	u32 insn = (u32)le16_to_cpu(parcel[0]) | (u32)le16_to_cpu(parcel[1]) << 16;
>> +
>> +	insn &= keep;
>> +	insn |= set;
>> +
>> +	parcel[0] = cpu_to_le32(insn);
>
> Why cpu_to_le32(insn)? Unless I've misunderstood something downcasting unsigned
> to unsigned values in C (eg. from u32 to u16) is defined to always discard the
> most signifcant bits, so cpu_to_le16(insn) should be fine.

cpu_to_le32(insn) can't be right here anyway, since it also swaps the
two u16 halves and would be the same as cpu_to_le16(insn >> 16) on big
endian.

-- 
Andreas Schwab, schwab@xxxxxxxxxxxxxx
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