Re: [PATCH v1 1/5] lib/string: Add memset_simple()

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

On 8/6/21 5:36 PM, Wolfgang Denk wrote:
> Dear Stefan,
>
> In message <20210806133843.3642916-2-sr@denx.de> you wrote:
>> The optimized memset() ARM64 implementation cannot be used very early
>> on, since caches need to be enabled for this function to work. Otherwise
>> an exception occurs (only printed with very early DEBUG_UART enabled).
>>
>> This patch now implements a very simple memset() version, which will be
>> used in a few selected places in the ARM64 early boot process.
> ...
>
> We have already implementations of memset() elsewhere, for example in
> lib/string.c [hey, that's even the file you are modifying...], then
> again in lib/efi/efi_stub.c and also in
> lib/efi_loader/efi_freestanding.c - so do we really need another
> implementation?
>
> BTW: lib/efi_loader/efi_freestanding.c  looks completely useless to
> me.  Can we dump this? [Adding Heinich to Cc:]

EFI binaries are freestanding. They cannot use any U-Boot library
function except the UEFI API exposed via the system table.

We compile EFI binaries with GCC parameter -ffreestanding. As we do not
include any GCC library it is assumed that functions like memset() are
provided by the compiled source package. This is where
efi_freestanding.c comes in.

Please, have a look at

scripts/Makefile.lib:420:
targets += $(obj)/efi_crt0.o $(obj)/efi_reloc.o $(obj)/efi_freestanding.o

where we link the efi_freestanding.o module into every EFI binary.

Best regards

Heinrich

>
>
>> +void *memset_simple(void *s, int c, size_t count)
>> +{
>> +	char *s8 = (char *)s;
>> +
>> +	while (count--)
>> +		*s8++ = c;
>> +
>> +	return s;
>> +}
>
> In which way is this different from memset() as defined in the same
> file (further up) with CONFIG_TINY_MEMSET enabled?  And even without
> this option the memset() implementation here should work.  Or does
> it not?
>
> Best regards,
>
> Wolfgang Denk
>