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SubjectRe: [PATCH 2/2] MIPS: Add support for ZSTD-compressed kernels
Hi Nick,

Le lun. 24 août 2020 à 19:51, Nick Terrell <terrelln@fb.com> a écrit
:
>
>
>> On Aug 21, 2020, at 9:29 AM, Paul Cercueil <paul@crapouillou.net>
>> wrote:
>>
>> Add support for self-extracting kernels with a ZSTD compression.
>>
>> Tested on a kernel for the GCW-Zero, it allows to reduce the size
>> of the
>> kernel file from 4.1 MiB with gzip to 3.5 MiB with ZSTD, and boots
>> just
>> as fast.
>>
>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>> ---
>> arch/mips/Kconfig | 1 +
>> arch/mips/boot/compressed/Makefile | 1 +
>> arch/mips/boot/compressed/decompress.c | 4 ++++
>> arch/mips/boot/compressed/string.c | 16 ++++++++++++++++
>> 4 files changed, 22 insertions(+)
>>
>> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
>> index c95fa3a2484c..b9d7c4249dc9 100644
>> --- a/arch/mips/Kconfig
>> +++ b/arch/mips/Kconfig
>> @@ -1890,6 +1890,7 @@ config SYS_SUPPORTS_ZBOOT
>> select HAVE_KERNEL_LZMA
>> select HAVE_KERNEL_LZO
>> select HAVE_KERNEL_XZ
>> + select HAVE_KERNEL_ZSTD
>>
>> config SYS_SUPPORTS_ZBOOT_UART16550
>> bool
>> diff --git a/arch/mips/boot/compressed/Makefile
>> b/arch/mips/boot/compressed/Makefile
>> index 6e56caef69f0..86ddc6fc16f4 100644
>> --- a/arch/mips/boot/compressed/Makefile
>> +++ b/arch/mips/boot/compressed/Makefile
>> @@ -70,6 +70,7 @@ tool_$(CONFIG_KERNEL_LZ4) = lz4
>> tool_$(CONFIG_KERNEL_LZMA) = lzma
>> tool_$(CONFIG_KERNEL_LZO) = lzo
>> tool_$(CONFIG_KERNEL_XZ) = xzkern
>> +tool_$(CONFIG_KERNEL_ZSTD) = zstd
>
> You can use zstd22 here. It will give you slightly better compression
> without any additional memory usage. Also, you should add
> -D__DISABLE_EXPORTS to the KBUILD_CFLAGS like x86 does [1].

Indeed, it's 0.01% smaller :)

What is __DISABLE_EXPORTS for?

-Paul

>
> [1]
> https://github.com/torvalds/linux/blob/master/arch/x86/boot/compressed/Makefile
>
> -Nick
>
>> targets += vmlinux.bin.z
>> $(obj)/vmlinux.bin.z: $(obj)/vmlinux.bin FORCE
>> diff --git a/arch/mips/boot/compressed/decompress.c
>> b/arch/mips/boot/compressed/decompress.c
>> index 88f5d637b1c4..c61c641674e6 100644
>> --- a/arch/mips/boot/compressed/decompress.c
>> +++ b/arch/mips/boot/compressed/decompress.c
>> @@ -72,6 +72,10 @@ void error(char *x)
>> #include "../../../../lib/decompress_unxz.c"
>> #endif
>>
>> +#ifdef CONFIG_KERNEL_ZSTD
>> +#include "../../../../lib/decompress_unzstd.c"
>> +#endif
>> +
>> const unsigned long __stack_chk_guard = 0x000a0dff;
>>
>> void __stack_chk_fail(void)
>> diff --git a/arch/mips/boot/compressed/string.c
>> b/arch/mips/boot/compressed/string.c
>> index 43beecc3587c..ab95722ec0c9 100644
>> --- a/arch/mips/boot/compressed/string.c
>> +++ b/arch/mips/boot/compressed/string.c
>> @@ -27,3 +27,19 @@ void *memset(void *s, int c, size_t n)
>> ss[i] = c;
>> return s;
>> }
>> +
>> +void *memmove(void *dest, const void *src, size_t n)
>> +{
>> + unsigned int i;
>> + const char *s = src;
>> + char *d = dest;
>> +
>> + if ((uintptr_t)dest < (uintptr_t)src) {
>> + for (i = 0; i < n; i++)
>> + d[i] = s[i];
>> + } else {
>> + for (i = n; i > 0; i--)
>> + d[i - 1] = s[i - 1];
>> + }
>> + return dest;
>> +}
>> --
>> 2.28.0
>>


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