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Subject[PATCH v2 2/2] MIPS: Add support for ZSTD-compressed kernels
Date
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.

Compressed kernels are now also compiled with -D__DISABLE_EXPORTS in
order to disable the EXPORT_SYMBOL() macros inside of
lib/zstd/decompress.c.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---

Notes:
v2: Add -D__DISABLE_EXPORTS to CFLAGS and use zstd22

arch/mips/Kconfig | 1 +
arch/mips/boot/compressed/Makefile | 3 ++-
arch/mips/boot/compressed/decompress.c | 4 ++++
arch/mips/boot/compressed/string.c | 16 ++++++++++++++++
4 files changed, 23 insertions(+), 1 deletion(-)

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..9a9ba77b745e 100644
--- a/arch/mips/boot/compressed/Makefile
+++ b/arch/mips/boot/compressed/Makefile
@@ -22,7 +22,7 @@ KBUILD_CFLAGS := $(filter-out -pg, $(KBUILD_CFLAGS))

KBUILD_CFLAGS := $(filter-out -fstack-protector, $(KBUILD_CFLAGS))

-KBUILD_CFLAGS := $(KBUILD_CFLAGS) -D__KERNEL__ \
+KBUILD_CFLAGS := $(KBUILD_CFLAGS) -D__KERNEL__ -D__DISABLE_EXPORTS \
-DBOOT_HEAP_SIZE=$(BOOT_HEAP_SIZE) -D"VMLINUX_LOAD_ADDRESS_ULL=$(VMLINUX_LOAD_ADDRESS)ull"

KBUILD_AFLAGS := $(KBUILD_AFLAGS) -D__ASSEMBLY__ \
@@ -70,6 +70,7 @@ tool_$(CONFIG_KERNEL_LZ4) = lz4
tool_$(CONFIG_KERNEL_LZMA) = lzma
tool_$(CONFIG_KERNEL_LZO) = lzo
tool_$(CONFIG_KERNEL_XZ) = xzkern
+tool_$(CONFIG_KERNEL_ZSTD) = zstd22

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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