[PATCH v2 3/3] ARM: compressed: Enable ZSTD compression

[Andreas Kemnade <andreas@kemnade.info>]

With the previous two commits, it is possible to enable ZSTD
in the decompressor stub for 32-bit ARM.

KASAN logic for XZ is extended for ZSTD, since
the affected functions are also in use.

Measurement was done with clang-19.
Setup was: starting a fastboot image via u-boot,
serial console attached.
Time was measured using ts -s %.s </dev/ttyUSBx | tee logfile
from the last words from u-boot still the first
kernel message. No early serial output was in use.

GTA04 (OMAP3) with something based on omap2plus_defconfig:
     zImage size	time
GZIP 7997 KiB		1.6s
LZMA 5794 KiB		4.6s
ZSTD 6774 KiB		2.7s

Tolino Shine 2 HD (i.MX6SL) with something based on imx_v6_v7_defconfig

GZIP 10499 KiB		 0.9s
LZMA 7611 KiB		 3.8s
ZSTD 8884 KiB		 2.0s

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
---
 arch/arm/Kconfig                      |  1 +
 arch/arm/boot/compressed/Makefile     |  1 +
 arch/arm/boot/compressed/decompress.c | 11 ++++++++++-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 9187240a02db5..cf612ee4064c3 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -122,6 +122,7 @@ config ARM
 	select HAVE_KERNEL_LZMA
 	select HAVE_KERNEL_LZO
 	select HAVE_KERNEL_XZ
+	select HAVE_KERNEL_ZSTD
 	select HAVE_KPROBES if !XIP_KERNEL && !CPU_ENDIAN_BE32 && !CPU_V7M
 	select HAVE_KRETPROBES if HAVE_KPROBES
 	select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if (LD_VERSION >= 23600 || LD_IS_LLD) && LD_CAN_USE_KEEP_IN_OVERLAY
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index fa6ee23cd72eb..1c6638e1999ab 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -74,6 +74,7 @@ compress-$(CONFIG_KERNEL_LZO)  = lzo_with_size
 compress-$(CONFIG_KERNEL_LZMA) = lzma_with_size
 compress-$(CONFIG_KERNEL_XZ)   = xzkern_with_size
 compress-$(CONFIG_KERNEL_LZ4)  = lz4_with_size
+compress-$(CONFIG_KERNEL_ZSTD)  = zstd22_with_size
 
 libfdt_objs := fdt_rw.o fdt_ro.o fdt_wip.o fdt.o
 
diff --git a/arch/arm/boot/compressed/decompress.c b/arch/arm/boot/compressed/decompress.c
index b0352f379277f..5f82c0c754fa5 100644
--- a/arch/arm/boot/compressed/decompress.c
+++ b/arch/arm/boot/compressed/decompress.c
@@ -47,15 +47,24 @@ extern char * strchrnul(const char *, int);
 #include "../../../../lib/decompress_unlzma.c"
 #endif
 
-#ifdef CONFIG_KERNEL_XZ
+#if defined(CONFIG_KERNEL_XZ) || defined(CONFIG_KERNEL_ZSTD)
 /* Prevent KASAN override of string helpers in decompressor */
 #undef memmove
 #define memmove memmove
 #undef memcpy
 #define memcpy memcpy
+#undef memset
+#define memset memset
+#endif
+
+#ifdef CONFIG_KERNEL_XZ
 #include "../../../../lib/decompress_unxz.c"
 #endif
 
+#ifdef CONFIG_KERNEL_ZSTD
+#include "../../../../lib/decompress_unzstd.c"
+#endif
+
 #ifdef CONFIG_KERNEL_LZ4
 #include "../../../../lib/decompress_unlz4.c"
 #endif

-- 
2.47.3