[PATCH v2 12/16] xz: Add RISC-V BCJ filter

Lasse Collin
2024-07-21T13:37:16Z

A later commit updates lib/decompress_unxz.c to enable this filter for
kernel decompression. lib/decompress_unxz.c is already used if
CONFIG_EFI_ZBOOT=y && CONFIG_KERNEL_XZ=y.

This filter can be used by Squashfs without modifications to the Squashfs
kernel code (only needs support in userspace Squashfs-tools).

Reviewed-by: Sam James <sam@gentoo.org>
Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
---
lib/xz/Kconfig | 5 +++
lib/xz/xz_dec_bcj.c | 104 ++++++++++++++++++++++++++++++++++++++++++-
lib/xz/xz_dec_syms.c | 2 +-
lib/xz/xz_private.h | 6 ++-
4 files changed, 114 insertions(+), 3 deletions(-)

diff --git a/lib/xz/Kconfig b/lib/xz/Kconfig
index 1166627a87dc..20aa459bfb3e 100644
--- a/lib/xz/Kconfig
+++ b/lib/xz/Kconfig
@@ -40,6 +40,11 @@ config XZ_DEC_SPARC
default y
select XZ_DEC_BCJ

+config XZ_DEC_RISCV
+ bool "RISC-V BCJ filter decoder" if EXPERT
+ default y
+ select XZ_DEC_BCJ
+
config XZ_DEC_MICROLZMA
bool "MicroLZMA decoder"
default n
diff --git a/lib/xz/xz_dec_bcj.c b/lib/xz/xz_dec_bcj.c
index 941198a8a55b..42d7f268726f 100644
--- a/lib/xz/xz_dec_bcj.c
+++ b/lib/xz/xz_dec_bcj.c
@@ -24,7 +24,8 @@ struct xz_dec_bcj {
BCJ_ARM = 7, /* Little endian only */
BCJ_ARMTHUMB = 8, /* Little endian only */
BCJ_SPARC = 9, /* Big or little endian */
- BCJ_ARM64 = 10 /* AArch64 */
+ BCJ_ARM64 = 10, /* AArch64 */
+ BCJ_RISCV = 11 /* RV32GQC_Zfh, RV64GQC_Zfh */
} type;

/*
@@ -388,6 +389,99 @@ static size_t bcj_arm64(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
}
#endif

+#ifdef XZ_DEC_RISCV
+static size_t bcj_riscv(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
+{
+ size_t i;
+ uint32_t b1;
+ uint32_t b2;
+ uint32_t b3;
+ uint32_t instr;
+ uint32_t instr2;
+ uint32_t instr2_rs1;
+ uint32_t addr;
+
+ if (size < 8)
+ return 0;
+
+ size -= 8;
+
+ for (i = 0; i <= size; i += 2) {
+ instr = buf[i];
+
+ if (instr == 0xEF) {
+ /* JAL */
+ b1 = buf[i + 1];
+ if ((b1 & 0x0D) != 0)
+ continue;
+
+ b2 = buf[i + 2];
+ b3 = buf[i + 3];
+
+ addr = ((b1 & 0xF0) << 13) | (b2 << 9) | (b3 << 1);
+ addr -= s->pos + (uint32_t)i;
+
+ buf[i + 1] = (uint8_t)((b1 & 0x0F)
+ | ((addr >> 8) & 0xF0));
+
+ buf[i + 2] = (uint8_t)(((addr >> 16) & 0x0F)
+ | ((addr >> 7) & 0x10)
+ | ((addr << 4) & 0xE0));
+
+ buf[i + 3] = (uint8_t)(((addr >> 4) & 0x7F)
+ | ((addr >> 13) & 0x80));
+
+ i += 4 - 2;
+
+ } else if ((instr & 0x7F) == 0x17) {
+ /* AUIPC */
+ instr |= (uint32_t)buf[i + 1] << 8;
+ instr |= (uint32_t)buf[i + 2] << 16;
+ instr |= (uint32_t)buf[i + 3] << 24;
+
+ if (instr & 0xE80) {
+ /* AUIPC's rd doesn't equal x0 or x2. */
+ instr2 = get_unaligned_le32(buf + i + 4);
+
+ if (((instr << 8) ^ (instr2 - 3)) & 0xF8003) {
+ i += 6 - 2;
+ continue;
+ }
+
+ addr = (instr & 0xFFFFF000) + (instr2 >> 20);
+
+ instr = 0x17 | (2 << 7) | (instr2 << 12);
+ instr2 = addr;
+ } else {
+ /* AUIPC's rd equals x0 or x2. */
+ instr2_rs1 = instr >> 27;
+
+ if ((uint32_t)((instr - 0x3117) << 18)
+ >= (instr2_rs1 & 0x1D)) {
+ i += 4 - 2;
+ continue;
+ }
+
+ addr = get_unaligned_be32(buf + i + 4);
+ addr -= s->pos + (uint32_t)i;
+
+ instr2 = (instr >> 12) | (addr << 20);
+
+ instr = 0x17 | (instr2_rs1 << 7)
+ | ((addr + 0x800) & 0xFFFFF000);
+ }
+
+ put_unaligned_le32(instr, buf + i);
+ put_unaligned_le32(instr2, buf + i + 4);
+
+ i += 8 - 2;
+ }
+ }
+
+ return i;
+}
+#endif
+
/*
* Apply the selected BCJ filter. Update *pos and s->pos to match the amount
* of data that got filtered.
@@ -439,6 +533,11 @@ static void bcj_apply(struct xz_dec_bcj *s,
case BCJ_ARM64:
filtered = bcj_arm64(s, buf, size);
break;
+#endif
+#ifdef XZ_DEC_RISCV
+ case BCJ_RISCV:
+ filtered = bcj_riscv(s, buf, size);
+ break;
#endif
default:
/* Never reached but silence compiler warnings. */
@@ -615,6 +714,9 @@ XZ_EXTERN enum xz_ret xz_dec_bcj_reset(struct xz_dec_bcj *s, uint8_t id)
#endif
#ifdef XZ_DEC_ARM64
case BCJ_ARM64:
+#endif
+#ifdef XZ_DEC_RISCV
+ case BCJ_RISCV:
#endif
break;

diff --git a/lib/xz/xz_dec_syms.c b/lib/xz/xz_dec_syms.c
index 495d2cc2e6e8..f40817d65897 100644
--- a/lib/xz/xz_dec_syms.c
+++ b/lib/xz/xz_dec_syms.c
@@ -22,6 +22,6 @@ EXPORT_SYMBOL(xz_dec_microlzma_end);
#endif

MODULE_DESCRIPTION("XZ decompressor");
-MODULE_VERSION("1.1");
+MODULE_VERSION("1.2");
MODULE_AUTHOR("Lasse Collin <lasse.collin@tukaani.org> and Igor Pavlov");
MODULE_LICENSE("Dual BSD/GPL");
diff --git a/lib/xz/xz_private.h b/lib/xz/xz_private.h
index 307e0de8c260..a8b1cbe8d21d 100644
--- a/lib/xz/xz_private.h
+++ b/lib/xz/xz_private.h
@@ -39,6 +39,9 @@
# ifdef CONFIG_XZ_DEC_ARM64
# define XZ_DEC_ARM64
# endif
+# ifdef CONFIG_XZ_DEC_RISCV
+# define XZ_DEC_RISCV
+# endif
# ifdef CONFIG_XZ_DEC_MICROLZMA
# define XZ_DEC_MICROLZMA
# endif
@@ -102,7 +105,8 @@
# if defined(XZ_DEC_X86) || defined(XZ_DEC_POWERPC) \
|| defined(XZ_DEC_IA64) \
|| defined(XZ_DEC_ARM) || defined(XZ_DEC_ARMTHUMB) \
- || defined(XZ_DEC_SPARC) || defined(XZ_DEC_ARM64)
+ || defined(XZ_DEC_SPARC) || defined(XZ_DEC_ARM64) \
+ || defined(XZ_DEC_RISCV)
# define XZ_DEC_BCJ
# endif
#endif
--
2.45.2