This is a note to let you know that I've just added the patch titled
RISC-V: add infrastructure to allow different str* implementations
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
risc-v-add-infrastructure-to-allow-different-str-imp.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2a28b42819c86b1c46e790a94840fea8e3195e99
Author: Heiko Stuebner <heiko.stuebner@xxxxxxxx>
Date: Fri Jan 13 22:23:00 2023 +0100
RISC-V: add infrastructure to allow different str* implementations
[ Upstream commit 56e0790c7f9e59ba6a0f4b59981d1d6fbf43efb0 ]
Depending on supported extensions on specific RISC-V cores,
optimized str* functions might make sense.
This adds basic infrastructure to allow patching the function calls
via alternatives later on.
The Linux kernel provides standard implementations for string functions
but when architectures want to extend them, they need to provide their
own.
The added generic string functions are done in assembler (taken from
disassembling the main-kernel functions for now) to allow us to control
the used registers and extend them with optimized variants.
This doesn't override the compiler's use of builtin replacements. So still
first of all the compiler will select if a builtin will be better suitable
i.e. for known strings. For all regular cases we will want to later
select possible optimized variants and in the worst case fall back to the
generic implemention added with this change.
Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
Signed-off-by: Heiko Stuebner <heiko.stuebner@xxxxxxxx>
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230113212301.3534711-2-heiko@xxxxxxxxx
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Stable-dep-of: d83806c4c0cc ("purgatory: fix disabling debug info")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h
index 9090493665555..a96b1fea24fe4 100644
--- a/arch/riscv/include/asm/string.h
+++ b/arch/riscv/include/asm/string.h
@@ -18,6 +18,16 @@ extern asmlinkage void *__memcpy(void *, const void *, size_t);
#define __HAVE_ARCH_MEMMOVE
extern asmlinkage void *memmove(void *, const void *, size_t);
extern asmlinkage void *__memmove(void *, const void *, size_t);
+
+#define __HAVE_ARCH_STRCMP
+extern asmlinkage int strcmp(const char *cs, const char *ct);
+
+#define __HAVE_ARCH_STRLEN
+extern asmlinkage __kernel_size_t strlen(const char *);
+
+#define __HAVE_ARCH_STRNCMP
+extern asmlinkage int strncmp(const char *cs, const char *ct, size_t count);
+
/* For those files which don't want to check by kasan. */
#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
#define memcpy(dst, src, len) __memcpy(dst, src, len)
diff --git a/arch/riscv/kernel/riscv_ksyms.c b/arch/riscv/kernel/riscv_ksyms.c
index 5ab1c7e1a6ed5..a72879b4249a5 100644
--- a/arch/riscv/kernel/riscv_ksyms.c
+++ b/arch/riscv/kernel/riscv_ksyms.c
@@ -12,6 +12,9 @@
EXPORT_SYMBOL(memset);
EXPORT_SYMBOL(memcpy);
EXPORT_SYMBOL(memmove);
+EXPORT_SYMBOL(strcmp);
+EXPORT_SYMBOL(strlen);
+EXPORT_SYMBOL(strncmp);
EXPORT_SYMBOL(__memset);
EXPORT_SYMBOL(__memcpy);
EXPORT_SYMBOL(__memmove);
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index 25d5c9664e57e..6c74b0bedd60d 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -3,6 +3,9 @@ lib-y += delay.o
lib-y += memcpy.o
lib-y += memset.o
lib-y += memmove.o
+lib-y += strcmp.o
+lib-y += strlen.o
+lib-y += strncmp.o
lib-$(CONFIG_MMU) += uaccess.o
lib-$(CONFIG_64BIT) += tishift.o
diff --git a/arch/riscv/lib/strcmp.S b/arch/riscv/lib/strcmp.S
new file mode 100644
index 0000000000000..8babd712b9587
--- /dev/null
+++ b/arch/riscv/lib/strcmp.S
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm-generic/export.h>
+
+/* int strcmp(const char *cs, const char *ct) */
+SYM_FUNC_START(strcmp)
+ /*
+ * Returns
+ * a0 - comparison result, value like strcmp
+ *
+ * Parameters
+ * a0 - string1
+ * a1 - string2
+ *
+ * Clobbers
+ * t0, t1
+ */
+1:
+ lbu t0, 0(a0)
+ lbu t1, 0(a1)
+ addi a0, a0, 1
+ addi a1, a1, 1
+ bne t0, t1, 2f
+ bnez t0, 1b
+ li a0, 0
+ ret
+2:
+ /*
+ * strcmp only needs to return (< 0, 0, > 0) values
+ * not necessarily -1, 0, +1
+ */
+ sub a0, t0, t1
+ ret
+SYM_FUNC_END(strcmp)
diff --git a/arch/riscv/lib/strlen.S b/arch/riscv/lib/strlen.S
new file mode 100644
index 0000000000000..0a3b11853efdb
--- /dev/null
+++ b/arch/riscv/lib/strlen.S
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm-generic/export.h>
+
+/* int strlen(const char *s) */
+SYM_FUNC_START(strlen)
+ /*
+ * Returns
+ * a0 - string length
+ *
+ * Parameters
+ * a0 - String to measure
+ *
+ * Clobbers:
+ * t0, t1
+ */
+ mv t1, a0
+1:
+ lbu t0, 0(t1)
+ beqz t0, 2f
+ addi t1, t1, 1
+ j 1b
+2:
+ sub a0, t1, a0
+ ret
+SYM_FUNC_END(strlen)
diff --git a/arch/riscv/lib/strncmp.S b/arch/riscv/lib/strncmp.S
new file mode 100644
index 0000000000000..1f644d0a93f68
--- /dev/null
+++ b/arch/riscv/lib/strncmp.S
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm-generic/export.h>
+
+/* int strncmp(const char *cs, const char *ct, size_t count) */
+SYM_FUNC_START(strncmp)
+ /*
+ * Returns
+ * a0 - comparison result, value like strncmp
+ *
+ * Parameters
+ * a0 - string1
+ * a1 - string2
+ * a2 - number of characters to compare
+ *
+ * Clobbers
+ * t0, t1, t2
+ */
+ li t2, 0
+1:
+ beq a2, t2, 2f
+ lbu t0, 0(a0)
+ lbu t1, 0(a1)
+ addi a0, a0, 1
+ addi a1, a1, 1
+ bne t0, t1, 3f
+ addi t2, t2, 1
+ bnez t0, 1b
+2:
+ li a0, 0
+ ret
+3:
+ /*
+ * strncmp only needs to return (< 0, 0, > 0) values
+ * not necessarily -1, 0, +1
+ */
+ sub a0, t0, t1
+ ret
+SYM_FUNC_END(strncmp)
diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile
index dd58e1d993972..d16bf715a586b 100644
--- a/arch/riscv/purgatory/Makefile
+++ b/arch/riscv/purgatory/Makefile
@@ -2,6 +2,7 @@
OBJECT_FILES_NON_STANDARD := y
purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o
+purgatory-y += strcmp.o strlen.o strncmp.o
targets += $(purgatory-y)
PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
@@ -18,6 +19,15 @@ $(obj)/memcpy.o: $(srctree)/arch/riscv/lib/memcpy.S FORCE
$(obj)/memset.o: $(srctree)/arch/riscv/lib/memset.S FORCE
$(call if_changed_rule,as_o_S)
+$(obj)/strcmp.o: $(srctree)/arch/riscv/lib/strcmp.S FORCE
+ $(call if_changed_rule,as_o_S)
+
+$(obj)/strlen.o: $(srctree)/arch/riscv/lib/strlen.S FORCE
+ $(call if_changed_rule,as_o_S)
+
+$(obj)/strncmp.o: $(srctree)/arch/riscv/lib/strncmp.S FORCE
+ $(call if_changed_rule,as_o_S)
+
$(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE
$(call if_changed_rule,cc_o_c)
@@ -77,6 +87,9 @@ CFLAGS_ctype.o += $(PURGATORY_CFLAGS)
AFLAGS_REMOVE_entry.o += -Wa,-gdwarf-2
AFLAGS_REMOVE_memcpy.o += -Wa,-gdwarf-2
AFLAGS_REMOVE_memset.o += -Wa,-gdwarf-2
+AFLAGS_REMOVE_strcmp.o += -Wa,-gdwarf-2
+AFLAGS_REMOVE_strlen.o += -Wa,-gdwarf-2
+AFLAGS_REMOVE_strncmp.o += -Wa,-gdwarf-2
$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
$(call if_changed,ld)
