RISC-V: add infrastructure to allow different str*
From: Heiko Stuebner <heiko.stuebner@...> Date: Thu, 22 Sep 2022 17:39:14 +0200
Commit-Message
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. Signed-off-by: Heiko Stuebner <heiko.stuebner@...>
Patch-Comment
arch/riscv/include/asm/string.h | 10 +++++++++ arch/riscv/kernel/riscv_ksyms.c | 3 +++ arch/riscv/lib/Makefile | 3 +++ arch/riscv/lib/strcmp.S | 37 ++++++++++++++++++++++++++++++ arch/riscv/lib/strlen.S | 28 +++++++++++++++++++++++ arch/riscv/lib/strncmp.S | 40 +++++++++++++++++++++++++++++++++ arch/riscv/purgatory/Makefile | 13 +++++++++++ 7 files changed, 134 insertions(+) create mode 100644 arch/riscv/lib/strcmp.S create mode 100644 arch/riscv/lib/strlen.S create mode 100644 arch/riscv/lib/strncmp.S
Statistics
- 134 lines added
- 0 lines removed
Changes
----------------------- arch/riscv/include/asm/string.h ------------------------
index 909049366555..a96b1fea24fe 100644
@@ -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)
----------------------- arch/riscv/kernel/riscv_ksyms.c ------------------------
index 5ab1c7e1a6ed..a72879b4249a 100644
@@ -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);
--------------------------- arch/riscv/lib/Makefile ----------------------------
index 25d5c9664e57..6c74b0bedd60 100644
@@ -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
--------------------------- arch/riscv/lib/strcmp.S ----------------------------
new file mode 100644
index 000000000000..94440fb8390c
@@ -0,0 +1,37 @@
+/* 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, t2
+ */
+ mv t2, a1
+1:
+ lbu t1, 0(a0)
+ lbu t0, 0(a1)
+ addi a0, a0, 1
+ addi a1, a1, 1
+ beq t1, t0, 3f
+ li a0, 1
+ bgeu t1, t0, 2f
+ li a0, -1
+2:
+ mv a1, t2
+ ret
+3:
+ bnez t1, 1b
+ li a0, 0
+ j 2b
+SYM_FUNC_END(strcmp)
--------------------------- arch/riscv/lib/strlen.S ----------------------------
new file mode 100644
index 000000000000..09a7aaff26c8
@@ -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)
+ bnez t0, 2f
+ sub a0, t1, a0
+ ret
+2:
+ addi t1, t1, 1
+ j 1b
+SYM_FUNC_END(strlen)
--------------------------- arch/riscv/lib/strncmp.S ---------------------------
new file mode 100644
index 000000000000..493ab6febcb2
@@ -0,0 +1,40 @@
+/* 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 t0, 0
+1:
+ beq a2, t0, 4f
+ add t1, a0, t0
+ add t2, a1, t0
+ lbu t1, 0(t1)
+ lbu t2, 0(t2)
+ beq t1, t2, 3f
+ li a0, 1
+ bgeu t1, t2, 2f
+ li a0, -1
+2:
+ ret
+3:
+ addi t0, t0, 1
+ bnez t1, 1b
+4:
+ li a0, 0
+ j 2b
+SYM_FUNC_END(strncmp)
------------------------ arch/riscv/purgatory/Makefile -------------------------
index dd58e1d99397..d16bf715a586 100644
@@ -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)