[PATCH] um: allow using glibc string functions instead of generics
anton.ivanov at cambridgegreys.com
anton.ivanov at cambridgegreys.com
Tue Nov 10 11:30:34 EST 2020
From: Anton Ivanov <anton.ivanov at cambridgegreys.com>
UML kernel runs as a normal userspace process and can use the
optimized glibc strings functions like strcpy, memcpy, etc.
The support is optional and is turned on/of using a config
option.
Using glibc functions results in a slightly smaller executable
when linked dynamically as well as anything between 1% and 5%
performance improvements.
Signed-off-by: Anton Ivanov <anton.ivanov at cambridgegreys.com>
---
arch/um/Kconfig | 11 +++++
arch/um/include/asm/string.h | 72 +++++++++++++++++++++++++++
arch/um/include/shared/os_string.h | 30 ++++++++++++
arch/um/os-Linux/Makefile | 4 +-
arch/um/os-Linux/string.c | 78 ++++++++++++++++++++++++++++++
5 files changed, 193 insertions(+), 2 deletions(-)
create mode 100644 arch/um/include/asm/string.h
create mode 100644 arch/um/include/shared/os_string.h
create mode 100644 arch/um/os-Linux/string.c
diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 4b799fad8b48..961cf3af3ff0 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -189,6 +189,17 @@ config UML_TIME_TRAVEL_SUPPORT
It is safe to say Y, but you probably don't need this.
+config UML_USE_HOST_STRINGS
+ bool
+ default y
+ prompt "Use glibc strings and memory functions"
+ help
+ UML runs as a normal userspace process. As a result it can use
+ the optimized strcpy, memcpy, etc from glibc instead of the
+ kernel generic equivalents. This provides some minimal speedup
+ in the 1% or so range for most applications. It also results in
+ a smaller executable.
+
endmenu
source "arch/um/drivers/Kconfig"
diff --git a/arch/um/include/asm/string.h b/arch/um/include/asm/string.h
new file mode 100644
index 000000000000..1fba8d59afe5
--- /dev/null
+++ b/arch/um/include/asm/string.h
@@ -0,0 +1,72 @@
+#ifndef __ASM_UM_STRING_H
+#define __ASM_UM_STRING_H
+
+#ifdef CONFIG_UML_USE_HOST_STRINGS
+
+/* UML saves and restores registers when going to/from
+ * userspace. This allows the use of normal userspace
+ * functions for strings with all relevant glibc processor
+ * optimizations
+ */
+
+#include <os_string.h>
+
+#define __HAVE_ARCH_STRCPY
+
+#define strcpy(dest, src) os_strcpy(dest, src);
+
+#define __HAVE_ARCH_STRNCPY
+
+#define strncpy(dest, src, count) os_strncpy(dest, src, count)
+
+#define __HAVE_ARCH_STRCAT
+
+#define strcat(dest, src) os_strcat(dest, src)
+
+#define __HAVE_ARCH_STRNCAT
+
+#define strncat(dest, src, count) os_strncat(dest, src, count)
+
+#define __HAVE_ARCH_STRCMP
+
+#define strcmp(cs, ct) os_strcmp(cs, ct)
+
+#define __HAVE_ARCH_STRNCMP
+
+#define strncmp(cs, ct, count) os_strncmp(cs, ct, count)
+
+#define __HAVE_ARCH_STRCHR
+
+#define strchr(s, c) os_strchr(s, c)
+
+#define __HAVE_ARCH_STRLEN
+
+#define strlen(s) os_strlen(s)
+
+#define __HAVE_ARCH_MEMCPY
+
+#define memcpy(dst, src, n) os_memcpy(dst, src, n)
+
+#define __HAVE_ARCH_MEMMOVE
+
+#define memmove(dest, src, n) os_memmove(dest, src, n)
+
+#define __HAVE_ARCH_MEMCHR
+
+#define memchr(cs, c, count) os_memchr(cs, c, count)
+
+#define __HAVE_ARCH_STRNLEN
+
+#define strnlen(s, count) os_strnlen(s, count)
+
+#define __HAVE_ARCH_STRSTR
+
+#define strstr(cs, ct) os_strstr(cs, ct)
+
+#define __HAVE_ARCH_MEMSET
+
+#define memset(dst, c, n) os_memset(dst, c, n)
+
+#endif
+
+#endif /* __ASM_GENERIC_STRING_H */
diff --git a/arch/um/include/shared/os_string.h b/arch/um/include/shared/os_string.h
new file mode 100644
index 000000000000..b9662f622e77
--- /dev/null
+++ b/arch/um/include/shared/os_string.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
+ * Copyright (C) 2015 Thomas Meyer (thomas at m3y3r.de)
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#ifndef __OS_STRING_H__
+#define __OS_STRING_H__
+
+#include <stddef.h>
+
+/* string.c */
+
+extern char *os_strcpy(char *dest, const char *src);
+extern char *os_strncpy(char *dest, const char *src, size_t count);
+extern char *os_strcat(char *dest, const char *src);
+extern char *os_strncat(char *dest, const char *src, size_t count);
+extern int os_strcmp(const char *cs, const char *ct);
+extern int os_strncmp(const char *cs, const char *ct, size_t count);
+extern char *os_strchr(const char *s, int c);
+extern size_t os_strlen(const char *s);
+extern void *os_memcpy(void *dest, const void *src, size_t n);
+extern void *os_memmove(void *dest, const void *src, size_t n);
+extern void *os_memchr(const void *cs, int c, size_t count);
+extern size_t os_strnlen(const char *s, size_t count);
+extern char *os_strstr(const char *cs, const char *ct);
+extern void *os_memset(void *s, int c, size_t n);
+
+#endif
diff --git a/arch/um/os-Linux/Makefile b/arch/um/os-Linux/Makefile
index 839915b8c31c..f117f2514191 100644
--- a/arch/um/os-Linux/Makefile
+++ b/arch/um/os-Linux/Makefile
@@ -8,12 +8,12 @@ KCOV_INSTRUMENT := n
obj-y = execvp.o file.o helper.o irq.o main.o mem.o process.o \
registers.o sigio.o signal.o start_up.o time.o tty.o \
- umid.o user_syms.o util.o drivers/ skas/
+ umid.o user_syms.o util.o string.o drivers/ skas/
obj-$(CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA) += elf_aux.o
USER_OBJS := $(user-objs-y) elf_aux.o execvp.o file.o helper.o irq.o \
main.o mem.o process.o registers.o sigio.o signal.o start_up.o time.o \
- tty.o umid.o util.o
+ tty.o umid.o util.o string.o
include arch/um/scripts/Makefile.rules
diff --git a/arch/um/os-Linux/string.c b/arch/um/os-Linux/string.c
new file mode 100644
index 000000000000..abc76e2aecb3
--- /dev/null
+++ b/arch/um/os-Linux/string.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <stddef.h>
+#include <unistd.h>
+#include <string.h>
+#include <os_string.h>
+
+inline char *os_strcpy(char *dest, const char *src)
+{
+ return strcpy(dest, src);
+}
+
+inline char *os_strncpy(char *dest, const char *src, size_t count)
+{
+ return strncpy(dest, src, count);
+}
+
+inline char *os_strcat(char *dest, const char *src)
+{
+ return strcat(dest, src);
+}
+inline char *os_strncat(char *dest, const char *src, size_t count)
+{
+ return strncat(dest, src, count);
+}
+
+inline int os_strcmp(const char *cs, const char *ct)
+{
+ return strcmp(cs, ct);
+}
+
+inline int os_strncmp(const char *cs, const char *ct, size_t count)
+{
+ return strncmp(cs, ct, count);
+}
+
+inline char *os_strchr(const char *s, int c)
+{
+ return strchr(s, c);
+}
+inline size_t os_strlen(const char *s)
+{
+ return strlen(s);
+}
+
+inline void *os_memcpy(void *dest, const void *src, size_t n)
+{
+ return memcpy(dest, src, n);
+}
+
+inline void *os_memmove(void *dest, const void *src, size_t n)
+{
+ return memmove(dest, src, n);
+}
+
+inline void *os_memchr(const void *cs, int c, size_t count)
+{
+ return memchr(cs, c, count);
+}
+
+inline size_t os_strnlen(const char *s, size_t count)
+{
+ return strnlen(s, count);
+}
+
+inline char *os_strstr(const char *cs, const char *ct)
+{
+ return strstr(cs, ct);
+}
+
+inline void *os_memset(void *s, int c, size_t n)
+{
+ return memset(s, c, n);
+}
+
--
2.20.1
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