Adds a endianness test function called native_endianness().
It has very low overhead (possibly none) compared to a simple
variable assignment.
Signed-off-by: Andreas Robinson <andr345@xxxxxxxxx>
---
depmod.c | 17 ++++-------------
depmod.h | 15 ---------------
modinfo.c | 22 ++--------------------
util.c | 12 ++++++++++++
util.h | 20 ++++++++++++++++++++
5 files changed, 38 insertions(+), 48 deletions(-)
diff --git a/depmod.c b/depmod.c
index 30d870c..9b6fda7 100644
--- a/depmod.c
+++ b/depmod.c
@@ -261,18 +261,6 @@ static int ends_in(const char *name, const char *ext)
return 0;
}
-/* "\177ELF" <byte> where byte = 001 for 32-bit, 002 for 64 */
-int needconv(const char *elfhdr)
-{
- union { short s; char c[2]; } endian_test;
-
- endian_test.s = 1;
- if (endian_test.c[1] == 1) return elfhdr[EI_DATA] != ELFDATA2MSB;
- if (endian_test.c[0] == 1) return elfhdr[EI_DATA] != ELFDATA2LSB;
- else
- abort();
-}
-
static struct module *grab_module(const char *dirname, const char *filename)
{
struct module *new;
@@ -313,7 +301,7 @@ static struct module *grab_module(const char *dirname, const char *filename)
new->pathname, ((char *)new->data)[EI_CLASS]);
goto fail;
}
- new->conv = needconv(new->data);
+ new->conv = ((char *)new->data)[EI_DATA] != native_endianness();
return new;
fail:
@@ -1166,6 +1154,9 @@ int main(int argc, char *argv[])
int i;
const char *config = NULL;
+ if (native_endianness() == 0)
+ abort();
+
/* Don't print out any errors just yet, we might want to exec
backwards compat version. */
opterr = 0;
diff --git a/depmod.h b/depmod.h
index decdf2e..32cab3d 100644
--- a/depmod.h
+++ b/depmod.h
@@ -60,19 +60,4 @@ struct module
char pathname[0];
};
-#define END(x, conv) \
-({ \
- typeof(x) __x; \
- if (conv) __convert_endian(&(x), &(__x), sizeof(__x)); \
- else __x = (x); \
- __x; \
-})
-
-static inline void __convert_endian(const void *src, void *dest,
- unsigned int size)
-{
- unsigned int i;
- for (i = 0; i < size; i++)
- ((unsigned char*)dest)[i] = ((unsigned char*)src)[size - i-1];
-}
#endif /* MODINITTOOLS_DEPMOD_H */
diff --git a/modinfo.c b/modinfo.c
index 2208b19..80e00d4 100644
--- a/modinfo.c
+++ b/modinfo.c
@@ -22,22 +22,8 @@
#endif
static int elf_endian;
-static int my_endian;
-static inline void __endian(const void *src, void *dest, unsigned int size)
-{
- unsigned int i;
- for (i = 0; i < size; i++)
- ((unsigned char*)dest)[i] = ((unsigned char*)src)[size - i-1];
-}
-
-#define TO_NATIVE(x) \
-({ \
- typeof(x) __x; \
- if (elf_endian != my_endian) __endian(&(x), &(__x), sizeof(__x)); \
- else __x = x; \
- __x; \
-})
+#define TO_NATIVE(x) END(x, elf_endian != native_endianness())
static void *get_section32(void *file, unsigned long *size, const char *name)
{
@@ -348,7 +334,6 @@ static void usage(const char *name)
int main(int argc, char *argv[])
{
- union { short s; char c[2]; } endian_test;
const char *field = NULL;
const char *kernel = NULL;
char sep = '\n';
@@ -356,10 +341,7 @@ int main(int argc, char *argv[])
int opt, ret = 0;
char *basedir = "";
- endian_test.s = 1;
- if (endian_test.c[1] == 1) my_endian = ELFDATA2MSB;
- else if (endian_test.c[0] == 1) my_endian = ELFDATA2LSB;
- else
+ if (native_endianness() == 0)
abort();
while ((opt = getopt_long(argc,argv,"adlpVhn0F:k:b:",options,NULL)) >= 0){
diff --git a/util.c b/util.c
index b65b090..3a390f7 100644
--- a/util.c
+++ b/util.c
@@ -1,5 +1,6 @@
#include <stdio.h>
#include <stdlib.h>
+#include <stdint.h>
#include <string.h>
#include "logging.h"
#include "util.h"
@@ -130,3 +131,14 @@ const char *next_string(const char *string, unsigned long *secsize)
}
return string;
}
+
+/*
+ * Get CPU endianness. 0 = unknown, 1 = ELFDATA2LSB = little, 2 = ELFDATA2MSB = big
+ */
+int __attribute__ ((pure)) native_endianness()
+{
+ /* Encoding the endianness enums in a string and then reading that
+ * string as a 32-bit int, returns the correct endianness automagically.
+ */
+ return (char) *((uint32_t*)("\1\0\0\2"));
+}
diff --git a/util.h b/util.h
index 9d41529..60e85e1 100644
--- a/util.h
+++ b/util.h
@@ -10,6 +10,26 @@ char *underscores(char *string);
const char *next_string(const char *string, unsigned long *secsize);
+/*
+ * Change endianness of x if conv is true.
+ */
+#define END(x, conv) \
+({ \
+ typeof(x) __x; \
+ if (conv) __swap_bytes(&(x), &(__x), sizeof(__x)); \
+ else __x = (x); \
+ __x; \
+})
+
+static inline void __swap_bytes(const void *src, void *dest, unsigned int size)
+{
+ unsigned int i;
+ for (i = 0; i < size; i++)
+ ((unsigned char*)dest)[i] = ((unsigned char*)src)[size - i-1];
+}
+
+int native_endianness(void);
+
#define streq(a,b) (strcmp((a),(b)) == 0)
#define strstarts(a,start) (strncmp((a),(start), strlen(start)) == 0)
#define my_basename(path) ((strrchr((path), '/') ?: (path) - 1) + 1)
--
1.5.6.3
--
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