The patch titled
kernel/sys.c: implement prctl(PR_GET_ENDIAN) for all architectures
has been added to the -mm tree. Its filename is
kernel-sysc-implement-prctlpr_get_endian-for-all-architectures.patch
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------------------------------------------------------
Subject: kernel/sys.c: implement prctl(PR_GET_ENDIAN) for all architectures
From: Helge Deller <deller@xxxxxx>
The PR_GET_ENDIAN and PR_SET_ENDIAN prctl() calls have been implemented to
allow to switch processes at runtime from big-endian to little-endian mode
(and vice versa) on PowerPC processors. Since the other architectures
don't support this feature, they currently will just fail and return
-EINVAL.
This patch adds just minimal overhead and implements the PR_GET_ENDIAN
call for all other architectures by returning the native endianess of the
architecture. Furthermore, calling prctl(PR_SET_ENDIAN) with the native
endianess of the architecture will succeed, while trying to set another
(not-supported) endianess, will fail.
The patch can be tested with the following program:
#include <stdio.h>
#include <linux/prctl.h>
int main(int argc, char **argv)
{
int endian, ret;
ret = prctl(PR_GET_ENDIAN, &endian);
if (ret)
perror("prctl(PR_GET_ENDIAN) not implemented");
printf("current process/machine is running in %s endian mode (%d)\n",
endian == PR_ENDIAN_LITTLE ? "little":"big", endian);
/* setting native endianess should succeed */
ret = prctl(PR_SET_ENDIAN, endian);
printf("prctl(PR_SET_ENDIAN,%d) should succeed: %s\n",
endian, ret == 0 ? "OK":"FAIL");
/* setting foreign endianess should fail */
endian = (endian == PR_ENDIAN_LITTLE) ?
PR_ENDIAN_BIG : PR_ENDIAN_LITTLE;
ret = prctl(PR_SET_ENDIAN, endian);
printf("prctl(PR_SET_ENDIAN,%d) should fail: %s\n",
endian, ret == 0 ? "OK":"FAIL");
}
Signed-off-by: Helge Deller <deller@xxxxxx>
Cc: Anton Blanchard <anton@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN kernel/sys.c~kernel-sysc-implement-prctlpr_get_endian-for-all-architectures kernel/sys.c
--- a/kernel/sys.c~kernel-sysc-implement-prctlpr_get_endian-for-all-architectures
+++ a/kernel/sys.c
@@ -46,6 +46,15 @@
#include <asm/io.h>
#include <asm/unistd.h>
+#if defined(__BIG_ENDIAN)
+# define PRCTL_ENDIAN_DEFAULT (PR_ENDIAN_BIG)
+#elif defined(__LITTLE_ENDIAN)
+# define PRCTL_ENDIAN_DEFAULT (PR_ENDIAN_LITTLE)
+#else
+# error "No endianess?"
+#endif
+
+
#ifndef SET_UNALIGN_CTL
# define SET_UNALIGN_CTL(a,b) (-EINVAL)
#endif
@@ -65,10 +74,12 @@
# define GET_FPEXC_CTL(a,b) (-EINVAL)
#endif
#ifndef GET_ENDIAN
-# define GET_ENDIAN(a,b) (-EINVAL)
+# define GET_ENDIAN(task,addr) \
+ put_user(PRCTL_ENDIAN_DEFAULT, (int __user *) (addr))
#endif
#ifndef SET_ENDIAN
-# define SET_ENDIAN(a,b) (-EINVAL)
+# define SET_ENDIAN(task,value) \
+ ( (value) == PRCTL_ENDIAN_DEFAULT ? 0 : -EINVAL )
#endif
#ifndef GET_TSC_CTL
# define GET_TSC_CTL(a) (-EINVAL)
_
Patches currently in -mm which might be from deller@xxxxxx are
linux-next.patch
kernel-sysc-implement-prctlpr_get_endian-for-all-architectures.patch
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