[patch] sharing maximum errno symbol used in __syscall_return(i386)

[Masatake YAMATO]

Hi,

__syscall_return in unistd.h is maintained?

In the macro the value returned from system call is
compared with the maximum error number defined in a header file 
to know the call is successful or not. However, the maximum error number 
is hard-coded and is not updated.

Here is an example(i386):

 /*
  * user-visible error numbers are in the range -1 - -128: see
  * <asm-i386/errno.h>
  */
 #define __syscall_return(type, res) \
 do { \
	if ((unsigned long)(res) >= (unsigned long)(-(128 + 1))) { \
 		errno = -(res); \
 		res = -1; \
 	} \

The comment says the maximum errno is 128.
However, the actual C code says 128 + 1. What does "+ 1" mean?

Look at <asm-i386/errno.h>:

    #ifndef _I386_ERRNO_H
    #define _I386_ERRNO_H

    #include <asm-generic/errno.h>

    #endif

The look at <asm-generic/errno.h>:

    #define	EKEYREVOKED	128	/* Key has been revoked */
    #define	EKEYREJECTED	129	/* Key was rejected by service */

    /* for robust mutexes */
    #define	EOWNERDEAD	130	/* Owner died */
    #define	ENOTRECOVERABLE	131	/* State not recoverable */

Here the maximum errno is 131. 


In many architectures, <asm-foo/errno.h> just includes 
<asm-generic/errno.h>. So I think <asm-generic/errno.h> should
exports the real maximum errno and the other headers can
use it. So in many cases, we can just maintain
the real maximum errno in <asm-generic/errno.h>.

Here is the patch for i386. If this patch is approved, I will write
patches for the other architectures. (However, it may be better to be
done by each architecture's maintainer.)

Signed-off-by: Masatake YAMATO <jet@xxxxxxxx>

diff --git a/include/asm-generic/errno.h b/include/asm-generic/errno.h
index e8852c0..4e1238e 100644
--- a/include/asm-generic/errno.h
+++ b/include/asm-generic/errno.h
@@ -106,4 +106,8 @@ #define	EKEYREJECTED	129	/* Key was reje
 #define	EOWNERDEAD	130	/* Owner died */
 #define	ENOTRECOVERABLE	131	/* State not recoverable */
 
+/* 
+ * If you add a new error, Don't forget to update `GENERIC_ERRNO_MAX' 
+ */
+#define GENERIC_ERRNO_MAX ENOTRECOVERABLE
 #endif
diff --git a/include/asm-i386/errno.h b/include/asm-i386/errno.h
index 969b343..9892b2d 100644
--- a/include/asm-i386/errno.h
+++ b/include/asm-i386/errno.h
@@ -2,5 +2,5 @@ #ifndef _I386_ERRNO_H
 #define _I386_ERRNO_H
 
 #include <asm-generic/errno.h>
-
+#define  i386_ERRNO_MAX GENERIC_ERRNO_MAX
 #endif
diff --git a/include/asm-i386/unistd.h b/include/asm-i386/unistd.h
index eb4b152..f52ec68 100644
--- a/include/asm-i386/unistd.h
+++ b/include/asm-i386/unistd.h
@@ -326,12 +326,13 @@ #define __NR_vmsplice		316
 #define NR_syscalls 317
 
 /*
- * user-visible error numbers are in the range -1 - -128: see
- * <asm-i386/errno.h>
+ * user-visible error numbers are in the range -1 - -i386_ERRNO_MAX
  */
+#include <asm-i386/errno.h>
+
 #define __syscall_return(type, res) \
 do { \
-	if ((unsigned long)(res) >= (unsigned long)(-(128 + 1))) { \
+	if ((unsigned long)(res) >= (unsigned long)(-(i386_ERRNO_MAX))) { \
 		errno = -(res); \
 		res = -1; \
 	} \
-
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