[v2,1/2] sysdeps/stat: Handle 64-bit ino_t types on 32-bit hosts

Message ID 20190918235448.5037-1-alistair.francis@wdc.com
State Superseded
Headers show
Series
  • [v2,1/2] sysdeps/stat: Handle 64-bit ino_t types on 32-bit hosts
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Commit Message

Alistair Francis Sept. 18, 2019, 11:54 p.m.
On a 32-bit platform with a 64-bit ino_t type (__INO_T_MATCHES_INO64_T
defined) we want to update the stat struct to remove the padding as it
isn't required. As we don't have the padding we also need to update the
overflow checker to not access the undefined members.

2019-09-16  Alistair Francis  <alistair.francis@wdc.com>

	* sysdeps/unix/sysv/linux/generic/bits/stat.h: Handle 64-bit ino_t types
	on 32-bit hosts.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/overflow.h: Likewise.
---
v2:
 - Fix the #if logic

 sysdeps/unix/sysv/linux/generic/bits/stat.h            | 5 ++++-
 sysdeps/unix/sysv/linux/generic/wordsize-32/overflow.h | 4 ++++
 2 files changed, 8 insertions(+), 1 deletion(-)

-- 
2.23.0

Comments

Joseph Myers Sept. 19, 2019, 8:33 p.m. | #1
On Wed, 18 Sep 2019, Alistair Francis wrote:

> On a 32-bit platform with a 64-bit ino_t type (__INO_T_MATCHES_INO64_T

> defined) we want to update the stat struct to remove the padding as it

> isn't required. As we don't have the padding we also need to update the

> overflow checker to not access the undefined members.


When posting a patch, please *always* say how it was tested.  Typically 
that would include running the glibc testsuite for at least one 
configuration (but there may be exceptions, e.g. documentation patches).

> -#if defined __USE_FILE_OFFSET64

> +#if defined(__USE_FILE_OFFSET64) || __INO_T_MATCHES_INO64_T == 1

> +# if __INO_T_MATCHES_INO64_T == 1 && __OFF_T_MATCHES_OFF64_T != 1


The rule in glibc is that we compile with -Wundef and do not rely on 
undefined macros being interpreted as 0 in #if.

Both __INO_T_MATCHES_INO64_T and __OFF_T_MATCHES_OFF64_T are in fact 
defined/undefined macros, not macros that might sometimes be defined to 1 
and sometimes to 0.  So testing with == there is problematic; I'd expect 
it to cause -Wundef errors for any existing 32-bit linux/generic 
architecture where those macros are undefined (i.e. csky and nios2).

There are two possible approaches to fixing this.

(a) Do a preliminary patch that changes these macros from defined / 
undefined to always-defined with 1 / 0 values.  This involves updating a 
lot of places that use the macros (mainly using __OFF_T_MATCHES_OFF64_T), 
as well as ensuring that all bits/typesizes.h headers provide appropriate 
definitions.

(b) Change this patch to do defined / undefined tests rather than testing 
the macro values.

Also, when a macro is 0 / 1 I'd expect boolean tests just to test the 
macro as a boolean (so plain "__INO_T_MATCHES_INO64_T" inside #if, not 
"__INO_T_MATCHES_INO64_T == 1").

Also, if using "defined" with (), like a function call there should be a 
space before '('.

-- 
Joseph S. Myers
joseph@codesourcery.com

Patch

diff --git a/sysdeps/unix/sysv/linux/generic/bits/stat.h b/sysdeps/unix/sysv/linux/generic/bits/stat.h
index 62aeea5a88d..acd8e7c79a6 100644
--- a/sysdeps/unix/sysv/linux/generic/bits/stat.h
+++ b/sysdeps/unix/sysv/linux/generic/bits/stat.h
@@ -40,7 +40,10 @@ 
 /* Versions of the `xmknod' interface.  */
 #define _MKNOD_VER_LINUX	0
 
-#if defined __USE_FILE_OFFSET64
+#if defined(__USE_FILE_OFFSET64) || __INO_T_MATCHES_INO64_T == 1
+# if __INO_T_MATCHES_INO64_T == 1 && __OFF_T_MATCHES_OFF64_T != 1
+#  error "ino_t and off_t must both be the same type"
+# endif
 # define __field64(type, type64, name) type64 name
 #elif __WORDSIZE == 64
 # define __field64(type, type64, name) type name
diff --git a/sysdeps/unix/sysv/linux/generic/wordsize-32/overflow.h b/sysdeps/unix/sysv/linux/generic/wordsize-32/overflow.h
index 45efcd8fd34..7ae01c189eb 100644
--- a/sysdeps/unix/sysv/linux/generic/wordsize-32/overflow.h
+++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/overflow.h
@@ -36,12 +36,16 @@  static inline off_t lseek_overflow (loff_t res)
 
 static inline int stat_overflow (struct stat *buf)
 {
+#if __INO_T_MATCHES_INO64_T
+  return 0;
+#else
   if (buf->__st_ino_pad == 0 && buf->__st_size_pad == 0
       && buf->__st_blocks_pad == 0)
     return 0;
 
   __set_errno (EOVERFLOW);
   return -1;
+#endif
 }
 
 /* Note that f_files and f_ffree may validly be a sign-extended -1.  */