powerpc: Add compat_sys_truncate

The truncate syscall has a signed long parameter, so when using a 32-
bit userspace with a 64-bit kernel the argument is zero-extended
instead of sign-extended. Adding the compat_sys_truncate function
fixes the issue.

This was noticed during an LSB truncate test failure. The test was
checking for the correct error number set when truncate is called with
a length of -1. The test can be found at:

http://bzr.linuxfoundation.org/lsb/devel/runtime-test?cmd=inventory;rev=stewb%40linux-foundation.org-20090626205411-sfb23cc0tjj7jzgm;path=modules/vsx-pcts/tset/POSIX.os/files/truncate/

BenH: Added compat_sys_ftruncate() as well, same issue.
Signed-off-by: Chase Douglas <cndougla@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/systbl.h

@@ -95,8 +95,8 @@ SYSCALL(reboot)
 SYSX(sys_ni_syscall,compat_sys_old_readdir,sys_old_readdir)
 SYSCALL_SPU(mmap)
 SYSCALL_SPU(munmap)
-SYSCALL_SPU(truncate)
-SYSCALL_SPU(ftruncate)
+COMPAT_SYS_SPU(truncate)
+COMPAT_SYS_SPU(ftruncate)
 SYSCALL_SPU(fchmod)
 SYSCALL_SPU(fchown)
 COMPAT_SYS_SPU(getpriority)

arch/powerpc/kernel/sys_ppc32.c

@@ -343,6 +343,18 @@ off_t ppc32_lseek(unsigned int fd, u32 offset, unsigned int origin)
 	return sys_lseek(fd, (int)offset, origin);
 }
 
+long compat_sys_truncate(const char __user * path, u32 length)
+{
+	/* sign extend length */
+	return sys_truncate(path, (int)length);
+}
+
+long compat_sys_ftruncate(int fd, u32 length)
+{
+	/* sign extend length */
+	return sys_ftruncate(fd, (int)length);
+}
+
 /* Note: it is necessary to treat bufsiz as an unsigned int,
  * with the corresponding cast to a signed int to insure that the 
  * proper conversion (sign extension) between the register representation of a signed int (msr in 32-bit mode)