[Qemu-devel] [PATCH] linux-user: ppc64: use the correct values for F_*LK64s

[Shivaprasad G Bhat]

Qemu includes the glibc headers for the host defines and target headers are
part of the qemu source themselves. The glibc has the F_GETLK64, F_SETLK64
and F_SETLKW64 defined to 12, 13 and 14 for all archs(generic) in
sysdeps/unix/sysv/linux/bits/fcntl-linux.h. The linux kernel generic
definition for F_*LK is 5, 6 & 7 and F_*LK64* is 12,13, and 14 as seen in
include/uapi/asm-generic/fcntl.h. On 64bit machine, by default the kernel
assumes all F_*LK to 64bit calls and doesnt support use of F_*LK64* as
can be seen in include/linux/fcntl.h in linux source.

On x86_64 host, the values for F_*LK64* are set to 5, 6 and 7
explicitly in /usr/include/x86_64-linux-gnu/bits/fcntl.h by the glibc.
Whereas, a PPC64 host doesn't have such a definition in
/usr/include/powerpc64le-linux-gnu/bits/fcntl.h by the glibc. So,
the sources on PPC64 host sees the default value of F_*LK64*
as 12, 13 & 14(fcntl-linux.h).

Since the 64bit kernel doesnt support 12, 13 & 14; the glibc fcntl syscall
implementation(__libc_fcntl*(), __fcntl64_nocancel) does the F_*LK64* value
convertion back to F_*LK* values on PPC64 as seen in
sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h with FCNTL_ADJUST_CMD()
macro. Whereas on x86_64 host the values for F_*LK64* are set to 5, 6 and 7
and no adjustments are needed.

Since qemu doesnt use the glibc fcntl, but makes the safe_syscall* on its
own, the PPC64 qemu is calling the syscall with 12, 13, and 14(without
adjustment) and they all fail. The fcntl calls to F_GETLK/F_SETLK|W all
fail by all pplications run on PPC64 host user emulation.

The fix here could be to see why on PPC64 the glibc is still keeping
F_*LK64* different from F_*LK and why adjusting them to 5, 6 and 7 before
the syscall for PPC only. See if we can make the
/usr/include/powerpc64le-linux-gnu/bits/fcntl.h to have the values
5, 6 & 7 just like x86_64 and remove the adjustment code in glibc. That way,
qemu sources see the kernel supported values in glibc headers.

OR

On PPC64 host, qemu sources see both F_LK* & F_LK64* as same and set to
12, 13 and 14 because __USE_FILE_OFFSET64 is defined in qemu
sources(also refer sysdeps/unix/sysv/linux/bits/fcntl-linux.h).
Since F_*LK and F_*LK64 are same, the value adjument like done by glibc in
qemu sources is difficult. So, Overwrite the glibc defaults with the actual
supported values in Qemu. The current patch is doing this.

Signed-off-by: Shivaprasad G Bhat <address@hidden>
---
 linux-user/syscall.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 7b9ac3b408..1693e69ce0 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -250,6 +250,20 @@ static type name (type1 arg1,type2 arg2,type3 arg3,type4 
arg4,type5 arg5,  \
 #define TARGET_NR__llseek TARGET_NR_llseek
 #endif
 
+/* glibc headers has these defined to 12, 13 and 14 and is not supported
+ * by kernel. The glibc fcntl call actually adjusts them back to 5, 6 and 7
+ * before making the syscall(). Since we make the syscall directly,
+ * overwite/adjust to what is supported by the kernel.
+ */
+#if defined(__linux__) && defined(__powerpc64__)
+#undef F_GETLK64
+#define F_GETLK64      5       /* Get record locking info.  */
+#undef F_SETLK64
+#define F_SETLK64      6       /* Set record locking info (non-blocking).  */
+#undef F_SETLKW64
+#define F_SETLKW64     7       /* Set record locking info (blocking).  */
+#endif
+
 #ifdef __NR_gettid
 _syscall0(int, gettid)
 #else