Re: [PATCH 20/25] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it
From: Zhangjian (Bamvor)
Date: Wed May 11 2016 - 23:46:31 EST
Hi, Arnd
On 2016/5/11 22:50, Arnd Bergmann wrote:
On Wednesday 11 May 2016 19:16:44 Zhangjian wrote:
Hi,
On 2016/5/11 18:12, Zhangjian (Bamvor) wrote:
Hi, Arnd
On 2016/5/11 16:09, Arnd Bergmann wrote:
> On Wednesday 11 May 2016 10:04:16 Zhangjian wrote:
>>> I don't remember. It's probably not important whether we have the shift
>>> in there, as long as it's independent of the actual kernel page size and
>>> user space and kernel agree on the calling conventions.
>> Well. I am ok with where to shift the pages size because we get the same
>> result. I was just thinking if we should get rid of the name of mmap2 in our
>> ILP32 porting. Actually, it is mmap but we name it as mmap2. User may confused
>> if they do not know the implementations.
>
> That is a good point: If the implementation matches the mmap() behavior rather than
> mmap2(), we should rename the macro by doing
>
> #undef __NR_mmap2
> #define __NR_mmap 222
>
> in the uapi/asm/unistd.h file for ilp32 mode.
Do you mean define the following things in kernel:
```
diff --git a/arch/arm64/include/uapi/asm/unistd.h b/arch/arm64/include/uapi/asm/unistd.h
index 1caadc2..3f79640 100644
--- a/arch/arm64/include/uapi/asm/unistd.h
+++ b/arch/arm64/include/uapi/asm/unistd.h
@@ -14,3 +14,9 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <asm-generic/unistd.h>
+
+#ifdef __ILP32__
+#undef __NR_mmap2
+#define __NR_mmap 222
+#endif /* #ifdef __ILP32__ */
+
```
Then glibc could call mmap instead of mmap2.
I could not try it now. Because after change off_t to 64bit in glibc, stat
is fail. I may need to revert the stat relative patch.
After revert stat relative patch in glibc, mmap01-mmap14 success. But mmap16
success with segfault. I will investigate it later.
There is pointer and size_t in mmap, so, IIUC, we need to clear the top halves
of register by using COMPAT_SYSCALL_WRAP6.
Correct, good catch!
And after check the function in
arch/s390/kernel/compat_linux.c, I feel that we need to do the same thing for
pread64 and pwrite64.
But I got following error when I try to add
COMPAT_SYSCALL_WRAP4(pread64, unsigned int, fd, char __user *, buf,
size_t, count, loff_t, pos);
COMPAT_SYSCALL_WRAP4(pwrite64, unsigned int, fd, const char __user *, buf,
size_t, count, loff_t, pos);
Hmm, that is indeed tricky. I think COMPAT_SYSCALL_WRAP4 rightfully
refuses the loff_t argument here, as the common case is that this is
not possible.
It works if I apply the following patch, I defined the wrong `__TYPE_IS_xxx`
yesterday. Should we merge this into ILP32 series or send the compat.h
and syscalls.h individually? The current series of ILP32 is a little bit
long and hard to review.
diff --git a/include/linux/compat.h b/include/linux/compat.h
index ba6ebe0..22a9565 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -747,7 +747,8 @@ asmlinkage long compat_sys_fanotify_mark(int, unsigned int, __u32, __u32,
#ifndef __SC_COMPAT_CAST
#define __SC_COMPAT_CAST(t, a) ({ \
BUILD_BUG_ON((sizeof(t) > 4) && !__TYPE_IS_L(t) && \
- !__TYPE_IS_UL(t) && !__TYPE_IS_PTR(t)); \
+ !__TYPE_IS_UL(t) && !__TYPE_IS_PTR(t) && \
+ !__TYPE_IS_LOFFT(t)); \
((t) ((t)(-1) < 0 ? (s64)(s32)(a) : (u64)(u32)(a))); \
})
#endif
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 6e57d9c..66eb85d 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -47,6 +47,7 @@
#define __TYPE_IS_L(t) (__same_type((t)0, 0L))
#define __TYPE_IS_UL(t) (__same_type((t)0, 0UL))
#define __TYPE_IS_LL(t) (__same_type((t)0, 0LL) || __same_type((t)0, 0ULL))
+#define __TYPE_IS_LOFFT(t) (__same_type((t)0, (loff_t)0))
#define __SC_LONG(t, a) __typeof(__builtin_choose_expr(__TYPE_IS_LL(t), 0LL, 0L)) a
#define __SC_CAST(t, a) (t) a
#define __SC_ARGS(t, a) a
diff --git a/kernel/compat_wrapper.c b/kernel/compat_wrapper.c
index 98b68b8..28f02d0 100644
--- a/kernel/compat_wrapper.c
+++ b/kernel/compat_wrapper.c
@@ -304,3 +304,7 @@ COMPAT_SYSCALL_WRAP3(getpeername, int, fd, struct sockaddr __user *, usockaddr,
COMPAT_SYSCALL_WRAP6(sendto, int, fd, void __user *, buff, size_t, len,
unsigned int, flags, struct sockaddr __user *, addr,
int, addr_len);
+COMPAT_SYSCALL_WRAP4(pread64, unsigned int, fd, char __user *, buf,
+ size_t, count, loff_t, pos);
+COMPAT_SYSCALL_WRAP4(pwrite64, unsigned int, fd, const char __user *, buf,
+ size_t, count, loff_t, pos);
>
> Can you open-code this using a COMPAT_SYSCALL4 definition similar to what
> arch/tile has, but without the merging of the two halves of the argument?
I am lost here. Tile do not use the wrapper, and it do not use the loff_t
either:
COMPAT_SYSCALL_DEFINE6(pread64, unsigned int, fd, char __user *, ubuf,
size_t, count, u32, dummy, u32, low, u32, high)
Regards
Bamvor
Arnd