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Re: [PATCH] x86-64: Add p{read,write}[v]64 to syscalls.list [BZ #20348]
On Wed, Jul 13, 2016 at 8:25 AM, Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
> On 12/07/2016 17:19, H.J. Lu wrote:
>> On Tue, Jul 12, 2016 at 8:49 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Tue, Jul 12, 2016 at 8:19 AM, Adhemerval Zanella
>>> <adhemerval.zanella@linaro.org> wrote:
>>>>
>>>>
>>>> On 12/07/2016 16:03, H.J. Lu wrote:
>>>>> On Tue, Jul 12, 2016 at 7:04 AM, Adhemerval Zanella
>>>>> <adhemerval.zanella@linaro.org> wrote:
>>>>>>
>>>>>>
>>>>>> On 12/07/2016 14:26, H.J. Lu wrote:
>>>>>>> 64-bit off_t in pread64, preadv, pwrite64 and pwritev syscalls is pased
>>>>>>> in one 64-bit register for both x32 and x86-64. Since the inline
>>>>>>> asm statement only passes long, which is 32-bit for x32, in registers,
>>>>>>> 64-bit off_t is truncated to 32-bit on x32. Since __ASSUME_PREADV and
>>>>>>> __ASSUME_PWRITEV are defined unconditionally, these syscalls can be
>>>>>>> implemented in syscalls.list to pass 64-bit off_t in one 64-bit register.
>>>>>>>
>>>>>>> Tested on x86-64 and x32 with off_t > 4GB on pread64/pwrite64 and
>>>>>>> preadv64/pwritev64.
>>>>>>>
>>>>>>> OK for master?
>>>>>>>
>>>>>>> H.J.
>>>>>>> ---
>>>>>>> [BZ #20348]
>>>>>>> * sysdeps/unix/sysv/linux/x86_64/syscalls.list: Add pread64,
>>>>>>> preadv64, pwrite64 and pwritev64.
>>>>>>> ---
>>>>>>> sysdeps/unix/sysv/linux/x86_64/syscalls.list | 4 ++++
>>>>>>> 1 file changed, 4 insertions(+)
>>>>>>>
>>>>>>> diff --git a/sysdeps/unix/sysv/linux/x86_64/syscalls.list b/sysdeps/unix/sysv/linux/x86_64/syscalls.list
>>>>>>> index d09d101..bcf6370 100644
>>>>>>> --- a/sysdeps/unix/sysv/linux/x86_64/syscalls.list
>>>>>>> +++ b/sysdeps/unix/sysv/linux/x86_64/syscalls.list
>>>>>>> @@ -6,6 +6,10 @@ msgctl - msgctl i:iip __msgctl msgctl
>>>>>>> msgget - msgget i:ii __msgget msgget
>>>>>>> msgrcv - msgrcv Ci:ibnii __msgrcv msgrcv
>>>>>>> msgsnd - msgsnd Ci:ibni __msgsnd msgsnd
>>>>>>> +pread64 - pread64 Ci:ipii __libc_pread __libc_pread64 __pread64 pread64 __pread pread
>>>>>>> +preadv64 - preadv Ci:ipii preadv64 preadv
>>>>>>> +pwrite64 - pwrite64 Ci:ipii __libc_pwrite __pwrite64 pwrite64 __pwrite pwrite
>>>>>>> +pwritev64 - pwritev Ci:ipii pwritev64 pwritev
>>>>>>> shmat - shmat i:ipi __shmat shmat
>>>>>>> shmctl - shmctl i:iip __shmctl shmctl
>>>>>>> shmdt - shmdt i:s __shmdt shmdt
>>>>>>>
>>>>>>
>>>>>> This is pretty much what I suggested [1] with the difference that my
>>>>>> idea is to re-add the auto-generated wrappers just for x32. I would
>>>>>> prefer to keep x86_64 continue to use default implementation and
>>>>>> work on fix {INLINE,INTERNAL}_SYSCALL to work with 64-bit arguments
>>>>>> in x32.
>>>>>
>>>>> syscalls.list is the preferred way to implement a system call, not
>>>>> {INLINE,INTERNAL}_SYSCALL. There is no reason only to do it
>>>>> for x32. As for {INLINE,INTERNAL}_SYSCALL with 64-bit argument,
>>>>> they are only used in p{read,write}[v]64 and it is incorrect to pass long
>>>>> as 64-bit integer to x32 syscall if the argument is long or pointer.
>>>>
>>>> The idea I am trying to push with all these consolidation are twofold:
>>>>
>>>> 1. Remove the complexity implementation files and way to call syscalls
>>>> inside GLIBC and make easier to implement new ports
>>>
>>> That is fine.
>>>
>>>> 2. Remove the redundant sysdep-cancel.h requirement for each port
>>>> which basically implementations pic/nopic function calls in assembly.
>>>> This is also remove implementation complexity and make easier for
>>>> new port implementation.
>>>>
>>>> Also, for 2. it also helps the long standing pthread cancellation
>>>> (bz#12683) by focusing all cancellation calls in only one implementation.
>>>>
>>>> I do get the idea the auto-generation call is currently preferred way
>>>> to implementation syscalls, but I think for *cancellable* way we should
>>>> push to implement using SYSCALL_CANCEL (which is in turn based on
>>>> INTERNAL_SYSCALL).
>>>
>>> That is fine also. But on x86-64, we should use syscalls.list if possible,
>>> especially for cancellation calls.
>>>
>>> With {INLINE,INTERNAL}_SYSCALL:
>>>
>>> 0000000000000000 <__libc_pread>:
>>> 0: 8b 05 00 00 00 00 mov 0x0(%rip),%eax # 6 <__libc_pread+0x6>
>>> 6: 49 89 ca mov %rcx,%r10
>>> 9: 85 c0 test %eax,%eax
>>> b: 75 2b jne 38 <__libc_pread+0x38>
>>> d: 48 63 ff movslq %edi,%rdi
>>> 10: b8 11 00 00 00 mov $0x11,%eax
>>> 15: 0f 05 syscall
>>> 17: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax
>>> 1d: 77 01 ja 20 <__libc_pread+0x20>
>>> 1f: c3 retq
>>> 20: 48 8b 15 00 00 00 00 mov 0x0(%rip),%rdx # 27 <__libc_pread+0x27>
>>> 27: f7 d8 neg %eax
>>> 29: 64 89 02 mov %eax,%fs:(%rdx)
>>> 2c: 48 c7 c0 ff ff ff ff mov $0xffffffffffffffff,%rax
>>> 33: c3 retq
>>> 34: 0f 1f 40 00 nopl 0x0(%rax)
>>> 38: 41 55 push %r13
>>> 3a: 41 54 push %r12
>>> 3c: 49 89 cd mov %rcx,%r13
>>> 3f: 55 push %rbp
>>> 40: 53 push %rbx
>>> 41: 49 89 d4 mov %rdx,%r12
>>> 44: 48 89 f5 mov %rsi,%rbp
>>> 47: 89 fb mov %edi,%ebx
>>> 49: 48 83 ec 18 sub $0x18,%rsp
>>> 4d: e8 00 00 00 00 callq 52 <__libc_pread+0x52>
>>> 52: 4d 89 ea mov %r13,%r10
>>> 55: 41 89 c0 mov %eax,%r8d
>>> 58: 4c 89 e2 mov %r12,%rdx
>>> 5b: 48 89 ee mov %rbp,%rsi
>>> 5e: 48 63 fb movslq %ebx,%rdi
>>> 61: b8 11 00 00 00 mov $0x11,%eax
>>> 66: 0f 05 syscall
>>> 68: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax
>>> 6e: 77 1d ja 8d <__libc_pread+0x8d>
>>> 70: 44 89 c7 mov %r8d,%edi
>>> 73: 48 89 44 24 08 mov %rax,0x8(%rsp)
>>> 78: e8 00 00 00 00 callq 7d <__libc_pread+0x7d>
>>> 7d: 48 8b 44 24 08 mov 0x8(%rsp),%rax
>>> 82: 48 83 c4 18 add $0x18,%rsp
>>> 86: 5b pop %rbx
>>> 87: 5d pop %rbp
>>> 88: 41 5c pop %r12
>>> 8a: 41 5d pop %r13
>>> 8c: c3 retq
>>> 8d: 48 8b 15 00 00 00 00 mov 0x0(%rip),%rdx # 94 <__libc_pread+0x94>
>>> 94: f7 d8 neg %eax
>>> 96: 64 89 02 mov %eax,%fs:(%rdx)
>>> 99: 48 c7 c0 ff ff ff ff mov $0xffffffffffffffff,%rax
>>> a0: eb ce jmp 70 <__libc_pread+0x70>
>>>
>>> With syscalls.list:
>>>
>>> Disassembly of section .text:
>>>
>>> 0000000000000000 <__libc_pread>:
>>> 0: 83 3d 00 00 00 00 00 cmpl $0x0,0x0(%rip) # 7 <__libc_pread+0x7>
>>> 7: 75 17 jne 20 <__pread64_nocancel+0x17>
>>>
>>> 0000000000000009 <__pread64_nocancel>:
>>> 9: 49 89 ca mov %rcx,%r10
>>> c: b8 11 00 00 00 mov $0x11,%eax
>>> 11: 0f 05 syscall
>>> 13: 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax
>>> 19: 0f 83 00 00 00 00 jae 1f <__pread64_nocancel+0x16>
>>> 1f: c3 retq
>>> 20: 48 83 ec 08 sub $0x8,%rsp
>>> 24: e8 00 00 00 00 callq 29 <__pread64_nocancel+0x20>
>>> 29: 48 89 04 24 mov %rax,(%rsp)
>>> 2d: 49 89 ca mov %rcx,%r10
>>> 30: b8 11 00 00 00 mov $0x11,%eax
>>> 35: 0f 05 syscall
>>> 37: 48 8b 3c 24 mov (%rsp),%rdi
>>> 3b: 48 89 c2 mov %rax,%rdx
>>> 3e: e8 00 00 00 00 callq 43 <__pread64_nocancel+0x3a>
>>> 43: 48 89 d0 mov %rdx,%rax
>>> 46: 48 83 c4 08 add $0x8,%rsp
>>> 4a: 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax
>>> 50: 0f 83 00 00 00 00 jae 56 <__pread64_nocancel+0x4d>
>>> 56: c3 retq
>>>
>>> This one is much better.
>
> I think SYSCALL_CANCEL can be slight improved by using INTERNAL_SYSCALL
> instead of INLINE_SYSCALL and checking the error outside of cancellation
> handling. I see a slight improvement, however sysdep-cancel.h is
> still slight better.
>
> However the idea is I am trying to push in the end is to remove the
> sysdep-cancel.h because the new cancellation scheme will require it
> to basically do a function call instead of calling the cancellation
> enable/disable (which will be also removed).
>
>>>
>>>>>
>>>>>> Also, I think we should remove the first try to fix LO_HI_LONG [2],
>>>>>> since 64 bits argument does not work correct in x32 anyway.
>>>>>
>>>>> I think LO_HI_LONG should be defined only if __WORDSIZE != 64
>>>>> and p{read,write}[v]64 should be added to wordsize-64/syscalls.list.
>>>>
>>>> Indeed this is something I will get back now that I see x32 fails
>>>> with current implementation. I got the wrong idea all ILP32 would
>>>> use the compat code (as MIPS64n64).
>>
>> x86/entry/syscalls/syscall_64.tbl has
>>
>> 17 common pread64 sys_pread64
>> 295 64 preadv sys_preadv
>> 534 x32 preadv compat_sys_preadv64
>>
>> compat_sys_preadv64 takes 64-bit offset in one piece.
>>
>>>> About the patch, based on current timeframe I think your solution is
>>>> the safest one for x86.
>>
>> I will check it in.
>>
>>>> However I do would like to re-enable it on x86, including x32, when 2.25
>>>> opens. The patch below changes slight on how {INLINE,INTERNAL}_SYSCALL
>>>> works on x32: int/long/pointer should be passed as before and uint64_t
>>>> arguments should be passed as register all well without casting.
>>>> If you have time I would like to check if it would be acceptable for
>>>> 2.25. It shows no regression on x32, including the tst-preadwrite{64}
>>>> testcase you sent earlier:
>>>
>>> I will give it a try.
>>
>> I got no regressions on x32. But on x86-64, I got
>>
>> Inconsistency detected by ld.so: dl-tls.c: 493: _dl_allocate_tls_init:
>> Assertion `listp->slotinfo[cnt].gen <= GL(dl_tls_generation)' failed!
>> FAIL: nptl/tst-stack4
>>
>> It doesn't fail every time. I am wondering if typeof returns the
>> correct type on
>> signed/unsigned integer constants.
>>
>
> I think the issue is not really related to this patch. I also see this
> very issue in i386, powerpc64le and aarch64 in a inconsistent way
>
> Regarding typeof type for signed/unsigned, it looks like gcc gets it
> right:
>
> $ cat test.c
> #include <stdio.h>
>
> unsigned char uc;
> signed char sc;
>
> int foo_1 ()
> {
> typeof (uc) c = 255;
> return c > 128;
> }
>
> int foo_2 ()
> {
> typeof (sc) c = 255;
> return c > 128;
> }
>
> int
> main (void)
> {
> printf ("%i\n%i\n", foo_1 (), foo_2 ());
> return 0;
> }
> $ gcc test.c
> $ ./a.out
> 1
> 0
>
That is not what I meant:
hjl@gnu-6 tmp]$ cat y.c
#define NUM (-214)
typedef typeof (NUM) t1;
t1
foo1 ()
{
return NUM;
}
typedef long int t2;
t2
foo2 ()
{
return NUM;
}
[hjl@gnu-6 tmp]$ gcc -S -O2 y.c
[hjl@gnu-6 tmp]$ cat y.s
.file "y.c"
.text
.p2align 4,,15
.globl foo1
.type foo1, @function
foo1:
.LFB0:
.cfi_startproc
movl $-214, %eax
^^^^^^^^^^^^^^^^^^^^
ret
.cfi_endproc
.LFE0:
.size foo1, .-foo1
.p2align 4,,15
.globl foo2
.type foo2, @function
foo2:
.LFB1:
.cfi_startproc
movq $-214, %rax
^^^^^^^^^^^^^^^^^^^^^
ret
.cfi_endproc
.LFE1:
.size foo2, .-foo2
.ident "GCC: (GNU) 6.1.1 20160621 (Red Hat 6.1.1-3)"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-6 tmp]$
--
H.J.