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社区首页 >问答首页 >在同一个ptr/大小上与成功的建议(DONTDUMP)(DONTDUMP)在EINVAL中失败

问在同一个ptr/大小上与成功的建议(DONTDUMP)(DONTDUMP)在EINVAL中失败
EN

Stack Overflow用户
提问于 2018-09-28 04:24:22
回答 1查看 390关注 0票数 1

在启动时测试mysqld (10.3分支)的MariaDB异常：

内存分配返回用于ptr=0x7fffe1a00000的bytes=2097152

在之前，/proc/{pid}/smap条目是：

代码语言：javascript
复制
7fffe1a00000-7fffe1c00000 rw-s 00000000 00:0f 18481215                   /SYSV00000000 (deleted)
Size:               2048 kB
KernelPageSize:     2048 kB
MMUPageSize:        2048 kB
Rss:                   0 kB
Pss:                   0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
VmFlags: rd wr sh mr mw me ms de ht sd

电话后：

代码语言：javascript
复制
madvise(ptr, bytes, MADV_DONTDUMP)

该页面按照预期选择dd“不要转储”标志：

代码语言：javascript
复制
7fffe1a00000-7fffe1c00000 rw-s 00000000 00:0f 18481215                   /SYSV00000000 (deleted)
Size:               2048 kB
KernelPageSize:     2048 kB
MMUPageSize:        2048 kB
Rss:                   0 kB
Pss:                   0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
VmFlags: rd wr sh mr mw me ms de ht dd sd

稍后，就在madvise(ptr, m_size, MADV_DODUMP)之前，地图是相同的：

代码语言：javascript
复制
7fffe1a00000-7fffe1c00000 rw-s 00000000 00:0f 18481215                   /SYSV00000000 (deleted)
Size:               2048 kB
KernelPageSize:     2048 kB
MMUPageSize:        2048 kB
Rss:                   0 kB
Pss:                   0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
VmFlags: rd wr sh mr mw me ms de ht dd sd

下一个代码是：

代码语言：javascript
复制
madvise(ptr, m_size, MADV_DODUMP)

GDB显示使用了相同的值：

代码语言：javascript
复制
(gdb) p size
$1 = 2097152
(gdb) p ptr
$2 = (void *) 0x7fffe1a00000

madvise(ptr,size,MADV_DODUMP)是返回-1，errno=EINVAL，并且页面映射保持不变。

内核版本：

代码语言：javascript
复制
$ uname -a
Linux 4.18.9-300.fc29.x86_64 #1 SMP Thu Sep 20 02:32:53 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

为了完整起见，从分配给同一程序(不同执行)的strace -fe trace=%memory ...中提取一个EINVAL：

代码语言：javascript
复制
[pid  6036] shmat(18874431, NULL, 0)    = 0x7f6ebda00000
[pid  6036] madvise(0x7f6ebda00000, 2097152, MADV_DONTDUMP) = 0
[pid  6036] mmap(NULL, 2215936, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f6ebd7e3000
[pid  6036] brk(NULL)                   = 0x55caa0d76000
[pid  6036] brk(0x55caa0de7000)         = 0x55caa0de7000
[pid  6036] brk(NULL)                   = 0x55caa0de7000
[pid  6036] brk(0x55caa0e38000)         = 0x55caa0e38000
[pid  6036] brk(NULL)                   = 0x55caa0e38000
[pid  6036] brk(0x55caa0e8a000)         = 0x55caa0e8a000
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6ebcfe2000
[pid  6036] mprotect(0x7f6ebcfe3000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6039 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6ebc7e1000
[pid  6036] mprotect(0x7f6ebc7e2000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6040 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6ead3ff000
[pid  6036] mprotect(0x7f6ead400000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6041 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6eacbfe000
[pid  6036] mprotect(0x7f6eacbff000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6042 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6eac3fd000
[pid  6036] mprotect(0x7f6eac3fe000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6043 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6eabbfc000
[pid  6036] mprotect(0x7f6eabbfd000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6044 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6eab3fb000
[pid  6036] mprotect(0x7f6eab3fc000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6045 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6eaabfa000
[pid  6036] mprotect(0x7f6eaabfb000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6046 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6eaa3f9000
[pid  6036] mprotect(0x7f6eaa3fa000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6047 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6ea9bf8000
[pid  6036] mprotect(0x7f6ea9bf9000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6048 attached
[pid  6036] mmap(NULL, 8392704, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f6ea93f7000
[pid  6036] mprotect(0x7f6ea93f8000, 8388608, PROT_READ|PROT_WRITE) = 0
strace: Process 6049 attached
[pid  6049] mmap(NULL, 134217728, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x7f6ea13f7000
[pid  6049] munmap(0x7f6ea13f7000, 46174208) = 0
[pid  6049] munmap(0x7f6ea8000000, 20934656) = 0
[pid  6049] mprotect(0x7f6ea4000000, 135168, PROT_READ|PROT_WRITE) = 0
[pid  6036] brk(NULL)                   = 0x55caa0e8a000
[pid  6036] brk(0x55caa0eab000)         = 0x55caa0eab000
[pid  6036] mmap(NULL, 2117632, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f6ebc5dc000
[pid  6036] munmap(0x7f6ebd7e3000, 2215936) = 0
[pid  6036] brk(NULL)                   = 0x55caa0eab000
[pid  6036] brk(0x55caa10d5000)         = 0x55caa10d5000
[pid  6036] brk(NULL)                   = 0x55caa10d5000
[pid  6036] brk(0x55caa1118000)         = 0x55caa1118000
[pid  6036] brk(NULL)                   = 0x55caa1118000
[pid  6036] brk(0x55caa115c000)         = 0x55caa115c000
[pid  6036] madvise(0x7f6ebda00000, 2097152, MADV_DODUMP) = -1 EINVAL (Invalid argument)

关于为什么为madvise(MADV_DODUMP)返回EINVAL的任何线索

代码是: mariadb-10.3分支

c
linux
memory
system-calls
EN

回答 1

Stack Overflow用户

回答已采纳

发布于 2018-09-28 05:04:01

de引用了VM_DONTEXPAND，内核显式地拒绝了MADV_DODUMP的标志

代码语言：javascript
复制
#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP | VM_MIXEDMAP)
…
    case MADV_DODUMP:
            if (new_flags & VM_SPECIAL) {
                    error = -EINVAL;
                    goto out;
            }
            new_flags &= ~VM_DONTDUMP;
            break;

此检查自2012年提交0103bd16fb90bc741c7a03fd1e4e8a505abad23(“mm:准备在驱动程序中使用VM_DONTDUMP”)以来一直存在。

此映射可能来自hugetlbfs (hugetlbfs_file_mmap in fs/hugetlbfs/inode.c)，因为ht位也是设置的。

票数 1
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/52548260

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