sys_pread64 [fs/read_write.c]
Reads number of bytes from a device (file, socket, etc.) using specified offset and preserving the current file position. Arguments
eax | 180
ebx | Device descriptor.
ecx | Pointer to the buffer that will receive the data.
edx | Number of bytes to be read.
esi | The low order 32-bits of a signed value that specifies the offset.
edi | The high order 32-bits of a signed value that specifies the offset.
Return values If the system call succeeds the return value is the number of bytes read. If the system call fails the return value is one of the following errno values:
`-EBADF` | `ebx is not avlid descriptor.`
`-EINVAL` | `edx is invalid. -or- The specified file offset is invalid.`
`-ESPIPE` | `The file descriptor is associated with a pipe, socket, or FIFO.`
`-EFAULT` | `ecx points outside the allocated address space.`
Remarks On success, the return value may be smaller than the number of bytes requested; this may happen for example because fewer bytes are actually available right now (maybe because we were close to end-of-file, or because we are reading from a pipe, or from a terminal), or because sys_read was interrupted by a signal. On NFS file systems, reading small amounts of data will only update the time stamp the first time, subsequent calls may not do so. This is caused by client side attribute caching, because most if not all NFS clients leave st_atime (last file access time) updates to the server and client side reads satisfied from the client's cache will not cause st_atime updates on the server as there are no server side reads. UNIX semantics can be obtained by disabling client side attribute caching, but in most situations this will substantially increase server load and decrease performance. Many filesystems and disks were considered to be fast enough that the implementation of O_NONBLOCK was deemed unnecessary. So, O_NONBLOCK may not be available on files and/or disks. Compatibility n/a