de5a9a3e8b
Some code relies on having the file descriptor in m_in.fd. Consequently,
m_in is not only used to provide syscall parameters from user space to
VFS, but also as a global variable to store temporary data within VFS.
This has the ugly side effect that m_in gets overwritten during core
dumping.*
To work around this problem VFS now uses a so called "scratchpad" to
store temporary data that has to be globally accessible. This is a simple
table indexed by process number, just like fproc. The scratchpad allows
us to store the buffer pointer and buffer size for suspended system calls
(i.e., read, write, open, lock) instead of using fproc. This makes fproc
a bit smaller and fproc iterators a bit faster. Moreover, suspension of
processes becomes simpler altogether and suspended operations on pipes
are now less of a special case.
* This patch fixes a bug where due to unexpected m_in overwriting a
coredump would fail, and consequently resources are leaked. The coredump
was triggered with:
$ a() { a; }
$ a
19 lines
385 B
C
19 lines
385 B
C
#ifndef __VFS_SCRATCHPAD_H__
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#define __VFS_SCRATCHPAD_H__
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/* This is the per-process information. A slot is reserved for each potential
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* process. Thus NR_PROCS must be the same as in the kernel.
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*/
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EXTERN struct scratchpad {
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union sp_data {
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int fd_nr;
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struct filp *filp;
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} file;
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struct io_cmd {
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char *io_buffer;
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size_t io_nbytes;
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} io;
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} scratchpad[NR_PROCS];
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#endif
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