565f13088f
Change the kernel to add features to vircopy and safecopies so that
transparent copy fixing won't happen to avoid deadlocks, and such copies
fail with EFAULT.
Transparently making copying work from filesystems (as normally done by
the kernel & VM when copying fails because of missing/readonly memory)
is problematic as it can happen that, for file-mapped ranges, that that
same filesystem that is blocked on the copy request is needed to satisfy
the memory range, leading to deadlock. Dito for VFS itself, if done with
a blocking call.
This change makes the copying done from a filesystem fail in such cases
with EFAULT by VFS adding the CPF_TRY flag to the grants. If a FS call
fails with EFAULT, VFS will then request the range to be made available
to VM after the FS is unblocked, allowing it to be used to satisfy the
range if need be in another VFS thread.
Similarly, for datacopies that VFS itself does, it uses the failable
vircopy variant and callers use a wrapper that talk to VM if necessary
to get the copy to work.
. kernel: add CPF_TRY flag to safecopies
. kernel: only request writable ranges to VM for the
target buffer when copying fails
. do copying in VFS TRY-first
. some fixes in VM to build SANITYCHECK mode
. add regression test for the cases where
- a FS system call needs memory mapped in a process that the
FS itself must map.
- such a range covers more than one file-mapped region.
. add 'try' mode to vircopy, physcopy
. add flags field to copy kernel call messages
. if CP_FLAG_TRY is set, do not transparently try
to fix memory ranges
. for use by VFS when accessing user buffers to avoid
deadlock
. remove some obsolete backwards compatability assignments
. VFS: let thread scheduling work for VM requests too
Allows VFS to make calls to VM while suspending and resuming
the currently running thread. Does currently not work for the
main thread.
. VM: add fix memory range call for use by VFS
Change-Id: I295794269cea51a3163519a9cfe5901301d90b32
92 lines
3 KiB
C
92 lines
3 KiB
C
/* The kernel call implemented in this file:
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* m_type: SYS_VIRCOPY, SYS_PHYSCOPY
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*
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* The parameters for this kernel call are:
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* m5_l1: CP_SRC_ADDR source offset within segment
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* m5_i1: CP_SRC_ENDPT source process number
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* m5_l2: CP_DST_ADDR destination offset within segment
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* m5_i2: CP_DST_ENDPT destination process number
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* m5_l3: CP_NR_BYTES number of bytes to copy
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*/
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#include "kernel/system.h"
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#include "kernel/vm.h"
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#include <minix/type.h>
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#include <assert.h>
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#if (USE_VIRCOPY || USE_PHYSCOPY)
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/*===========================================================================*
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* do_copy *
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*===========================================================================*/
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int do_copy(struct proc * caller, message * m_ptr)
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{
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/* Handle sys_vircopy() and sys_physcopy(). Copy data using virtual or
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* physical addressing. Although a single handler function is used, there
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* are two different kernel calls so that permissions can be checked.
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*/
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struct vir_addr vir_addr[2]; /* virtual source and destination address */
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phys_bytes bytes; /* number of bytes to copy */
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int i;
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#if 0
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if (caller->p_endpoint != PM_PROC_NR && caller->p_endpoint != VFS_PROC_NR &&
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caller->p_endpoint != RS_PROC_NR && caller->p_endpoint != MEM_PROC_NR &&
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caller->p_endpoint != VM_PROC_NR)
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{
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static int first=1;
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if (first)
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{
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first= 0;
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printf(
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"do_copy: got request from %d (source %d, destination %d)\n",
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caller->p_endpoint,
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m_ptr->CP_SRC_ENDPT,
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m_ptr->CP_DST_ENDPT);
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}
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}
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#endif
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/* Dismember the command message. */
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vir_addr[_SRC_].proc_nr_e = m_ptr->CP_SRC_ENDPT;
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vir_addr[_DST_].proc_nr_e = m_ptr->CP_DST_ENDPT;
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vir_addr[_SRC_].offset = (vir_bytes) m_ptr->CP_SRC_ADDR;
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vir_addr[_DST_].offset = (vir_bytes) m_ptr->CP_DST_ADDR;
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bytes = (phys_bytes) m_ptr->CP_NR_BYTES;
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/* Now do some checks for both the source and destination virtual address.
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* This is done once for _SRC_, then once for _DST_.
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*/
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for (i=_SRC_; i<=_DST_; i++) {
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int p;
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/* Check if process number was given implicitly with SELF and is valid. */
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if (vir_addr[i].proc_nr_e == SELF)
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vir_addr[i].proc_nr_e = caller->p_endpoint;
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if (vir_addr[i].proc_nr_e != NONE) {
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if(! isokendpt(vir_addr[i].proc_nr_e, &p)) {
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printf("do_copy: %d: %d not ok endpoint\n", i, vir_addr[i].proc_nr_e);
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return(EINVAL);
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}
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}
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}
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/* Check for overflow. This would happen for 64K segments and 16-bit
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* vir_bytes. Especially copying by the PM on do_fork() is affected.
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*/
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if (bytes != (phys_bytes) (vir_bytes) bytes) return(E2BIG);
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/* Now try to make the actual virtual copy. */
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if(m_ptr->CP_FLAGS & CP_FLAG_TRY) {
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int r;
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assert(caller->p_endpoint == VFS_PROC_NR);
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r = virtual_copy(&vir_addr[_SRC_], &vir_addr[_DST_], bytes);
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if(r == EFAULT_SRC || r == EFAULT_DST) return r = EFAULT;
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return r;
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} else {
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return( virtual_copy_vmcheck(caller, &vir_addr[_SRC_],
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&vir_addr[_DST_], bytes) );
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}
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}
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#endif /* (USE_VIRCOPY || USE_PHYSCOPY) */
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