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syscall_emul: don't check host fd when allocating target fd

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There's a well-meaning check in Process::allocFD() to return an invalid
target fd (-1) if the incoming host fd is -1.  However, this means that
emulated drivers, which want to allocate a target fd that doesn't
correspond to a host fd, can't use -1 to indicate an intentionally
invalid host fd.

It turns out the allocFD() check is redundant, as callers always test
the host fd for validity before calling.  Also, callers never test the
return value of allocFD() for validity, so even if the test failed,
it would likely have the undesirable result of returning -1 to the
target app as a file descriptor without setting errno.

Thus the check is pointless and is now getting in the way, so it seems
we should just get rid of it.
This commit is contained in:
Steve Reinhardt 2015-12-09 14:47:43 -05:00
parent 7c4a6604b9
commit 28d7e261ed
1 changed files with 0 additions and 3 deletions
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3
src/sim/process.cc
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@ -242,9 +242,6 @@ int
Process::allocFD(int sim_fd, const string& filename, int flags, int mode, Process::allocFD(int sim_fd, const string& filename, int flags, int mode,
bool pipe) bool pipe)
{ {
if (sim_fd == -1)
return -1;
for (int free_fd = 0; free_fd < fd_array->size(); free_fd++) { for (int free_fd = 0; free_fd < fd_array->size(); free_fd++) {
FDEntry *fde = getFDEntry(free_fd); FDEntry *fde = getFDEntry(free_fd);
if (fde->isFree()) { if (fde->isFree()) {