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libc: mmap: use VFS handle as reference for shared mappings

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Fixes #4050
This commit is contained in:
Christian Prochaska 2021-03-17 14:02:56 +01:00 committed by Christian Helmuth
parent 446df00d0d
commit 3d432331b9
2 changed files with 31 additions and 14 deletions
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8
repos/libports/src/lib/libc/internal/vfs_plugin.h
View File

@ -75,13 +75,13 @@ class Libc::Vfs_plugin final : public Plugin
struct Mmap_entry : Registry<Mmap_entry>::Element
{
void * const start;
Libc::File_descriptor * const fd;
void * const start;
Vfs::Vfs_handle * const reference_handle;
Mmap_entry(Registry<Mmap_entry> &registry, void *start,
Libc::File_descriptor *fd)
Vfs::Vfs_handle *reference_handle)
: Registry<Mmap_entry>::Element(registry, *this), start(start),
fd(fd) { }
reference_handle(reference_handle) { }
};
Genode::Allocator &_alloc;

37
repos/libports/src/lib/libc/vfs_plugin.cc
View File

@ -1946,11 +1946,19 @@ void *Libc::Vfs_plugin::mmap(void *addr_in, ::size_t length, int prot, int flags
} else if (flags & MAP_SHARED) {
/* duplicate the file descriptor to keep the file open as long as the mapping exists */
/* create another VFS handle to keep the file open as long as the mapping exists */
Libc::File_descriptor *dup_fd = dup(fd);
Vfs::Vfs_handle *reference_handle = nullptr;
typedef Vfs::Directory_service::Open_result Result;
Result vfs_open_result;
monitor().monitor([&] {
vfs_open_result = _root_fs.open(fd->fd_path, fd->flags,
&reference_handle, _alloc);
return Fn::COMPLETE;
});
if (!dup_fd) {
if (vfs_open_result != Result::OPEN_OK) {
error("mmap could not create reference VFS handle");
errno = ENFILE;
return MAP_FAILED;
}
@ -1964,7 +1972,10 @@ void *Libc::Vfs_plugin::mmap(void *addr_in, ::size_t length, int prot, int flags
if (!ds_cap.valid()) {
Genode::error("mmap got invalid dataspace capability");
close(dup_fd);
monitor().monitor([&] {
reference_handle->close();
return Fn::COMPLETE;
});
errno = ENODEV;
return MAP_FAILED;
}
@ -1972,12 +1983,15 @@ void *Libc::Vfs_plugin::mmap(void *addr_in, ::size_t length, int prot, int flags
try {
addr = region_map().attach(ds_cap, length, offset);
} catch (...) {
close(dup_fd);
monitor().monitor([&] {
reference_handle->close();
return Fn::COMPLETE;
});
errno = ENOMEM;
return MAP_FAILED;
}
new (_alloc) Mmap_entry(_mmap_registry, addr, dup_fd);
new (_alloc) Mmap_entry(_mmap_registry, addr, reference_handle);
}
return addr;
@ -1994,20 +2008,23 @@ int Libc::Vfs_plugin::munmap(void *addr, ::size_t)
/* shared mapping */
Libc::File_descriptor *fd = nullptr;
Vfs::Vfs_handle *reference_handle = nullptr;
_mmap_registry.for_each([&] (Mmap_entry &entry) {
if (entry.start == addr) {
fd = entry.fd;
reference_handle = entry.reference_handle;
destroy(_alloc, &entry);
region_map().detach(addr);
}
});
if (!fd)
if (!reference_handle)
return Errno(EINVAL);
close(fd);
monitor().monitor([&] {
reference_handle->close();
return Fn::COMPLETE;
});
return 0;
}