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Let process lib deal with fork semantics

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The startup procedure of forked processes differs from Genode's
normal process creation by omitting all steps related to ELF loading
and the start of the main thread. To let the process lib support this
distinction, an invalid ELF-binary capability is handled as valid
argument now.
This commit is contained in:
Norman Feske 2012-02-18 01:36:05 +01:00
parent 759af6d9c1
commit decfe7c4bb
1 changed files with 31 additions and 11 deletions
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28
base/src/base/process/process.cc
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@ -190,8 +190,18 @@ Process::Process(Dataspace_capability elf_ds_cap,
throw THREAD_FAIL;
}
/*
* The argument 'elf_ds_cap' may be invalid, which is not an error.
* This can happen when the process library is used to set up a process
* forked from another. In this case, all process initialization should
* be done except for the ELF loading and the startup of the main
* thread (as a forked process does not start its execution at the ELF
* entrypoint).
*/
bool const forked = !elf_ds_cap.valid();
/* check for dynamic program header */
if (_check_dynamic_elf(elf_ds_cap)) {
if (!forked && _check_dynamic_elf(elf_ds_cap)) {
if (!_dynamic_linker_cap.valid()) {
PERR("Dynamically linked file found, but no dynamic linker binary present");
throw ELF_FAIL;
@ -203,11 +213,14 @@ Process::Process(Dataspace_capability elf_ds_cap,
Ram_session_client ram(ram_session_cap);
/* parse ELF binary and setup segment dataspaces */
addr_t entry = _setup_elf(parent_cap, elf_ds_cap, ram, _rm_session_client);
addr_t entry = 0;
if (elf_ds_cap.valid()) {
entry = _setup_elf(parent_cap, elf_ds_cap, ram, _rm_session_client);
if (!entry) {
PERR("Setup ELF failed");
throw ELF_FAIL;
}
}
/* register parent interface for new protection domain */
if (_pd.assign_parent(parent_cap)) {
@ -238,13 +251,20 @@ Process::Process(Dataspace_capability elf_ds_cap,
throw THREAD_PAGER_FAIL;
}
/* start thread */
/*
* Inhibit start of main thread if the new process happens to be forked
* from another. In this case, the main thread will get manually
* started after constructing the 'Process'.
*/
if (!forked) {
/* start main thread */
err = _cpu_session_client.start(_thread0_cap, entry, 0 /* unused */);
if (err) {
PERR("Thread0 startup failed");
throw THREAD_START_FAIL;
}
}
}
catch (Local_exception cause) {