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Kernel: Move E2BIG calculation from Thread to Process

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Thread::make_userspace_stack_for_main_thread is only ever called from
Process::do_exec, after all the fun ELF loading and TSS setup has
occured.

The calculations in there that check if the combined argv + envp
size will exceed the default stack size are not used in the rest of
the stack setup. So, it should be safe to move this to the beginning
of do_exec and bail early with -E2BIG, just like the man pages say.

Additionally, advertise this limit in limits.h to be a good POSIX.1
citizen. :)
This commit is contained in:
Andrew Kaster 2019-10-20 10:11:40 -06:00 • committed by Andreas Kling
parent 3014fdf3bd
commit 98c86e5109
4 changed files with 20 additions and 16 deletions
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14
Kernel/Thread.cpp
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@ -40,9 +40,6 @@ HashTable<Thread*>& thread_table()
return *table;
}
static const u32 default_kernel_stack_size = 65536;
static const u32 default_userspace_stack_size = 65536;
Thread::Thread(Process& process)
: m_process(process)
, m_tid(process.m_next_tid++)
@ -515,17 +512,6 @@ void Thread::make_userspace_stack_for_main_thread(Vector<String> arguments, Vect
char** env = argv + arguments.size() + 1;
char* bufptr = stack_base + (sizeof(char*) * (arguments.size() + 1)) + (sizeof(char*) * (environment.size() + 1));
size_t total_blob_size = 0;
for (auto& a : arguments)
total_blob_size += a.length() + 1;
for (auto& e : environment)
total_blob_size += e.length() + 1;
size_t total_meta_size = sizeof(char*) * (arguments.size() + 1) + sizeof(char*) * (environment.size() + 1);
// FIXME: It would be better if this didn't make us panic.
ASSERT((total_blob_size + total_meta_size) < default_userspace_stack_size);
for (int i = 0; i < arguments.size(); ++i) {
argv[i] = bufptr;
memcpy(bufptr, arguments[i].characters(), arguments[i].length());