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Kernel: Move syscall precondition validates to MM

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Move these to MM to simplify the flow of the syscall handler.

While here, also make sure we hold the process space lock for
the duration of the validation to avoid potential issues where
another thread attempts to modify the process space during the
validation. This will allow us to move the validation out of the
big process lock scope in a future change.

Additionally utilize the new no_lock variants of functions to avoid
unnecessary recursive process space spinlock acquisitions.
This commit is contained in:
Brian Gianforcaro 2021-07-18 09:31:28 -07:00 • committed by Gunnar Beutner
parent af543328ea
commit 27e1120dff
3 changed files with 50 additions and 35 deletions
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34
Kernel/Syscall.cpp
View file

@ -199,39 +199,7 @@ NEVER_INLINE void syscall_handler(TrapFrame* trap)
// NOTE: We take the big process lock before inspecting memory regions.
process.big_lock().lock();
VirtualAddress userspace_sp;
#if ARCH(I386)
userspace_sp = VirtualAddress { regs.userspace_esp };
#else
userspace_sp = VirtualAddress { regs.userspace_rsp };
#endif
if (!MM.validate_user_stack(process.space(), userspace_sp)) {
dbgln("Invalid stack pointer: {:p}", userspace_sp);
handle_crash(regs, "Bad stack on syscall entry", SIGSTKFLT);
}
VirtualAddress ip;
#if ARCH(I386)
ip = VirtualAddress { regs.eip };
#else
ip = VirtualAddress { regs.rip };
#endif
auto* calling_region = MM.find_user_region_from_vaddr(process.space(), ip);
if (!calling_region) {
dbgln("Syscall from {:p} which has no associated region", ip);
handle_crash(regs, "Syscall from unknown region", SIGSEGV);
}
if (calling_region->is_writable()) {
dbgln("Syscall from writable memory at {:p}", ip);
handle_crash(regs, "Syscall from writable memory", SIGSEGV);
}
if (process.space().enforces_syscall_regions() && !calling_region->is_syscall_region()) {
dbgln("Syscall from non-syscall region");
handle_crash(regs, "Syscall from non-syscall region", SIGSEGV);
}
MM.validate_syscall_preconditions(process.space(), regs);
FlatPtr function;
FlatPtr arg1;