Applied, thanks! Sergey Bugaev, le jeu. 11 mai 2023 22:28:59 +0300, a ecrit: > ...like it's already done when exiting a trap. This is required, since > handing a syscall can result in an AST; in particular this happens when > the current thread is being terminated, which sets AST_TERMINATE and > expects the thread to never return to userspace. > > Fixes a kernel crash upon calling exit () or pthread_exit () in glibc. > --- > > Differences to v1: > * Remove the TODO entry about checking for AST > * Attempt to save the syscall return value > > Are we actually aligning the stack correctly before the call to syscall > implementation? > > x86_64/locore.S | 28 +++++++++++++++++++++++++--- > 1 file changed, 25 insertions(+), 3 deletions(-) > > diff --git a/x86_64/locore.S b/x86_64/locore.S > index 366ef292..2b8e4c44 100644 > --- a/x86_64/locore.S > +++ b/x86_64/locore.S > @@ -1341,7 +1341,6 @@ END(syscall) > - for now we assume the return address is canonical, but apparently > there > can be cases where it's not (see how Linux handles this). Does it > apply > here? > - - do we need to check for ast on syscalls? Maybe on interrupts is enough > - check that the case where a task is suspended, and later returns via > iretq from return_from_trap, works fine in all combinations > */ > @@ -1428,10 +1427,33 @@ _syscall64_args_stack: > > _syscall64_call: > call *EXT(mach_trap_table)+8(%rax) /* call procedure */ > - // XXX: check ast on exit? > > - /* Restore thread state and return to user using sysret. */ > +_syscall64_check_for_ast: > + /* Check for ast. */ > CPU_NUMBER(%r11) > + cmpl $0,CX(EXT(need_ast),%r11) > + jz _syscall64_restore_state > + > + /* Save the syscall return value, both on our stack, for the case > + * i386_astintr returns normally, and in the PCB stack, in case it > + * instead calls thread_block(thread_exception_return). > + */ > + pushq %rax /* save the return value on our > stack */ > + pushq $0 /* dummy value to keep the > stack aligned */ > + > + /* Find the PCB stack. */ > + movq %rsp,%rcx > + or $(KERNEL_STACK_SIZE-1),%rcx > + movq -7-IKS_SIZE(%rcx),%rcx > + > + movq %rax,R_EAX(%rcx) /* save the return value in the > PCB stack */ > + call EXT(i386_astintr) > + popq %rax > + popq %rax /* restore the return value */ > + jmp _syscall64_check_for_ast /* check again */ > + > +_syscall64_restore_state: > + /* Restore thread state and return to user using sysret. */ > movq CX(EXT(active_threads),%r11),%r11 /* point to current thread */ > movq TH_PCB(%r11),%r11 /* point to pcb */ > addq $ PCB_ISS,%r11 /* point to saved state */ > -- > 2.40.1 > >
-- Samuel --- Pour une évaluation indépendante, transparente et rigoureuse ! Je soutiens la Commission d'Évaluation de l'Inria.
