diff options
| author | Sergey Bugaev <bugaevc@gmail.com> | 2023-05-11 22:28:59 +0300 |
|---|---|---|
| committer | Samuel Thibault <samuel.thibault@ens-lyon.org> | 2023-05-12 01:02:05 +0200 |
| commit | 8cc2ed2eeca01c46c04682939d0ecd34927cde7b (patch) | |
| tree | 9330601dd9a150ac0759eca1f32e07bc3a4a13e0 /x86_64 | |
| parent | 9132d71a75edd11d94076047afa4553a730333c7 (diff) | |
x86_64: Check for AST when exiting a syscall
...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.
Message-Id: <20230511192859.890693-1-bugaevc@gmail.com>
Diffstat (limited to 'x86_64')
| -rw-r--r-- | x86_64/locore.S | 28 |
1 files 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 */ |