Since a thread is supposed to be returned from Switch_context,
this fixes a bug where the thread is always returned as 0x0 on 64b UP,
hence the idle thread was being called too often instead of a chosen thread.
Also, this fixes a potential future bug with 64b SMP where the non-zero
cpu number is returned as a valid thread and causes a crash.
TESTED: By compiling gnumach on hurd-amd64 with
--enable-ncpus=1 --disable-linux-groups --enable-kdb --enable-apic
and booting hurd-amd64 in UP on qemu.
---
x86_64/cswitch.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/x86_64/cswitch.S b/x86_64/cswitch.S
index 9c4640fd..a6b390e8 100644
--- a/x86_64/cswitch.S
+++ b/x86_64/cswitch.S
@@ -83,10 +83,10 @@ ENTRY(Switch_context)
lea KERNEL_STACK_SIZE-IKS_SIZE-IEL_SIZE(%rcx),%rbx
/* point to stack top */
- CPU_NUMBER(%eax)
+ CPU_NUMBER(%edx) /* Don't overwrite returned
value %rax */
movq %rsi,MY(ACTIVE_THREAD) /* new thread is active */
movq %rcx,MY(ACTIVE_STACK) /* set current stack */
- movq %rbx,CX(EXT(kernel_stack),%rax) /* set stack top */
+ movq %rbx,CX(EXT(kernel_stack),%rdx) /* set stack top */
movq KSS_ESP(%rcx),%rsp /* switch stacks */
movq KSS_EBP(%rcx),%rbp /* restore registers */
--
2.51.0
