From: Lai Jiangshan <la...@linux.alibaba.com> cpu_tss_rw is not directly referenced by hardware, but cpu_tss_rw is also used in CPU entry code, especially when #DB shifts its stacks. If a data breakpoint is on the cpu_tss_rw.x86_tss.ist[IST_INDEX_DB], it will cause recursive #DB (and then #DF soon for #DB is generated after the access, IST-shifting, is done).
Signed-off-by: Lai Jiangshan <la...@linux.alibaba.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Link: https://lkml.kernel.org/r/20200526014221.2119-4-la...@linux.alibaba.com --- arch/x86/kernel/hw_breakpoint.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/arch/x86/kernel/hw_breakpoint.c +++ b/arch/x86/kernel/hw_breakpoint.c @@ -255,6 +255,15 @@ static inline bool within_cpu_entry(unsi if (within_area(addr, end, (unsigned long)get_cpu_gdt_rw(cpu), GDT_SIZE)) return true; + + /* + * cpu_tss_rw is not directly referenced by hardware, but + * cpu_tss_rw is also used in CPU entry code, + */ + if (within_area(addr, end, + (unsigned long)&per_cpu(cpu_tss_rw, cpu), + sizeof(struct tss_struct))) + return true; } return false;
