Messages in this thread | | | Subject | Re: [PATCH 2/5] ARM: stacktrace: Avoid duplicate saving of exception PC value | From | Li Huafei <> | Date | Tue, 26 Jul 2022 17:10:23 +0800 |
| |
On 2022/7/18 17:01, Linus Walleij wrote: > On Tue, Jul 12, 2022 at 4:18 AM Li Huafei <lihuafei1@huawei.com> wrote: > >> Because an exception stack frame is not created in the exception entry, >> save_trace() does special handling for the exception PC, but this is >> only needed when CONFIG_FRAME_POINTER_UNWIND=y. When >> CONFIG_ARM_UNWIND=y, unwind annotations have been added to the exception >> entry and save_trace() will repeatedly save the exception PC: >> >> [0x7f000090] hrtimer_hander+0x8/0x10 [hrtimer] >> [0x8019ec50] __hrtimer_run_queues+0x18c/0x394 >> [0x8019f760] hrtimer_run_queues+0xbc/0xd0 >> [0x8019def0] update_process_times+0x34/0x80 >> [0x801ad2a4] tick_periodic+0x48/0xd0 >> [0x801ad3dc] tick_handle_periodic+0x1c/0x7c >> [0x8010f2e0] twd_handler+0x30/0x40 >> [0x80177620] handle_percpu_devid_irq+0xa0/0x23c >> [0x801718d0] generic_handle_domain_irq+0x24/0x34 >> [0x80502d28] gic_handle_irq+0x74/0x88 >> [0x8085817c] generic_handle_arch_irq+0x58/0x78 >> [0x80100ba8] __irq_svc+0x88/0xc8 >> [0x80108114] arch_cpu_idle+0x38/0x3c >> [0x80108114] arch_cpu_idle+0x38/0x3c <==== duplicate saved exception PC >> [0x80861bf8] default_idle_call+0x38/0x130 >> [0x8015d5cc] do_idle+0x150/0x214 >> [0x8015d978] cpu_startup_entry+0x18/0x1c >> [0x808589c0] rest_init+0xd8/0xdc >> [0x80c00a44] arch_post_acpi_subsys_init+0x0/0x8 >> >> We can move the special handling of the exception PC in save_trace() to >> the unwind_frame() of the frame pointer unwinder. >> >> Signed-off-by: Li Huafei <lihuafei1@huawei.com> > > This is another very nice patch! > Reviewed-by: Linus Waleij <linus.walleij@linaro.org> > > Nitpick: > >> + if ((unsigned long)®s[1] > ALIGN(frame->sp, THREAD_SIZE)) >> + return -EINVAL; > > It'd be nice to add a comment saying what is in regs[1] at this point > so it is easier to understand the code. Not your fault as it is just > moved code, but if you have time please add a small comment. >
It is necessary to add the comment. This check is to ensure that 'regs + sizeof(struct pt_regs)' (that is, ®s[1]) does not go beyond the bottom of the stack, to avoid accessing data outside the task's stack, see commit 40ff1ddb5570 ("ARM: 8948/1: Prevent OOB access in stacktrace") for details. I will add a comment in the next version.
Thanks, Huafei
> Yours, > Linus Walleij > . >
| |