Messages in this thread | | | Date | Thu, 28 Apr 2022 14:13:00 +0100 | From | Will Deacon <> | Subject | Re: [PATCH v2] arm64: add the printing of tpidr_elx in __show_regs() |
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On Thu, Apr 28, 2022 at 08:03:50PM +0800, Leizhen (ThunderTown) wrote: > > > On 2022/4/28 19:07, Leizhen (ThunderTown) wrote: > > > > > > On 2022/4/28 18:21, Will Deacon wrote: > >> On Wed, Mar 16, 2022 at 02:24:08PM +0800, Zhen Lei wrote: > >>> Commit 7158627686f0 ("arm64: percpu: implement optimised pcpu access > >>> using tpidr_el1") and commit 6d99b68933fb ("arm64: alternatives: use > >>> tpidr_el2 on VHE hosts") use tpidr_elx to cache my_cpu_offset to optimize > >>> pcpu access. However, when performing reverse execution based on the > >>> registers and the memory contents in kdump, this information is sometimes > >>> required if there is a pcpu access. > >>> > >>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > >>> --- > >>> arch/arm64/kernel/process.c | 11 +++++++++++ > >>> 1 file changed, 11 insertions(+) > >>> > >>> v1 --> v2: > >>> Directly print the tpidr_elx register of the current exception level. > >>> Avoid coupling with the implementation of 'my_cpu_offset'. > >>> > >>> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > >>> index 5369e649fa79ff8..738932e6fa4e947 100644 > >>> --- a/arch/arm64/kernel/process.c > >>> +++ b/arch/arm64/kernel/process.c > >>> @@ -216,6 +216,17 @@ void __show_regs(struct pt_regs *regs) > >>> show_regs_print_info(KERN_DEFAULT); > >>> print_pstate(regs); > >>> > >>> + switch (read_sysreg(CurrentEL)) { > >> > >> This should use is_kernel_in_hyp_mode() to detect if we're running at El2. > > static inline bool is_kernel_in_hyp_mode(void) > { > return read_sysreg(CurrentEL) == CurrentEL_EL2; > } > > I think it's more intuitive to use "switch (read_sysreg(CurrentEL))".
No, I disagree with you here, sorry.
> >>> + case CurrentEL_EL1: > >>> + printk("tpidr_el1 : %016llx\n", read_sysreg(TPIDR_EL1)); > >>> + break; > >>> + case CurrentEL_EL2: > >>> + printk("tpidr_el2 : %016llx\n", read_sysreg(TPIDR_EL2)); > >>> + break; > >>> + default: > >>> + break; > >>> + } > >> > >> I think this path can be triggered directly from usermode, so we really > >> shouldn't be printing raw kernel virtual addresses here. > > > > I run echo c > /proc/sysrq-trigger and didn't trigger this path, but maybe > > there's another way. Analysis from the other side, except for the instruction > > address, all generic registers r0-r31 is output as raw. There's also an > > opportunity to contain the instruction address. > > On second thought, there seemed to be nothing wrong with it. The user need > to have capable() first. Then the address of the perpcu memory is not static, > the memory is dynamically allocated, exposing it is no different than exposing sp.
If show_unhandled_signals is set, then I think any fatal signal takes this path, no?
Will
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