Messages in this thread | | | Subject | Re: [PATCH v3] arm64: add the printing of tpidr_elx in __show_regs() | From | "Leizhen (ThunderTown)" <> | Date | Thu, 5 May 2022 21:34:24 +0800 |
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On 2022/5/5 21:26, Leizhen (ThunderTown) wrote: > > > On 2022/5/5 21:04, Mark Rutland wrote: >> On Thu, May 05, 2022 at 05:56:40PM +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 | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> v2 --> v3: >>> 1) Relace "switch (read_sysreg(CurrentEL))" statement with >>> "if (is_kernel_in_hyp_mode())" statement. >>> 2) Change the register name to lowercase. >>> >>> 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 7fa97df55e3ad3f..7b6bccce9721c36 100644 >>> --- a/arch/arm64/kernel/process.c >>> +++ b/arch/arm64/kernel/process.c >>> @@ -216,6 +216,11 @@ void __show_regs(struct pt_regs *regs) >>> show_regs_print_info(KERN_DEFAULT); >>> print_pstate(regs); >>> >>> + if (is_kernel_in_hyp_mode()) >>> + printk("tpidr_el2 : %016llx\n", read_sysreg(tpidr_el2)); >>> + else >>> + printk("tpidr_el1 : %016llx\n", read_sysreg(tpidr_el1)); >> >> If we care about the offset specifically, this would be simpler as: >> >> printk("cpu offset : 0x%016lx\n", __my_cpu_offset()); > > The function name is __show_regs(), so not using register name may not be good. > In fact, some other architectures may also have this problem. If we use my_cpu_offset, > we may need to put it in a public.
The other idea is to back up each my_cpu_offset in an array. In this way, the offset can be queried through vmcore even if it is not printed.
> >> >> ... which should do the right thing even if we repurpose the TPIDRs and move the offset elsewhere. >> >> As Will says, we should only log this for !user_mode(regs), so it could >> be placed in the block below, immediately before we print the kernel PC, i.e. >> >> if (!user_mode_regs) { >> printk("cpu offset : %016lx\n", __my_cpu_offset()); >> printk("pc : %pS\n", (void *)regs->pc); >> printk("lr : %pS\n", (void *)ptrauth_strip_insn_pac(lr)); >> ... >> } >> >> ... or in a separate block which checks the same condition. >> >> Thanks, >> Mark. >> >>> + >>> if (!user_mode(regs)) { >>> printk("pc : %pS\n", (void *)regs->pc); >>> printk("lr : %pS\n", (void *)ptrauth_strip_insn_pac(lr)); >>> -- >>> 2.25.1 >>> >> . >> >
-- Regards, Zhen Lei
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