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 21:26:44 +0800 |
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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.
> > ... 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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