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Message-ID: <ec447291-078f-d1ea-6c5a-21b092965e81@loongson.cn>
Date: Mon, 5 Sep 2022 08:54:19 +0800
From: Youling Tang <tangyouling@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Baoquan He <bhe@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>,
WANG Xuerui <kernel@...0n.name>,
Vivek Goyal <vgoyal@...hat.com>,
Dave Young <dyoung@...hat.com>, Guo Ren <guoren@...nel.org>,
Jiaxun Yang <jiaxun.yang@...goat.com>,
kexec@...ts.infradead.org, loongarch@...ts.linux.dev,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] LoongArch: Add kdump support
Hi, Huacai
On 09/04/2022 08:21 PM, Huacai Chen wrote:
> Hi, Youling,
>
> I think crash.c can be merged into crash_dump.c
Most architectures only implement copy_oldmem_page() in crash_dump.c,
I'm not sure if merging crash.c into crash_dump.c will break its
consistency?
Thanks,
Youling
>
> Huacai
>
> On Mon, Aug 29, 2022 at 12:37 PM Youling Tang <tangyouling@...ngson.cn> wrote:
>>
>> This patch adds support for kdump, the kernel will reserve a region
>> for the crash kernel and jump there on panic.
>>
>> Arch-specific functions are added to allow for implementing a crash
>> dump file interface, /proc/vmcore, which can be viewed as a ELF file.
>>
>> A user space tool, like kexec-tools, is responsible for allocating a
>> separate region for the core's ELF header within crash kdump kernel
>> memory and filling it in when executing kexec_load().
>>
>> Then, its location will be advertised to crash dump kernel via a new
>> device-tree property, "linux,elfcorehdr", and crash dump kernel preserves
>> the region for later use with fdt_reserve_elfcorehdr() at boot time.
>>
>> At the same time, it will also limit the crash kdump kernel to the
>> crashkernel area via a new device-tree property, "linux, usable-memory-range",
>> so as not to destroy the original kernel dump data.
>>
>> On crash dump kernel, /proc/vmcore will access the primary kernel's memory
>> with copy_oldmem_page().
>>
>> I tested this on LoongArch 3A5000 machine and works as expected (Suggest
>> crashkernel parameter is "crashkernel=512M@...0M"), you may test it by
>> triggering a crash through /proc/sysrq_trigger:
>>
>> $ sudo kexec -p /boot/vmlinux-kdump --reuse-cmdline --append="nr_cpus=1"
>> # echo c > /proc/sysrq_trigger
>>
>> Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
>> ---
>> arch/loongarch/Kconfig | 22 ++++++
>> arch/loongarch/Makefile | 4 +
>> arch/loongarch/kernel/Makefile | 3 +-
>> arch/loongarch/kernel/crash.c | 100 ++++++++++++++++++++++++
>> arch/loongarch/kernel/crash_dump.c | 19 +++++
>> arch/loongarch/kernel/machine_kexec.c | 12 ++-
>> arch/loongarch/kernel/mem.c | 6 ++
>> arch/loongarch/kernel/relocate_kernel.S | 6 ++
>> arch/loongarch/kernel/setup.c | 49 ++++++++++++
>> arch/loongarch/kernel/traps.c | 4 +
>> 10 files changed, 217 insertions(+), 8 deletions(-)
>> create mode 100644 arch/loongarch/kernel/crash.c
>> create mode 100644 arch/loongarch/kernel/crash_dump.c
>>
>> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
>> index 903c82fa958d..7c1b07a5b5bd 100644
>> --- a/arch/loongarch/Kconfig
>> +++ b/arch/loongarch/Kconfig
>> @@ -420,6 +420,28 @@ config KEXEC
>>
>> The name comes from the similarity to the exec system call.
>>
>> +config CRASH_DUMP
>> + bool "Build kdump crash kernel"
>> + help
>> + Generate crash dump after being started by kexec. This should
>> + be normally only set in special crash dump kernels which are
>> + loaded in the main kernel with kexec-tools into a specially
>> + reserved region and then later executed after a crash by
>> + kdump/kexec.
>> +
>> + For more details see Documentation/admin-guide/kdump/kdump.rst
>> +
>> +config PHYSICAL_START
>> + hex "Physical address where the kernel is loaded"
>> + default "0x9000000091000000" if 64BIT
>> + depends on CRASH_DUMP
>> + help
>> + This gives the XKPRANGE address where the kernel is loaded.
>> + If you plan to use kernel for capturing the crash dump change
>> + this value to start of the reserved region (the "X" value as
>> + specified in the "crashkernel=YM@XM" command line boot parameter
>> + passed to the panic-ed kernel).
>> +
>> config SECCOMP
>> bool "Enable seccomp to safely compute untrusted bytecode"
>> depends on PROC_FS
>> diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
>> index 4bc47f47cfd8..7dabd580426d 100644
>> --- a/arch/loongarch/Makefile
>> +++ b/arch/loongarch/Makefile
>> @@ -48,7 +48,11 @@ KBUILD_CFLAGS_MODULE += -fplt -Wa,-mla-global-with-abs,-mla-local-with-abs
>> cflags-y += -ffreestanding
>> cflags-y += $(call cc-option, -mno-check-zero-division)
>>
>> +ifdef CONFIG_PHYSICAL_START
>> +load-y = $(CONFIG_PHYSICAL_START)
>> +else
>> load-y = 0x9000000000200000
>> +endif
>> bootvars-y = VMLINUX_LOAD_ADDRESS=$(load-y)
>>
>> drivers-$(CONFIG_PCI) += arch/loongarch/pci/
>> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
>> index 20b64ac3f128..df5aea129364 100644
>> --- a/arch/loongarch/kernel/Makefile
>> +++ b/arch/loongarch/kernel/Makefile
>> @@ -17,7 +17,8 @@ obj-$(CONFIG_CPU_HAS_FPU) += fpu.o
>> obj-$(CONFIG_MODULES) += module.o module-sections.o
>> obj-$(CONFIG_STACKTRACE) += stacktrace.o
>>
>> -obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
>> +obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o crash.o
>> +obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
>>
>> obj-$(CONFIG_PROC_FS) += proc.o
>>
>> diff --git a/arch/loongarch/kernel/crash.c b/arch/loongarch/kernel/crash.c
>> new file mode 100644
>> index 000000000000..b4f249ec6301
>> --- /dev/null
>> +++ b/arch/loongarch/kernel/crash.c
>> @@ -0,0 +1,100 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2022 Loongson Technology Corporation Limited
>> + *
>> + * Derived from MIPS
>> + */
>> +#include <linux/kernel.h>
>> +#include <linux/smp.h>
>> +#include <linux/reboot.h>
>> +#include <linux/crash_dump.h>
>> +#include <linux/delay.h>
>> +#include <linux/irq.h>
>> +#include <linux/types.h>
>> +#include <linux/sched.h>
>> +#include <linux/sched/task_stack.h>
>> +#include <asm/cacheflush.h>
>> +#include <asm/kexec.h>
>> +
>> +static cpumask_t cpus_in_crash = CPU_MASK_NONE;
>> +
>> +#ifdef CONFIG_SMP
>> +static void crash_shutdown_secondary(void *passed_regs)
>> +{
>> + struct pt_regs *regs = passed_regs;
>> + int cpu = smp_processor_id();
>> +
>> + /*
>> + * If we are passed registers, use those. Otherwise get the
>> + * regs from the last interrupt, which should be correct, as
>> + * we are in an interrupt. But if the regs are not there,
>> + * pull them from the top of the stack. They are probably
>> + * wrong, but we need something to keep from crashing again.
>> + */
>> + if (!regs)
>> + regs = get_irq_regs();
>> + if (!regs)
>> + regs = task_pt_regs(current);
>> +
>> + local_irq_disable();
>> + if (!cpumask_test_cpu(cpu, &cpus_in_crash))
>> + crash_save_cpu(regs, cpu);
>> + cpumask_set_cpu(cpu, &cpus_in_crash);
>> +
>> + while (!atomic_read(&kexec_ready_to_reboot))
>> + cpu_relax();
>> +
>> + kexec_reboot();
>> +}
>> +
>> +/* Override the weak function in kernel/panic.c */
>> +void crash_smp_send_stop(void)
>> +{
>> + static int cpus_stopped;
>> + unsigned long timeout;
>> + unsigned int ncpus;
>> +
>> + /*
>> + * This function can be called twice in panic path, but obviously
>> + * we execute this only once.
>> + */
>> + if (cpus_stopped)
>> + return;
>> +
>> + cpus_stopped = 1;
>> +
>> + /* Excluding the panic cpu */
>> + ncpus = num_online_cpus() - 1;
>> +
>> + smp_call_function(crash_shutdown_secondary, NULL, 0);
>> + smp_wmb();
>> +
>> + /*
>> + * The crash CPU sends an IPI and wait for other CPUs to
>> + * respond. Delay of at least 10 seconds.
>> + */
>> + pr_emerg("Sending IPI to other cpus...\n");
>> + timeout = USEC_PER_SEC * 10;
>> + while ((cpumask_weight(&cpus_in_crash) < ncpus) && timeout--) {
>> + cpu_relax();
>> + udelay(1);
>> + }
>> +}
>> +
>> +#endif
>> +
>> +void machine_crash_shutdown(struct pt_regs *regs)
>> +{
>> + int crashing_cpu;
>> +
>> + local_irq_disable();
>> +
>> + crashing_cpu = smp_processor_id();
>> + crash_save_cpu(regs, crashing_cpu);
>> +
>> + /* shutdown non-crashing cpus */
>> + crash_smp_send_stop();
>> + cpumask_set_cpu(crashing_cpu, &cpus_in_crash);
>> +
>> + pr_info("Starting crashdump kernel...\n");
>> +}
>> diff --git a/arch/loongarch/kernel/crash_dump.c b/arch/loongarch/kernel/crash_dump.c
>> new file mode 100644
>> index 000000000000..13e5d2f7870d
>> --- /dev/null
>> +++ b/arch/loongarch/kernel/crash_dump.c
>> @@ -0,0 +1,19 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +#include <linux/highmem.h>
>> +#include <linux/crash_dump.h>
>> +#include <linux/io.h>
>> +
>> +ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
>> + size_t csize, unsigned long offset)
>> +{
>> + void *vaddr;
>> +
>> + if (!csize)
>> + return 0;
>> +
>> + vaddr = kmap_local_pfn(pfn);
>> + csize = copy_to_iter(vaddr + offset, csize, iter);
>> + kunmap_local(vaddr);
>> +
>> + return csize;
>> +}
>> diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
>> index 4ffcd4cd9c8c..f793a3ff09a3 100644
>> --- a/arch/loongarch/kernel/machine_kexec.c
>> +++ b/arch/loongarch/kernel/machine_kexec.c
>> @@ -69,7 +69,7 @@ int machine_kexec_prepare(struct kimage *kimage)
>> continue;
>> }
>>
>> - /* kexec need a safe page to save reboot_code_buffer */
>> + /* kexec/kdump need a safe page to save reboot_code_buffer */
>> kimage->control_code_page = virt_to_page((void *)KEXEC_CTRL_CODE);
>>
>> reboot_code_buffer =
>> @@ -113,10 +113,6 @@ static void kexec_shutdown_secondary(void *)
>>
>> kexec_reboot();
>> }
>> -
>> -void machine_crash_shutdown(struct pt_regs *regs)
>> -{
>> -}
>> #endif
>>
>> void machine_shutdown(void)
>> @@ -135,7 +131,8 @@ void machine_kexec(struct kimage *image)
>>
>> jump_addr = (unsigned long)phys_to_virt(image->start);
>>
>> - first_ind_entry = (unsigned long)phys_to_virt(image->head & PAGE_MASK);
>> + if (image->type == KEXEC_TYPE_DEFAULT)
>> + first_ind_entry = (unsigned long)phys_to_virt(image->head & PAGE_MASK);
>>
>> /*
>> * The generic kexec code builds a page list with physical
>> @@ -167,7 +164,8 @@ void machine_kexec(struct kimage *image)
>>
>> /*
>> * We know we were online, and there will be no incoming IPIs at
>> - * this point.
>> + * this point. Mark online again before rebooting so that the crash
>> + * analysis tool will see us correctly.
>> */
>> set_cpu_online(smp_processor_id(), true);
>>
>> diff --git a/arch/loongarch/kernel/mem.c b/arch/loongarch/kernel/mem.c
>> index 7423361b0ebc..c6def6ff81c8 100644
>> --- a/arch/loongarch/kernel/mem.c
>> +++ b/arch/loongarch/kernel/mem.c
>> @@ -5,6 +5,7 @@
>> #include <linux/efi.h>
>> #include <linux/initrd.h>
>> #include <linux/memblock.h>
>> +#include <linux/of_fdt.h>
>>
>> #include <asm/bootinfo.h>
>> #include <asm/loongson.h>
>> @@ -61,4 +62,9 @@ void __init memblock_init(void)
>>
>> /* Reserve the initrd */
>> reserve_initrd_mem();
>> +
>> + /* Mainly reserved memory for the elf core head */
>> + early_init_fdt_scan_reserved_mem();
>> + /* Parse linux,usable-memory-range is for crash dump kernel */
>> + early_init_dt_check_for_usable_mem_range();
>> }
>> diff --git a/arch/loongarch/kernel/relocate_kernel.S b/arch/loongarch/kernel/relocate_kernel.S
>> index d1f242f74ea8..4ee5ac4ac2d7 100644
>> --- a/arch/loongarch/kernel/relocate_kernel.S
>> +++ b/arch/loongarch/kernel/relocate_kernel.S
>> @@ -28,6 +28,12 @@ SYM_CODE_START(relocate_new_kernel)
>> move s2, a2
>> move s3, a3
>>
>> + /*
>> + * In case of a kdump/crash kernel, the indirection page is not
>> + * populated as the kernel is directly copied to a reserved location
>> + */
>> + beqz s2, done
>> +
>> process_entry:
>> PTR_L s4, s2, 0
>> PTR_ADDI s2, s2, SZREG
>> diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
>> index f938aae3e92c..ea34b77e402f 100644
>> --- a/arch/loongarch/kernel/setup.c
>> +++ b/arch/loongarch/kernel/setup.c
>> @@ -19,6 +19,8 @@
>> #include <linux/memblock.h>
>> #include <linux/initrd.h>
>> #include <linux/ioport.h>
>> +#include <linux/kexec.h>
>> +#include <linux/crash_dump.h>
>> #include <linux/root_dev.h>
>> #include <linux/console.h>
>> #include <linux/pfn.h>
>> @@ -186,6 +188,50 @@ static int __init early_parse_mem(char *p)
>> }
>> early_param("mem", early_parse_mem);
>>
>> +static void __init loongarch_parse_crashkernel(void)
>> +{
>> +#ifdef CONFIG_KEXEC
>> + unsigned long long start;
>> + unsigned long long total_mem;
>> + unsigned long long crash_size, crash_base;
>> + int ret;
>> +
>> + total_mem = memblock_phys_mem_size();
>> + ret = parse_crashkernel(boot_command_line, total_mem,
>> + &crash_size, &crash_base);
>> + if (ret != 0 || crash_size <= 0)
>> + return;
>> +
>> +
>> + start = memblock_phys_alloc_range(crash_size, 1, crash_base,
>> + crash_base + crash_size);
>> + if (start != crash_base) {
>> + pr_warn("Invalid memory region reserved for crash kernel\n");
>> + return;
>> + }
>> +
>> + crashk_res.start = crash_base;
>> + crashk_res.end = crash_base + crash_size - 1;
>> +#endif
>> +}
>> +
>> +static void __init request_crashkernel(struct resource *res)
>> +{
>> +#ifdef CONFIG_KEXEC
>> + int ret;
>> +
>> + if (crashk_res.start == crashk_res.end)
>> + return;
>> +
>> + ret = request_resource(res, &crashk_res);
>> + if (!ret)
>> + pr_info("Reserving %ldMB of memory at %ldMB for crashkernel\n",
>> + (unsigned long)((crashk_res.end -
>> + crashk_res.start + 1) >> 20),
>> + (unsigned long)(crashk_res.start >> 20));
>> +#endif
>> +}
>> +
>> void __init platform_init(void)
>> {
>> efi_init();
>> @@ -229,6 +275,8 @@ static void __init arch_mem_init(char **cmdline_p)
>>
>> check_kernel_sections_mem();
>>
>> + loongarch_parse_crashkernel();
>> +
>> /*
>> * In order to reduce the possibility of kernel panic when failed to
>> * get IO TLB memory under CONFIG_SWIOTLB, it is better to allocate
>> @@ -290,6 +338,7 @@ static void __init resource_init(void)
>> request_resource(res, &code_resource);
>> request_resource(res, &data_resource);
>> request_resource(res, &bss_resource);
>> + request_crashkernel(res);
>> }
>> }
>>
>> diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
>> index aa1c95aaf595..0e610872f3f4 100644
>> --- a/arch/loongarch/kernel/traps.c
>> +++ b/arch/loongarch/kernel/traps.c
>> @@ -10,6 +10,7 @@
>> #include <linux/entry-common.h>
>> #include <linux/init.h>
>> #include <linux/kernel.h>
>> +#include <linux/kexec.h>
>> #include <linux/module.h>
>> #include <linux/extable.h>
>> #include <linux/mm.h>
>> @@ -246,6 +247,9 @@ void __noreturn die(const char *str, struct pt_regs *regs)
>>
>> oops_exit();
>>
>> + if (regs && kexec_should_crash(current))
>> + crash_kexec(regs);
>> +
>> if (in_interrupt())
>> panic("Fatal exception in interrupt");
>>
>> --
>> 2.36.0
>>
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