回复: Re: [PATCH] LoongArch: kdump: add arch_crash_save_vmcoreinfo() support

[廉洋洋]

Hi Tao,

Thanks for testing the patch on the Loongson-3A6000 and for the
Tested-by. You are right about VMEMMAP_END: it is an inclusive bound
on LoongArch, while the doc and tools expect an exclusive bound. I
have sent a v2 that exports VMEMMAP_END + 1 to keep the semantics
consistent with arm64 and riscv64, and added your Tested-by tag.

Thanks,
Yangyang Lian

 

主   题：Re: [PATCH] LoongArch: kdump: add arch_crash_save_vmcoreinfo() support
日   期：2026年09月24日10:23
发件人：Tao Cui
收件人：Andrew Morton,Baoquan He,Mike Rapoport,Pasha Tatashin,Pratyush Yadav,Huacai Chen,Tao Cui
抄送人：cui.tao,Dave Young,WANG Xuerui,kexec,loongarch,linux-kernel,姜浩然,郭东太

Hi Yangyang, 在 2026/9/23 14:03, Yangyang Lian 写道: > Since commit 23c85094fe18 ("proc/kcore: add vmcoreinfo note to > /proc/kcore") the kernel has exported the vmcoreinfo PT_NOTE on > /proc/kcore as wellas /proc/vmcore. > > LoongArch does not provide arch_crash_save_vmcoreinfo(), so the > arch-specific values are missing from the vmcoreinfo PT_NOTE. The > generic exporter in kernel/vmcore_info.c already provides > NUMBER(VMALLOC_START), but tools like crash cannot derive the module > and vmemmap ranges, VA_BITS, or the KASLR offset of a LoongArch dump. > > Since commit 18210a104bb9 ("LoongArch: Expand module virtual address > space to 2GB") the vmalloc and module boundaries are no longer stable > across kernel versions either, so vmcoreinfo is the only reliable > source for them. > I gave this patch a run on a Loongson-3A6000 box: built next-20260922 with it applied and booted the kernel as a KVM guest. Without the patch /proc/kcore only has the generic fields (OSRELEASE, PAGESIZE, NUMBER(VMALLOC_START) and the usual symbols/offsets). With it, the note now looks like: OSRELEASE=7.3.0-rc4-next-20260922-eagersplit+ PAGESIZE=16384 NUMBER(VMALLOC_START)=0xffff800082008000 NUMBER(VA_BITS)=47 NUMBER(VMALLOC_END)=0xfffffebffd7f8000 NUMBER(MODULES_VADDR)=0xffff800002008000 NUMBER(MODULES_END)=0xffff800082008000 NUMBER(VMEMMAP_START)=0xfffffebffe000000 NUMBER(VMEMMAP_END)=0xfffffffffdffffff NUMBER(PHYS_OFFSET)=0x0 KERNELOFFSET=0 (KASLR is off in my guest cmdline, hence KERNELOFFSET=0.) One thing worth a look: as also pointed out in the sashiko review, VMEMMAP_END on LoongArch is an inclusive bound (note the ...fdffffff above), while the doc added in this patch says VMEMMAP_START ~ VMEMMAP_END-1, and tools like makedumpfile compute the size as VMEMMAP_END - VMEMMAP_START. So exporting VMEMMAP_END + 1 would probably match what consumers expect. Works fine otherwise. Tested-by: Tao Cui <cuitao@xxxxxxxxxx> > Provide this function in a separate file that is built at the same time > as its caller in kernel/vmcore_info.c, and add a LOONGARCH64 section to > Documentation/admin-guide/kdump/vmcoreinfo.rst. > > Reported-by: Haoran Jiang <jianghaoran@xxxxxxxxxx> > Suggested-by: Haoran Jiang <jianghaoran@xxxxxxxxxx> > Co-developed-by: George Guo <guodongtai@xxxxxxxxxx> > Signed-off-by: George Guo <guodongtai@xxxxxxxxxx> > Signed-off-by: Yangyang Lian <lianyangyang@xxxxxxxxxx> > --- > .../admin-guide/kdump/vmcoreinfo.rst | 29 +++++++++++++++++++ > arch/loongarch/kernel/Makefile | 1 + > arch/loongarch/kernel/vmcore_info.c | 21 ++++++++++++++ > 3 files changed, 51 insertions(+) > create mode 100644 arch/loongarch/kernel/vmcore_info.c > > diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst > index 7663c610fe90..2ff921232616 100644 > --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst > +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst > @@ -594,3 +594,32 @@ va_kernel_pa_offset > > Indicates the offset between the kernel virtual and physical mappings. > Used to translate virtual to physical addresses. > + > +LOONGARCH64 > +=========== > + > +VA_BITS > +------- > + > +The maximum number of bits for virtual addresses. Used to compute the > +virtual memory ranges. > + > +PHYS_OFFSET > +----------- > + > +Indicates the physical address of the start of memory. Used to translate > +virtual to physical addresses. > + > +KERNELOFFSET > +------------ > + > +The kernel randomization offset. Used to locate the kernel text in > +virtual memory. If KASLR is disabled, this value is zero. > + > +MODULES_VADDR|MODULES_END|VMALLOC_START|VMALLOC_END|VMEMMAP_START|VMEMMAP_END > +----------------------------------------------------------------------------- > + > +Used to get the correct ranges: > + MODULES_VADDR ~ MODULES_END-1 : Kernel module space. > + VMALLOC_START ~ VMALLOC_END-1 : vmalloc() / ioremap() space. > + VMEMMAP_START ~ VMEMMAP_END-1 : vmemmap region, used for struct page array. > diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile > index 001924877772..6260c15adaba 100644 > --- a/arch/loongarch/kernel/Makefile > +++ b/arch/loongarch/kernel/Makefile > @@ -64,6 +64,7 @@ obj-$(CONFIG_RELOCATABLE) += relocate.o > obj-$(CONFIG_KEXEC_CORE) += machine_kexec.o relocate_kernel.o > obj-$(CONFIG_KEXEC_FILE) += machine_kexec_file.o kexec_efi.o kexec_elf.o > obj-$(CONFIG_CRASH_DUMP) += crash_dump.o > +obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o > > obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o > obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o > diff --git a/arch/loongarch/kernel/vmcore_info.c b/arch/loongarch/kernel/vmcore_info.c > new file mode 100644 > index 000000000000..1128f6cdfe0d > --- /dev/null > +++ b/arch/loongarch/kernel/vmcore_info.c > @@ -0,0 +1,21 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#include > +#include > +#include > +#include > + > +void arch_crash_save_vmcoreinfo(void) > +{ > + VMCOREINFO_NUMBER(VA_BITS); > + /* NUMBER(VMALLOC_START) is exported by the generic code */ > + vmcoreinfo_append_str("NUMBER(VMALLOC_END)=0x%lx\n", VMALLOC_END); > +#ifdef CONFIG_64BIT > + vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n", MODULES_VADDR); > + vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n", MODULES_END); > + vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n", (unsigned long)vmemmap); > + vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n", VMEMMAP_END); > +#endif > + vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%lx\n", PHYS_OFFSET); > + vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset()); > +} </lianyangyang@xxxxxxxxxx></guodongtai@xxxxxxxxxx></guodongtai@xxxxxxxxxx></jianghaoran@xxxxxxxxxx></jianghaoran@xxxxxxxxxx></cuitao@xxxxxxxxxx>

 

 

 

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