Messages in this thread | | | From | Thiago Jung Bauermann <> | Subject | Re: [PATCH v4 06/12] ppc64/kexec_file: restrict memory usage of kdump kernel | Date | Fri, 24 Jul 2020 21:32:59 -0300 |
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Hari Bathini <hbathini@linux.ibm.com> writes:
> On 24/07/20 5:36 am, Thiago Jung Bauermann wrote: >> >> Hari Bathini <hbathini@linux.ibm.com> writes: >> >>> Kdump kernel, used for capturing the kernel core image, is supposed >>> to use only specific memory regions to avoid corrupting the image to >>> be captured. The regions are crashkernel range - the memory reserved >>> explicitly for kdump kernel, memory used for the tce-table, the OPAL >>> region and RTAS region as applicable. Restrict kdump kernel memory >>> to use only these regions by setting up usable-memory DT property. >>> Also, tell the kdump kernel to run at the loaded address by setting >>> the magic word at 0x5c. >>> >>> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> >>> Tested-by: Pingfan Liu <piliu@redhat.com> >>> --- >>> >>> v3 -> v4: >>> * Updated get_node_path() to be an iterative function instead of a >>> recursive one. >>> * Added comment explaining why low memory is added to kdump kernel's >>> usable memory ranges though it doesn't fall in crashkernel region. >>> * For correctness, added fdt_add_mem_rsv() for the low memory being >>> added to kdump kernel's usable memory ranges. >> >> Good idea. >> >>> * Fixed prop pointer update in add_usable_mem_property() and changed >>> duple to tuple as suggested by Thiago. >> >> <snip> >> >>> +/** >>> + * get_node_pathlen - Get the full path length of the given node. >>> + * @dn: Node. >>> + * >>> + * Also, counts '/' at the end of the path. >>> + * For example, /memory@0 will be "/memory@0/\0" => 11 bytes. >> >> Wouldn't this function return 10 in the case of /memory@0? > > Actually, it does return 11. +1 while returning is for counting %NUL. > On top of that we count an extra '/' for root node.. so, it ends up as 11. > ('/'memory@0'/''\0'). Note the extra '/' before '\0'. Let me handle root node > separately. That should avoid the confusion.
Ah, that is true. I forgot to count the iteration for the root node. Sorry about that.
-- Thiago Jung Bauermann IBM Linux Technology Center
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