On 11/07/25 at 05:00pm, Pingfan Liu wrote: > On Fri, Nov 07, 2025 at 01:25:41PM +0800, Baoquan He wrote: > > On 11/07/25 at 01:13pm, Pingfan Liu wrote: > > > On Fri, Nov 7, 2025 at 9:51 AM Baoquan He <[email protected]> wrote: > > > > > > > > On 11/06/25 at 06:01pm, Pingfan Liu wrote: > > > > > On Thu, Nov 6, 2025 at 4:01 PM Baoquan He <[email protected]> wrote: > > > > > > > > > > > > On 11/06/25 at 02:59pm, Pingfan Liu wrote: > > > > > > > When I tested kexec with the latest kernel, I ran into the > > > > > > > following warning: > > > > > > > > > > > > > > [ 40.712410] ------------[ cut here ]------------ > > > > > > > [ 40.712576] WARNING: CPU: 2 PID: 1562 at > > > > > > > kernel/kexec_core.c:1001 kimage_map_segment+0x144/0x198 > > > > > > > [...] > > > > > > > [ 40.816047] Call trace: > > > > > > > [ 40.818498] kimage_map_segment+0x144/0x198 (P) > > > > > > > [ 40.823221] ima_kexec_post_load+0x58/0xc0 > > > > > > > [ 40.827246] __do_sys_kexec_file_load+0x29c/0x368 > > > > > > > [...] > > > > > > > [ 40.855423] ---[ end trace 0000000000000000 ]--- > > > > > > > > > > > > > > This is caused by the fact that kexec allocates the destination > > > > > > > directly > > > > > > > in the CMA area. In that case, the CMA kernel address should be > > > > > > > exported > > > > > > > directly to the IMA component, instead of using the vmalloc'd > > > > > > > address. > > > > > > > > > > > > Well, you didn't update the log accordingly. > > > > > > > > > > > > > > > > I am not sure what you mean. Do you mean the earlier content which I > > > > > replied to you? > > > > > > > > No. In v1, you return cma directly. But in v2, you return its direct > > > > mapping address, isnt' it? > > > > > > > > > > Yes. But I think it is a fault in the code, which does not convey the > > > expression in the commit log. Do you think I should rephrase the words > > > "the CMA kernel address" as "the CMA kernel direct mapping address"? > > > > That's fine to me. > > > > > > > > > > > > > > > > Do you know why cma area can't be mapped into vmalloc? > > > > > > > > > > > Should not the kernel direct mapping be used? > > > > > > > > When image->segment_cma[i] has value, image->ima_buffer_addr also > > > > contains the physical address of the cma area, why cma physical address > > > > can't be mapped into vmalloc and cause the failure and call trace? > > > > > > > > > > It could be done using the vmalloc approach, but it's unnecessary. > > > IIUC, kimage_map_segment() was introduced to provide a contiguous > > > virtual address for IMA access, since the IND_SRC pages are scattered > > > throughout the kernel. However, in the CMA case, there is already a > > > contiguous virtual address in the kernel direct mapping range. > > > Normally, when we have a physical address, we simply use > > > phys_to_virt() to get its corresponding kernel virtual address. > > > > OK, I understand cma area is contiguous, and no need to map into > > vmalloc. I am wondering why in the old code mapping cma addrss into > > vmalloc cause the warning which you said is a IMA problem. > > > > It doesn't go that far. The old code doesn't map CMA into vmalloc'd > area. > > void *kimage_map_segment(struct kimage *image, int idx) > { > ... > for_each_kimage_entry(image, ptr, entry) { > if (entry & IND_DESTINATION) { > dest_page_addr = entry & PAGE_MASK; > } else if (entry & IND_SOURCE) { > if (dest_page_addr >= addr && dest_page_addr < eaddr) > { > src_page_addr = entry & PAGE_MASK; > src_pages[i++] = > virt_to_page(__va(src_page_addr)); > if (i == npages) > break; > dest_page_addr += PAGE_SIZE; > } > } > } > > /* Sanity check. */ > WARN_ON(i < npages); //--> This is the warning thrown by kernel > > vaddr = vmap(src_pages, npages, VM_MAP, PAGE_KERNEL); > kfree(src_pages); > > if (!vaddr) > pr_err("Could not map ima buffer.\n"); > > return vaddr; > } > > When CMA is used, there is no IND_SOURCE, so we have i=0 < npages. > Now, I see how my words ("In that case, the CMA kernel address should be > exported directly to the IMA component, instead of using the vmalloc'd > address.") confused you. As for "instead of using the vmalloc'd > address", I meant to mention "vmap()" approach.
Ok, I got it. It's truly a bug because if image->segment_cma[idx] is valid, the current kimage_map_segment() can't collect the source pages at all since they are not marked with IND_DESTINATION|IND_SOURCE as normal segment does. In that situation, we can take the direct mapping address of image->segment_cma[idx] which is more efficient, instead of collecting source pages and vmap().
