From: Sourabh Jain Date: Thu, 12 Mar 2026 08:30:49 +0000 (+0530) Subject: powerpc/crash: fix backup region offset update to elfcorehdr X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=789335cacdf37da93bb7c70322dff8c7e82881df;p=thirdparty%2Flinux.git powerpc/crash: fix backup region offset update to elfcorehdr update_backup_region_phdr() in file_load_64.c iterates over all the program headers in the kdump kernel’s elfcorehdr and updates the p_offset of the program header whose physical address starts at 0. However, the loop logic is incorrect because the program header pointer is not updated during iteration. Since elfcorehdr typically contains PT_NOTE entries first, the PT_LOAD program header with physical address 0 is never reached. As a result, its p_offset is not updated to point to the backup region. Because of this behavior, the capture kernel exports the first 64 KB of the crashed kernel’s memory at offset 0, even though that memory actually lives in the backup region. When a crash happens, purgatory copies the first 64 KB of the crashed kernel’s memory into the backup region so the capture kernel can safely use it. This has not caused problems so far because the first 64 KB is usually identical in both the crashed and capture kernels. However, this is just an assumption and is not guaranteed to always hold true. Fix update_backup_region_phdr() to correctly update the p_offset of the program header with a starting physical address of 0 by correcting the logic used to iterate over the program headers. Fixes: cb350c1f1f86 ("powerpc/kexec_file: Prepare elfcore header for crashing kernel") Reviewed-by: Aditya Gupta Signed-off-by: Sourabh Jain Reviewed-by: Hari Bathini Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20260312083051.1935737-2-sourabhjain@linux.ibm.com --- diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c index 5f6d50e4c3d45..a7db7eca0481b 100644 --- a/arch/powerpc/kexec/file_load_64.c +++ b/arch/powerpc/kexec/file_load_64.c @@ -391,7 +391,7 @@ static void update_backup_region_phdr(struct kimage *image, Elf64_Ehdr *ehdr) unsigned int i; phdr = (Elf64_Phdr *)(ehdr + 1); - for (i = 0; i < ehdr->e_phnum; i++) { + for (i = 0; i < ehdr->e_phnum; i++, phdr++) { if (phdr->p_paddr == BACKUP_SRC_START) { phdr->p_offset = image->arch.backup_start; kexec_dprintk("Backup region offset updated to 0x%lx\n",