kexec_file: Correctly output debugging information for the PT_LOAD ELF header

Currently, when we enable the debugging switch to debug kexec_file,
we always get the following incorrect results:

  kexec_file: Crash PT_LOAD elf header. phdr=00000000c988639b vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=51 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=000000003cca69a0 vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=52 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=00000000c584cb9f vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=53 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=00000000cf85d57f vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=54 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=00000000a4a8f847 vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=55 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=00000000272ec49f vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=56 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=00000000ea0b65de vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=57 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=000000001f5e490c vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=58 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=00000000dfe4109e vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=59 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=00000000480ed2b6 vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=60 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=0000000080b65151 vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=61 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=0000000024e31c5e vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=62 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=00000000332e0385 vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=63 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=000000002754d5da vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=64 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=00000000783320dd vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=65 p_offset=0x0
  kexec_file: Crash PT_LOAD elf header. phdr=0000000076fe5b64 vaddr=0x0, paddr=0x0, sz=0x0 e_phnum=66 p_offset=0x0

The reason is that kernel always prints the values of the next PT_LOAD
instead of the current PT_LOAD. Change it to ensure that we can get the
correct debugging information.

[ mingo: Amended changelog, capitalized "ELF". ]

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Dave Young <dyoung@redhat.com>
Link: https://lore.kernel.org/r/20200804044933.1973-4-lijiang@redhat.com

Author: lian-bo

kernel/kexec_file.c

@@ -1246,15 +1246,15 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
 	unsigned long long notes_addr;
 	unsigned long mstart, mend;
 
-	/* extra phdr for vmcoreinfo elf note */
+	/* extra phdr for vmcoreinfo ELF note */
 	nr_phdr = nr_cpus + 1;
 	nr_phdr += mem->nr_ranges;
 
 	/*
 	 * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping
 	 * area (for example, ffffffff80000000 - ffffffffa0000000 on x86_64).
 	 * I think this is required by tools like gdb. So same physical
-	 * memory will be mapped in two elf  headers. One will contain kernel
+	 * memory will be mapped in two ELF headers. One will contain kernel
 	 * text virtual addresses and other will have __va(physical) addresses.
 	 */
 
@@ -1323,10 +1323,10 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
 		phdr->p_filesz = phdr->p_memsz = mend - mstart + 1;
 		phdr->p_align = 0;
 		ehdr->e_phnum++;
-		phdr++;
-		pr_debug("Crash PT_LOAD elf header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
+		pr_debug("Crash PT_LOAD ELF header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
 			phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz,
 			ehdr->e_phnum, phdr->p_offset);
+		phdr++;
 	}
 
 	*addr = buf;