kernel/kexec_file.c: make purgatory_info->ehdr const

The kexec_purgatory buffer is read-only.  Thus all pointers into
kexec_purgatory are read-only, too.  Point this out by explicitly
marking purgatory_info->ehdr as 'const' and update the comments in
purgatory_info.

Link: http://lkml.kernel.org/r/20180321112751.22196-4-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo <prudo@linux.vnet.ibm.com>
Acked-by: Dave Young <dyoung@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 81ba4f782486..12cf9c9ff0bc 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -941,7 +941,7 @@ int kexec_load_purgatory(struct kimage *image, unsigned long min,
         if (kexec_purgatory_size <= 0)
                 return -EINVAL;
 
-        pi->ehdr = (Elf_Ehdr *)kexec_purgatory;
+        pi->ehdr = (const Elf_Ehdr *)kexec_purgatory;
 
         ret = __kexec_load_purgatory(image, min, max, top_down);
         if (ret)
@@ -965,9 +965,9 @@ out:
 static Elf_Sym *kexec_purgatory_find_symbol(struct purgatory_info *pi,
                                             const char *name)
 {
+        const Elf_Ehdr *ehdr;
         Elf_Sym *syms;
         Elf_Shdr *sechdrs;
-        Elf_Ehdr *ehdr;
         int i, k;
         const char *strtab;