[Xen-devel] [PATCH] create-diff-object: more precisely identify .rodata sections

[Pawel Wieczorkiewicz <wipawel@xxxxxxxxx>]

This is needed for more precise patchability verification.
Only non-special .rodata sections should be subject
for such a non-referenced check in kpatch_verify_patchability().
Current check (non-standard, non-rela, non-debug) is too weak and
allows also non-rodata sections without referenced symbols to slip
through.

Detect .rodata section by checking section's type (SHT_PROGBITS),
flags (no exec, no write) and finally name prefix.

Signed-off-by: Pawel Wieczorkiewicz <wipawel@xxxxxxxxx>
Reviewed-by: Andra-Irina Paraschiv <andraprs@xxxxxxxxxx>
Reviewed-by: Bjoern Doebel <doebel@xxxxxxxxx>
Reviewed-by: Norbert Manthey <nmanthey@xxxxxxxxx>
---
 common.c             |  7 +++++++
 common.h             |  1 +
 create-diff-object.c | 13 ++++++-------
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/common.c b/common.c
index 0ddc9fa..8f553ea 100644
--- a/common.c
+++ b/common.c
@@ -249,6 +249,13 @@ int is_text_section(struct section *sec)
                (sec->sh.sh_flags & SHF_EXECINSTR));
 }
 
+int is_rodata_section(struct section *sec)
+{
+       return sec->sh.sh_type == SHT_PROGBITS &&
+              !(sec->sh.sh_flags & (SHF_EXECINSTR | SHF_WRITE)) &&
+              !strncmp(sec->name, ".rodata", 7);
+}
+
 int is_debug_section(struct section *sec)
 {
        char *name;
diff --git a/common.h b/common.h
index 7c6fb73..b6489db 100644
--- a/common.h
+++ b/common.h
@@ -159,6 +159,7 @@ struct symbol *find_symbol_by_index(struct list_head *list, 
size_t index);
 struct symbol *find_symbol_by_name(struct list_head *list, const char *name);
 
 int is_text_section(struct section *sec);
+int is_rodata_section(struct section *sec);
 int is_debug_section(struct section *sec);
 int is_rela_section(struct section *sec);
 int is_standard_section(struct section *sec);
diff --git a/create-diff-object.c b/create-diff-object.c
index e4592a6..2f0e162 100644
--- a/create-diff-object.c
+++ b/create-diff-object.c
@@ -1672,13 +1672,12 @@ static void kpatch_verify_patchability(struct 
kpatch_elf *kelf)
                }
 
                if (sec->include) {
-                       if (!is_standard_section(sec) && !is_rela_section(sec) 
&&
-                           !is_debug_section(sec) && !is_special_section(sec)) 
{
-                               if (!is_referenced_section(sec, kelf)) {
-                                       log_normal("section %s included, but 
not referenced\n",
-                                                  sec->name);
-                                       errs++;
-                               }
+                       if (is_rodata_section(sec) &&
+                           !is_special_section(sec) &&
+                           !is_referenced_section(sec, kelf)) {
+                               log_normal(".rodata section %s included, but 
not referenced\n",
+                                          sec->name);
+                               errs++;
                        }
 
                        /* Check if a RELA section does not contain any entries 
with
-- 
2.16.5




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