Re: [PATCH v6 02/10] dump: Write ELF section headers right after ELF header

[Marc-André Lureau]

On Mon, Oct 17, 2022 at 12:39 PM Janosch Frank <frankja@linux.ibm.com> wrote:

Let's start bundling the writes of the headers and of the data so we
have a clear ordering between them. Since the ELF header uses offsets
to the headers we can freely order them.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

 

---
 dump/dump.c | 31 ++++++++++++++-----------------
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/dump/dump.c b/dump/dump.c
index e7a3b54ebe..b168a25321 100644
--- a/dump/dump.c
+++ b/dump/dump.c
@@ -583,6 +583,8 @@ static void dump_begin(DumpState *s, Error **errp)
      *   --------------
      *   |  elf header |
      *   --------------
+     *   |  sctn_hdr   |
+     *   --------------
      *   |  PT_NOTE    |
      *   --------------
      *   |  PT_LOAD    |
@@ -591,8 +593,6 @@ static void dump_begin(DumpState *s, Error **errp)
      *   --------------
      *   |  PT_LOAD    |
      *   --------------
-     *   |  sec_hdr    |
-     *   --------------
      *   |  elf note   |
      *   --------------
      *   |  memory     |
@@ -608,6 +608,12 @@ static void dump_begin(DumpState *s, Error **errp)
         return;
     }

+    /* write section headers to vmcore */
+    write_elf_section_headers(s, errp);
+    if (*errp) {
+        return;
+    }
+
     /* write PT_NOTE to vmcore */
     write_elf_phdr_note(s, errp);
     if (*errp) {
@@ -620,12 +626,6 @@ static void dump_begin(DumpState *s, Error **errp)
         return;
     }

-    /* write section headers to vmcore */
-    write_elf_section_headers(s, errp);
-    if (*errp) {
-        return;
-    }
-
     /* write notes to vmcore */
     write_elf_notes(s, errp);
 }
@@ -1868,16 +1868,13 @@ static void dump_init(DumpState *s, int fd, bool has_format,
     }

     if (dump_is_64bit(s)) {
-        s->phdr_offset = sizeof(Elf64_Ehdr);
-        s->shdr_offset = s->phdr_offset + sizeof(Elf64_Phdr) * s->phdr_num;
-        s->note_offset = s->shdr_offset + sizeof(Elf64_Shdr) * s->shdr_num;
-        s->memory_offset = s->note_offset + s->note_size;
+        s->shdr_offset = sizeof(Elf64_Ehdr);
+        s->phdr_offset = s->shdr_offset + sizeof(Elf64_Shdr) * s->shdr_num;
+        s->note_offset = s->phdr_offset + sizeof(Elf64_Phdr) * s->phdr_num;
     } else {
-
-        s->phdr_offset = sizeof(Elf32_Ehdr);
-        s->shdr_offset = s->phdr_offset + sizeof(Elf32_Phdr) * s->phdr_num;
-        s->note_offset = s->shdr_offset + sizeof(Elf32_Shdr) * s->shdr_num;
-        s->memory_offset = s->note_offset + s->note_size;
+        s->shdr_offset = sizeof(Elf32_Ehdr);
+        s->phdr_offset = s->shdr_offset + sizeof(Elf32_Shdr) * s->shdr_num;
+        s->note_offset = s->phdr_offset + sizeof(Elf32_Phdr) * s->phdr_num;
     }

     return;
--
2.34.1