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[v5,11/18] dump: Swap segment and section header locations

Message ID 20220811121111.9878-12-frankja@linux.ibm.com
State New
Headers show
Series dump: Add arch section and s390x PV dump | expand

Commit Message

Janosch Frank Aug. 11, 2022, 12:11 p.m. UTC 
For the upcoming string table and arch section support we need to
modify the elf layout a bit. Instead of the segments, i.e. the guest's
memory contents, being the last area the section data will live at
the end of the file. This will allow us to write the section data
after all guest memory has been dumped which is important for the s390
PV dump support.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 dump/dump.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)
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Patch

diff --git a/dump/dump.c b/dump/dump.c
index 0051c71d08..31eb20108c 100644
--- a/dump/dump.c
+++ b/dump/dump.c
@@ -595,6 +595,9 @@  static void dump_begin(DumpState *s, Error **errp)
      *   --------------
      *   |  memory     |
      *   --------------
+     *   |  sectn data |
+     *   --------------
+
      *
      * we only know where the memory is saved after we write elf note into
      * vmcore.
@@ -1842,17 +1845,16 @@  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;
     }
+    s->memory_offset = s->note_offset + s->note_size;
+    s->section_offset = s->memory_offset + s->total_size;
 
     return;