[Qemu-devel] [PATCH] linux-user: correct core dump format

[Laurent Vivier]

This patch allows to really use the core dumped by qemu with guest
architecture tools.

- it adds a missing bswap_phdr() for the program headers
  of memory regions.

  "objdump -x" sample:

BEFORE:

0x1000000 off    0x00200000 vaddr 0x00000400 paddr 0x00000000 align 2**21
         filesz 0x00000000 memsz 0x00100000 flags ---
0x1000000 off    0x00200000 vaddr 0x00100400 paddr 0x00000000 align 2**21
         filesz 0x00000000 memsz 0x00080000 flags --- 6000000

AFTER:

    LOAD off    0x00002000 vaddr 0x00040000 paddr 0x00000000 align 2**13
         filesz 0x00000000 memsz 0x00001000 flags ---
    LOAD off    0x00002000 vaddr 0x00041000 paddr 0x00000000 align 2**13
         filesz 0x00000000 memsz 0x00000800 flags rw-

- it doesn't pad the note size to sizeof(int32_t).
  On m68k the NT_PRSTATUS note size is 154 and
  must not be rounded up to 156, because this value is checked by
  objdump and gdb.

  "gdb" symptoms:

      "warning: Couldn't find general-purpose registers in core file."

  "objdump -x" sample:

BEFORE:

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 note0         000001c4  00000000  00000000  000003b4  2**0
                  CONTENTS, READONLY
  1 .auxv         00000070  00000000  00000000  00000508  2**2
                  CONTENTS
  2 proc1         00100000  00000400  00000000  00200000  2**10
                  READONLY

AFTER:

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 note0         000001c4  00000000  00000000  000003b4  2**0
                  CONTENTS, READONLY
  1 .reg/19022    00000050  00000000  00000000  0000040e  2**2
                  CONTENTS
  2 .reg          00000050  00000000  00000000  0000040e  2**2
                  CONTENTS
  3 .auxv         00000070  00000000  00000000  00000508  2**2
                  CONTENTS
  4 load1         00000000  00040000  00000000  00002000  2**13
                  ALLOC, READONLY

Signed-off-by: Laurent Vivier <address@hidden>
---
 linux-user/elfload.c |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 33d776d..6ba6549 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1688,6 +1688,7 @@ struct memelfnote {
     size_t     namesz_rounded;
     int        type;
     size_t     datasz;
+    size_t     datasz_rounded;
     void       *data;
     size_t     notesz;
 };
@@ -1713,7 +1714,7 @@ struct target_elf_prstatus {
     struct target_timeval pr_cstime; /* XXX Cumulative system time */
     target_elf_gregset_t      pr_reg;       /* GP registers */
     int                pr_fpvalid;   /* XXX */
-};
+} __attribute__((packed));
 
 #define ELF_PRARGSZ     (80) /* Number of chars for args */
 
@@ -1963,7 +1964,9 @@ static void fill_note(struct memelfnote *note, const char 
*name, int type,
     note->namesz = namesz;
     note->namesz_rounded = roundup(namesz, sizeof (int32_t));
     note->type = type;
-    note->datasz = roundup(sz, sizeof (int32_t));;
+    note->datasz = sz;
+    note->datasz_rounded = roundup(sz, sizeof (int32_t));
+
     note->data = data;
 
     /*
@@ -1971,7 +1974,7 @@ static void fill_note(struct memelfnote *note, const char 
*name, int type,
      * ELF document.
      */
     note->notesz = sizeof (struct elf_note) +
-        note->namesz_rounded + note->datasz;
+        note->namesz_rounded + note->datasz_rounded;
 }
 
 static void fill_elf_header(struct elfhdr *elf, int segs, uint16_t machine,
@@ -2191,7 +2194,7 @@ static int write_note(struct memelfnote *men, int fd)
         return (-1);
     if (dump_write(fd, men->name, men->namesz_rounded) != 0)
         return (-1);
-    if (dump_write(fd, men->data, men->datasz) != 0)
+    if (dump_write(fd, men->data, men->datasz_rounded) != 0)
         return (-1);
 
     return (0);
@@ -2407,7 +2410,7 @@ static int elf_core_dump(int signr, const CPUState *env)
      * ELF specification wants data to start at page boundary so
      * we align it here.
      */
-    offset = roundup(offset, ELF_EXEC_PAGESIZE);
+    data_offset = offset = roundup(offset, ELF_EXEC_PAGESIZE);
 
     /*
      * Write program headers for memory regions mapped in
@@ -2430,6 +2433,7 @@ static int elf_core_dump(int signr, const CPUState *env)
             phdr.p_flags |= PF_X;
         phdr.p_align = ELF_EXEC_PAGESIZE;
 
+        bswap_phdr(&phdr, 1);
         dump_write(fd, &phdr, sizeof (phdr));
     }
 
@@ -2441,8 +2445,6 @@ static int elf_core_dump(int signr, const CPUState *env)
         goto out;
 
     /* align data to page boundary */
-    data_offset = lseek(fd, 0, SEEK_CUR);
-    data_offset = TARGET_PAGE_ALIGN(data_offset);
     if (lseek(fd, data_offset, SEEK_SET) != data_offset)
         goto out;
 
-- 
1.7.1