Re: [PATCH 2/2] [nto] Improve ABI sniffing.

Aleksandar Ristovski
2015-10-21T14:19:42Z

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On 15-10-21 09:47 AM, Pedro Alves wrote:
> On 10/21/2015 02:34 PM, Aleksandar Ristovski wrote:
>
>> +static void
>> +nto_sniff_abi_note_section (bfd *abfd, asection *sect, void *obj)
>> +{
>> + const char *sectname;
>> + unsigned int sectsize;
>> + /* Buffer holding the section contents. */
>> + char *note;
>> + unsigned int namelen;
>> + const char *name;
>> +
>> + sectname = bfd_get_section_name (abfd, sect);
>> + sectsize = bfd_section_size (abfd, sect);
>> +
>> + if (sectsize > 128)
>> + sectsize = 128;
>> +
>> + if (sectname != NULL && strstr (sectname, QNX_INFO_SECT_NAME) != NULL)
>> + *(enum gdb_osabi *) obj = GDB_OSABI_QNXNTO;
>> +
>> + if (sectname != NULL && strstr (sectname, "note") != NULL)
>
> This can be "else if".

Ok.

>
>> + {
>> + const unsigned sizeof_Elf_Nhdr = 12;
>> +
>> + note = XNEWVEC (char, sectsize);
>> + bfd_get_section_contents (abfd, sect, note, 0, sectsize);
>> + namelen = (unsigned int) bfd_h_get_32 (abfd, note);
>
> You also need to check that the section's size
> is enough to contain 'namelen', _before_ extracting it, otherwise
> you may be reading garbage.
>

Done.

>
>> + name = note + sizeof_Elf_Nhdr;
>> + if (sectsize < namelen + sizeof_Elf_Nhdr
>
>> + || namelen > sizeof (QNX_NOTE_NAME) + 1)

Removed "+ 1" here.

>> + {
>> + /* Can not be QNX note. */
>> + XDELETEVEC (note);
>> + return;
>
> Thanks,
> Pedro Alves
>
>

And compare to exact expected length of the qnx name.
+ if (namelen == sizeof (QNX_NOTE_NAME)

+ && 0 == strcmp (name, QNX_NOTE_NAME))

Attached the latest version.

Thanks,

Aleksandar Ristovski

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From 5b3605345909dccecaeded1c48a1844ec192fa0d Mon Sep 17 00:00:00 2001
From: Aleksandar Ristovski <aristovski@qnx.com>
Date: Wed, 21 Oct 2015 09:29:54 -0400
Subject: [PATCH 2/2] [nto] Improve ABI sniffing.

Use qnx specific notes to figure out the OS.

gdb/ChangeLog:
* gdb/nto-tdep.c (QNX_NOTE_NAME, QNX_INFO_SECT_NAME): New defines.
(nto_sniff_abi_note_section): New function.
(nto_elf_osabi_sniffer): Use new function to recognize nto specific
binary.
---
gdb/nto-tdep.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 52 insertions(+), 3 deletions(-)

diff --git a/gdb/nto-tdep.c b/gdb/nto-tdep.c
index e50d302..cc3e94e 100644
--- a/gdb/nto-tdep.c
+++ b/gdb/nto-tdep.c
@@ -32,6 +32,9 @@
#include "gdbcore.h"
#include "objfiles.h"

+#define QNX_NOTE_NAME "QNX"
+#define QNX_INFO_SECT_NAME "QNX_info"
+
#ifdef __CYGWIN__
#include <sys/cygwin.h>
#endif
@@ -332,12 +335,58 @@ nto_dummy_supply_regset (struct regcache *regcache, char *regs)
/* Do nothing. */
}

+static void
+nto_sniff_abi_note_section (bfd *abfd, asection *sect, void *obj)
+{
+ const char *sectname;
+ unsigned int sectsize;
+ /* Buffer holding the section contents. */
+ char *note;
+ unsigned int namelen;
+ const char *name;
+ const unsigned sizeof_Elf_Nhdr = 12;
+
+ sectname = bfd_get_section_name (abfd, sect);
+ sectsize = bfd_section_size (abfd, sect);
+
+ if (sectsize > 128)
+ sectsize = 128;
+
+ if (sectname != NULL && strstr (sectname, QNX_INFO_SECT_NAME) != NULL)
+ *(enum gdb_osabi *) obj = GDB_OSABI_QNXNTO;
+ else if (sectname != NULL && strstr (sectname, "note") != NULL
+ && sectsize > sizeof_Elf_Nhdr)
+ {
+ note = XNEWVEC (char, sectsize);
+ bfd_get_section_contents (abfd, sect, note, 0, sectsize);
+ namelen = (unsigned int) bfd_h_get_32 (abfd, note);
+ name = note + sizeof_Elf_Nhdr;
+ if (sectsize < namelen + sizeof_Elf_Nhdr
+ || namelen > sizeof (QNX_NOTE_NAME))
+ {
+ /* Can not be QNX note. */
+ XDELETEVEC (note);
+ return;
+ }
+
+ if (namelen == sizeof (QNX_NOTE_NAME)
+ && 0 == strcmp (name, QNX_NOTE_NAME))
+ *(enum gdb_osabi *) obj = GDB_OSABI_QNXNTO;
+
+ XDELETEVEC (note);
+ }
+}
+
enum gdb_osabi
nto_elf_osabi_sniffer (bfd *abfd)
{
- if (nto_is_nto_target)
- return nto_is_nto_target (abfd);
- return GDB_OSABI_UNKNOWN;
+ enum gdb_osabi osabi = GDB_OSABI_UNKNOWN;
+
+ bfd_map_over_sections (abfd,
+ nto_sniff_abi_note_section,
+ &osabi);
+
+ return osabi;
}

static const char *nto_thread_state_str[] =
--
1.9.1