11.1 Operating System ABI Variant Handling

GDB provides a mechanism for handling variations in OS ABIs. An OS ABI variant may have influence over any number of variables in the target architecture definition. There are two major components in the OS ABI mechanism: sniffers and handlers.

A sniffer examines a file matching a BFD architecture/flavour pair (the architecture may be wildcarded) in an attempt to determine the OS ABI of that file. Sniffers with a wildcarded architecture are considered to be generic, while sniffers for a specific architecture are considered to be specific. A match from a specific sniffer overrides a match from a generic sniffer. Multiple sniffers for an architecture/flavour may exist, in order to differentiate between two different operating systems which use the same basic file format. The OS ABI framework provides a generic sniffer for ELF-format files which examines the EI_OSABI field of the ELF header, as well as note sections known to be used by several operating systems.

A handler is used to fine-tune the gdbarch structure for the selected OS ABI. There may be only one handler for a given OS ABI for each BFD architecture.

The following OS ABI variants are defined in defs.h:

GDB_OSABI_UNINITIALIZED

Used for struct gdbarch_info if ABI is still uninitialized.

GDB_OSABI_UNKNOWN

The ABI of the inferior is unknown. The default gdbarch settings for the architecture will be used.

GDB_OSABI_SVR4

UNIX System V Release 4.

GDB_OSABI_HURD

GNU using the Hurd kernel.

GDB_OSABI_SOLARIS

Sun Solaris.

GDB_OSABI_OSF1

OSF/1, including Digital UNIX and Compaq Tru64 UNIX.

GDB_OSABI_LINUX

GNU using the Linux kernel.

GDB_OSABI_FREEBSD_AOUT

FreeBSD using the a.out executable format.

GDB_OSABI_FREEBSD_ELF

FreeBSD using the ELF executable format.

GDB_OSABI_NETBSD_AOUT

NetBSD using the a.out executable format.

GDB_OSABI_NETBSD_ELF

NetBSD using the ELF executable format.

GDB_OSABI_OPENBSD_ELF

OpenBSD using the ELF executable format.

GDB_OSABI_WINCE

Windows CE.

GDB_OSABI_GO32

DJGPP.

GDB_OSABI_IRIX

Irix.

GDB_OSABI_INTERIX

Interix (Posix layer for MS-Windows systems).

GDB_OSABI_HPUX_ELF

HP/UX using the ELF executable format.

GDB_OSABI_HPUX_SOM

HP/UX using the SOM executable format.

GDB_OSABI_QNXNTO

QNX Neutrino.

GDB_OSABI_CYGWIN

Cygwin.

GDB_OSABI_AIX

AIX.

Here are the functions that make up the OS ABI framework:

Function: const char * gdbarch_osabi_name (enum gdb_osabi osabi)

Return the name of the OS ABI corresponding to osabi.

Function: void gdbarch_register_osabi (enum bfd_architecture arch, unsigned long machine, enum gdb_osabi osabi, void (*init_osabi)(struct gdbarch_info info, struct gdbarch *gdbarch))

Register the OS ABI handler specified by init_osabi for the architecture, machine type and OS ABI specified by arch, machine and osabi. In most cases, a value of zero for the machine type, which implies the architecture’s default machine type, will suffice.

Function: void gdbarch_register_osabi_sniffer (enum bfd_architecture arch, enum bfd_flavour flavour, enum gdb_osabi (*sniffer)(bfd *abfd))

Register the OS ABI file sniffer specified by sniffer for the BFD architecture/flavour pair specified by arch and flavour. If arch is bfd_arch_unknown, the sniffer is considered to be generic, and is allowed to examine flavour-flavoured files for any architecture.

Function: enum gdb_osabi gdbarch_lookup_osabi (bfd *abfd)

Examine the file described by abfd to determine its OS ABI. The value GDB_OSABI_UNKNOWN is returned if the OS ABI cannot be determined.

Function: void gdbarch_init_osabi (struct gdbarch info info, struct gdbarch *gdbarch, enum gdb_osabi osabi)

Invoke the OS ABI handler corresponding to osabi to fine-tune the gdbarch structure specified by gdbarch. If a handler corresponding to osabi has not been registered for gdbarch’s architecture, a warning will be issued and the debugging session will continue with the defaults already established for gdbarch.

Function: void generic_elf_osabi_sniff_abi_tag_sections (bfd *abfd, asection *sect, void *obj)

Helper routine for ELF file sniffers. Examine the file described by abfd and look at ABI tag note sections to determine the OS ABI from the note. This function should be called via bfd_map_over_sections.