Re: [Kgdb-bugreport] Document hooks in kgdb

[Tom Rini <trini@kernel.crashing.org>]

On Wed, Mar 24, 2004 at 08:11:26PM +0530, Amit S. Kale wrote:
> That's a good idea. Go ahead.
> -Amit
> On Friday 19 Mar 2004 9:50 pm, Tom Rini wrote:
> > Hi.  The following is my first attempt at documenting the hooks found in
> > the KGDB found on kgdb.sf.net.  I'm not quite sure about the description
> > of some of the optional hooks (used under hw breakpoints) so corrections
> > / suggestions welcome.  After I got done with it, it hit me that maybe I
> > should have done this in the code, and in DocBook format, so I'll go and
> > do that next...
> >
> > <-- snip -->
> > This is an attempt to document the various architecture specific functions
> > that are part of KGDB.  There are a number of optional functions, depending
> > on hardware setps, for which empty defaults are provided.  There are also
> > functions which must be implemented and for which no default is provided.
> >
> > The required functions are:
> > int kgdb_arch_handle_exception(int vector, int signo, int err_code,
> > 		char *InBuffer, char *outBuffer, struct pt_regs *regs)
> > 	This function MUST handle the 'c' and 's' command packets,
> > 	as well packets to set / remove a hardware breakpoint, if used.
> >
> > void regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
> > 	Convert the ptrace regs in regs into what GDB expects to
> > 	see for registers, in gdb_regs.
> >
> > void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct
> > task_struct *p) Like regs_to_gdb_regs, except that the process in p is
> > sleeping,
> > 	so we cannot get as much information.
> >
> > void gdb_regs_to_regs(unsigned long *gdb_regs, struct pt_regs *regs)
> > 	Convert the GDB regs in gdb_regs into the ptrace regs pointed
> > 	to in regs.
> >
> > The optional functions are:
> > int kgdb_arch_init(void) :
> > 	This function will handle the initalization of any architecture
> > 	specific hooks.  If there is a suitable early output driver,
> > 	kgdb_serial can be pointed at it now.
> >
> > void kgdb_printexceptioninfo(int exceptionNo, int errorcode, char *buffer)
> > 	Write into buffer and information about the exception that has
> > 	occured that can be gleaned from exceptionNo and errorcode.
> >
> > void kgdb_disable_hw_debug(struct pt_regs *regs)
> > 	Disable hardware debugging while we are in kgdb.
> >
> > void kgdb_correct_hw_break(void)
> > 	A hook to allow for changes to the hardware breakpoint, called
> > 	after a single step (s) or continue (c) packet, and once we're about
> > 	to let the kernel continue running.
> >
> > void kgdb_post_master_code(struct pt_regs *regs, int eVector, int err_code)
> > 	Store the raw vector and error, for later retreival.
> >
> > void kgdb_shadowinfo(struct pt_regs *regs, char *buffer, unsigned threadid)
> > struct task_struct *kgdb_get_shadow_thread(struct pt_regs *regs, int
> > threadid) struct pt_regs *kgdb_shadow_regs(struct pt_regs *regs, int
> > threadid) If we have a shadow thread (determined by setting
> > 	kgdb_ops->shadowth = 1), these functions are required to return
> > 	information about this thread.
> 
> An addition: shadow threads are needed to provide information not retrievable 
> by gdb. e.g. Backtraces beyond interrupt entrypoints, that aren't retrievable 
> in absence of debugging info for interrupt entrypoint code.

If I follow everything right, this could go in favor of cfi macros,
right ?

-- 
Tom Rini
http://gate.crashing.org/~trini/