Re: [Kgdb-bugreport] Document hooks in kgdb

From: Amit S. Kale
Date: Wed Mar 24 2004 - 09:45:11 EST

That's a good idea. Go ahead.
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 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.

Rest is fine.

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