Add some more information in the ktrace(1)/kdump(1) output

[Peter Jeremy]

On Wed, 2006-Apr-19 13:39:52 -0700, David Kirchner wrote:
>For example, the output before:
>
> 32229 telnet   CALL  mmap(0,0x8000,0x3,0x1002,0xffffffff,0,0,0)
> 32229 telnet   CALL  open(0x2807bc28,0,0x1b6)
> 32229 telnet   CALL  socket(0x2,0x2,0)
>
>is now:
>
> 32229 telnet   CALL 
>mmap(0,0x8000,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANON,0xffffffff,0,0,0)
> 32229 telnet   CALL  open(0x2807bc28,O_RDONLY,<unused>0x1b6)
> 32229 telnet   CALL  socket(PF_INET,SOCK_DGRAM,0)

Looks good.  One improvement I'd suggest is to report both raw hex as well
as decoded output - eg the way a printf(9) %b format looks.  This would
make the above look like:

 32229 telnet   CALL  mmap(0,0x8000,0x3<PROT_READ|PROT_WRITE>,0x1002<MAP_PRIVATE|MAP_ANON>,0xffffffff,0,0,0)
 32229 telnet   CALL  open(0x2807bc28,0<O_RDONLY>,<unused>0x1b6)
 32229 telnet   CALL  socket(PF_INET,SOCK_DGRAM,0)

>more data in the dump output. I'm thinking, specifically, adding
>KTR_STAT for stat() results and KTR_SOCKADDR for connect(), bind()
>arguments, and accept() results.

Wonderful.  IMHO, the lack of struct sockaddr decoding is the biggest
drawback of ktrace (though I admit I've never been sufficiently
annoyed at the lack of support to actually implement it).

Some comments on the code approach (these are personal opinions -
feel free to ignore them):
- I find case statements easier to follow than very long "else if"
  clauses.
- Have you considered a semi-interpreted approach to allow more
  generalised decoding (less special-cased code)?

As an example of the following, the Tru64 alpha syscall trace code
(see ftp://ftp.iastate.edu/pub/unix/osf1/trace/alpha-trace-1.34.tar.Z)
has an array similar to /sys/kern/init_sysent.c:sysent[] which looks
like:
/*001*/ { SYS_exit , "exit(d)v" , 1 , printargs_gen , printret_gen } ,
/*002*/ { SYS_fork , "fork()d" , 0 , printargs_gen , printret_gen } ,
/*003*/ { SYS_read , "read(dpd)d" , 3 , printargs_read , printret_read } ,
/*004*/ { SYS_write , "write(dbd)d" , 3 , printargs_write , printret_write } ,

The string contains the syscall name, the argument types in
parenthesis (b - buffer, d - signed decimal, p - pointer, o - octal
etc) and a return type, the number of arguments and functions to print
the arguments and return values.  (The return handling wouldn't be
relevant to ktrace).  About 3/4 of the Tru64 syscalls can be handled
using the generic printargs_gen().

Since ktrace doesn't need special handling for syscalls that have I/O
buffers or various structures (they are passed via different KTR_xxx
records), FreeBSD is even more amenable to generic argument processing.
I suspect that virtually all of the FreeBSD syscalls could be handled
in a similar manner if a %b option string and an enum decoding
structure (or two) could be passed via a similar sort of table.

-- 
Peter Jeremy