Re: [RFC] kallsyms C_SYMBOL_PREFIX support

[Yoshinori Sato]

At Tue, 12 Apr 2005 12:43:34 +0100,
Paulo Marques wrote:
> 
> Yoshinori Sato wrote:
> > kallsyms does not consider SYMBOL_PREFIX of C.
> > Consequently do not work in architecture using prefix character (h8300, v850) really.
> > 
> > Because I can want to use this, I made a patch.
> > Please comment.
> > 
> > [...]
> 
> > @@ -177,6 +184,11 @@
> >  		"_SDA2_BASE_",		/* ppc */
> >  		NULL };
> >  	int i;
> > +	int offset = 1;
> > +
> > +	/* skip prefix char */
> > +	if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
> > +		offset++;
> 
> maybe something like:
> 
> char *sname;
> sname = s->sym + 1;
> if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
> 	sname++;
> 
> would avoid all the "(s->sym + offset)" below, turning them to just "sname".
> 
> I know that it was "(s->sym + 1)" before, so its really not your fault, 
> but you could take this opportunity to clean that up, too.

This one is fine.
 
> >  
> >  	/* if --all-symbols is not specified, then symbols outside the text
> >  	 * and inittext sections are discarded */
> > @@ -190,17 +202,17 @@
> >  		 * they may get dropped in pass 2, which breaks the kallsyms
> >  		 * rules.
> >  		 */
> > -		if ((s->addr == _etext && strcmp(s->sym + 1, "_etext")) ||
> > -		    (s->addr == _einittext && strcmp(s->sym + 1, "_einittext")))
> > +		if ((s->addr == _etext && strcmp(s->sym + offset, "_etext")) ||
> > +		    (s->addr == _einittext && strcmp(s->sym + offset, "_einittext")))
> >  			return 0;
> >  	}
> >  
> >  	/* Exclude symbols which vary between passes. */
> > -	if (strstr(s->sym + 1, "_compiled."))
> > +	if (strstr(s->sym + offset, "_compiled."))
> >  		return 0;
> >  
> >  	for (i = 0; special_symbols[i]; i++)
> > -		if( strcmp(s->sym + 1, special_symbols[i]) == 0 )
> > +		if( strcmp(s->sym + offset, special_symbols[i]) == 0 )
> >  			return 0;
> >  
> >  	return 1;
> > @@ -225,9 +237,15 @@
> 
> >  [...]
> >  
> >  /* uncompress a compressed symbol. When this function is called, the best table
> > @@ -665,6 +683,13 @@
> >  
> >  	insert_real_symbols_in_table();
> >  
> > +	/* When valid symbol is not registered, exit to error */
> > +	if (good_head.left == good_head.right &&
> > +	    bad_head.left == bad_head.right) {
> > +		fprintf(stderr, "No valid symbol.\n");
> > +		exit(1);
> > +	}
> > +
> >  	optimize_result();
> >  }
> 
> This should only trigger if there are no symbols at all, or if there are 
> some symbols that are considered invalid, and do not go into the final 
> result.
> 
> Maybe we should just do a return here instead of exit, so that even if 
> this happens, kallsyms will still produce an empty result, that will at 
> least allow the kernel to compile.
> 
> It should give the error output to warn the user that there is something 
> fishy, nevertheless. Maybe even a bigger message, since this should not 
> happen at all, and if this triggers it means that something is seriously 
> wrong.

Not surely possible normally.
But raise SEGV if there is not a check. I do not think that this is good action.
 
> > @@ -672,9 +697,21 @@
> >  int
> >  main(int argc, char **argv)
> >  {
> > -	if (argc == 2 && strcmp(argv[1], "--all-symbols") == 0)
> > -		all_symbols = 1;
> > -	else if (argc != 1)
> > +	if (argc >= 2) {
> 
> This test is unnecessary.
> 
> > +		int i;
> > +		for (i = 1; i < argc; i++) { 
> > +			if(strcmp(argv[i], "--all-symbols") == 0)
> > +				all_symbols = 1;
> > +			else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
> > +				char *p = &argv[i][16];
> > +				/* skip quote */
> > +				if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
> > +					p++;
> > +				symbol_prefix_char = *p;
> > +			} else
> > +				usage();
> > +		}
> > +	} else if (argc != 1)
> >  		usage();
> 
> and so is this.
> 
> >  
> >  	read_map(stdin);
> > @@ -683,4 +720,3 @@
> >  
> >  	return 0;
> >  }
> 
> At least the patch seems to not affect architectures that don't use the 
> "--symbol-prefix" option, so it should be harmless for most.

I think of the same thread which are an issue with it being worked if do not appoint "--symbol-prefix".
Use CONFIG_ARCH and may judge it, but will it be good to refer to include/linux here?
 
> Anyway, appart from the few comments, it has my acknowledge.
> 
> -- 
> Paulo Marques - www.grupopie.com
> 
> All that is necessary for the triumph of evil is that good men do nothing.
> Edmund Burke (1729 - 1797)

-- 
Yoshinori Sato
<ysato@xxxxxxxxxxxxxxxxxxxx>
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