Re: [PATCH*] show last kernel-image symbol in /proc/kallsyms

From: Rusty Russell
Date: Sun May 09 2004 - 23:16:50 EST

On Mon, 2004-05-10 at 10:14, Randy.Dunlap wrote:
> 'cat' or 'tail' of /proc/kallsyms (2.6.6-rc2 or -rc3, & probably much
> earlier) does not include the last kernel-image symbol (_einittext).
> _einittext is the last symbol generated in .tmp_kallsyms2.S
> and the symbol count in that file also appears to be correct,
> but the iterator code for /proc/kallsyms comes up 1 short somehow.
> Here are 2 patches. Either one of them "fixes" the problem.
> Neither of them is the correct fix AFAIK.

Ah, I see you are a student of the Morton school of patch extraction.
Well, it worked.

Name: Show Last Symbol in /proc/kallsyms
Status: Tested on 2.6.6-rc3.bk11

The current code doesn't show the last symbol (usually _einittext) in
/proc/kallsyms. The reason for this is subtle: s_start() returns an
empty string for position 0 (ignored by s_show()), and s_next()
returns the first symbol for position 1.

What should happen is that update_iter() for position 0 should fill in
the first symbol. Unfortunately, the get_ksymbol_core() fills in the
symbol information, *and* updates the iterator: we have to split these
functions, which we do by making it return the length of the name

Then we can call get_ksymbol_core() without moving the iterator,
meaning that we can call it at position 0 (ie. s_start()).

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.6-rc3-bk11/kernel/kallsyms.c working-2.6.6-rc3-bk11/kernel/kallsyms.c
--- linux-2.6.6-rc3-bk11/kernel/kallsyms.c 2004-03-12 07:57:28.000000000 +1100
+++ working-2.6.6-rc3-bk11/kernel/kallsyms.c 2004-05-10 13:11:06.000000000 +1000
@@ -171,21 +171,23 @@ static int get_ksymbol_mod(struct kallsy
return 1;

-static void get_ksymbol_core(struct kallsym_iter *iter)
+/* Returns space to next name. */
+static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
- unsigned stemlen;
+ unsigned stemlen, off = iter->nameoff;

/* First char of each symbol name indicates prefix length
shared with previous name (stem compression). */
- stemlen = kallsyms_names[iter->nameoff++];
+ stemlen = kallsyms_names[off++];

- strlcpy(iter->name+stemlen, kallsyms_names+iter->nameoff, 128-stemlen);
- iter->nameoff += strlen(kallsyms_names + iter->nameoff) + 1;
+ strlcpy(iter->name+stemlen, kallsyms_names + off, 128-stemlen);
+ off += strlen(kallsyms_names + off) + 1;
iter->owner = NULL;
iter->value = kallsyms_addresses[iter->pos];
iter->type = 't';

+ return off - iter->nameoff;

static void reset_iter(struct kallsym_iter *iter)
@@ -210,16 +212,16 @@ static int update_iter(struct kallsym_it

/* We need to iterate through the previous symbols: can be slow */
for (; iter->pos != pos; iter->pos++) {
- get_ksymbol_core(iter);
+ iter->nameoff += get_ksymbol_core(iter);
+ get_ksymbol_core(iter);
return 1;

Anyone who quotes me in their signature is an idiot -- Rusty Russell

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