Dave Hansen wrote:
One of the top ten sysfs problems is that users use statically
allocated kobjects. This patch reminds them that this is a
naughty thing.
One _really_ nice thing this patch does, is us the kallsyms
mechanism to print out exactly which symbol is being complained
about:
The kobject at, or inside 'statickobj.2'@(0xc040d020) is not dynamically allocated.
This patch replaces the previous implementation's use of a
_sdata symbol in favor of using kallsyms_lookup(). If a
kobject's address is a resolvable symbol, then it isn't
dynamically allocated.
Just a few concerns that I'm not sure of having been addressed:
- doing a kallsyms_lookup() is more expensive then just a simple range
test. This might be a concern if this is called very often. In this case
you could keep the range check and only do the lookup for symbols that
fail that check
- kallsyms_lookup() never finds a symbol if CONFIG_KALLSYMS is not
selected
- more comments below
The one exception to this is init symbols. The patch also
checks to see whether __init memory has been freed and if
it has will allow kobjects in those sections.
Signed-off-by: Dave Hansen <[email protected]>
---
lxc-dave/arch/i386/kernel/vmlinux.lds.S | 2 --
lxc-dave/include/linux/init.h | 1 +
lxc-dave/init/main.c | 9 +++++++++
lxc-dave/lib/kobject.c | 31 ++++++++++++++++++++++---------
4 files changed, 32 insertions(+), 11 deletions(-)
diff -puN lib/kobject.c~make-kobject-allocation-debugging-check-use-kallsyms_lookup lib/kobject.c
--- lxc/lib/kobject.c~make-kobject-allocation-debugging-check-use-kallsyms_lookup 2007-08-22 14:51:50.000000000 -0700
+++ lxc-dave/lib/kobject.c 2007-08-22 14:51:50.000000000 -0700
@@ -139,23 +139,36 @@ static int ptr_in_range(void *ptr, void
return 0;
}
-static void verify_dynamic_kobject_allocation(struct kobject *kobj)
+void verify_dynamic_kobject_allocation(struct kobject *kobj)
{
- if (ptr_in_range(kobj, &_sdata[0], &_edata[0]))
- goto warn;
- if (ptr_in_range(kobj, &__bss_start[0], &__bss_stop[0]))
- goto warn;
- return;
-warn:
+ char *namebuf;
+ const char *ret;
+
+ namebuf = kzalloc(KSYM_NAME_LEN, GFP_KERNEL);
You don't need kzalloc here. kmalloc will do just fine.
+ ret = kallsyms_lookup((unsigned long)kobj, NULL, NULL, NULL,
+ namebuf);
+ /*
+ * This is the X86_32-only part of this function.
+ * This is here because it is valid to have a kobject
+ * in an __init section, but only after those
+ * sections have been freed back to the dynamic pool.
+ */
+ if (!initmem_now_dynamic &&
+ ptr_in_range(kobj, __init_begin, __init_end))
+ goto out;
+ if (!ret || !strlen(ret))
The "!strlen(ret)" is not only weird (why not write as "!ret[0] or
!*ret) but is also unnecessary. When kallsyms_lookup fails to find a
symbol it should always return NULL.
+ goto out;
pr_debug("---- begin silly warning ----\n");
pr_debug("This is a janitorial warning, not a kernel bug.\n");
#ifdef CONFIG_DEBUG_KOBJECT
- print_symbol("The kobject at, or inside %s is not dynamically allocated.\n",
- (unsigned long)kobj);
+ pr_debug("The kobject at, or inside '%s'@(0x%p) is not dynamically allocated.\n",
+ namebuf, kobj);
#endif
pr_debug("kobjects must be dynamically allocated, not static\n");
/* dump_stack(); */
pr_debug("---- end silly warning ----\n");
+out:
+ kfree(namebuf);
}
#else
[...]
--
Paulo Marques - www.grupopie.com
"You're just jealous because the voices only talk to me."
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