lkml.org 
[lkml]   [2007]   [Sep]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [PATCH] Reduce __print_symbol/sprint_symbol stack usage.
From
Date
Hello all, Satyam,

This is my second stab at solving the "stack over flow due to
dump_strace when close to stack-overflow is detected by do_IRQ" problem.
(Hopefully) this patch is creates less noise then the previous one.

[snip]
> I'll try and create an option 2 (static allocation, minimal locking)
> patch and post ASAP.
> Hopefully it'll fare better. (While keeping the current interface intact
> and reducing the damage/noise)
>
> - Gilboa

- Gilboa

--- linux-2.6/kernel/kallsyms.orig 2007-09-15 11:46:54.000000000 +0300
+++ linux-2.6/kernel/kallsyms.c 2007-09-15 21:06:55.000000000 +0300
@@ -306,13 +306,14 @@ int lookup_symbol_attrs(unsigned long ad
return lookup_module_symbol_attrs(addr, size, offset, modname, name);
}

-/* Look up a kernel symbol and return it in a text buffer. */
-int sprint_symbol(char *buffer, unsigned long address)
+/* Internal version:
+ Look up a kernel symbol and module name and return them to the
+ caller's buffer/namebuf buffers. */
+int __sprint_symbol(char *buffer, char *namebuf, unsigned long address)
{
- char *modname;
- const char *name;
unsigned long offset, size;
- char namebuf[KSYM_NAME_LEN];
+ const char *name;
+ char *modname;

name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
if (!name)
@@ -325,14 +326,35 @@ int sprint_symbol(char *buffer, unsigned
return sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
}

+/* Exported version:
+ Look up a kernel symbol and return it in a text buffer. */
+int sprint_symbol(char *buffer, unsigned long address)
+{
+ char namebuf[KSYM_NAME_LEN];
+
+ return __sprint_symbol(buffer, namebuf, address);
+}
+
+static DEFINE_SPINLOCK(symbol_lock);
+
/* Look up a kernel symbol and print it to the kernel messages. */
void __print_symbol(const char *fmt, unsigned long address)
{
- char buffer[KSYM_SYMBOL_LEN];
+ /* Use static buffers instead of char array to reduce
+ stack footprint in i386/4KSTACKS.
+ Buffers must be protected against re-entry. */
+ static char namebuf[KSYM_NAME_LEN];
+ static char buffer[KSYM_SYMBOL_LEN];
+ unsigned long flags;
+

- sprint_symbol(buffer, address);
+ spin_lock_irqsave(&symbol_lock, flags);
+
+ __sprint_symbol(buffer, namebuf, address);

printk(fmt, buffer);
+
+ spin_unlock_irqrestore(&symbol_lock, flags);
}

/* To avoid using get_symbol_offset for every symbol, we carry prefix
along. */

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-09-15 20:11    [from the cache]
©2003-2011 Jasper Spaans