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Message-ID: <20110719184536.GA27224@redhat.com>
Date: Tue, 19 Jul 2011 20:45:36 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Rusty Russell <rusty@...tcorp.com.au>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org
Subject: [may-be-patch?] introduce MODULE_USE_UNEXPORTED()
Hi.
>From time to time I need to write a module for debugging purposes,
and it is a bit annoying I can't simply use, say, put_task_struct().
Can't we do something like the simple patch below? Of course, it
is very unsafe to use kallsyms_lookup_name() by many reasons. But
it looks handy for the testing/debugging.
Yes, I am not saying this feature is terribly useful, so I agree
in advance with the "go away, we don't need this hack" nack.
Still, what do you think?
Oleg.
include/linux/module.h | 2 ++
include/linux/kernel.h | 1 +
kernel/module.c | 13 +++++++++++++
kernel/panic.c | 2 ++
4 files changed, 18 insertions(+)
--- x/include/linux/module.h~MODSYM 2011-05-20 18:35:10.000000000 +0200
+++ x/include/linux/module.h 2011-07-19 19:59:22.000000000 +0200
@@ -139,6 +139,8 @@ extern struct module __this_module;
*/
#define MODULE_LICENSE(_license) MODULE_INFO(license, _license)
+#define MODULE_USE_UNEXPORTED() MODULE_INFO(use_unexported, "")
+
/*
* Author(s), use "Name <email>" or just "Name", for multiple
* authors use multiple MODULE_AUTHOR() statements/lines.
--- x/include/linux/kernel.h~MODSYM 2011-06-16 20:16:04.000000000 +0200
+++ x/include/linux/kernel.h 2011-07-19 19:59:45.000000000 +0200
@@ -361,6 +361,7 @@ extern enum system_states {
#define TAINT_WARN 9
#define TAINT_CRAP 10
#define TAINT_FIRMWARE_WORKAROUND 11
+#define TAINT_USE_UNEXPORTED 12
extern const char hex_asc[];
#define hex_asc_lo(x) hex_asc[((x) & 0x0f)]
--- x/kernel/module.c~MODSYM 2011-05-24 18:51:32.000000000 +0200
+++ x/kernel/module.c 2011-07-19 20:01:08.000000000 +0200
@@ -1791,6 +1791,8 @@ static int verify_export_symbols(struct
return 0;
}
+static char *get_modinfo(struct load_info *info, const char *tag);
+
/* Change all symbols so that st_value encodes the pointer directly. */
static int simplify_symbols(struct module *mod, const struct load_info *info)
{
@@ -1832,6 +1834,17 @@ static int simplify_symbols(struct modul
if (!ksym && ELF_ST_BIND(sym[i].st_info) == STB_WEAK)
break;
+ if (!ksym && get_modinfo(info, "use_unexported")) {
+ unsigned long addr = kallsyms_lookup_name(name);
+ if (addr) {
+ sym[i].st_value = addr;
+ if (!test_taint(TAINT_USE_UNEXPORTED))
+ printk(KERN_WARNING "bla bla bla\n");
+ add_taint_module(mod, TAINT_USE_UNEXPORTED);
+ break;
+ }
+ }
+
printk(KERN_WARNING "%s: Unknown symbol %s (err %li)\n",
mod->name, name, PTR_ERR(ksym));
ret = PTR_ERR(ksym) ?: -ENOENT;
--- x/kernel/panic.c~MODSYM 2011-04-06 21:33:50.000000000 +0200
+++ x/kernel/panic.c 2011-07-19 20:00:06.000000000 +0200
@@ -175,6 +175,7 @@ static const struct tnt tnts[] = {
{ TAINT_WARN, 'W', ' ' },
{ TAINT_CRAP, 'C', ' ' },
{ TAINT_FIRMWARE_WORKAROUND, 'I', ' ' },
+ { TAINT_USE_UNEXPORTED, 'X', ' ' },
};
/**
@@ -192,6 +193,7 @@ static const struct tnt tnts[] = {
* 'W' - Taint on warning.
* 'C' - modules from drivers/staging are loaded.
* 'I' - Working around severe firmware bug.
+ * 'X' - Module uses unexported symbol.
*
* The string is overwritten by the next call to print_tainted().
*/
--
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