From: Kris Van Hees <kris.van.hees@oracle.com>
Date: Thu, 13 Aug 2015 16:23:54 +0000 (-0400)
Subject: dtrace: ensure SDT module probes work with NORX
X-Git-Tag: v4.1.12-92~303^2
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=8ba78aab5aa9a55cf673876e49381a38a48864a2;p=users%2Fjedix%2Flinux-maple.git

dtrace: ensure SDT module probes work with NORX

When the CONFIG_DEBUG_SET_MODULE_RONX option is enabled in the kernel,
the executable code of the module is marked read-only prior to calling
the module notifier.  This causes the patching of NOPs in the probe
locations to fail with a system crash.

Because patching of SDT probe locations should happen upon module load
for DTrace-enabled kernels regardless of whether or not DTrace will be
used, it is both cleaner and more correct to make a direct call to the
code that handles the patching rather than using the notifier mechanism.
The new call takes place prior to marking the pages read-only, avoiding
the problem altogether.

Orabug: 21630297
Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Acked-by: Nick Alcock <nick.alcock@oracle.com>
---

diff --git a/kernel/dtrace/dtrace_sdt.h b/include/linux/dtrace_sdt.h
similarity index 91%
rename from kernel/dtrace/dtrace_sdt.h
rename to include/linux/dtrace_sdt.h
index 18a745fc1fc7..90ca2f5c74fe 100644
--- a/kernel/dtrace/dtrace_sdt.h
+++ b/include/linux/dtrace_sdt.h
@@ -3,6 +3,7 @@
 #ifndef _DTRACE_SDT_H_
 #define	_DTRACE_SDT_H_
 
+#include <linux/module.h>
 #include <asm/dtrace_arch.h>
 
 /*
@@ -21,6 +22,7 @@ extern void *dtrace_sdt_probes __attribute__((weak));
 
 extern void dtrace_sdt_init(void);
 extern void dtrace_sdt_register(struct module *);
+extern void dtrace_sdt_register_module(struct module *);
 extern void dtrace_sdt_exit(void);
 
 /*
diff --git a/kernel/dtrace/dtrace_os.c b/kernel/dtrace/dtrace_os.c
index 415967fd5680..c8076468d709 100644
--- a/kernel/dtrace/dtrace_os.c
+++ b/kernel/dtrace/dtrace_os.c
@@ -8,6 +8,7 @@
 #include <linux/binfmts.h>
 #include <linux/dtrace_cpu.h>
 #include <linux/dtrace_os.h>
+#include <linux/dtrace_sdt.h>
 #include <linux/fs.h>
 #include <linux/hardirq.h>
 #include <linux/interrupt.h>
@@ -22,7 +23,6 @@
 #include <linux/workqueue.h>
 #include <linux/mm.h>
 #include <asm/ptrace.h>
-#include "dtrace_sdt.h"
 
 #if defined(CONFIG_DT_FASTTRAP) || defined(CONFIG_DT_FASTTRAP_MODULE)
 # include <linux/uprobes.h>
diff --git a/kernel/dtrace/dtrace_sdt_core.c b/kernel/dtrace/dtrace_sdt_core.c
index ce953b85df8e..5e4f189df157 100644
--- a/kernel/dtrace/dtrace_sdt_core.c
+++ b/kernel/dtrace/dtrace_sdt_core.c
@@ -9,13 +9,13 @@
 #include <linux/memory.h>
 #include <linux/module.h>
 #include <linux/dtrace_os.h>
+#include <linux/dtrace_sdt.h>
 #include <linux/sdt.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/vmalloc.h>
 #include <asm-generic/bitsperlong.h>
 #include <asm-generic/sections.h>
-#include "dtrace_sdt.h"
 
 const char		*sdt_prefix = "__dtrace_probe_";
 
@@ -125,25 +125,14 @@ static int __init nosdt(char *str)
 
 early_param("nosdt", nosdt);
 
-static int dtrace_mod_notifier(struct notifier_block *nb, unsigned long val,
-			       void *args)
+void dtrace_sdt_register_module(struct module *mp)
 {
-	struct module		*mp = args;
 	int			i, cnt;
 	sdt_probedesc_t		*sdp;
 	asm_instr_t		**addrs;
 
-	/*
-	 * We only need to capture modules in the COMING state, we need a valid
-	 * module structure as argument, and the module needs to actually have
-	 * SDT probes.  If not, ignore...
-	 */
-	if (val != MODULE_STATE_COMING)
-		return NOTIFY_DONE;
-	if (!mp)
-		return NOTIFY_DONE;
 	if (mp->sdt_probec == 0 || mp->sdt_probes == NULL)
-		return NOTIFY_DONE;
+		return;
 
 	/*
 	 * Create a list of addresses (SDT probe locations) that need to be
@@ -154,7 +143,7 @@ static int dtrace_mod_notifier(struct notifier_block *nb, unsigned long val,
 	if (addrs == NULL) {
 		pr_warning("%s: cannot allocate SDT probe address list (%s)\n",
 			   __func__, mp->name);
-		return NOTIFY_DONE;
+		return;
 	}
 
 	for (i = cnt = 0, sdp = mp->sdt_probes; i < mp->sdt_probec;
@@ -178,18 +167,11 @@ static int dtrace_mod_notifier(struct notifier_block *nb, unsigned long val,
 	dtrace_sdt_nop_multi(addrs, cnt);
 
 	vfree(addrs);
-
-	return NOTIFY_DONE;
 }
 
-static struct notifier_block	dtrace_modfix = {
-	.notifier_call = dtrace_mod_notifier,
-};
-
 void dtrace_sdt_init(void)
 {
 	dtrace_sdt_init_arch();
-	register_module_notifier(&dtrace_modfix);
 }
 
 #if defined(CONFIG_DT_DT_PERF) || defined(CONFIG_DT_DT_PERF_MODULE)
diff --git a/kernel/module.c b/kernel/module.c
index be8c504975e8..fb4149f42423 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -51,6 +51,7 @@
 #include <asm/mmu_context.h>
 #include <linux/license.h>
 #include <asm/sections.h>
+#include <linux/dtrace_sdt.h>
 #include <linux/tracepoint.h>
 #include <linux/ftrace.h>
 #include <linux/async.h>
@@ -3201,6 +3202,8 @@ static int complete_formation(struct module *mod, struct load_info *info)
 {
 	int err;
 
+	dtrace_sdt_register_module(mod);
+
 	mutex_lock(&module_mutex);
 
 	/* Find duplicate symbols (must be called under lock). */