LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: akpm@linux-foundation.org, linux-kernel@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
	Andi Kleen <andi@firstfloor.org>
Subject: [patch 04/10] Text Edit Lock - Architecture Independent Code
Date: Mon, 27 Aug 2007 11:56:05 -0400	[thread overview]
Message-ID: <20070827155851.276400014@polymtl.ca> (raw)
In-Reply-To: <20070827155601.360241608@polymtl.ca>

[-- Attachment #1: text-edit-lock-architecture-independent-code.patch --]
[-- Type: text/plain, Size: 3160 bytes --]

This is an architecture independant synchronization around kernel text
modifications through use of a global mutex.

A mutex has been chosen so that kprobes, the main user of this, can sleep during
memory allocation between the memory read of the instructions it must replace
and the memory write of the breakpoint.

Other user of this interface: immediate values.

Paravirt and alternatives are always done when SMP is inactive, so there is no
need to use locks.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Andi Kleen <andi@firstfloor.org>
---
 include/linux/memory.h |    7 +++++++
 mm/memory.c            |   34 ++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

Index: linux-2.6-lttng/include/linux/memory.h
===================================================================
--- linux-2.6-lttng.orig/include/linux/memory.h	2007-08-27 11:16:10.000000000 -0400
+++ linux-2.6-lttng/include/linux/memory.h	2007-08-27 11:49:04.000000000 -0400
@@ -86,4 +86,11 @@ extern int remove_memory_block(unsigned 
 	register_memory_notifier(&fn##_mem_nb);			\
 }
 
+/*
+ * Take and release the kernel text modification lock, used for code patching.
+ * Users of this lock can sleep.
+ */
+extern void kernel_text_lock(void);
+extern void kernel_text_unlock(void);
+
 #endif /* _LINUX_MEMORY_H_ */
Index: linux-2.6-lttng/mm/memory.c
===================================================================
--- linux-2.6-lttng.orig/mm/memory.c	2007-08-27 11:16:10.000000000 -0400
+++ linux-2.6-lttng/mm/memory.c	2007-08-27 11:49:04.000000000 -0400
@@ -50,6 +50,8 @@
 #include <linux/delayacct.h>
 #include <linux/init.h>
 #include <linux/writeback.h>
+#include <linux/kprobes.h>
+#include <linux/mutex.h>
 
 #include <asm/pgalloc.h>
 #include <asm/uaccess.h>
@@ -84,6 +86,12 @@ EXPORT_SYMBOL(high_memory);
 
 int randomize_va_space __read_mostly = 1;
 
+/*
+ * mutex protecting text section modification (dynamic code patching).
+ * some users need to sleep (allocating memory...) while they hold this lock.
+ */
+static DEFINE_MUTEX(text_mutex);
+
 static int __init disable_randmaps(char *s)
 {
 	randomize_va_space = 0;
@@ -2752,3 +2760,29 @@ int access_process_vm(struct task_struct
 	return buf - old_buf;
 }
 EXPORT_SYMBOL_GPL(access_process_vm);
+
+/**
+ * kernel_text_lock     -   Take the kernel text modification lock
+ *
+ * Insures mutual write exclusion of kernel and modules text live text
+ * modification. Should be used for code patching.
+ * Users of this lock can sleep.
+ */
+void __kprobes kernel_text_lock(void)
+{
+	mutex_lock(&text_mutex);
+}
+EXPORT_SYMBOL_GPL(kernel_text_lock);
+
+/**
+ * kernel_text_unlock   -   Release the kernel text modification lock
+ *
+ * Insures mutual write exclusion of kernel and modules text live text
+ * modification. Should be used for code patching.
+ * Users of this lock can sleep.
+ */
+void __kprobes kernel_text_unlock(void)
+{
+	mutex_unlock(&text_mutex);
+}
+EXPORT_SYMBOL_GPL(kernel_text_unlock);

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

  parent reply	other threads:[~2007-08-27 16:44 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-27 15:56 [patch 00/10] Text Edit Lock Mathieu Desnoyers
2007-08-27 15:56 ` [patch 01/10] Kprobes - use a mutex to protect the instruction pages list Mathieu Desnoyers
2007-08-27 15:56 ` [patch 02/10] Kprobes - do not use kprobes mutex in arch code Mathieu Desnoyers
2007-08-27 15:56 ` [patch 03/10] Kprobes - declare kprobe_mutex static Mathieu Desnoyers
2007-08-27 15:56 ` Mathieu Desnoyers [this message]
2007-08-27 15:56 ` [patch 05/10] Text Edit Lock - Alternative code for i386 and x86_64 Mathieu Desnoyers
2007-08-27 15:56 ` [patch 06/10] Text Edit Lock - kprobes architecture independent support Mathieu Desnoyers
2007-08-27 15:56 ` [patch 07/10] Text Edit Lock - kprobes i386 Mathieu Desnoyers
2007-08-27 15:56 ` [patch 08/10] Text Edit Lock - kprobes x86_64 Mathieu Desnoyers
2007-08-27 15:56 ` [patch 09/10] Text Edit Lock - i386 standardize debug rodata Mathieu Desnoyers
2007-08-27 15:56 ` [patch 10/10] Text Edit Lock - x86_64 " Mathieu Desnoyers
2007-09-06 20:01 [patch 00/10] Text Edit Lock for 2.6.23-rc4-mm1 Mathieu Desnoyers
2007-09-06 20:01 ` [patch 04/10] Text Edit Lock - Architecture Independent Code Mathieu Desnoyers

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20070827155851.276400014@polymtl.ca \
    --to=mathieu.desnoyers@polymtl.ca \
    --cc=akpm@linux-foundation.org \
    --cc=andi@firstfloor.org \
    --cc=linux-kernel@vger.kernel.org \
    --subject='Re: [patch 04/10] Text Edit Lock - Architecture Independent Code' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).