From: Dmitry Kovalenko <d.kovalenko@samsung.com>
Date: Sat, 11 Jul 2015 18:39:10 +0000 (+0300)
Subject: [IMPROVE] Add interface for syscalls patching
X-Git-Tag: submit/tizen/20151123.110932~35
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=refs%2Fchanges%2F22%2F43622%2F3;p=kernel%2Fswap-modules.git

[IMPROVE] Add interface for syscalls patching

Change-Id: I95035afda4f70432b3e192f2ee6730ae2bc90efe
Signed-off-by: Dmitry Kovalenko <d.kovalenko@samsung.com>
---

diff --git a/uprobe/Kbuild b/uprobe/Kbuild
index beb9b6a..11be1b1 100644
--- a/uprobe/Kbuild
+++ b/uprobe/Kbuild
@@ -10,4 +10,5 @@ swap_uprobe-$(CONFIG_ARM) += arch/arm/swap-asm/swap_uprobes.o \
 
 
 ### X86
-swap_uprobe-$(CONFIG_X86) += arch/x86/swap-asm/swap_uprobes.o
+swap_uprobe-$(CONFIG_X86) += arch/x86/swap-asm/swap_uprobes.o \
+			     arch/x86/swap-asm/swap_sc_patch.o
diff --git a/uprobe/arch/x86/swap-asm/swap_sc_patch.c b/uprobe/arch/x86/swap-asm/swap_sc_patch.c
new file mode 100644
index 0000000..01b4ea7
--- /dev/null
+++ b/uprobe/arch/x86/swap-asm/swap_sc_patch.c
@@ -0,0 +1,88 @@
+/**
+ * swap_sc_patch.c
+ * @author Dmitry Kovalenko <d.kovalenko@samsung.com>
+ * @section LICENSE
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * @section COPYRIGHT
+ *
+ * Copyright (C) Samsung Electronics, 2015
+ *
+ * @section DESCRIPTION
+ *
+ * Patching of sys_call_table
+ */
+
+#include <ksyms/ksyms.h>
+#include "swap_sc_patch.h"
+
+static unsigned long original_syscall;
+static int patched_syscall = -1;
+
+/* disable write protection */
+#define swap_disable_wprot()		\
+	asm("pushl %eax \n"		\
+	    "movl %cr0, %eax \n"	\
+	    "andl $0xfffeffff, %eax \n"	\
+	    "movl %eax, %cr0 \n"	\
+	    "popl %eax");
+
+/* enable write protection */
+#define swap_enable_wprot()	       \
+	asm("push %eax \n"	       \
+	    "movl %cr0, %eax \n"       \
+	    "orl $0x00010000, %eax \n" \
+	    "movl %eax, %cr0 \n"       \
+	    "popl %eax");
+
+void patch_syscall(int syscall_n, unsigned long new_syscall_addr)
+{
+	unsigned long tmp;
+	unsigned long *sc_table;
+
+	/*
+	 * Search for sys_call_table (4 bytes before sysenter_after_call)
+	 * sysenter_do_call function which locates before sysenter_after_call
+	 * has sys_call_table address in call instruction (latest instruction)
+	 */
+	tmp = swap_ksyms("sysenter_after_call");
+	sc_table = *(unsigned long **)(tmp - 4);
+
+	swap_disable_wprot();
+	original_syscall = sc_table[syscall_n];
+	sc_table[syscall_n] = new_syscall_addr;
+	patched_syscall = syscall_n;
+	swap_enable_wprot();
+}
+
+void swap_depatch_syscall(void)
+{
+	patch_syscall(patched_syscall, original_syscall);
+	patched_syscall = -1;
+}
+
+asmlinkage long sys_swap_func(void)
+{
+	/* Your code here */
+
+	return -ENOSYS;
+}
+
+#define NI_SYSCALL4SWAP 31
+void swap_patch_syscall(void)
+{
+	patch_syscall(NI_SYSCALL4SWAP, (unsigned long)&sys_swap_func);
+}
diff --git a/uprobe/arch/x86/swap-asm/swap_sc_patch.h b/uprobe/arch/x86/swap-asm/swap_sc_patch.h
new file mode 100644
index 0000000..9b42fac
--- /dev/null
+++ b/uprobe/arch/x86/swap-asm/swap_sc_patch.h
@@ -0,0 +1,2 @@
+void swap_depatch_syscall(void);
+void swap_patch_syscall(void);