[PATCH 1/2] kprobes: add a new module parameter

[PATCH 1/2] kprobes: add a new module parameter

[Huang Shijie]

This patch adds a new module parameter which can be used as the
symbol name. With this parameter, the module becomes more flexable.

Signed-off-by: Huang Shijie <shijie.huang@arm.com>
---
 samples/kprobes/kprobe_example.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/samples/kprobes/kprobe_example.c b/samples/kprobes/kprobe_example.c
index 727eb21..2bb190d 100644
--- a/samples/kprobes/kprobe_example.c
+++ b/samples/kprobes/kprobe_example.c
@@ -14,9 +14,13 @@
 #include <linux/module.h>
 #include <linux/kprobes.h>
 
+#define MAX_SYMBOL_LEN	64
+static char symbol[MAX_SYMBOL_LEN] = "_do_fork";
+module_param_string(symbol, symbol, sizeof(symbol), 0644);
+
 /* For each probe you need to allocate a kprobe structure */
 static struct kprobe kp = {
-	.symbol_name	= "_do_fork",
+	.symbol_name	= symbol,
 };
 
 /* kprobe pre_handler: called just before the probed instruction is executed */
-- 
2.5.5

[PATCH 2/2] kprobes: print out the symbol name for the hooks

[Huang Shijie]

Print out the symbol name for the hooks, it makes the logs more readable.

Signed-off-by: Huang Shijie <shijie.huang@arm.com>
---
 samples/kprobes/kprobe_example.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/samples/kprobes/kprobe_example.c b/samples/kprobes/kprobe_example.c
index 2bb190d..ed0ca0c 100644
--- a/samples/kprobes/kprobe_example.c
+++ b/samples/kprobes/kprobe_example.c
@@ -27,24 +27,24 @@ static struct kprobe kp = {
 static int handler_pre(struct kprobe *p, struct pt_regs *regs)
 {
 #ifdef CONFIG_X86
-	printk(KERN_INFO "pre_handler: p->addr = 0x%p, ip = %lx,"
+	printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, ip = %lx,"
 			" flags = 0x%lx\n",
-		p->addr, regs->ip, regs->flags);
+		p->symbol_name, p->addr, regs->ip, regs->flags);
 #endif
 #ifdef CONFIG_PPC
-	printk(KERN_INFO "pre_handler: p->addr = 0x%p, nip = 0x%lx,"
+	printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, nip = 0x%lx,"
 			" msr = 0x%lx\n",
-		p->addr, regs->nip, regs->msr);
+		p->symbol_name, p->addr, regs->nip, regs->msr);
 #endif
 #ifdef CONFIG_MIPS
-	printk(KERN_INFO "pre_handler: p->addr = 0x%p, epc = 0x%lx,"
+	printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, epc = 0x%lx,"
 			" status = 0x%lx\n",
-		p->addr, regs->cp0_epc, regs->cp0_status);
+		p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
 #endif
 #ifdef CONFIG_TILEGX
-	printk(KERN_INFO "pre_handler: p->addr = 0x%p, pc = 0x%lx,"
+	printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
 			" ex1 = 0x%lx\n",
-		p->addr, regs->pc, regs->ex1);
+		p->symbol_name, p->addr, regs->pc, regs->ex1);
 #endif
 
 	/* A dump_stack() here will give a stack backtrace */
@@ -56,20 +56,20 @@ static void handler_post(struct kprobe *p, struct pt_regs *regs,
 				unsigned long flags)
 {
 #ifdef CONFIG_X86
-	printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n",
-		p->addr, regs->flags);
+	printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n",
+		p->symbol_name, p->addr, regs->flags);
 #endif
 #ifdef CONFIG_PPC
-	printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n",
-		p->addr, regs->msr);
+	printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n",
+		p->symbol_name, p->addr, regs->msr);
 #endif
 #ifdef CONFIG_MIPS
-	printk(KERN_INFO "post_handler: p->addr = 0x%p, status = 0x%lx\n",
-		p->addr, regs->cp0_status);
+	printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
+		p->symbol_name, p->addr, regs->cp0_status);
 #endif
 #ifdef CONFIG_TILEGX
-	printk(KERN_INFO "post_handler: p->addr = 0x%p, ex1 = 0x%lx\n",
-		p->addr, regs->ex1);
+	printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, ex1 = 0x%lx\n",
+		p->symbol_name, p->addr, regs->ex1);
 #endif
 }
 
-- 
2.5.5

Re: [PATCH 1/2] kprobes: add a new module parameter

[Andrew Morton]

On Wed, 18 May 2016 09:36:56 +0800 Huang Shijie <shijie.huang@arm.com> wrote:

> This patch adds a new module parameter which can be used as the
> symbol name. With this parameter, the module becomes more flexable.

This changelog is too vague.  What does "more flexible" mean?  Please
describe the benefits of the change in much more detail.

[PATCH v2] kprobes: add a new module parameter

[Huang Shijie]

This patch adds a new module parameter which can be used as the
symbol name. Without this patch, we can only test the "_do_fork" function
with this kernel module. With this patch, the module becomes more flexable,
we can test any functions with this module with:
   #insmod kprobe_example.ko symbol="xxx"

Signed-off-by: Huang Shijie <shijie.huang@arm.com>
---
v1 -- > v2:
	Add more comment for this patch.
---
 samples/kprobes/kprobe_example.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/samples/kprobes/kprobe_example.c b/samples/kprobes/kprobe_example.c
index 727eb21..2bb190d 100644
--- a/samples/kprobes/kprobe_example.c
+++ b/samples/kprobes/kprobe_example.c
@@ -14,9 +14,13 @@
 #include <linux/module.h>
 #include <linux/kprobes.h>
 
+#define MAX_SYMBOL_LEN	64
+static char symbol[MAX_SYMBOL_LEN] = "_do_fork";
+module_param_string(symbol, symbol, sizeof(symbol), 0644);
+
 /* For each probe you need to allocate a kprobe structure */
 static struct kprobe kp = {
-	.symbol_name	= "_do_fork",
+	.symbol_name	= symbol,
 };
 
 /* kprobe pre_handler: called just before the probed instruction is executed */
-- 
2.5.5