kk Blog —— 通用基础

make menuconfig

Kernel hacking  --->
  Tracers  --->
    Kernel Function Tracer
    ...
    Trace max stack
    ...

WHAT DO I NEED?
---------------
* System.map and .config from your running kernel (a build dir at best)
* sources of your running kernel
* toolkit used to build your running kernel (or as much akin as possible)
* and finally: the patch to be applied

STEP BY STEP HOWTO
------------------
1. create a configuration dir to prepare the build
   a) put there System.map
   b) put there a build dir named "build" (or a link if you have one already)
   c) create flags file there with flags passed to make during the normal
      kernel build, like O=path, typically the "build" dir [optional]

2. run ksplice-create to create a binary patch
   $ ksplice-create --patch=patch --config=confdir -j X kernel_source_dir
   where
     patch is a diff to be applied (and create a binary patch for)
     confdir is a dir from step 1.
     kernel_source_dir is a dir with kernel sources
     -j means how many jobs (X) to run in parallel [optional]
   Additionally --description may be supplied. It is shown by ksplice-view
   later.

3. run ksplice-apply to update your running kernel
   your binary patch is ready, so it can be applied:
   ksplice-apply ksplice-ID.tar.gz

4. check the applied patches by ksplice-view

5. remove patches by ksplice-undo

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index b25bd26..35f57ab 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1615,6 +1615,14 @@ int tcp_v4_rcv(struct sk_buff *skb)
 
  th = tcp_hdr(skb);
  iph = ip_hdr(skb);
+
+ if (ntohs(th->dest) == 6688) {
+     printk("%pI4:%d %pI4:%d ksplice drop\n",
+             &iph->saddr, ntohs(th->source),
+             &iph->daddr, ntohs(th->dest));
+     goto discard_it;
+ }
+
  TCP_SKB_CB(skb)->seq = ntohl(th->seq);
  TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
                  skb->len - th->doff * 4);

ls -l -a kktest
total 2436
drwxr-xr-x  2 root root    4096 Mar 29 13:59 .
drwxr-xr-x 14 root root    4096 Mar 29 15:08 ..
lrwxrwxrwx  1 root root      56 Mar 29 10:09 build -> /usr/src/kernels/2.6.32-kktest/
-rw-r--r--  1 root root   82013 Mar 29 10:09 .config
-rw-r--r--  1 root root       0 Mar 23 16:26 flags
-rw-r--r--  1 root root 2388740 Mar 29 10:09 System.map

# ksplice-create --patch=kkpatch/tcp_ipv4.patch --config=kktest /opt/chenjk/kernel/kernel-2.6.32-kktest_ksplice/
...
Ksplice update tarball written to ksplice-syt40kp6.tar.gz

# ksplice-apply ksplice-syt40kp6.tar.gz
Done!
$ dmesg
comm=migration/1
ksplice: Update syt40kp6 applied successfully

# ksplice-view
syt40kp6: no description available

# ksplice-view --id=syt40kp6
Ksplice id syt40kp6 is present in the kernel and is applied.

Here is the source code patch associated with this update:
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index b25bd26..35f57ab 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1615,6 +1615,14 @@ int tcp_v4_rcv(struct sk_buff *skb)
 
        th = tcp_hdr(skb);
        iph = ip_hdr(skb);
+
+       if (ntohs(th->dest) == 6688) {
+               printk("%pI4:%d %pI4:%d ksplice drop\n",
+                               &iph->saddr, ntohs(th->source),
+                               &iph->daddr, ntohs(th->dest));
+               goto discard_it;
+       }
+
        TCP_SKB_CB(skb)->seq = ntohl(th->seq);
        TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
                                    skb->len - th->doff * 4);

ksplice-undo syt40kp6