undefined symbol: timer_create

[alex]

In my attempt to fuzz the kernel X.509 API (#58), I've ran into an interesting bug. I'm using the following patch:

diff --git a/arch/lkl/Makefile b/arch/lkl/Makefile
index cd4ae2a..b3e62dc 100644
--- a/arch/lkl/Makefile
+++ b/arch/lkl/Makefile
@@ -22,7 +22,7 @@ endif

 LDFLAGS_vmlinux += -r
 LKL_ENTRY_POINTS := lkl_start_kernel lkl_sys_halt lkl_syscall lkl_trigger_irq \
-   lkl_get_free_irq lkl_put_irq
+   lkl_get_free_irq lkl_put_irq x509_cert_parse

 core-y += arch/lkl/kernel/

diff --git a/tools/lkl/Makefile b/tools/lkl/Makefile
index e3bd8b2..78148a2 100644
--- a/tools/lkl/Makefile
+++ b/tools/lkl/Makefile
@@ -61,6 +61,14 @@ lib/liblkl-hijack.so: $(hijack_objs) Makefile lib/liblkl.so

 lib/lkl.o:
    $(MAKE) -C ../.. ARCH=lkl defconfig
+   echo "CONFIG_ASN1=y" >> ../../.config
+   echo "CONFIG_ASYMMETRIC_KEY_TYPE=y" >> ../../.config
+   echo "CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE=y" >> ../../.config
+   echo "CONFIG_PUBLIC_KEY_ALGO_RSA=y" >> ../../.config
+   echo "CONFIG_X509_CERTIFICATE_PARSER=y" >> ../../.config
+   echo "CONFIG_PKCS7_MESSAGE_PARSER=n" >> ../../.config
+   echo "CONFIG_KEYS=y" >> ../../.config
+   $(MAKE) -C ../.. ARCH=lkl silentoldconfig
    $(MAKE) -C ../.. ARCH=lkl $(KOPT) install INSTALL_PATH=$(PWD)

 %: %.o

And it all compiles ok, but when I try to load liblkl.so, no bueno:

vagrant@vagrant-ubuntu-trusty-64:/vagrant/lkl-linux/tools/lkl$ python -c "import ctypes; ctypes.CDLL('./lib/liblkl.so')"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python2.7/ctypes/__init__.py", line 365, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: ./lib/liblkl.so: undefined symbol: timer_create

Here's the complete build log:
build.log.txt

[tommie-lie]

liblkl.so depends on some other libraries for its host-specific stuff, in your case it needs librt.
The way liblkl.so is currently build does not include these dependencies, they are only added for liblkl-hijack.so. If you want to use liblkl.so independently, you have to link with -lrt -lpthread and probably -ldl. Just add those to line 55 of the Makefile and ctypes should pick them up automatically (see line 60).

[alex]

Ahh, I didn't realize that liblkl-hijack.so was the right entrypoint:

vagrant@vagrant-ubuntu-trusty-64:/vagrant/lkl-linux/tools/lkl$ env LD_LIBRARY_PATH=$(pwd)/lib:$LD_LIBRARY_PATH python -c "import ctypes; ctypes.CDLL('./lib/liblkl-hijack.so')"
vagrant@vagrant-ubuntu-trusty-64:/vagrant/lkl-linux/tools/lkl$ echo $?
0

Thanks!