Another build issue

[lucabe72]

Hi,

I tried to build vbh with an older version of the Linux kernel (which has the definitions for ASM_VMX_VMREAD_RDX_RAX and similar),, but I get a new error:
[...]
CC [M] /home/luca/Src/Virt/vbh/sources/vbh_setup.o
AS [M] /home/luca/Src/Virt/vbh/sources/vmcall.o
CC [M] /home/luca/Src/Virt/vbh/sources/vcpu.o
LD [M] /home/luca/Src/Virt/vbh/sources/vmx-switch.o
Building modules, stage 2.
MODPOST 1 modules
WARNING: "__stack_chk_fail" [/home/luca/Src/Virt/vbh/sources/vmx-switch.ko] undefined!
[...]
and of course the module cannot be inserted in the kernel, because it tries to link the __stack_chk_fail symbol that does not exist...

It seems to me that the problem is due to the fact that you unconditionally add "-fstack-protector-strong" to the compiler options...
(as a side note, why are you adding all those cflags and ldflags? Doesn't kbuild use the correct flags by default?)

Thanks,
Luca

[sainath14]

We just made it working with Linux kernel v5.4. Please give it a try.

[lucabe72]

Hi,

I pulled the new commit, and I tried recompiling. Indeed, the issue with "ASM_VMX_VMREAD_RDX_RAX" & friends (bug #14) is fixed. But this specific bug (#15: __stack_chk_fail undefined) is still present.

So, I investigated it a little bit, and it seems that this bug happens when the vbh module is built against a kernel that has "CONFIG_STACKPROTECTOR_STRONG" disabled.
I think the bug is your "ccflags-y += $(INCLUDES) -O2 -Wall -fstack-protector-strong ..." in the Makefile: "-fstack-protector-strong" requires the kernel to define "__stack_chk_fail", so it cannot be used if the kernel is not built with "CONFIG_STACKPROTECTOR_STRONG=y"... On the other hand, if the kernel is built with "CONFIG_STACKPROTECTOR_STRONG=y" then kbuild automatically adds "-fstack-protector-strong" to the modules' build options (so your "ccflags-y += ..." seems to be redundant).

Luca