PVOPS: missing some xen symbols in vmlinux

PVOPS: missing some xen symbols in vmlinux

[Mukesh Rathor]

Hi Jeremy,

I noticed in PVOPS kernels that lot of the xen functions in arch/x86/xen
are not properly symbolized in vmlinux. 

These symbols show up just fine in arch/x86/built-in.o, but seem to be 
getting dropped along the way, it appears in the following step:

  ld -m elf_x86_64 --build-id  -o .tmp_vmlinux1 -T arch/x86/kernel/vmlinux.lds arch/x86/kernel/head_64.o arch/x86/kernel/head64.o arch/x86/kernel/head.o arch/x86/kernel/init_task.o  init/built-in.o --start-group  usr/built-in.o  arch/x86/built-in.o  kernel/built-in.o  mm/built-in.o  fs/built-in.o  ipc/built-in.o  security/built-in.o  crypto/built-in.o  block/built-in.o  lib/lib.a  arch/x86/lib/lib.a  lib/built-in.o  arch/x86/lib/built-in.o  drivers/built-in.o  sound/built-in.o  firmware/built-in.o  arch/x86/pci/built-in.o  arch/x86/power/built-in.o  arch/x86/video/built-in.o  net/built-in.o --end-group

[mantra]../linux-2.6.39-mine/obj> nm .tmp_vmlinux1|grep xen_start_k
ffffffff818c5b42 T xen_start_kernel

bash> gdb .tmp_vmlinux1
(gdb) disass xen_start_kernel
No function contains specified address.
(gdb) disass 0xffffffff818c5b42
No function contains specified address.
(gdb) disass native_read_cr4_safe
Dump of assembler code for function native_read_cr4_safe:
0xffffffff8100300e <native_read_cr4_safe+0>:    push   %rbp
0xffffffff8100300f <native_read_cr4_safe+1>:    mov    %rsp,%rbp
...
(gdb) disass xen_write_cr3
Dump of assembler code for function __brk_reservation_fn_level1_ident_pgt__:
End of assembler dump.
(gdb) disass arch_pick_mmap_layout
Dump of assembler code for function arch_pick_mmap_layout:
0xffffffff81039bcb <arch_pick_mmap_layout+0>:   push   %rbp
0xffffffff81039bcc <arch_pick_mmap_layout+1>:   mov    %rsp,%rbp
(gdb) disass raw_pci_read
Dump of assembler code for function raw_pci_read:
0xffffffff813f82ac <raw_pci_read+0>:    push   %rbp
0xffffffff813f82ad <raw_pci_read+1>:    mov    %rsp,%rbp
...
(gdb) disass make_lowmem_page_readonly
Dump of assembler code for function __brk_reservation_fn_level1_ident_pgt__:
End of assembler dump.

bash> gdb vmlinux
(gdb) disass make_lowmem_page_readonly
Dump of assembler code for function __brk_reservation_fn_level1_ident_pgt__:
End of assembler dump.


I am trying to figure out what is it about those xen functions, any
thoughts?

thanks,
Mukesh

Re: PVOPS: missing some xen symbols in vmlinux

[Jeremy Fitzhardinge]

On 05/26/2011 06:59 PM, Mukesh Rathor wrote:
> I am trying to figure out what is it about those xen functions, any
> thoughts?

I'd noticed that myself - I'm not really sure what causes it.  For the
asm ones it can be caused by missing the proper type/length directives
for the symbol, but AFAICS those are all C functions.  xen_start_kernel
is asmlinkage, but I don't think that should matter.

Is it just that gdb doesn't find the symbols?  Or are there other
functional problems as well?

What version of the toolchain are you using?  Do you have
CONFIG_DEBUG_INFO enabled?

Thanks,
    J

Re: PVOPS: missing some xen symbols in vmlinux

[Mukesh Rathor]

On Fri, 27 May 2011 18:04:36 -0700
Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> 
> I'd noticed that myself - I'm not really sure what causes it.  For the
> asm ones it can be caused by missing the proper type/length directives
> for the symbol, but AFAICS those are all C functions.
> xen_start_kernel is asmlinkage, but I don't think that should matter.
> 
> Is it just that gdb doesn't find the symbols?  Or are there other
> functional problems as well?
> 
> What version of the toolchain are you using?  Do you have
> CONFIG_DEBUG_INFO enabled?

Hi Jeremy,

I am using gdb version (7.0.1-50.fc12), but I will try different version,
There are no functional problems, just debugging is harder in case of
panics for my hybrid guest I am working on.

I have CONFIG_DEBUG_INFO enabled.

Thanks. I'll let you know if different verions of gdb work.

Mukesh