On 2/25/25 3:54 PM, Weinan Liu wrote:
On Tue, Feb 25, 2025 at 11:38 AM Indu Bhagat <indu.bha...@oracle.com> wrote:
On Mon, Feb 10, 2025 at 12:30 AM Weinan Liu <wn...@google.com> wrote:
I already have a WIP patch to add sframe support to the kernel module.
However, it is not yet working. I had trouble unwinding frames for the
kernel module using the current algorithm.
Indu has likely identified the issue and will be addressing it from the
toolchain side.
https://sourceware.org/bugzilla/show_bug.cgi?id=32666
I have a working in progress patch that adds sframe support for kernel
module.
https://github.com/heuza/linux/tree/sframe_unwinder.rfc
According to the sframe table values I got during runtime testing, looks
like the offsets are not correct .
I hope to sanitize the fix for 32666 and post upstream soon (I had to
address other related issues). Unless fixed, relocating .sframe
sections using the .rela.sframe is expected to generate incorrect output.
When unwind symbols init_module(0xffff80007b155048) from the kernel
module(livepatch-sample.ko), the start_address of the FDE entries in the
sframe table of the kernel modules appear incorrect.
init_module will apply the relocations on the .sframe section, isnt it ?
For instance, the first FDE's start_addr is reported as -20564. Adding
this offset to the module's sframe section address (0xffff80007b15a040)
yields 0xffff80007b154fec, which is not within the livepatch-sample.ko
memory region(It should be larger than 0xffff80007b155000).
Hmm..something seems off here. Having tested a potential fix for 32666
locally, I do not expect the first FDE to show this symptom.
Yes, I think init_module will apply the relocation as well.
To further investigate, here's the relevant relocation and symbol table
information for the kernel module:
Relocation section '.rela.sframe' at offset 0x28350 contains 3 entries:
Offset Info Type Sym. Value Sym. Name +
Addend
00000000001c 000100000105 R_AARCH64_PREL32 0000000000000000 .text + 8
000000000030 000100000105 R_AARCH64_PREL32 0000000000000000 .text + 28
000000000044 000100000105 R_AARCH64_PREL32 0000000000000000 .text + 68
The offsets look OK..
Symbol table '.symtab' contains 68 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 SECTION LOCAL DEFAULT 1 .text
...
32: 0000000000000008 12 FUNC LOCAL DEFAULT 1 livepatch_exit
33: 0000000000000008 0 NOTYPE LOCAL DEFAULT 3 $d
34: 0000000000000028 44 FUNC LOCAL DEFAULT 1 livepatch_init
35: 0000000000000000 0 NOTYPE LOCAL DEFAULT 9 $d
36: 0000000000000010 0 NOTYPE LOCAL DEFAULT 3 $d
37: 0000000000000068 56 FUNC LOCAL DEFAULT 1
livepatch_cmdlin[...]
...
63: 0000000000000008 12 FUNC GLOBAL DEFAULT 1 cleanup_module
64: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND klp_enable_patch
65: 0000000000000028 44 FUNC GLOBAL DEFAULT 1 init_module
