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 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
