kernel/linux.git/scripts/gdb/linux/symbols.py, branch v6.19.11

scripts/gdb/symbols: make BPF debug info available to GDB

2025-11-20T22:03:42+00:00

One can debug BPF programs with QEMU gdbstub by setting a breakpoint on bpf_prog_kallsyms_add(), waiting for a hit with a matching aux.name, and then setting a breakpoint on bpf_func. This is tedious, error-prone, and also lacks line numbers. Automate this in a way similar to the existing support for modules in lx-symbols. Enumerate and monitor changes to both BPF kallsyms and JITed progs. For each ksym, generate and compile a synthetic .s file containing the name, code, and size. In addition, if this ksym is also a prog, and not a trampoline, add line number information. Ensure that this is a no-op if the kernel is built without BPF support or if "as" is missing. In theory the "as" dependency may be dropped by generating the synthetic .o file manually, but this is too much complexity for too little benefit. Now one can debug BPF progs out of the box like this: (gdb) lx-symbols -bpf (gdb) b bpf_prog_4e612a6a881a086b_arena_list_add Breakpoint 2 (bpf_prog_4e612a6a881a086b_arena_list_add) pending. # ./test_progs -t arena_list Thread 4 hit Breakpoint 2, bpf_prog_4e612a6a881a086b_arena_list_add () at linux/tools/testing/selftests/bpf/progs/arena_list.c:51 51 list_head = &global_head; (gdb) n bpf_prog_4e612a6a881a086b_arena_list_add () at linux/tools/testing/selftests/bpf/progs/arena_list.c:53 53 for (i = zero; i < cnt && can_loop; i++) { This also works for subprogs. Link: https://lkml.kernel.org/r/20251106124600.86736-3-iii@linux.ibm.com Signed-off-by: Ilya Leoshkevich Cc: Alexander Gordeev Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Daniel Borkman Cc: Heiko Carstens Cc: Jan Kiszka Cc: Kieran Bingham Cc: Vasily Gorbik Signed-off-by: Andrew Morton

scripts/gdb/symbols: make lx-symbols skip the s390 decompressor

2025-07-10T12:42:10+00:00

When one starts QEMU with the -S flag and attaches GDB, the kernel is not yet loaded, and the current instruction is an entry point to the decompressor. In case the intention is to debug the early kernel boot, and not the decompressor, e.g., put a breakpoint on some kernel function and see all the invocations, one has to skip the decompressor. There are many ways to do this, and so far people wrote private scripts or memorized certain command sequences. Make it work out of the box like this: $ gdb -ex 'target remote :6812' -ex 'source vmlinux-gdb.py' vmlinux Remote debugging using :6812 0x0000000000010000 in ?? () (gdb) lx-symbols loading vmlinux (gdb) x/i $pc => 0x3ffe0100000 : lghi %r2,0 Implement this by reading the address of the jump_to_kernel() function from the lowcore, and step until DAT is turned on. Signed-off-by: Ilya Leoshkevich Acked-by: Jan Kiszka Tested-by: Alexander Gordeev Link: https://lore.kernel.org/r/20250625154220.75300-3-iii@linux.ibm.com Signed-off-by: Alexander Gordeev

scripts/gdb/symbols: determine KASLR offset on s390 during early boot

2025-05-21T17:48:25+00:00

Using lx-symbols during s390 early boot fails with: Error occurred in Python: 'utf-8' codec can't decode byte 0xcb in position 0: invalid continuation byte The reason is that s390 decompressor's startup_kernel() does not create vmcoreinfo note, and sets vmcore_info to kernel's physical base. This confuses get_vmcore_s390(). Fix by handling this special case. Extract vm_layout.kaslr_offset from the kernel image in physical memory, which is placed there by the decompressor using the __bootdata_preserved mechanism, and generate a synthetic vmcoreinfo note from it. Link: https://lkml.kernel.org/r/20250515155811.114392-4-iii@linux.ibm.com Signed-off-by: Ilya Leoshkevich Cc: Alexander Gordeev Cc: Heiko Carstens Cc: Jan Kiszka Cc: Kieran Bingham Cc: Vasily Gorbik Signed-off-by: Andrew Morton

scripts/gdb/symbols: factor out pagination_off()

2025-05-21T17:48:24+00:00

Move the code that turns off pagination into a separate function. It will be useful later in order to prevent hangs when loading symbols for kernel image in physical memory during s390 early boot. Link: https://lkml.kernel.org/r/20250515155811.114392-3-iii@linux.ibm.com Signed-off-by: Ilya Leoshkevich Cc: Alexander Gordeev Cc: Heiko Carstens Cc: Jan Kiszka Cc: Kieran Bingham Cc: Vasily Gorbik Signed-off-by: Andrew Morton

scripts/gdb/symbols: factor out get_vmlinux()

2025-05-21T17:48:24+00:00

Patch series "scripts/gdb/symbols: determine KASLR offset on s390 during early boot". I noticed that debugging s390 early boot using the support I introduced in commit 28939c3e9925 ("scripts/gdb/symbols: determine KASLR offset on s390") does not work. The reason is that decompressor does not provide the vmcoreinfo note, so KASLR offset needs to be extracted in a different way, which this series implements. Patches 1-2 are trivial refactorings, and patch 3 is the implementation. This patch (of 3): Move the code that determines the current vmlinux file into a separate function. It will be useful later in order to analyze the kernel image in physical memory during s390 early boot. Link: https://lkml.kernel.org/r/20250515155811.114392-1-iii@linux.ibm.com Link: https://lkml.kernel.org/r/20250515155811.114392-2-iii@linux.ibm.com Signed-off-by: Ilya Leoshkevich Cc: Alexander Gordeev Cc: Heiko Carstens Cc: Jan Kiszka Cc: Kieran Bingham Cc: Vasily Gorbik Signed-off-by: Andrew Morton

scripts/gdb/symbols: determine KASLR offset on s390

2025-03-17T19:17:00+00:00

Use QEMU's qemu.PhyMemMode [1] functionality to read vmcore from the physical memory the same way the existing dump tooling does this. Gracefully handle non-QEMU targets, early boot, and memory corruptions; print a warning if such situation is detected. [1] https://qemu-project.gitlab.io/qemu/system/gdb.html#examining-physical-memory Link: https://lkml.kernel.org/r/20250303110437.79070-1-iii@linux.ibm.com Signed-off-by: Ilya Leoshkevich Acked-by: Jan Kiszka Cc: Alexander Gordeev Cc: Andrew Donnellan Cc: Christian Borntraeger Cc: Heiko Carstens Cc: Kieran Bingham Cc: Nina Schoetterl-Glausch Cc: Vasily Gorbik Signed-off-by: Andrew Morton

scripts/gdb/linux/symbols.py: address changes to module_sect_attrs

2025-03-17T19:16:59+00:00

When loading symbols from kernel modules we used to iterate from 0 to module_sect_attrs::nsections, in order to retrieve their name and address. However module_sect_attrs::nsections has been removed from the struct by a previous commit. Re-arrange the iteration by accessing all items in module_sect_attrs::grp::bin_attrs[] until NULL is found (it's a NULL terminated array). At the same time the symbol address cannot be extracted from module_sect_attrs::attrs[]::address anymore because it has also been deleted. Fetch it from module_sect_attrs::grp::bin_attrs[]::private as described in 4b2c11e4aaf7. Link: https://lkml.kernel.org/r/20250221204034.4430-1-antonio@mandelbit.com Fixes: d8959b947a8d ("module: sysfs: Drop member 'module_sect_attrs::nsections'") Fixes: 4b2c11e4aaf7 ("module: sysfs: Drop member 'module_sect_attr::address'") Signed-off-by: Antonio Quartulli Reviewed-by: Jan Kiszka Cc: Thomas Weißschuh Cc: Kieran Bingham Signed-off-by: Andrew Morton

gdb: lx-symbols: do not error out on monolithic build

2024-11-15T06:51:14+00:00

This avoids spurious message: (gdb) lx-symbols loading vmlinux No source file named kernel/module/main.c. Link: https://lkml.kernel.org/r/Zy5ALByQtpO-ddh4@Z926fQmE5jqhFMgp6 Signed-off-by: Etienne Buira Cc: Andrew Ballance Cc: Kieran Bingham Signed-off-by: Andrew Morton

scripts/gdb/symbols: fix invalid escape sequence warning

2024-03-08T00:14:19+00:00

With python 3.12, '\.' results in this warning SyntaxWarning: invalid escape sequence '\.' Link: https://lkml.kernel.org/r/20240304012507.240380-1-andrewjballance@gmail.com Signed-off-by: Andrew Ballance Cc: Jan Kiszka Cc: Kieran Bingham Cc: Koudai Iwahori Cc: Kuan-Ying Lee Cc: Luis Chamberlain Cc: Pankaj Raghav Cc: Shuah Khan Signed-off-by: Andrew Morton

revert "scripts/gdb/symbols: add specific ko module load command"

2023-09-19T20:21:33+00:00

Revert 11f956538c07 ("scripts/gdb/symbols: add specific ko module load command") due to breakage identified by Johannes Berg in [1]. Fixes: 11f956538c07 ("scripts/gdb/symbols: add specific ko module load command") Reported-by: Johannes Berg Closes: https://lkml.kernel.org/r/c44b748307a074d0c250002cdcfe209b8cce93c9.camel@sipsolutions.net [1] Cc: AngeloGioacchino Del Regno Cc: Chinwen Chang Cc: Jan Kiszka Cc: Kieran Bingham Cc: Kuan-Ying Lee Cc: Matthias Brugger Cc: Qun-Wei Lin Signed-off-by: Andrew Morton