From 3545414f2590177a76f86c985130dc4824d3adc9 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Thu, 15 May 2025 17:52:11 +0200 Subject: scripts/gdb/symbols: factor out get_vmlinux() 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/linux/symbols.py | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) (limited to 'scripts/gdb/linux/symbols.py') diff --git a/scripts/gdb/linux/symbols.py b/scripts/gdb/linux/symbols.py index b255177301e9..25c4627c60e5 100644 --- a/scripts/gdb/linux/symbols.py +++ b/scripts/gdb/linux/symbols.py @@ -178,11 +178,7 @@ lx-symbols command.""" saved_states.append({'breakpoint': bp, 'enabled': bp.enabled}) # drop all current symbols and reload vmlinux - orig_vmlinux = 'vmlinux' - for obj in gdb.objfiles(): - if (obj.filename.endswith('vmlinux') or - obj.filename.endswith('vmlinux.debug')): - orig_vmlinux = obj.filename + orig_vmlinux = utils.get_vmlinux() gdb.execute("symbol-file", to_string=True) kerneloffset = get_kerneloffset() if kerneloffset is None: -- cgit From e97c4a27cb9c4c06fdc6d0760d7ea031c98b58a5 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Thu, 15 May 2025 17:52:12 +0200 Subject: scripts/gdb/symbols: factor out pagination_off() 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/linux/symbols.py | 20 +++++++------------- 1 file changed, 7 insertions(+), 13 deletions(-) (limited to 'scripts/gdb/linux/symbols.py') diff --git a/scripts/gdb/linux/symbols.py b/scripts/gdb/linux/symbols.py index 25c4627c60e5..0c7af712c44c 100644 --- a/scripts/gdb/linux/symbols.py +++ b/scripts/gdb/linux/symbols.py @@ -38,19 +38,13 @@ if hasattr(gdb, 'Breakpoint'): # Disable pagination while reporting symbol (re-)loading. # The console input is blocked in this context so that we would # get stuck waiting for the user to acknowledge paged output. - show_pagination = gdb.execute("show pagination", to_string=True) - pagination = show_pagination.endswith("on.\n") - gdb.execute("set pagination off") - - if module_name in cmd.loaded_modules: - gdb.write("refreshing all symbols to reload module " - "'{0}'\n".format(module_name)) - cmd.load_all_symbols() - else: - cmd.load_module_symbols(module) - - # restore pagination state - gdb.execute("set pagination %s" % ("on" if pagination else "off")) + with utils.pagination_off(): + if module_name in cmd.loaded_modules: + gdb.write("refreshing all symbols to reload module " + "'{0}'\n".format(module_name)) + cmd.load_all_symbols() + else: + cmd.load_module_symbols(module) return False -- cgit From c164679bed3a5f0d235723c2395d9a5122b151c4 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Thu, 15 May 2025 17:52:13 +0200 Subject: scripts/gdb/symbols: determine KASLR offset on s390 during early boot 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/linux/symbols.py | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'scripts/gdb/linux/symbols.py') diff --git a/scripts/gdb/linux/symbols.py b/scripts/gdb/linux/symbols.py index 0c7af712c44c..2332bd8eddf1 100644 --- a/scripts/gdb/linux/symbols.py +++ b/scripts/gdb/linux/symbols.py @@ -54,6 +54,18 @@ def get_vmcore_s390(): vmcore_info = 0x0e0c paddr_vmcoreinfo_note = gdb.parse_and_eval("*(unsigned long long *)" + hex(vmcore_info)) + if paddr_vmcoreinfo_note == 0 or paddr_vmcoreinfo_note & 1: + # In the early boot case, extract vm_layout.kaslr_offset from the + # vmlinux image in physical memory. + if paddr_vmcoreinfo_note == 0: + kaslr_offset_phys = 0 + else: + kaslr_offset_phys = paddr_vmcoreinfo_note - 1 + with utils.pagination_off(): + gdb.execute("symbol-file {0} -o {1}".format( + utils.get_vmlinux(), hex(kaslr_offset_phys))) + kaslr_offset = gdb.parse_and_eval("vm_layout.kaslr_offset") + return "KERNELOFFSET=" + hex(kaslr_offset)[2:] inferior = gdb.selected_inferior() elf_note = inferior.read_memory(paddr_vmcoreinfo_note, 12) n_namesz, n_descsz, n_type = struct.unpack(">III", elf_note) -- cgit