From 6be7045c7756caf2d445dc66473e45ac5779cd55 Mon Sep 17 00:00:00 2001 From: Illia Ostapyshyn Date: Sat, 3 May 2025 14:32:31 +0200 Subject: scripts/gdb: fix kgdb probing on single-core systems Patch series "scripts/gdb: Fixes related to lx_per_cpu()". These patches (1) fix kgdb detection on systems featuring a single CPU and (2) update the documentation to reflect the current usage of lx_per_cpu() and update an outdated example of its usage. This patch (of 2): When requested the list of threads via qfThreadInfo, gdb_cmd_query in kernel/debug/gdbstub.c first returns "shadow" threads for CPUs followed by the actual tasks in the system. Extended qThreadExtraInfo queries yield "shadowCPU%d" as the name for the CPU core threads. This behavior is used by get_gdbserver_type() to probe for KGDB by matching the name for the thread 2 against "shadowCPU". This breaks down on single-core systems, where thread 2 is the first nonshadow thread. Request the name for thread 1 instead. As GDB assigns thread IDs in the order of their appearance, it is safe to assume shadowCPU0 at ID 1 as long as CPU0 is not hotplugged. Before: (gdb) info threads Id Target Id Frame 1 Thread 4294967294 (shadowCPU0) kgdb_breakpoint () * 2 Thread 1 (swapper/0) kgdb_breakpoint () 3 Thread 2 (kthreadd) 0x0000000000000000 in ?? () ... (gdb) p $lx_current().comm Sorry, obtaining the current CPU is not yet supported with this gdb server. After: (gdb) info threads Id Target Id Frame 1 Thread 4294967294 (shadowCPU0) kgdb_breakpoint () * 2 Thread 1 (swapper/0) kgdb_breakpoint () 3 Thread 2 (kthreadd) 0x0000000000000000 in ?? () ... (gdb) p $lx_current().comm $1 = "swapper/0\000\000\000\000\000\000" Link: https://lkml.kernel.org/r/20250503123234.2407184-1-illia@yshyn.com Link: https://lkml.kernel.org/r/20250503123234.2407184-2-illia@yshyn.com Signed-off-by: Illia Ostapyshyn Cc: Alex Shi Cc: Brendan Jackman Cc: Dongliang Mu Cc: Florian Rommel Cc: Hu Haowen <2023002089@link.tyut.edu.cn> Cc: Jan Kiszka Cc: Jonathan Corbet Cc: Kieran Bingham Cc: Yanteng Si Signed-off-by: Andrew Morton --- scripts/gdb/linux/utils.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'scripts/gdb/linux') diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py index 03ebdccf5f69..877404e92dbb 100644 --- a/scripts/gdb/linux/utils.py +++ b/scripts/gdb/linux/utils.py @@ -200,7 +200,7 @@ def get_gdbserver_type(): def probe_kgdb(): try: - thread_info = gdb.execute("info thread 2", to_string=True) + thread_info = gdb.execute("info thread 1", to_string=True) return "shadowCPU" in thread_info except gdb.error: return False -- cgit v1.2.3 From 09e1d93a421fa5f6699a9dbdbfc09c1008de4b9a Mon Sep 17 00:00:00 2001 From: Illia Ostapyshyn Date: Sat, 3 May 2025 14:32:32 +0200 Subject: scripts/gdb: update documentation for lx_per_cpu Commit db08c53fdd542bb7f83b ("scripts/gdb: fix parameter handling in $lx_per_cpu") changed the parameter handling of lx_per_cpu to use GdbValue instead of parsing the variable name. Update the documentation to reflect the new lx_per_cpu usage. Update the hrtimer_bases example to use rb_tree instead of the timerqueue_head.next pointer removed in commit 511885d7061eda3eb1fa ("lib/timerqueue: Rely on rbtree semantics for next timer"). Link: https://lkml.kernel.org/r/20250503123234.2407184-3-illia@yshyn.com Signed-off-by: Illia Ostapyshyn Cc: Alex Shi Cc: Brendan Jackman Cc: Dongliang Mu Cc: Florian Rommel Cc: Hu Haowen <2023002089@link.tyut.edu.cn> Cc: Jan Kiszka Cc: Jonathan Corbet Cc: Kieran Bingham Cc: Yanteng Si Signed-off-by: Andrew Morton --- .../process/debugging/gdb-kernel-debugging.rst | 34 ++++++++++------------ .../zh_CN/dev-tools/gdb-kernel-debugging.rst | 34 ++++++++++------------ .../zh_TW/dev-tools/gdb-kernel-debugging.rst | 34 ++++++++++------------ scripts/gdb/linux/cpus.py | 4 +-- 4 files changed, 47 insertions(+), 59 deletions(-) (limited to 'scripts/gdb/linux') diff --git a/Documentation/process/debugging/gdb-kernel-debugging.rst b/Documentation/process/debugging/gdb-kernel-debugging.rst index 895285c037c7..9475c759c722 100644 --- a/Documentation/process/debugging/gdb-kernel-debugging.rst +++ b/Documentation/process/debugging/gdb-kernel-debugging.rst @@ -127,35 +127,31 @@ Examples of using the Linux-provided gdb helpers - Make use of the per-cpu function for the current or a specified CPU:: - (gdb) p $lx_per_cpu("runqueues").nr_running + (gdb) p $lx_per_cpu(runqueues).nr_running $3 = 1 - (gdb) p $lx_per_cpu("runqueues", 2).nr_running + (gdb) p $lx_per_cpu(runqueues, 2).nr_running $4 = 0 - Dig into hrtimers using the container_of helper:: - (gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next - (gdb) p *$container_of($next, "struct hrtimer", "node") + (gdb) set $leftmost = $lx_per_cpu(hrtimer_bases).clock_base[0].active.rb_root.rb_leftmost + (gdb) p *$container_of($leftmost, "struct hrtimer", "node") $5 = { node = { node = { - __rb_parent_color = 18446612133355256072, - rb_right = 0x0 , - rb_left = 0x0 + __rb_parent_color = 18446612686384860673, + rb_right = 0xffff888231da8b00, + rb_left = 0x0 }, - expires = { - tv64 = 1835268000000 - } + expires = 1228461000000 }, - _softexpires = { - tv64 = 1835268000000 - }, - function = 0xffffffff81078232 , - base = 0xffff88003fd0d6f0, - state = 1, - start_pid = 0, - start_site = 0xffffffff81055c1f , - start_comm = "swapper/2\000\000\000\000\000\000" + _softexpires = 1228461000000, + function = 0xffffffff8137ab20 , + base = 0xffff888231d9b4c0, + state = 1 '\001', + is_rel = 0 '\000', + is_soft = 0 '\000', + is_hard = 1 '\001' } diff --git a/Documentation/translations/zh_CN/dev-tools/gdb-kernel-debugging.rst b/Documentation/translations/zh_CN/dev-tools/gdb-kernel-debugging.rst index 3c133a918f30..282aacd33442 100644 --- a/Documentation/translations/zh_CN/dev-tools/gdb-kernel-debugging.rst +++ b/Documentation/translations/zh_CN/dev-tools/gdb-kernel-debugging.rst @@ -120,35 +120,31 @@ Kgdb内核调试器、QEMU等虚拟机管理程序或基于JTAG的硬件接口 - 对当前或指定的CPU使用per-cpu函数:: - (gdb) p $lx_per_cpu("runqueues").nr_running + (gdb) p $lx_per_cpu(runqueues).nr_running $3 = 1 - (gdb) p $lx_per_cpu("runqueues", 2).nr_running + (gdb) p $lx_per_cpu(runqueues, 2).nr_running $4 = 0 - 使用container_of查看更多hrtimers信息:: - (gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next - (gdb) p *$container_of($next, "struct hrtimer", "node") + (gdb) set $leftmost = $lx_per_cpu(hrtimer_bases).clock_base[0].active.rb_root.rb_leftmost + (gdb) p *$container_of($leftmost, "struct hrtimer", "node") $5 = { node = { node = { - __rb_parent_color = 18446612133355256072, - rb_right = 0x0 , - rb_left = 0x0 + __rb_parent_color = 18446612686384860673, + rb_right = 0xffff888231da8b00, + rb_left = 0x0 }, - expires = { - tv64 = 1835268000000 - } + expires = 1228461000000 }, - _softexpires = { - tv64 = 1835268000000 - }, - function = 0xffffffff81078232 , - base = 0xffff88003fd0d6f0, - state = 1, - start_pid = 0, - start_site = 0xffffffff81055c1f , - start_comm = "swapper/2\000\000\000\000\000\000" + _softexpires = 1228461000000, + function = 0xffffffff8137ab20 , + base = 0xffff888231d9b4c0, + state = 1 '\001', + is_rel = 0 '\000', + is_soft = 0 '\000', + is_hard = 1 '\001' } diff --git a/Documentation/translations/zh_TW/dev-tools/gdb-kernel-debugging.rst b/Documentation/translations/zh_TW/dev-tools/gdb-kernel-debugging.rst index c881e8872b19..b595af59ba78 100644 --- a/Documentation/translations/zh_TW/dev-tools/gdb-kernel-debugging.rst +++ b/Documentation/translations/zh_TW/dev-tools/gdb-kernel-debugging.rst @@ -116,35 +116,31 @@ Kgdb內核調試器、QEMU等虛擬機管理程序或基於JTAG的硬件接口 - 對當前或指定的CPU使用per-cpu函數:: - (gdb) p $lx_per_cpu("runqueues").nr_running + (gdb) p $lx_per_cpu(runqueues).nr_running $3 = 1 - (gdb) p $lx_per_cpu("runqueues", 2).nr_running + (gdb) p $lx_per_cpu(runqueues, 2).nr_running $4 = 0 - 使用container_of查看更多hrtimers信息:: - (gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next - (gdb) p *$container_of($next, "struct hrtimer", "node") + (gdb) set $leftmost = $lx_per_cpu(hrtimer_bases).clock_base[0].active.rb_root.rb_leftmost + (gdb) p *$container_of($leftmost, "struct hrtimer", "node") $5 = { node = { node = { - __rb_parent_color = 18446612133355256072, - rb_right = 0x0 , - rb_left = 0x0 + __rb_parent_color = 18446612686384860673, + rb_right = 0xffff888231da8b00, + rb_left = 0x0 }, - expires = { - tv64 = 1835268000000 - } + expires = 1228461000000 }, - _softexpires = { - tv64 = 1835268000000 - }, - function = 0xffffffff81078232 , - base = 0xffff88003fd0d6f0, - state = 1, - start_pid = 0, - start_site = 0xffffffff81055c1f , - start_comm = "swapper/2\000\000\000\000\000\000" + _softexpires = 1228461000000, + function = 0xffffffff8137ab20 , + base = 0xffff888231d9b4c0, + state = 1 '\001', + is_rel = 0 '\000', + is_soft = 0 '\000', + is_hard = 1 '\001' } diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py index f506965ea759..6edf4ef61636 100644 --- a/scripts/gdb/linux/cpus.py +++ b/scripts/gdb/linux/cpus.py @@ -141,7 +141,7 @@ LxCpus() class PerCpu(gdb.Function): """Return per-cpu variable. -$lx_per_cpu("VAR"[, CPU]): Return the per-cpu variable called VAR for the +$lx_per_cpu(VAR[, CPU]): Return the per-cpu variable called VAR for the given CPU number. If CPU is omitted, the CPU of the current context is used. Note that VAR has to be quoted as string.""" @@ -158,7 +158,7 @@ PerCpu() class PerCpuPtr(gdb.Function): """Return per-cpu pointer. -$lx_per_cpu_ptr("VAR"[, CPU]): Return the per-cpu pointer called VAR for the +$lx_per_cpu_ptr(VAR[, CPU]): Return the per-cpu pointer called VAR for the given CPU number. If CPU is omitted, the CPU of the current context is used. Note that VAR has to be quoted as string.""" -- cgit v1.2.3 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 +----- scripts/gdb/linux/utils.py | 9 +++++++++ 2 files changed, 10 insertions(+), 5 deletions(-) (limited to 'scripts/gdb/linux') 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: diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py index 877404e92dbb..6e125830d3f2 100644 --- a/scripts/gdb/linux/utils.py +++ b/scripts/gdb/linux/utils.py @@ -251,3 +251,12 @@ def parse_vmcore(s): else: kerneloffset = int(match.group(1), 16) return VmCore(kerneloffset=kerneloffset) + + +def get_vmlinux(): + vmlinux = 'vmlinux' + for obj in gdb.objfiles(): + if (obj.filename.endswith('vmlinux') or + obj.filename.endswith('vmlinux.debug')): + vmlinux = obj.filename + return vmlinux -- cgit v1.2.3 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 +++++++------------- scripts/gdb/linux/utils.py | 11 +++++++++++ 2 files changed, 18 insertions(+), 13 deletions(-) (limited to 'scripts/gdb/linux') 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 diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py index 6e125830d3f2..e11f6f67961a 100644 --- a/scripts/gdb/linux/utils.py +++ b/scripts/gdb/linux/utils.py @@ -260,3 +260,14 @@ def get_vmlinux(): obj.filename.endswith('vmlinux.debug')): vmlinux = obj.filename return vmlinux + + +@contextlib.contextmanager +def pagination_off(): + show_pagination = gdb.execute("show pagination", to_string=True) + pagination = show_pagination.endswith("on.\n") + gdb.execute("set pagination off") + try: + yield + finally: + gdb.execute("set pagination %s" % ("on" if pagination else "off")) -- cgit v1.2.3 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') 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 v1.2.3