From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Date: Fri, 19 Mar 2021 12:21:43 +0000 Subject: [PATCH -tip v3 00/11] kprobes: Fix stacktrace with kretprobes on x86 Message-Id: <161615650355.306069.17260992641363840330.stgit@devnote2> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Steven Rostedt , Ingo Molnar Cc: X86 ML , Masami Hiramatsu , Daniel Xu , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, tglx@linutronix.de, kernel-team@fb.com, yhs@fb.com, Josh Poimboeuf , linux-ia64@vger.kernel.org Hello, Here is the 3rd version of the series to fix the stacktrace with kretprobe on x86. The previous version is; https://lore.kernel.org/bpf/161553130371.1038734.7661319550287837734.stgit@devnote2/ Instead of solving generic stacktrace, this version is focusing on x86 stack unwinders. Anyway this introduces the generic APIs for the solution, other architectures can fix their unwinder with that. In this version, generic stacktrace fixups in [4/11] is dropped. Instead, [4/11] is just providing kretprobe_find_ret_addr(). And previous ORC unwinder fix patch is splitted into [9/11] and [10/11]. [9/11] fixes x86 kretprobe trampoline so that it pushes an additional kretprobe_trampoline at the bottom of stackframe as a fake return address according to Josh's suggestion. And [10/11] fixes all unwinders in x86 (guess, frame, and ORC). Finally, [11/11] is renewed to check the kretprobe_trampoline address correctly instead of removing all indicator logic, because except for the x86, it will see the kretprobe_trampoline in the stack trace until it is fixed on each architecture. With this series, unwinder can unwind stack correctly from ftrace as below; # cd /sys/kernel/debug/tracing # echo > trace # echo r vfs_read >> kprobe_events # echo r full_proxy_read >> kprobe_events # echo traceoff:1 > events/kprobes/r_vfs_read_0/trigger # echo stacktrace:1 > events/kprobes/r_full_proxy_read_0/trigger # echo 1 > events/kprobes/enable # echo 1 > options/sym-offset # cat /sys/kernel/debug/kprobes/list ffffffff8133b740 r full_proxy_read+0x0 [FTRACE] ffffffff812560b0 r vfs_read+0x0 [FTRACE] # echo 0 > events/kprobes/enable # cat trace # tracer: nop # # entries-in-buffer/entries-written: 3/3 #P:8 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | <...>-135 [005] ...1 9.422114: r_full_proxy_read_0: (vfs_read+0xab/0x1a0 <- full_proxy_read) <...>-135 [005] ...1 9.422158: => kretprobe_trace_func+0x209/0x2f0 => kretprobe_dispatcher+0x4a/0x70 => __kretprobe_trampoline_handler+0xca/0x150 => trampoline_handler+0x44/0x70 => kretprobe_trampoline+0x2a/0x50 => vfs_read+0xab/0x1a0 => ksys_read+0x5f/0xe0 => do_syscall_64+0x33/0x40 => entry_SYSCALL_64_after_hwframe+0x44/0xae => 0 This shows the double return probes (vfs_read and full_proxy_read) on the stack correctly unwinded. (vfs_read was called from ksys_read+0x5f and full_proxy_read was called from vfs_read+0xab) This actually changes the kretprobe behavisor a bit, now the instraction pointer in the pt_regs passed to kretprobe user handler is correctly set the real return address. So user handlers can get it via instruction_pointer() API. You can also get this series from git://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git kprobes/kretprobe-stackfix-v3 Thank you, --- Josh Poimboeuf (1): x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Masami Hiramatsu (10): ia64: kprobes: Fix to pass correct trampoline address to the handler kprobes: treewide: Replace arch_deref_entry_point() with dereference_function_descriptor() kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() kprobes: Add kretprobe_find_ret_addr() for searching return address ARC: Add instruction_pointer_set() API ia64: Add instruction_pointer_set() API kprobes: Setup instruction pointer in __kretprobe_trampoline_handler x86/kprobes: Push a fake return address at kretprobe_trampoline x86/unwind: Recover kretprobe trampoline entry tracing: Show kretprobe unknown indicator only for kretprobe_trampoline arch/arc/include/asm/ptrace.h | 5 ++ arch/arc/kernel/kprobes.c | 2 - arch/arm/probes/kprobes/core.c | 3 - arch/arm64/kernel/probes/kprobes.c | 3 - arch/csky/kernel/probes/kprobes.c | 2 - arch/ia64/include/asm/ptrace.h | 8 ++- arch/ia64/kernel/kprobes.c | 15 ++--- arch/mips/kernel/kprobes.c | 3 - arch/parisc/kernel/kprobes.c | 4 + arch/powerpc/kernel/kprobes.c | 13 ----- arch/riscv/kernel/probes/kprobes.c | 2 - arch/s390/kernel/kprobes.c | 2 - arch/sh/kernel/kprobes.c | 2 - arch/sparc/kernel/kprobes.c | 2 - arch/x86/include/asm/kprobes.h | 1 arch/x86/include/asm/unwind.h | 17 ++++++ arch/x86/include/asm/unwind_hints.h | 5 ++ arch/x86/kernel/kprobes/core.c | 30 ++++++++--- arch/x86/kernel/unwind_frame.c | 4 + arch/x86/kernel/unwind_guess.c | 3 - arch/x86/kernel/unwind_orc.c | 6 +- include/linux/kprobes.h | 41 ++++++++++++-- kernel/kprobes.c | 99 ++++++++++++++++++++++++----------- kernel/trace/trace_output.c | 17 +----- lib/error-inject.c | 3 + 25 files changed, 187 insertions(+), 105 deletions(-) -- Masami Hiramatsu (Linaro)