Hi Josh, Would you have any comment on this series? Thank you, On Thu, 27 May 2021 15:39:03 +0900 Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > Hello, > > Here is the 7th version of the series to fix the stacktrace with kretprobe on x86. > > The previous version is; > > https://lore.kernel.org/bpf/162201612941.278331.5293566981784464165.stgit@devnote2/ > > This version is adding Tested-by from Andrii and do minor cleanups to solve some > warnings from kernel test bots. > > Changes from v6: > For x86 and generic patch: > - Add Andrii's Tested-by. (Andrii, I think you have tested only x86, is it OK?) > [11/13]: > - Remove superfluous #include <linux/kprobes.h>. > [13/13]: > - Add a prototype for arch_kretprobe_fixup_return(). > > > With this series, unwinder can unwind stack correctly from ftrace as below; > > # cd /sys/kernel/debug/tracing > # echo > trace > # echo 1 > options/sym-offset > # 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 > # 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 > # | | | |||| | | > <...>-134 [007] ...1 16.185877: r_full_proxy_read_0: (vfs_read+0x98/0x180 <- full_proxy_read) > <...>-134 [007] ...1 16.185901: <stack trace> > => kretprobe_trace_func+0x209/0x300 > => kretprobe_dispatcher+0x4a/0x70 > => __kretprobe_trampoline_handler+0xd4/0x170 > => trampoline_handler+0x43/0x60 > => kretprobe_trampoline+0x2a/0x50 > => vfs_read+0x98/0x180 > => ksys_read+0x5f/0xe0 > => do_syscall_64+0x37/0x90 > => entry_SYSCALL_64_after_hwframe+0x44/0xae > <...>-134 [007] ...1 16.185902: r_vfs_read_0: (ksys_read+0x5f/0xe0 <- vfs_read) > > This shows the double return probes (vfs_read and full_proxy_read) on the stack > correctly unwinded. (vfs_read will return to ksys_read+0x5f and full_proxy_read > will return to vfs_read+0x98) > > 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-v7 > > > Thank you, > > --- > > Josh Poimboeuf (1): > x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code > > Masami Hiramatsu (12): > ia64: kprobes: Fix to pass correct trampoline address to the handler > kprobes: treewide: Replace arch_deref_entry_point() with dereference_symbol_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 > arm: kprobes: Make a space for regs->ARM_pc at kretprobe_trampoline > 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 > x86/kprobes: Fixup return address in generic trampoline handler > > > arch/arc/include/asm/ptrace.h | 5 ++ > arch/arc/kernel/kprobes.c | 2 - > arch/arm/probes/kprobes/core.c | 5 +- > arch/arm64/kernel/probes/kprobes.c | 3 - > arch/csky/kernel/probes/kprobes.c | 2 - > arch/ia64/include/asm/ptrace.h | 5 ++ > 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 | 23 +++++++ > arch/x86/include/asm/unwind_hints.h | 5 ++ > arch/x86/kernel/kprobes/core.c | 53 +++++++++++++++-- > arch/x86/kernel/unwind_frame.c | 3 - > arch/x86/kernel/unwind_guess.c | 3 - > arch/x86/kernel/unwind_orc.c | 18 +++++- > include/linux/kprobes.h | 44 ++++++++++++-- > kernel/kprobes.c | 108 +++++++++++++++++++++++++---------- > kernel/trace/trace_output.c | 17 +----- > lib/error-inject.c | 3 + > 25 files changed, 238 insertions(+), 105 deletions(-) > > -- > Masami Hiramatsu (Linaro) <mhiramat@xxxxxxxxxx> -- Masami Hiramatsu
