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    Subject[PATCH -tip v6 00/13] kprobes: Fix stacktrace with kretprobes on x86
    Date
    Hello,

    Here is the 6th version of the series to fix the stacktrace with kretprobe
    on x86.

    The previous version is;

    https://lore.kernel.org/bpf/161676170650.330141.6214727134265514123.stgit@devnote2/

    This version is rebased on the latest tip tree and add some patches for
    improving stacktrace[13/13].

    Changes from v5:
    [02/13]:
    - Use dereference_symbol_descriptor() instead of dereference_function_descriptor()
    [04/13]:
    - Replace BUG_ON() with WARN_ON_ONCE() in __kretprobe_trampoline_handler().
    [13/13]:
    - Add a new patch to fix return address in earlier stage.


    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-v6


    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 | 4 +
    arch/x86/kernel/unwind_guess.c | 3 -
    arch/x86/kernel/unwind_orc.c | 19 +++++-
    include/linux/kprobes.h | 41 +++++++++++--
    kernel/kprobes.c | 108 +++++++++++++++++++++++++----------
    kernel/trace/trace_output.c | 17 +-----
    lib/error-inject.c | 3 +
    25 files changed, 237 insertions(+), 105 deletions(-)

    --
    Masami Hiramatsu (Linaro) <mhiramat@kernel.org>

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