linux/kernel/kprobes.c, branch v6.8

kprobes: Remove unnecessary initial values of variables

2024-02-08T14:29:29Z

ri and sym is assigned first, so it does not need to initialize the assignment. Link: https://lore.kernel.org/all/20230919012823.7815-1-zeming@nfschina.com/ Signed-off-by: Li zeming Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google)

kprobes: consistent rcu api usage for kretprobe holder

2023-12-01T05:53:55Z

It seems that the pointer-to-kretprobe "rp" within the kretprobe_holder is RCU-managed, based on the (non-rethook) implementation of get_kretprobe(). The thought behind this patch is to make use of the RCU API where possible when accessing this pointer so that the needed barriers are always in place and to self-document the code. The __rcu annotation to "rp" allows for sparse RCU checking. Plain writes done to the "rp" pointer are changed to make use of the RCU macro for assignment. For the single read, the implementation of get_kretprobe() is simplified by making use of an RCU macro which accomplishes the same, but note that the log warning text will be more generic. I did find that there is a difference in assembly generated between the usage of the RCU macros vs without. For example, on arm64, when using rcu_assign_pointer(), the corresponding store instruction is a store-release (STLR) which has an implicit barrier. When normal assignment is done, a regular store (STR) is found. In the macro case, this seems to be a result of rcu_assign_pointer() using smp_store_release() when the value to write is not NULL. Link: https://lore.kernel.org/all/20231122132058.3359-1-inwardvessel@gmail.com/ Fixes: d741bf41d7c7 ("kprobes: Remove kretprobe hash") Cc: stable@vger.kernel.org Signed-off-by: JP Kobryn Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google)

kprobes: kretprobe scalability improvement

2023-10-18T14:59:54Z

kretprobe is using freelist to manage return-instances, but freelist, as LIFO queue based on singly linked list, scales badly and reduces the overall throughput of kretprobed routines, especially for high contention scenarios. Here's a typical throughput test of sys_prctl (counts in 10 seconds, measured with perf stat -a -I 10000 -e syscalls:sys_enter_prctl): OS: Debian 10 X86_64, Linux 6.5rc7 with freelist HW: XEON 8336C x 2, 64 cores/128 threads, DDR4 3200MT/s 1T 2T 4T 8T 16T 24T 24150045 29317964 15446741 12494489 18287272 17708768 32T 48T 64T 72T 96T 128T 16200682 13737658 11645677 11269858 10470118 9931051 This patch introduces objpool to replace freelist. objpool is a high performance queue, which can bring near-linear scalability to kretprobed routines. Tests of kretprobe throughput show the biggest ratio as 159x of original freelist. Here's the result: 1T 2T 4T 8T 16T native: 41186213 82336866 164250978 328662645 658810299 freelist: 24150045 29317964 15446741 12494489 18287272 objpool: 23926730 48010314 96125218 191782984 385091769 32T 48T 64T 96T 128T native: 1330338351 1969957941 2512291791 2615754135 2671040914 freelist: 16200682 13737658 11645677 10470118 9931051 objpool: 764481096 1147149781 1456220214 1502109662 1579015050 Testings on 96-core ARM64 output similarly, but with the biggest ratio up to 448x: OS: Debian 10 AARCH64, Linux 6.5rc7 HW: Kunpeng-920 96 cores/2 sockets/4 NUMA nodes, DDR4 2933 MT/s 1T 2T 4T 8T 16T native: . 30066096 63569843 126194076 257447289 505800181 freelist: 16152090 11064397 11124068 7215768 5663013 objpool: 13997541 28032100 55726624 110099926 221498787 24T 32T 48T 64T 96T native: 763305277 1015925192 1521075123 2033009392 3021013752 freelist: 5015810 4602893 3766792 3382478 2945292 objpool: 328192025 439439564 668534502 887401381 1319972072 Link: https://lore.kernel.org/all/20231017135654.82270-4-wuqiang.matt@bytedance.com/ Signed-off-by: wuqiang.matt Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google)

kernel: kprobes: Use struct_size()

2023-08-23T00:38:17Z

Use struct_size() instead of hand-writing it, when allocating a structure with a flex array. This is less verbose. Link: https://lore.kernel.org/all/20230725195424.3469242-1-ruanjinjie@huawei.com/ Signed-off-by: Ruan Jinjie Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google)

kprobes: Prohibit probing on CFI preamble symbol

2023-07-29T14:32:26Z

Do not allow to probe on "__cfi_" or "__pfx_" started symbol, because those are used for CFI and not executed. Probing it will break the CFI. Link: https://lore.kernel.org/all/168904024679.116016.18089228029322008512.stgit@devnote2/ Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Steven Rostedt (Google)

Merge tag 'probes-fixes-v6.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2023-07-12T19:01:16Z

Pull probes fixes from Masami Hiramatsu: - Fix fprobe's rethook release issues: - Release rethook after ftrace_ops is unregistered so that the rethook is not accessed after free. - Stop rethook before ftrace_ops is unregistered so that the rethook is NOT used after exiting unregister_fprobe() - Fix eprobe cleanup logic. If it attaches to multiple events and failes to enable one of them, rollback all enabled events correctly. - Fix fprobe to unlock ftrace recursion lock correctly when it missed by another running kprobe. - Cleanup kprobe to remove unnecessary NULL. - Cleanup kprobe to remove unnecessary 0 initializations. * tag 'probes-fixes-v6.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: fprobe: Ensure running fprobe_exit_handler() finished before calling rethook_free() kernel: kprobes: Remove unnecessary ‘0’ values kprobes: Remove unnecessary ‘NULL’ values from correct_ret_addr fprobe: add unlock to match a succeeded ftrace_test_recursion_trylock kernel/trace: Fix cleanup logic of enable_trace_eprobe fprobe: Release rethook after the ftrace_ops is unregistered

kernel: kprobes: Remove unnecessary ‘0’ values

2023-07-10T15:50:51Z

it is assigned first, so it does not need to initialize the assignment. Link: https://lore.kernel.org/all/20230711185353.3218-1-zeming@nfschina.com/ Signed-off-by: Li zeming Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google)

kprobes: Remove unnecessary ‘NULL’ values from correct_ret_addr

2023-07-10T15:50:35Z

The 'correct_ret_addr' pointer is always set in the later code, no need to initialize it at definition time. Link: https://lore.kernel.org/all/20230704194359.3124-1-zeming@nfschina.com/ Signed-off-by: Li zeming Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google)

fprobe: Pass return address to the handlers

2023-06-06T12:39:55Z

Pass return address as 'ret_ip' to the fprobe entry and return handlers so that the fprobe user handler can get the reutrn address without analyzing arch-dependent pt_regs. Link: https://lore.kernel.org/all/168507467664.913472.11642316698862778600.stgit@mhiramat.roam.corp.google.com/ Signed-off-by: Masami Hiramatsu (Google)

x86/kprobes: Fix arch_check_optimized_kprobe check within optimized_kprobe range

2023-02-20T23:49:16Z

When arch_prepare_optimized_kprobe calculating jump destination address, it copies original instructions from jmp-optimized kprobe (see __recover_optprobed_insn), and calculated based on length of original instruction. arch_check_optimized_kprobe does not check KPROBE_FLAG_OPTIMATED when checking whether jmp-optimized kprobe exists. As a result, setup_detour_execution may jump to a range that has been overwritten by jump destination address, resulting in an inval opcode error. For example, assume that register two kprobes whose addresses are and in "func" function. The original code of "func" function is as follows: 0xffffffff816cb5e9 <+9>: push %r12 0xffffffff816cb5eb <+11>: xor %r12d,%r12d 0xffffffff816cb5ee <+14>: test %rdi,%rdi 0xffffffff816cb5f1 <+17>: setne %r12b 0xffffffff816cb5f5 <+21>: push %rbp 1.Register the kprobe for , assume that is kp1, corresponding optimized_kprobe is op1. After the optimization, "func" code changes to: 0xffffffff816cc079 <+9>: push %r12 0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000 0xffffffff816cc080 <+16>: incl 0xf(%rcx) 0xffffffff816cc083 <+19>: xchg %eax,%ebp 0xffffffff816cc084 <+20>: (bad) 0xffffffff816cc085 <+21>: push %rbp Now op1->flags == KPROBE_FLAG_OPTIMATED; 2. Register the kprobe for , assume that is kp2, corresponding optimized_kprobe is op2. register_kprobe(kp2) register_aggr_kprobe alloc_aggr_kprobe __prepare_optimized_kprobe arch_prepare_optimized_kprobe __recover_optprobed_insn // copy original bytes from kp1->optinsn.copied_insn, // jump address = 3. disable kp1: disable_kprobe(kp1) __disable_kprobe ... if (p == orig_p || aggr_kprobe_disabled(orig_p)) { ret = disarm_kprobe(orig_p, true) // add op1 in unoptimizing_list, not unoptimized orig_p->flags |= KPROBE_FLAG_DISABLED; // op1->flags == KPROBE_FLAG_OPTIMATED | KPROBE_FLAG_DISABLED ... 4. unregister kp2 __unregister_kprobe_top ... if (!kprobe_disabled(ap) && !kprobes_all_disarmed) { optimize_kprobe(op) ... if (arch_check_optimized_kprobe(op) < 0) // because op1 has KPROBE_FLAG_DISABLED, here not return return; p->kp.flags |= KPROBE_FLAG_OPTIMIZED; // now op2 has KPROBE_FLAG_OPTIMIZED } "func" code now is: 0xffffffff816cc079 <+9>: int3 0xffffffff816cc07a <+10>: push %rsp 0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000 0xffffffff816cc080 <+16>: incl 0xf(%rcx) 0xffffffff816cc083 <+19>: xchg %eax,%ebp 0xffffffff816cc084 <+20>: (bad) 0xffffffff816cc085 <+21>: push %rbp 5. if call "func", int3 handler call setup_detour_execution: if (p->flags & KPROBE_FLAG_OPTIMIZED) { ... regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX; ... } The code for the destination address is 0xffffffffa021072c: push %r12 0xffffffffa021072e: xor %r12d,%r12d 0xffffffffa0210731: jmp 0xffffffff816cb5ee However, is not a valid start instruction address. As a result, an error occurs. Link: https://lore.kernel.org/all/20230216034247.32348-3-yangjihong1@huawei.com/ Fixes: f66c0447cca1 ("kprobes: Set unoptimized flag after unoptimizing code") Signed-off-by: Yang Jihong Cc: stable@vger.kernel.org Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google)