* [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() @ 2020-06-29 5:55 Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 1/4] perf: expose get/put_callchain_entry() Song Liu ` (4 more replies) 0 siblings, 5 replies; 11+ messages in thread From: Song Liu @ 2020-06-29 5:55 UTC (permalink / raw) To: bpf, netdev, linux-kernel Cc: peterz, ast, daniel, kernel-team, john.fastabend, kpsingh, Song Liu This set introduces a new helper bpf_get_task_stack(). The primary use case is to dump all /proc/*/stack to seq_file via bpf_iter__task. A few different approaches have been explored and compared: 1. A simple wrapper around stack_trace_save_tsk(), as v1 [1]. This approach introduces new syntax, which is different to existing helper bpf_get_stack(). Therefore, this is not ideal. 2. Extend get_perf_callchain() to support "task" as argument. This approach reuses most of bpf_get_stack(). However, extending get_perf_callchain() requires non-trivial changes to architecture specific code. Which is error prone. 3. Current (v2) approach, leverages most of existing bpf_get_stack(), and uses stack_trace_save_tsk() to handle architecture specific logic. [1] https://lore.kernel.org/netdev/20200623070802.2310018-1-songliubraving@fb.com/ Changes v3 => v4: 1. Simplify the selftests with bpf_iter.h. (Yonghong) 2. Add example output to commit log of 4/4. (Yonghong) Changes v2 => v3: 1. Rebase on top of bpf-next. (Yonghong) 2. Sanitize get_callchain_entry(). (Peter) 3. Use has_callchain_buf for bpf_get_task_stack. (Andrii) 4. Other small clean up. (Yonghong, Andrii). Changes v1 => v2: 1. Reuse most of bpf_get_stack() logic. (Andrii) 2. Fix unsigned long vs. u64 mismatch for 32-bit systems. (Yonghong) 3. Add %pB support in bpf_trace_printk(). (Daniel) 4. Fix buffer size to bytes. Song Liu (4): perf: expose get/put_callchain_entry() bpf: introduce helper bpf_get_task_stack() bpf: allow %pB in bpf_seq_printf() and bpf_trace_printk() selftests/bpf: add bpf_iter test with bpf_get_task_stack() include/linux/bpf.h | 1 + include/linux/perf_event.h | 2 + include/uapi/linux/bpf.h | 36 ++++++++- kernel/bpf/stackmap.c | 75 ++++++++++++++++++- kernel/bpf/verifier.c | 4 +- kernel/events/callchain.c | 13 ++-- kernel/trace/bpf_trace.c | 12 ++- scripts/bpf_helpers_doc.py | 2 + tools/include/uapi/linux/bpf.h | 36 ++++++++- .../selftests/bpf/prog_tests/bpf_iter.c | 17 +++++ .../selftests/bpf/progs/bpf_iter_task_stack.c | 37 +++++++++ 11 files changed, 220 insertions(+), 15 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c -- 2.24.1 ^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH v4 bpf-next 1/4] perf: expose get/put_callchain_entry() 2020-06-29 5:55 [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() Song Liu @ 2020-06-29 5:55 ` Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 2/4] bpf: introduce helper bpf_get_task_stack() Song Liu ` (3 subsequent siblings) 4 siblings, 0 replies; 11+ messages in thread From: Song Liu @ 2020-06-29 5:55 UTC (permalink / raw) To: bpf, netdev, linux-kernel Cc: peterz, ast, daniel, kernel-team, john.fastabend, kpsingh, Song Liu, Andrii Nakryiko Sanitize and expose get/put_callchain_entry(). This would be used by bpf stack map. Suggested-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Song Liu <songliubraving@fb.com> --- include/linux/perf_event.h | 2 ++ kernel/events/callchain.c | 13 ++++++------- 2 files changed, 8 insertions(+), 7 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index b4bb32082342c..00ab5efa38334 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1244,6 +1244,8 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, extern struct perf_callchain_entry *perf_callchain(struct perf_event *event, struct pt_regs *regs); extern int get_callchain_buffers(int max_stack); extern void put_callchain_buffers(void); +extern struct perf_callchain_entry *get_callchain_entry(int *rctx); +extern void put_callchain_entry(int rctx); extern int sysctl_perf_event_max_stack; extern int sysctl_perf_event_max_contexts_per_stack; diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index 334d48b16c36d..c6ce894e4ce94 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -149,7 +149,7 @@ void put_callchain_buffers(void) } } -static struct perf_callchain_entry *get_callchain_entry(int *rctx) +struct perf_callchain_entry *get_callchain_entry(int *rctx) { int cpu; struct callchain_cpus_entries *entries; @@ -159,8 +159,10 @@ static struct perf_callchain_entry *get_callchain_entry(int *rctx) return NULL; entries = rcu_dereference(callchain_cpus_entries); - if (!entries) + if (!entries) { + put_recursion_context(this_cpu_ptr(callchain_recursion), *rctx); return NULL; + } cpu = smp_processor_id(); @@ -168,7 +170,7 @@ static struct perf_callchain_entry *get_callchain_entry(int *rctx) (*rctx * perf_callchain_entry__sizeof())); } -static void +void put_callchain_entry(int rctx) { put_recursion_context(this_cpu_ptr(callchain_recursion), rctx); @@ -183,11 +185,8 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, int rctx; entry = get_callchain_entry(&rctx); - if (rctx == -1) - return NULL; - if (!entry) - goto exit_put; + return NULL; ctx.entry = entry; ctx.max_stack = max_stack; -- 2.24.1 ^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v4 bpf-next 2/4] bpf: introduce helper bpf_get_task_stack() 2020-06-29 5:55 [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 1/4] perf: expose get/put_callchain_entry() Song Liu @ 2020-06-29 5:55 ` Song Liu 2020-06-30 4:18 ` Alexei Starovoitov 2020-06-29 5:55 ` [PATCH v4 bpf-next 3/4] bpf: allow %pB in bpf_seq_printf() and bpf_trace_printk() Song Liu ` (2 subsequent siblings) 4 siblings, 1 reply; 11+ messages in thread From: Song Liu @ 2020-06-29 5:55 UTC (permalink / raw) To: bpf, netdev, linux-kernel Cc: peterz, ast, daniel, kernel-team, john.fastabend, kpsingh, Song Liu, Andrii Nakryiko Introduce helper bpf_get_task_stack(), which dumps stack trace of given task. This is different to bpf_get_stack(), which gets stack track of current task. One potential use case of bpf_get_task_stack() is to call it from bpf_iter__task and dump all /proc/<pid>/stack to a seq_file. bpf_get_task_stack() uses stack_trace_save_tsk() instead of get_perf_callchain() for kernel stack. The benefit of this choice is that stack_trace_save_tsk() doesn't require changes in arch/. The downside of using stack_trace_save_tsk() is that stack_trace_save_tsk() dumps the stack trace to unsigned long array. For 32-bit systems, we need to translate it to u64 array. Acked-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Song Liu <songliubraving@fb.com> --- include/linux/bpf.h | 1 + include/uapi/linux/bpf.h | 36 +++++++++++++++- kernel/bpf/stackmap.c | 75 ++++++++++++++++++++++++++++++++-- kernel/bpf/verifier.c | 4 +- kernel/trace/bpf_trace.c | 2 + scripts/bpf_helpers_doc.py | 2 + tools/include/uapi/linux/bpf.h | 36 +++++++++++++++- 7 files changed, 150 insertions(+), 6 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 3d2ade703a357..0cd7f6884c5cd 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1627,6 +1627,7 @@ extern const struct bpf_func_proto bpf_get_current_uid_gid_proto; extern const struct bpf_func_proto bpf_get_current_comm_proto; extern const struct bpf_func_proto bpf_get_stackid_proto; extern const struct bpf_func_proto bpf_get_stack_proto; +extern const struct bpf_func_proto bpf_get_task_stack_proto; extern const struct bpf_func_proto bpf_sock_map_update_proto; extern const struct bpf_func_proto bpf_sock_hash_update_proto; extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto; diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 0cb8ec9488168..54106ea667211 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3285,6 +3285,39 @@ union bpf_attr { * Dynamically cast a *sk* pointer to a *udp6_sock* pointer. * Return * *sk* if casting is valid, or NULL otherwise. + * + * long bpf_get_task_stack(struct task_struct *task, void *buf, u32 size, u64 flags) + * Description + * Return a user or a kernel stack in bpf program provided buffer. + * To achieve this, the helper needs *task*, which is a valid + * pointer to struct task_struct. To store the stacktrace, the + * bpf program provides *buf* with a nonnegative *size*. + * + * The last argument, *flags*, holds the number of stack frames to + * skip (from 0 to 255), masked with + * **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set + * the following flags: + * + * **BPF_F_USER_STACK** + * Collect a user space stack instead of a kernel stack. + * **BPF_F_USER_BUILD_ID** + * Collect buildid+offset instead of ips for user stack, + * only valid if **BPF_F_USER_STACK** is also specified. + * + * **bpf_get_task_stack**\ () can collect up to + * **PERF_MAX_STACK_DEPTH** both kernel and user frames, subject + * to sufficient large buffer size. Note that + * this limit can be controlled with the **sysctl** program, and + * that it should be manually increased in order to profile long + * user stacks (such as stacks for Java programs). To do so, use: + * + * :: + * + * # sysctl kernel.perf_event_max_stack=<new value> + * Return + * A non-negative value equal to or less than *size* on success, + * or a negative error in case of failure. + * */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -3427,7 +3460,8 @@ union bpf_attr { FN(skc_to_tcp_sock), \ FN(skc_to_tcp_timewait_sock), \ FN(skc_to_tcp_request_sock), \ - FN(skc_to_udp6_sock), + FN(skc_to_udp6_sock), \ + FN(get_task_stack), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 27dc9b1b08a52..0ba66b29ef227 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -348,6 +348,40 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, } } +static struct perf_callchain_entry * +get_callchain_entry_for_task(struct task_struct *task, u32 init_nr) +{ + struct perf_callchain_entry *entry; + int rctx; + + entry = get_callchain_entry(&rctx); + + if (!entry) + return NULL; + + entry->nr = init_nr + + stack_trace_save_tsk(task, (unsigned long *)(entry->ip + init_nr), + sysctl_perf_event_max_stack - init_nr, 0); + + /* stack_trace_save_tsk() works on unsigned long array, while + * perf_callchain_entry uses u64 array. For 32-bit systems, it is + * necessary to fix this mismatch. + */ + if (__BITS_PER_LONG != 64) { + unsigned long *from = (unsigned long *) entry->ip; + u64 *to = entry->ip; + int i; + + /* copy data from the end to avoid using extra buffer */ + for (i = entry->nr - 1; i >= (int)init_nr; i--) + to[i] = (u64)(from[i]); + } + + put_callchain_entry(rctx); + + return entry; +} + BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, u64, flags) { @@ -448,8 +482,8 @@ const struct bpf_func_proto bpf_get_stackid_proto = { .arg3_type = ARG_ANYTHING, }; -BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size, - u64, flags) +static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, + void *buf, u32 size, u64 flags) { u32 init_nr, trace_nr, copy_len, elem_size, num_elem; bool user_build_id = flags & BPF_F_USER_BUILD_ID; @@ -471,13 +505,22 @@ BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size, if (unlikely(size % elem_size)) goto clear; + /* cannot get valid user stack for task without user_mode regs */ + if (task && user && !user_mode(regs)) + goto err_fault; + num_elem = size / elem_size; if (sysctl_perf_event_max_stack < num_elem) init_nr = 0; else init_nr = sysctl_perf_event_max_stack - num_elem; + + if (kernel && task) + trace = get_callchain_entry_for_task(task, init_nr); + else trace = get_perf_callchain(regs, init_nr, kernel, user, - sysctl_perf_event_max_stack, false, false); + sysctl_perf_event_max_stack, + false, false); if (unlikely(!trace)) goto err_fault; @@ -505,6 +548,12 @@ BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size, return err; } +BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size, + u64, flags) +{ + return __bpf_get_stack(regs, NULL, buf, size, flags); +} + const struct bpf_func_proto bpf_get_stack_proto = { .func = bpf_get_stack, .gpl_only = true, @@ -515,6 +564,26 @@ const struct bpf_func_proto bpf_get_stack_proto = { .arg4_type = ARG_ANYTHING, }; +BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf, + u32, size, u64, flags) +{ + struct pt_regs *regs = task_pt_regs(task); + + return __bpf_get_stack(regs, task, buf, size, flags); +} + +static int bpf_get_task_stack_btf_ids[5]; +const struct bpf_func_proto bpf_get_task_stack_proto = { + .func = bpf_get_task_stack, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_BTF_ID, + .arg2_type = ARG_PTR_TO_UNINIT_MEM, + .arg3_type = ARG_CONST_SIZE_OR_ZERO, + .arg4_type = ARG_ANYTHING, + .btf_id = bpf_get_task_stack_btf_ids, +}; + /* Called from eBPF program */ static void *stack_map_lookup_elem(struct bpf_map *map, void *key) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7de98906ddf4a..b608185e1ffd5 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4864,7 +4864,9 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn if (err) return err; - if (func_id == BPF_FUNC_get_stack && !env->prog->has_callchain_buf) { + if ((func_id == BPF_FUNC_get_stack || + func_id == BPF_FUNC_get_task_stack) && + !env->prog->has_callchain_buf) { const char *err_str; #ifdef CONFIG_PERF_EVENTS diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 5d59dda5f6615..977ba3b6f6c64 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1137,6 +1137,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_ringbuf_query_proto; case BPF_FUNC_jiffies64: return &bpf_jiffies64_proto; + case BPF_FUNC_get_task_stack: + return &bpf_get_task_stack_proto; default: return NULL; } diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py index 6bab40ff442e8..dd12e3b18aae3 100755 --- a/scripts/bpf_helpers_doc.py +++ b/scripts/bpf_helpers_doc.py @@ -426,6 +426,7 @@ class PrinterHelpers(Printer): 'struct tcp_timewait_sock', 'struct tcp_request_sock', 'struct udp6_sock', + 'struct task_struct', 'struct __sk_buff', 'struct sk_msg_md', @@ -468,6 +469,7 @@ class PrinterHelpers(Printer): 'struct tcp_timewait_sock', 'struct tcp_request_sock', 'struct udp6_sock', + 'struct task_struct', } mapped_types = { 'u8': '__u8', diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 0cb8ec9488168..54106ea667211 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -3285,6 +3285,39 @@ union bpf_attr { * Dynamically cast a *sk* pointer to a *udp6_sock* pointer. * Return * *sk* if casting is valid, or NULL otherwise. + * + * long bpf_get_task_stack(struct task_struct *task, void *buf, u32 size, u64 flags) + * Description + * Return a user or a kernel stack in bpf program provided buffer. + * To achieve this, the helper needs *task*, which is a valid + * pointer to struct task_struct. To store the stacktrace, the + * bpf program provides *buf* with a nonnegative *size*. + * + * The last argument, *flags*, holds the number of stack frames to + * skip (from 0 to 255), masked with + * **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set + * the following flags: + * + * **BPF_F_USER_STACK** + * Collect a user space stack instead of a kernel stack. + * **BPF_F_USER_BUILD_ID** + * Collect buildid+offset instead of ips for user stack, + * only valid if **BPF_F_USER_STACK** is also specified. + * + * **bpf_get_task_stack**\ () can collect up to + * **PERF_MAX_STACK_DEPTH** both kernel and user frames, subject + * to sufficient large buffer size. Note that + * this limit can be controlled with the **sysctl** program, and + * that it should be manually increased in order to profile long + * user stacks (such as stacks for Java programs). To do so, use: + * + * :: + * + * # sysctl kernel.perf_event_max_stack=<new value> + * Return + * A non-negative value equal to or less than *size* on success, + * or a negative error in case of failure. + * */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -3427,7 +3460,8 @@ union bpf_attr { FN(skc_to_tcp_sock), \ FN(skc_to_tcp_timewait_sock), \ FN(skc_to_tcp_request_sock), \ - FN(skc_to_udp6_sock), + FN(skc_to_udp6_sock), \ + FN(get_task_stack), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call -- 2.24.1 ^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH v4 bpf-next 2/4] bpf: introduce helper bpf_get_task_stack() 2020-06-29 5:55 ` [PATCH v4 bpf-next 2/4] bpf: introduce helper bpf_get_task_stack() Song Liu @ 2020-06-30 4:18 ` Alexei Starovoitov 2020-06-30 6:12 ` Song Liu 0 siblings, 1 reply; 11+ messages in thread From: Alexei Starovoitov @ 2020-06-30 4:18 UTC (permalink / raw) To: Song Liu Cc: bpf, Network Development, LKML, Peter Zijlstra, Alexei Starovoitov, Daniel Borkmann, Kernel Team, John Fastabend, KP Singh, Andrii Nakryiko On Sun, Jun 28, 2020 at 10:58 PM Song Liu <songliubraving@fb.com> wrote: > > Introduce helper bpf_get_task_stack(), which dumps stack trace of given > task. This is different to bpf_get_stack(), which gets stack track of > current task. One potential use case of bpf_get_task_stack() is to call > it from bpf_iter__task and dump all /proc/<pid>/stack to a seq_file. > > bpf_get_task_stack() uses stack_trace_save_tsk() instead of > get_perf_callchain() for kernel stack. The benefit of this choice is that > stack_trace_save_tsk() doesn't require changes in arch/. The downside of > using stack_trace_save_tsk() is that stack_trace_save_tsk() dumps the > stack trace to unsigned long array. For 32-bit systems, we need to > translate it to u64 array. > > Acked-by: Andrii Nakryiko <andriin@fb.com> > Signed-off-by: Song Liu <songliubraving@fb.com> It doesn't apply: Applying: bpf: Introduce helper bpf_get_task_stack() Using index info to reconstruct a base tree... error: patch failed: kernel/bpf/stackmap.c:471 error: kernel/bpf/stackmap.c: patch does not apply error: Did you hand edit your patch? It does not apply to blobs recorded in its index. Patch failed at 0002 bpf: Introduce helper bpf_get_task_stack() ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v4 bpf-next 2/4] bpf: introduce helper bpf_get_task_stack() 2020-06-30 4:18 ` Alexei Starovoitov @ 2020-06-30 6:12 ` Song Liu 0 siblings, 0 replies; 11+ messages in thread From: Song Liu @ 2020-06-30 6:12 UTC (permalink / raw) To: Alexei Starovoitov Cc: bpf, Network Development, LKML, Peter Zijlstra, Alexei Starovoitov, Daniel Borkmann, Kernel Team, John Fastabend, KP Singh, Andrii Nakryiko > On Jun 29, 2020, at 9:18 PM, Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: > > On Sun, Jun 28, 2020 at 10:58 PM Song Liu <songliubraving@fb.com> wrote: >> >> Introduce helper bpf_get_task_stack(), which dumps stack trace of given >> task. This is different to bpf_get_stack(), which gets stack track of >> current task. One potential use case of bpf_get_task_stack() is to call >> it from bpf_iter__task and dump all /proc/<pid>/stack to a seq_file. >> >> bpf_get_task_stack() uses stack_trace_save_tsk() instead of >> get_perf_callchain() for kernel stack. The benefit of this choice is that >> stack_trace_save_tsk() doesn't require changes in arch/. The downside of >> using stack_trace_save_tsk() is that stack_trace_save_tsk() dumps the >> stack trace to unsigned long array. For 32-bit systems, we need to >> translate it to u64 array. >> >> Acked-by: Andrii Nakryiko <andriin@fb.com> >> Signed-off-by: Song Liu <songliubraving@fb.com> > > It doesn't apply: > Applying: bpf: Introduce helper bpf_get_task_stack() > Using index info to reconstruct a base tree... > error: patch failed: kernel/bpf/stackmap.c:471 > error: kernel/bpf/stackmap.c: patch does not apply > error: Did you hand edit your patch? > It does not apply to blobs recorded in its index. > Patch failed at 0002 bpf: Introduce helper bpf_get_task_stack() Hmm.. seems "git format-patch -b" (--ignore-space-change) breaks it: # without -b, works fine $ git format-patch HEAD~1 0001-bpf-introduce-helper-bpf_get_task_stack.patch $ git reset --hard HEAD~1 HEAD is now at c385fe4fbd7bc perf: expose get/put_callchain_entry() $ git am ./0001-bpf-introduce-helper-bpf_get_task_stack.patch Applying: bpf: introduce helper bpf_get_task_stack() # with -b, doesn't apply :( $ git format-patch -b HEAD~1 0001-bpf-introduce-helper-bpf_get_task_stack.patch $ git reset --hard HEAD~1 HEAD is now at c385fe4fbd7bc perf: expose get/put_callchain_entry() $ git am ./0001-bpf-introduce-helper-bpf_get_task_stack.patch Applying: bpf: introduce helper bpf_get_task_stack() error: patch failed: kernel/bpf/stackmap.c:471 error: kernel/bpf/stackmap.c: patch does not apply Patch failed at 0001 bpf: introduce helper bpf_get_task_stack() hint: Use 'git am --show-current-patch' to see the failed patch When you have resolved this problem, run "git am --continue". If you prefer to skip this patch, run "git am --skip" instead. To restore the original branch and stop patching, run "git am --abort". Let me see how to fix it... ^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH v4 bpf-next 3/4] bpf: allow %pB in bpf_seq_printf() and bpf_trace_printk() 2020-06-29 5:55 [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 1/4] perf: expose get/put_callchain_entry() Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 2/4] bpf: introduce helper bpf_get_task_stack() Song Liu @ 2020-06-29 5:55 ` Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack() Song Liu 2020-06-29 19:25 ` [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() Andrii Nakryiko 4 siblings, 0 replies; 11+ messages in thread From: Song Liu @ 2020-06-29 5:55 UTC (permalink / raw) To: bpf, netdev, linux-kernel Cc: peterz, ast, daniel, kernel-team, john.fastabend, kpsingh, Song Liu, Yonghong Song This makes it easy to dump stack trace in text. Acked-by: Yonghong Song <yhs@fb.com> Signed-off-by: Song Liu <songliubraving@fb.com> --- kernel/trace/bpf_trace.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 977ba3b6f6c64..1d874d8e4384b 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -376,7 +376,7 @@ static void bpf_trace_copy_string(char *buf, void *unsafe_ptr, char fmt_ptype, /* * Only limited trace_printk() conversion specifiers allowed: - * %d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %pks %pus %s + * %d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %pB %pks %pus %s */ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, u64, arg2, u64, arg3) @@ -420,6 +420,11 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, goto fmt_str; } + if (fmt[i + 1] == 'B') { + i++; + goto fmt_next; + } + /* disallow any further format extensions */ if (fmt[i + 1] != 0 && !isspace(fmt[i + 1]) && @@ -636,7 +641,8 @@ BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size, if (fmt[i] == 'p') { if (fmt[i + 1] == 0 || fmt[i + 1] == 'K' || - fmt[i + 1] == 'x') { + fmt[i + 1] == 'x' || + fmt[i + 1] == 'B') { /* just kernel pointers */ params[fmt_cnt] = args[fmt_cnt]; fmt_cnt++; -- 2.24.1 ^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v4 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack() 2020-06-29 5:55 [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() Song Liu ` (2 preceding siblings ...) 2020-06-29 5:55 ` [PATCH v4 bpf-next 3/4] bpf: allow %pB in bpf_seq_printf() and bpf_trace_printk() Song Liu @ 2020-06-29 5:55 ` Song Liu 2020-06-29 15:06 ` Yonghong Song 2020-06-29 19:25 ` [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() Andrii Nakryiko 4 siblings, 1 reply; 11+ messages in thread From: Song Liu @ 2020-06-29 5:55 UTC (permalink / raw) To: bpf, netdev, linux-kernel Cc: peterz, ast, daniel, kernel-team, john.fastabend, kpsingh, Song Liu The new test is similar to other bpf_iter tests. It dumps all /proc/<pid>/stack to a seq_file. Here is some example output: pid: 2873 num_entries: 3 [<0>] worker_thread+0xc6/0x380 [<0>] kthread+0x135/0x150 [<0>] ret_from_fork+0x22/0x30 pid: 2874 num_entries: 9 [<0>] __bpf_get_stack+0x15e/0x250 [<0>] bpf_prog_22a400774977bb30_dump_task_stack+0x4a/0xb3c [<0>] bpf_iter_run_prog+0x81/0x170 [<0>] __task_seq_show+0x58/0x80 [<0>] bpf_seq_read+0x1c3/0x3b0 [<0>] vfs_read+0x9e/0x170 [<0>] ksys_read+0xa7/0xe0 [<0>] do_syscall_64+0x4c/0xa0 [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Note: To print the output, it is necessary to modify the selftest. Signed-off-by: Song Liu <songliubraving@fb.com> --- .../selftests/bpf/prog_tests/bpf_iter.c | 17 +++++++++ .../selftests/bpf/progs/bpf_iter_task_stack.c | 37 +++++++++++++++++++ 2 files changed, 54 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c index 1e2e0fced6e81..fed42755416db 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c @@ -5,6 +5,7 @@ #include "bpf_iter_netlink.skel.h" #include "bpf_iter_bpf_map.skel.h" #include "bpf_iter_task.skel.h" +#include "bpf_iter_task_stack.skel.h" #include "bpf_iter_task_file.skel.h" #include "bpf_iter_tcp4.skel.h" #include "bpf_iter_tcp6.skel.h" @@ -110,6 +111,20 @@ static void test_task(void) bpf_iter_task__destroy(skel); } +static void test_task_stack(void) +{ + struct bpf_iter_task_stack *skel; + + skel = bpf_iter_task_stack__open_and_load(); + if (CHECK(!skel, "bpf_iter_task_stack__open_and_load", + "skeleton open_and_load failed\n")) + return; + + do_dummy_read(skel->progs.dump_task_stack); + + bpf_iter_task_stack__destroy(skel); +} + static void test_task_file(void) { struct bpf_iter_task_file *skel; @@ -452,6 +467,8 @@ void test_bpf_iter(void) test_bpf_map(); if (test__start_subtest("task")) test_task(); + if (test__start_subtest("task_stack")) + test_task_stack(); if (test__start_subtest("task_file")) test_task_file(); if (test__start_subtest("tcp4")) diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c new file mode 100644 index 0000000000000..e40d32a2ed93d --- /dev/null +++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c @@ -0,0 +1,37 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2020 Facebook */ +#include "bpf_iter.h" +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +char _license[] SEC("license") = "GPL"; + +#define MAX_STACK_TRACE_DEPTH 64 +unsigned long entries[MAX_STACK_TRACE_DEPTH]; +#define SIZE_OF_ULONG (sizeof(unsigned long)) + +SEC("iter/task") +int dump_task_stack(struct bpf_iter__task *ctx) +{ + struct seq_file *seq = ctx->meta->seq; + struct task_struct *task = ctx->task; + long i, retlen; + + if (task == (void *)0) + return 0; + + retlen = bpf_get_task_stack(task, entries, + MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, 0); + if (retlen < 0) + return 0; + + BPF_SEQ_PRINTF(seq, "pid: %8u num_entries: %8u\n", task->pid, + retlen / SIZE_OF_ULONG); + for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) { + if (retlen > i * SIZE_OF_ULONG) + BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]); + } + BPF_SEQ_PRINTF(seq, "\n"); + + return 0; +} -- 2.24.1 ^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH v4 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack() 2020-06-29 5:55 ` [PATCH v4 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack() Song Liu @ 2020-06-29 15:06 ` Yonghong Song 2020-06-29 16:56 ` Song Liu 0 siblings, 1 reply; 11+ messages in thread From: Yonghong Song @ 2020-06-29 15:06 UTC (permalink / raw) To: Song Liu, bpf, netdev, linux-kernel Cc: peterz, ast, daniel, kernel-team, john.fastabend, kpsingh On 6/28/20 10:55 PM, Song Liu wrote: > The new test is similar to other bpf_iter tests. It dumps all > /proc/<pid>/stack to a seq_file. Here is some example output: > > pid: 2873 num_entries: 3 > [<0>] worker_thread+0xc6/0x380 > [<0>] kthread+0x135/0x150 > [<0>] ret_from_fork+0x22/0x30 > > pid: 2874 num_entries: 9 > [<0>] __bpf_get_stack+0x15e/0x250 > [<0>] bpf_prog_22a400774977bb30_dump_task_stack+0x4a/0xb3c > [<0>] bpf_iter_run_prog+0x81/0x170 > [<0>] __task_seq_show+0x58/0x80 > [<0>] bpf_seq_read+0x1c3/0x3b0 > [<0>] vfs_read+0x9e/0x170 > [<0>] ksys_read+0xa7/0xe0 > [<0>] do_syscall_64+0x4c/0xa0 > [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Note: To print the output, it is necessary to modify the selftest. I do not know what this sentence means. It seems confusing and probably not needed. > > Signed-off-by: Song Liu <songliubraving@fb.com> Acked-by: Yonghong Song <yhs@fb.com> > --- > .../selftests/bpf/prog_tests/bpf_iter.c | 17 +++++++++ > .../selftests/bpf/progs/bpf_iter_task_stack.c | 37 +++++++++++++++++++ > 2 files changed, 54 insertions(+) > create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c > index 1e2e0fced6e81..fed42755416db 100644 > --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c > +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c > @@ -5,6 +5,7 @@ > #include "bpf_iter_netlink.skel.h" > #include "bpf_iter_bpf_map.skel.h" > #include "bpf_iter_task.skel.h" > +#include "bpf_iter_task_stack.skel.h" > #include "bpf_iter_task_file.skel.h" > #include "bpf_iter_tcp4.skel.h" > #include "bpf_iter_tcp6.skel.h" > @@ -110,6 +111,20 @@ static void test_task(void) > bpf_iter_task__destroy(skel); > } > > +static void test_task_stack(void) > +{ > + struct bpf_iter_task_stack *skel; > + > + skel = bpf_iter_task_stack__open_and_load(); > + if (CHECK(!skel, "bpf_iter_task_stack__open_and_load", > + "skeleton open_and_load failed\n")) > + return; > + > + do_dummy_read(skel->progs.dump_task_stack); > + > + bpf_iter_task_stack__destroy(skel); > +} > + > static void test_task_file(void) > { > struct bpf_iter_task_file *skel; > @@ -452,6 +467,8 @@ void test_bpf_iter(void) > test_bpf_map(); > if (test__start_subtest("task")) > test_task(); > + if (test__start_subtest("task_stack")) > + test_task_stack(); > if (test__start_subtest("task_file")) > test_task_file(); > if (test__start_subtest("tcp4")) > diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > new file mode 100644 > index 0000000000000..e40d32a2ed93d > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > @@ -0,0 +1,37 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2020 Facebook */ > +#include "bpf_iter.h" > +#include <bpf/bpf_helpers.h> > +#include <bpf/bpf_tracing.h> > + > +char _license[] SEC("license") = "GPL"; > + > +#define MAX_STACK_TRACE_DEPTH 64 > +unsigned long entries[MAX_STACK_TRACE_DEPTH]; > +#define SIZE_OF_ULONG (sizeof(unsigned long)) > + > +SEC("iter/task") > +int dump_task_stack(struct bpf_iter__task *ctx) > +{ > + struct seq_file *seq = ctx->meta->seq; > + struct task_struct *task = ctx->task; > + long i, retlen; > + > + if (task == (void *)0) > + return 0; > + > + retlen = bpf_get_task_stack(task, entries, > + MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, 0); > + if (retlen < 0) > + return 0; > + > + BPF_SEQ_PRINTF(seq, "pid: %8u num_entries: %8u\n", task->pid, > + retlen / SIZE_OF_ULONG); > + for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) { > + if (retlen > i * SIZE_OF_ULONG) > + BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]); > + } > + BPF_SEQ_PRINTF(seq, "\n"); > + > + return 0; > +} > ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v4 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack() 2020-06-29 15:06 ` Yonghong Song @ 2020-06-29 16:56 ` Song Liu 2020-06-29 18:22 ` Yonghong Song 0 siblings, 1 reply; 11+ messages in thread From: Song Liu @ 2020-06-29 16:56 UTC (permalink / raw) To: Yonghong Song Cc: bpf, Networking, open list, Peter Zijlstra, Alexei Starovoitov, Daniel Borkmann, Kernel Team, john.fastabend, kpsingh > On Jun 29, 2020, at 8:06 AM, Yonghong Song <yhs@fb.com> wrote: > > > > On 6/28/20 10:55 PM, Song Liu wrote: >> The new test is similar to other bpf_iter tests. It dumps all >> /proc/<pid>/stack to a seq_file. Here is some example output: >> pid: 2873 num_entries: 3 >> [<0>] worker_thread+0xc6/0x380 >> [<0>] kthread+0x135/0x150 >> [<0>] ret_from_fork+0x22/0x30 >> pid: 2874 num_entries: 9 >> [<0>] __bpf_get_stack+0x15e/0x250 >> [<0>] bpf_prog_22a400774977bb30_dump_task_stack+0x4a/0xb3c >> [<0>] bpf_iter_run_prog+0x81/0x170 >> [<0>] __task_seq_show+0x58/0x80 >> [<0>] bpf_seq_read+0x1c3/0x3b0 >> [<0>] vfs_read+0x9e/0x170 >> [<0>] ksys_read+0xa7/0xe0 >> [<0>] do_syscall_64+0x4c/0xa0 >> [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> Note: To print the output, it is necessary to modify the selftest. > > I do not know what this sentence means. It seems confusing > and probably not needed. It means current do_dummy_read() doesn't check/print the contents of the seq_file: /* not check contents, but ensure read() ends without error */ while ((len = read(iter_fd, buf, sizeof(buf))) > 0) ; > >> Signed-off-by: Song Liu <songliubraving@fb.com> > > Acked-by: Yonghong Song <yhs@fb.com> Thanks! [...] ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v4 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack() 2020-06-29 16:56 ` Song Liu @ 2020-06-29 18:22 ` Yonghong Song 0 siblings, 0 replies; 11+ messages in thread From: Yonghong Song @ 2020-06-29 18:22 UTC (permalink / raw) To: Song Liu Cc: bpf, Networking, open list, Peter Zijlstra, Alexei Starovoitov, Daniel Borkmann, Kernel Team, john.fastabend, kpsingh On 6/29/20 9:56 AM, Song Liu wrote: > > >> On Jun 29, 2020, at 8:06 AM, Yonghong Song <yhs@fb.com> wrote: >> >> >> >> On 6/28/20 10:55 PM, Song Liu wrote: >>> The new test is similar to other bpf_iter tests. It dumps all >>> /proc/<pid>/stack to a seq_file. Here is some example output: >>> pid: 2873 num_entries: 3 >>> [<0>] worker_thread+0xc6/0x380 >>> [<0>] kthread+0x135/0x150 >>> [<0>] ret_from_fork+0x22/0x30 >>> pid: 2874 num_entries: 9 >>> [<0>] __bpf_get_stack+0x15e/0x250 >>> [<0>] bpf_prog_22a400774977bb30_dump_task_stack+0x4a/0xb3c >>> [<0>] bpf_iter_run_prog+0x81/0x170 >>> [<0>] __task_seq_show+0x58/0x80 >>> [<0>] bpf_seq_read+0x1c3/0x3b0 >>> [<0>] vfs_read+0x9e/0x170 >>> [<0>] ksys_read+0xa7/0xe0 >>> [<0>] do_syscall_64+0x4c/0xa0 >>> [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 >>> Note: To print the output, it is necessary to modify the selftest. >> >> I do not know what this sentence means. It seems confusing >> and probably not needed. > > It means current do_dummy_read() doesn't check/print the contents of the > seq_file: > > /* not check contents, but ensure read() ends without error */ > while ((len = read(iter_fd, buf, sizeof(buf))) > 0) > ; I see. Thanks. It could be great if the commit message is more explicit about what 'modify' is. >> >>> Signed-off-by: Song Liu <songliubraving@fb.com> >> >> Acked-by: Yonghong Song <yhs@fb.com> > > Thanks! > > [...] > ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() 2020-06-29 5:55 [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() Song Liu ` (3 preceding siblings ...) 2020-06-29 5:55 ` [PATCH v4 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack() Song Liu @ 2020-06-29 19:25 ` Andrii Nakryiko 4 siblings, 0 replies; 11+ messages in thread From: Andrii Nakryiko @ 2020-06-29 19:25 UTC (permalink / raw) To: Song Liu Cc: bpf, Networking, open list, Peter Ziljstra, Alexei Starovoitov, Daniel Borkmann, Kernel Team, john fastabend, KP Singh On Mon, Jun 29, 2020 at 11:54 AM Song Liu <songliubraving@fb.com> wrote: > > This set introduces a new helper bpf_get_task_stack(). The primary use case > is to dump all /proc/*/stack to seq_file via bpf_iter__task. > > A few different approaches have been explored and compared: > > 1. A simple wrapper around stack_trace_save_tsk(), as v1 [1]. > > This approach introduces new syntax, which is different to existing > helper bpf_get_stack(). Therefore, this is not ideal. > > 2. Extend get_perf_callchain() to support "task" as argument. > > This approach reuses most of bpf_get_stack(). However, extending > get_perf_callchain() requires non-trivial changes to architecture > specific code. Which is error prone. > > 3. Current (v2) approach, leverages most of existing bpf_get_stack(), and > uses stack_trace_save_tsk() to handle architecture specific logic. > > [1] https://lore.kernel.org/netdev/20200623070802.2310018-1-songliubraving@fb.com/ > > Changes v3 => v4: > 1. Simplify the selftests with bpf_iter.h. (Yonghong) > 2. Add example output to commit log of 4/4. (Yonghong) > > Changes v2 => v3: > 1. Rebase on top of bpf-next. (Yonghong) > 2. Sanitize get_callchain_entry(). (Peter) > 3. Use has_callchain_buf for bpf_get_task_stack. (Andrii) > 4. Other small clean up. (Yonghong, Andrii). > > Changes v1 => v2: > 1. Reuse most of bpf_get_stack() logic. (Andrii) > 2. Fix unsigned long vs. u64 mismatch for 32-bit systems. (Yonghong) > 3. Add %pB support in bpf_trace_printk(). (Daniel) > 4. Fix buffer size to bytes. > > Song Liu (4): > perf: expose get/put_callchain_entry() > bpf: introduce helper bpf_get_task_stack() > bpf: allow %pB in bpf_seq_printf() and bpf_trace_printk() > selftests/bpf: add bpf_iter test with bpf_get_task_stack() > > include/linux/bpf.h | 1 + > include/linux/perf_event.h | 2 + > include/uapi/linux/bpf.h | 36 ++++++++- > kernel/bpf/stackmap.c | 75 ++++++++++++++++++- > kernel/bpf/verifier.c | 4 +- > kernel/events/callchain.c | 13 ++-- > kernel/trace/bpf_trace.c | 12 ++- > scripts/bpf_helpers_doc.py | 2 + > tools/include/uapi/linux/bpf.h | 36 ++++++++- > .../selftests/bpf/prog_tests/bpf_iter.c | 17 +++++ > .../selftests/bpf/progs/bpf_iter_task_stack.c | 37 +++++++++ > 11 files changed, 220 insertions(+), 15 deletions(-) > create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > > -- > 2.24.1 Thanks for working on this! This will enable a whole new set of tools and applications. Acked-by: Andrii Nakryiko <andriin@fb.com> ^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2020-06-30 6:13 UTC | newest] Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-06-29 5:55 [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 1/4] perf: expose get/put_callchain_entry() Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 2/4] bpf: introduce helper bpf_get_task_stack() Song Liu 2020-06-30 4:18 ` Alexei Starovoitov 2020-06-30 6:12 ` Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 3/4] bpf: allow %pB in bpf_seq_printf() and bpf_trace_printk() Song Liu 2020-06-29 5:55 ` [PATCH v4 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack() Song Liu 2020-06-29 15:06 ` Yonghong Song 2020-06-29 16:56 ` Song Liu 2020-06-29 18:22 ` Yonghong Song 2020-06-29 19:25 ` [PATCH v4 bpf-next 0/4] bpf: introduce bpf_get_task_stack() Andrii Nakryiko
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