From: Song Liu <songliubraving@fb.com>
Date: Fri, 5 Nov 2021 16:23:29 -0700
Subject: bpf: Introduce helper bpf_find_vma
Patch-mainline: v5.17-rc1
Git-commit: 7c7e3d31e7856a8260a254f8c71db416f7f9f5a1
References: jsc#PED-1368
In some profiler use cases, it is necessary to map an address to the
backing file, e.g., a shared library. bpf_find_vma helper provides a
flexible way to achieve this. bpf_find_vma maps an address of a task to
the vma (vm_area_struct) for this address, and feed the vma to an callback
BPF function. The callback function is necessary here, as we need to
ensure mmap_sem is unlocked.
It is necessary to lock mmap_sem for find_vma. To lock and unlock mmap_sem
safely when irqs are disable, we use the same mechanism as stackmap with
build_id. Specifically, when irqs are disabled, the unlocked is postponed
in an irq_work. Refactor stackmap.c so that the irq_work is shared among
bpf_find_vma and stackmap helpers.
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Hengqi Chen <hengqi.chen@gmail.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211105232330.1936330-2-songliubraving@fb.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
include/linux/bpf.h | 1
include/uapi/linux/bpf.h | 20 ++++++++++
kernel/bpf/btf.c | 5 ++
kernel/bpf/mmap_unlock_work.h | 65 +++++++++++++++++++++++++++++++++
kernel/bpf/stackmap.c | 80 +++--------------------------------------
kernel/bpf/task_iter.c | 76 +++++++++++++++++++++++++++++++++++---
kernel/bpf/verifier.c | 34 +++++++++++++++++
kernel/trace/bpf_trace.c | 2 +
tools/include/uapi/linux/bpf.h | 20 ++++++++++
9 files changed, 222 insertions(+), 81 deletions(-)
create mode 100644 kernel/bpf/mmap_unlock_work.h
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2154,6 +2154,7 @@ extern const struct bpf_func_proto bpf_b
extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
extern const struct bpf_func_proto bpf_kallsyms_lookup_name_proto;
+extern const struct bpf_func_proto bpf_find_vma_proto;
const struct bpf_func_proto *tracing_prog_func_proto(
enum bpf_func_id func_id, const struct bpf_prog *prog);
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4938,6 +4938,25 @@ union bpf_attr {
* **-ENOENT** if symbol is not found.
*
* **-EPERM** if caller does not have permission to obtain kernel address.
+ *
+ * long bpf_find_vma(struct task_struct *task, u64 addr, void *callback_fn, void *callback_ctx, u64 flags)
+ * Description
+ * Find vma of *task* that contains *addr*, call *callback_fn*
+ * function with *task*, *vma*, and *callback_ctx*.
+ * The *callback_fn* should be a static function and
+ * the *callback_ctx* should be a pointer to the stack.
+ * The *flags* is used to control certain aspects of the helper.
+ * Currently, the *flags* must be 0.
+ *
+ * The expected callback signature is
+ *
+ * long (\*callback_fn)(struct task_struct \*task, struct vm_area_struct \*vma, void \*callback_ctx);
+ *
+ * Return
+ * 0 on success.
+ * **-ENOENT** if *task->mm* is NULL, or no vma contains *addr*.
+ * **-EBUSY** if failed to try lock mmap_lock.
+ * **-EINVAL** for invalid **flags**.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5120,6 +5139,7 @@ union bpf_attr {
FN(trace_vprintk), \
FN(skc_to_unix_sock), \
FN(kallsyms_lookup_name), \
+ FN(find_vma), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6342,7 +6342,10 @@ const struct bpf_func_proto bpf_btf_find
.arg4_type = ARG_ANYTHING,
};
-BTF_ID_LIST_GLOBAL_SINGLE(btf_task_struct_ids, struct, task_struct)
+BTF_ID_LIST_GLOBAL(btf_task_struct_ids)
+BTF_ID(struct, task_struct)
+BTF_ID(struct, file)
+BTF_ID(struct, vm_area_struct)
/* BTF ID set registration API for modules */
--- /dev/null
+++ b/kernel/bpf/mmap_unlock_work.h
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2021 Facebook
+ */
+
+#ifndef __MMAP_UNLOCK_WORK_H__
+#define __MMAP_UNLOCK_WORK_H__
+#include <linux/irq_work.h>
+
+/* irq_work to run mmap_read_unlock() in irq_work */
+struct mmap_unlock_irq_work {
+ struct irq_work irq_work;
+ struct mm_struct *mm;
+};
+
+DECLARE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work);
+
+/*
+ * We cannot do mmap_read_unlock() when the irq is disabled, because of
+ * risk to deadlock with rq_lock. To look up vma when the irqs are
+ * disabled, we need to run mmap_read_unlock() in irq_work. We use a
+ * percpu variable to do the irq_work. If the irq_work is already used
+ * by another lookup, we fall over.
+ */
+static inline bool bpf_mmap_unlock_get_irq_work(struct mmap_unlock_irq_work **work_ptr)
+{
+ struct mmap_unlock_irq_work *work = NULL;
+ bool irq_work_busy = false;
+
+ if (irqs_disabled()) {
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ work = this_cpu_ptr(&mmap_unlock_work);
+ if (irq_work_is_busy(&work->irq_work)) {
+ /* cannot queue more up_read, fallback */
+ irq_work_busy = true;
+ }
+ } else {
+ /*
+ * PREEMPT_RT does not allow to trylock mmap sem in
+ * interrupt disabled context. Force the fallback code.
+ */
+ irq_work_busy = true;
+ }
+ }
+
+ *work_ptr = work;
+ return irq_work_busy;
+}
+
+static inline void bpf_mmap_unlock_mm(struct mmap_unlock_irq_work *work, struct mm_struct *mm)
+{
+ if (!work) {
+ mmap_read_unlock(mm);
+ } else {
+ work->mm = mm;
+
+ /* The lock will be released once we're out of interrupt
+ * context. Tell lockdep that we've released it now so
+ * it doesn't complain that we forgot to release it.
+ */
+ rwsem_release(&mm->mmap_lock.dep_map, _RET_IP_);
+ irq_work_queue(&work->irq_work);
+ }
+}
+
+#endif /* __MMAP_UNLOCK_WORK_H__ */
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -7,10 +7,10 @@
#include <linux/kernel.h>
#include <linux/stacktrace.h>
#include <linux/perf_event.h>
-#include <linux/irq_work.h>
#include <linux/btf_ids.h>
#include <linux/buildid.h>
#include "percpu_freelist.h"
+#include "mmap_unlock_work.h"
#define STACK_CREATE_FLAG_MASK \
(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \
@@ -31,25 +31,6 @@ struct bpf_stack_map {
struct stack_map_bucket *buckets[];
};
-/* irq_work to run up_read() for build_id lookup in nmi context */
-struct stack_map_irq_work {
- struct irq_work irq_work;
- struct mm_struct *mm;
-};
-
-static void do_up_read(struct irq_work *entry)
-{
- struct stack_map_irq_work *work;
-
- if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
- return;
-
- work = container_of(entry, struct stack_map_irq_work, irq_work);
- mmap_read_unlock_non_owner(work->mm);
-}
-
-static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
-
static inline bool stack_map_use_build_id(struct bpf_map *map)
{
return (map->map_flags & BPF_F_STACK_BUILD_ID);
@@ -149,35 +130,13 @@ static void stack_map_get_build_id_offse
u64 *ips, u32 trace_nr, bool user)
{
int i;
+ struct mmap_unlock_irq_work *work = NULL;
+ bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
struct vm_area_struct *vma;
- bool irq_work_busy = false;
- struct stack_map_irq_work *work = NULL;
-
- if (irqs_disabled()) {
- if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
- work = this_cpu_ptr(&up_read_work);
- if (irq_work_is_busy(&work->irq_work)) {
- /* cannot queue more up_read, fallback */
- irq_work_busy = true;
- }
- } else {
- /*
- * PREEMPT_RT does not allow to trylock mmap sem in
- * interrupt disabled context. Force the fallback code.
- */
- irq_work_busy = true;
- }
- }
- /*
- * We cannot do up_read() when the irq is disabled, because of
- * risk to deadlock with rq_lock. To do build_id lookup when the
- * irqs are disabled, we need to run up_read() in irq_work. We use
- * a percpu variable to do the irq_work. If the irq_work is
- * already used by another lookup, we fall back to report ips.
- *
- * Same fallback is used for kernel stack (!user) on a stackmap
- * with build_id.
+ /* If the irq_work is in use, fall back to report ips. Same
+ * fallback is used for kernel stack (!user) on a stackmap with
+ * build_id.
*/
if (!user || !current || !current->mm || irq_work_busy ||
!mmap_read_trylock(current->mm)) {
@@ -203,19 +162,7 @@ static void stack_map_get_build_id_offse
- vma->vm_start;
id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
}
-
- if (!work) {
- mmap_read_unlock(current->mm);
- } else {
- work->mm = current->mm;
-
- /* The lock will be released once we're out of interrupt
- * context. Tell lockdep that we've released it now so
- * it doesn't complain that we forgot to release it.
- */
- rwsem_release(¤t->mm->mmap_lock.dep_map, _RET_IP_);
- irq_work_queue(&work->irq_work);
- }
+ bpf_mmap_unlock_mm(work, current->mm);
}
static struct perf_callchain_entry *
@@ -719,16 +666,3 @@ const struct bpf_map_ops stack_trace_map
.map_btf_name = "bpf_stack_map",
.map_btf_id = &stack_trace_map_btf_id,
};
-
-static int __init stack_map_init(void)
-{
- int cpu;
- struct stack_map_irq_work *work;
-
- for_each_possible_cpu(cpu) {
- work = per_cpu_ptr(&up_read_work, cpu);
- init_irq_work(&work->irq_work, do_up_read);
- }
- return 0;
-}
-subsys_initcall(stack_map_init);
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -8,6 +8,7 @@
#include <linux/fdtable.h>
#include <linux/filter.h>
#include <linux/btf_ids.h>
+#include "mmap_unlock_work.h"
struct bpf_iter_seq_task_common {
struct pid_namespace *ns;
@@ -524,10 +525,6 @@ static const struct seq_operations task_
.show = task_vma_seq_show,
};
-BTF_ID_LIST(btf_task_file_ids)
-BTF_ID(struct, file)
-BTF_ID(struct, vm_area_struct)
-
static const struct bpf_iter_seq_info task_seq_info = {
.seq_ops = &task_seq_ops,
.init_seq_private = init_seq_pidns,
@@ -586,9 +583,74 @@ static struct bpf_iter_reg task_vma_reg_
.seq_info = &task_vma_seq_info,
};
+BPF_CALL_5(bpf_find_vma, struct task_struct *, task, u64, start,
+ bpf_callback_t, callback_fn, void *, callback_ctx, u64, flags)
+{
+ struct mmap_unlock_irq_work *work = NULL;
+ struct vm_area_struct *vma;
+ bool irq_work_busy = false;
+ struct mm_struct *mm;
+ int ret = -ENOENT;
+
+ if (flags)
+ return -EINVAL;
+
+ if (!task)
+ return -ENOENT;
+
+ mm = task->mm;
+ if (!mm)
+ return -ENOENT;
+
+ irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
+
+ if (irq_work_busy || !mmap_read_trylock(mm))
+ return -EBUSY;
+
+ vma = find_vma(mm, start);
+
+ if (vma && vma->vm_start <= start && vma->vm_end > start) {
+ callback_fn((u64)(long)task, (u64)(long)vma,
+ (u64)(long)callback_ctx, 0, 0);
+ ret = 0;
+ }
+ bpf_mmap_unlock_mm(work, mm);
+ return ret;
+}
+
+const struct bpf_func_proto bpf_find_vma_proto = {
+ .func = bpf_find_vma,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_btf_id = &btf_task_struct_ids[0],
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_PTR_TO_FUNC,
+ .arg4_type = ARG_PTR_TO_STACK_OR_NULL,
+ .arg5_type = ARG_ANYTHING,
+};
+
+DEFINE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work);
+
+static void do_mmap_read_unlock(struct irq_work *entry)
+{
+ struct mmap_unlock_irq_work *work;
+
+ if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
+ return;
+
+ work = container_of(entry, struct mmap_unlock_irq_work, irq_work);
+ mmap_read_unlock_non_owner(work->mm);
+}
+
static int __init task_iter_init(void)
{
- int ret;
+ struct mmap_unlock_irq_work *work;
+ int ret, cpu;
+
+ for_each_possible_cpu(cpu) {
+ work = per_cpu_ptr(&mmap_unlock_work, cpu);
+ init_irq_work(&work->irq_work, do_mmap_read_unlock);
+ }
task_reg_info.ctx_arg_info[0].btf_id = btf_task_struct_ids[0];
ret = bpf_iter_reg_target(&task_reg_info);
@@ -596,13 +658,13 @@ static int __init task_iter_init(void)
return ret;
task_file_reg_info.ctx_arg_info[0].btf_id = btf_task_struct_ids[0];
- task_file_reg_info.ctx_arg_info[1].btf_id = btf_task_file_ids[0];
+ task_file_reg_info.ctx_arg_info[1].btf_id = btf_task_struct_ids[1];
ret = bpf_iter_reg_target(&task_file_reg_info);
if (ret)
return ret;
task_vma_reg_info.ctx_arg_info[0].btf_id = btf_task_struct_ids[0];
- task_vma_reg_info.ctx_arg_info[1].btf_id = btf_task_file_ids[1];
+ task_vma_reg_info.ctx_arg_info[1].btf_id = btf_task_struct_ids[2];
return bpf_iter_reg_target(&task_vma_reg_info);
}
late_initcall(task_iter_init);
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6149,6 +6149,33 @@ static int set_timer_callback_state(stru
return 0;
}
+static int set_find_vma_callback_state(struct bpf_verifier_env *env,
+ struct bpf_func_state *caller,
+ struct bpf_func_state *callee,
+ int insn_idx)
+{
+ /* bpf_find_vma(struct task_struct *task, u64 addr,
+ * void *callback_fn, void *callback_ctx, u64 flags)
+ * (callback_fn)(struct task_struct *task,
+ * struct vm_area_struct *vma, void *callback_ctx);
+ */
+ callee->regs[BPF_REG_1] = caller->regs[BPF_REG_1];
+
+ callee->regs[BPF_REG_2].type = PTR_TO_BTF_ID;
+ __mark_reg_known_zero(&callee->regs[BPF_REG_2]);
+ callee->regs[BPF_REG_2].btf = btf_vmlinux;
+ callee->regs[BPF_REG_2].btf_id = btf_task_struct_ids[2];
+
+ /* pointer to stack or null */
+ callee->regs[BPF_REG_3] = caller->regs[BPF_REG_4];
+
+ /* unused */
+ __mark_reg_not_init(env, &callee->regs[BPF_REG_4]);
+ __mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
+ callee->in_callback_fn = true;
+ return 0;
+}
+
static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
{
struct bpf_verifier_state *state = env->cur_state;
@@ -6505,6 +6532,13 @@ static int check_helper_call(struct bpf_
if (err < 0)
return -EINVAL;
}
+
+ if (func_id == BPF_FUNC_find_vma) {
+ err = __check_func_call(env, insn, insn_idx_p, meta.subprogno,
+ set_find_vma_callback_state);
+ if (err < 0)
+ return -EINVAL;
+ }
if (func_id == BPF_FUNC_snprintf) {
err = check_bpf_snprintf_call(env, regs);
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1206,6 +1206,8 @@ bpf_tracing_func_proto(enum bpf_func_id
return &bpf_get_func_ip_proto_tracing;
case BPF_FUNC_get_branch_snapshot:
return &bpf_get_branch_snapshot_proto;
+ case BPF_FUNC_find_vma:
+ return &bpf_find_vma_proto;
case BPF_FUNC_trace_vprintk:
return bpf_get_trace_vprintk_proto();
default:
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4941,6 +4941,25 @@ union bpf_attr {
* **-ENOENT** if symbol is not found.
*
* **-EPERM** if caller does not have permission to obtain kernel address.
+ *
+ * long bpf_find_vma(struct task_struct *task, u64 addr, void *callback_fn, void *callback_ctx, u64 flags)
+ * Description
+ * Find vma of *task* that contains *addr*, call *callback_fn*
+ * function with *task*, *vma*, and *callback_ctx*.
+ * The *callback_fn* should be a static function and
+ * the *callback_ctx* should be a pointer to the stack.
+ * The *flags* is used to control certain aspects of the helper.
+ * Currently, the *flags* must be 0.
+ *
+ * The expected callback signature is
+ *
+ * long (\*callback_fn)(struct task_struct \*task, struct vm_area_struct \*vma, void \*callback_ctx);
+ *
+ * Return
+ * 0 on success.
+ * **-ENOENT** if *task->mm* is NULL, or no vma contains *addr*.
+ * **-EBUSY** if failed to try lock mmap_lock.
+ * **-EINVAL** for invalid **flags**.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5123,6 +5142,7 @@ union bpf_attr {
FN(trace_vprintk), \
FN(skc_to_unix_sock), \
FN(kallsyms_lookup_name), \
+ FN(find_vma), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper