This adds a helper for bpf programs to read the memory of other
tasks.
As an example use case at Meta, we are using a bpf task iterator program
and this new helper to print C++ async stack traces for all threads of
a given process.
Signed-off-by: Kenny Yu <kennyyu@xxxxxx>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 11 +++++++++++
kernel/bpf/helpers.c | 34 ++++++++++++++++++++++++++++++++++
kernel/trace/bpf_trace.c | 2 ++
tools/include/uapi/linux/bpf.h | 11 +++++++++++
5 files changed, 59 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e8ec8d2f2fe3..4f13642c6a47 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2238,6 +2238,7 @@ extern const struct bpf_func_proto bpf_kallsyms_lookup_name_proto;
extern const struct bpf_func_proto bpf_find_vma_proto;
extern const struct bpf_func_proto bpf_loop_proto;
extern const struct bpf_func_proto bpf_strncmp_proto;
+extern const struct bpf_func_proto bpf_copy_from_user_task_proto;
const struct bpf_func_proto *tracing_prog_func_proto(
enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 16a7574292a5..4a2f7041ebae 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5076,6 +5076,16 @@ union bpf_attr {
* associated to *xdp_md*, at *offset*.
* Return
* 0 on success, or a negative error in case of failure.
+ *
+ * long bpf_copy_from_user_task(void *dst, u32 size, const void *user_ptr, struct task_struct *tsk, u64 flags)
+ * Description
+ * Read *size* bytes from user space address *user_ptr* in *tsk*'s
+ * address space, and stores the data in *dst*. *flags* is not
+ * used yet and is provided for future extensibility. This helper
+ * can only be used by sleepable programs.
+ * Return
+ * 0 on success, or a negative error in case of failure. On error
+ * *dst* buffer is zeroed out.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5269,6 +5279,7 @@ union bpf_attr {
FN(xdp_get_buff_len), \
FN(xdp_load_bytes), \
FN(xdp_store_bytes), \
+ FN(copy_from_user_task), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 01cfdf40c838..2688b0064289 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -16,6 +16,7 @@
#include <linux/pid_namespace.h>
#include <linux/proc_ns.h>
#include <linux/security.h>
+#include <linux/btf_ids.h>
#include "../../lib/kstrtox.h"
@@ -671,6 +672,39 @@ const struct bpf_func_proto bpf_copy_from_user_proto = {
.arg3_type = ARG_ANYTHING,
};
+BPF_CALL_5(bpf_copy_from_user_task, void *, dst, u32, size,
+ const void __user *, user_ptr, struct task_struct *, tsk, u64, flags)
+{
+ int ret;
+
+ /* flags is not used yet */
+ if (flags)
+ return -EINVAL;
+
+ if (size == 0)
+ return 0;
+
+ ret = access_process_vm(tsk, (unsigned long)user_ptr, dst, size, 0);
+ if (ret == size)
+ return 0;
+
+ memset(dst, 0, size);
+ /* Return -EFAULT for partial read */
+ return (ret < 0) ? ret : -EFAULT;
+}
+
+const struct bpf_func_proto bpf_copy_from_user_task_proto = {
+ .func = bpf_copy_from_user_task,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_UNINIT_MEM,
+ .arg2_type = ARG_CONST_SIZE_OR_ZERO,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_PTR_TO_BTF_ID,
+ .arg4_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
+ .arg5_type = ARG_ANYTHING
+};
+
BPF_CALL_2(bpf_per_cpu_ptr, const void *, ptr, u32, cpu)
{
if (cpu >= nr_cpu_ids)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 06a9e220069e..a2024ba32a20 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1235,6 +1235,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_get_task_stack_proto;
case BPF_FUNC_copy_from_user:
return prog->aux->sleepable ? &bpf_copy_from_user_proto : NULL;
+ case BPF_FUNC_copy_from_user_task:
+ return prog->aux->sleepable ? &bpf_copy_from_user_task_proto : NULL;
case BPF_FUNC_snprintf_btf:
return &bpf_snprintf_btf_proto;
case BPF_FUNC_per_cpu_ptr:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 16a7574292a5..4a2f7041ebae 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5076,6 +5076,16 @@ union bpf_attr {
* associated to *xdp_md*, at *offset*.
* Return
* 0 on success, or a negative error in case of failure.
+ *
+ * long bpf_copy_from_user_task(void *dst, u32 size, const void *user_ptr, struct task_struct *tsk, u64 flags)
+ * Description
+ * Read *size* bytes from user space address *user_ptr* in *tsk*'s
+ * address space, and stores the data in *dst*. *flags* is not
+ * used yet and is provided for future extensibility. This helper
+ * can only be used by sleepable programs.
+ * Return
+ * 0 on success, or a negative error in case of failure. On error
+ * *dst* buffer is zeroed out.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5269,6 +5279,7 @@ union bpf_attr {
FN(xdp_get_buff_len), \
FN(xdp_load_bytes), \
FN(xdp_store_bytes), \
+ FN(copy_from_user_task), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.30.2
