Commit 376040e4 authored by Kenny Yu's avatar Kenny Yu Committed by Alexei Starovoitov
Browse files

bpf: Add bpf_copy_from_user_task() helper 



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: default avatarKenny Yu <kennyyu@fb.com>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220124185403.468466-3-kennyyu@fb.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent b77fb25d

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -2243,6 +2243,7 @@ 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);

include/uapi/linux/bpf.h

+11 −0
Original line number Diff line number Diff line
@@ -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

kernel/bpf/helpers.c

+34 −0
Original line number Diff line number Diff line
@@ -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 (unlikely(flags))

		return -EINVAL;



	if (unlikely(!size))

		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)

kernel/trace/bpf_trace.c

+2 −0
Original line number Diff line number Diff line
@@ -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:

tools/include/uapi/linux/bpf.h

+11 −0
Original line number Diff line number Diff line
@@ -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