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

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