Add helpers to work with new value being written to sysctl by user space. bpf_sysctl_get_new_value() copies value being written to sysctl into provided buffer. bpf_sysctl_set_new_value() overrides new value being written by user space with a one from provided buffer. Buffer should contain string representation of the value, similar to what can be seen in /proc/sys/. Both helpers can be used only on sysctl write. File position matters and can be managed by an interface that will be introduced separately. E.g. if user space calls sys_write to a file in /proc/sys/ at file position = X, where X > 0, then the value set by bpf_sysctl_set_new_value() will be written starting from X. If program wants to override whole value with specified buffer, file position has to be set to zero. Documentation for the new helpers is provided in bpf.h UAPI.
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| @@ -2541,6 +2541,40 @@ union bpf_attr { · 2540 unmodified lines | |||
| 2541 | * | 2541 | * |
| 2542 | * **-EINVAL** if current value was unavailable, e.g. because | 2542 | * **-EINVAL** if current value was unavailable, e.g. because |
| 2543 | * sysctl is uninitialized and read returns -EIO for it. | 2543 | * sysctl is uninitialized and read returns -EIO for it. |
| 2544 | * | ||
| 2545 | * int bpf_sysctl_get_new_value(struct bpf_sysctl *ctx, char *buf, size_t buf_len) | ||
| 2546 | * Description | ||
| 2547 | * Get new value being written by user space to sysctl (before | ||
| 2548 | * the actual write happens) and copy it as a string into | ||
| 2549 | * provided by program buffer *buf* of size *buf_len*. | ||
| 2550 | * | ||
| 2551 | * User space may write new value at file position > 0. | ||
| 2552 | * | ||
| 2553 | * The buffer is always NUL terminated, unless it's zero-sized. | ||
| 2554 | * Return | ||
| 2555 | * Number of character copied (not including the trailing NUL). | ||
| 2556 | * | ||
| 2557 | * **-E2BIG** if the buffer wasn't big enough (*buf* will contain | ||
| 2558 | * truncated name in this case). | ||
| 2559 | * | ||
| 2560 | * **-EINVAL** if sysctl is being read. | ||
| 2561 | * | ||
| 2562 | * int bpf_sysctl_set_new_value(struct bpf_sysctl *ctx, const char *buf, size_t buf_len) | ||
| 2563 | * Description | ||
| 2564 | * Override new value being written by user space to sysctl with | ||
| 2565 | * value provided by program in buffer *buf* of size *buf_len*. | ||
| 2566 | * | ||
| 2567 | * *buf* should contain a string in same form as provided by user | ||
| 2568 | * space on sysctl write. | ||
| 2569 | * | ||
| 2570 | * User space may write new value at file position > 0. To override | ||
| 2571 | * the whole sysctl value file position should be set to zero. | ||
| 2572 | * Return | ||
| 2573 | * 0 on success. | ||
| 2574 | * | ||
| 2575 | * **-E2BIG** if the *buf_len* is too big. | ||
| 2576 | * | ||
| 2577 | * **-EINVAL** if sysctl is being read. | ||
| 2544 | */ | 2578 | */ |
| 2545 | #define __BPF_FUNC_MAPPER(FN) \ | 2579 | #define __BPF_FUNC_MAPPER(FN) \ |
| 2546 | FN(unspec), \ | 2580 | FN(unspec), \ |
| @@ -2645,7 +2679,9 @@ union bpf_attr { · 98 unmodified lines | |||
| 2645 | FN(skc_lookup_tcp), \ | 2679 | FN(skc_lookup_tcp), \ |
| 2646 | FN(tcp_check_syncookie), \ | 2680 | FN(tcp_check_syncookie), \ |
| 2647 | FN(sysctl_get_name), \ | 2681 | FN(sysctl_get_name), \ |
| 2648 | FN(sysctl_get_current_value), | 2682 | FN(sysctl_get_current_value), \ |
| 2683 | FN(sysctl_get_new_value), \ | ||
| 2684 | FN(sysctl_set_new_value), | ||
| 2649 | 2685 | ||
| 2650 | /* integer value in 'imm' field of BPF_CALL instruction selects which helper | 2686 | /* integer value in 'imm' field of BPF_CALL instruction selects which helper |
| 2651 | * function eBPF program intends to call | 2687 | * function eBPF program intends to call |