Merge branch 'bpf_probe_read_user'

Daniel Borkmann says:

====================
This set adds probe_read_{user,kernel}(), probe_read_str_{user,kernel}()
helpers, fixes probe_write_user() helper and selftests. For details please
see individual patches.

Thanks!

v2 -> v3:
  - noticed two more things that are fixed in here:
   - bpf uapi helper description used 'int size' for *_str helpers, now u32
   - we need TASK_SIZE_MAX + guard page on x86-64 in patch 2 otherwise
     we'll trigger the 00c42373d397 warn as well, so full range covered now
v1 -> v2:
  - standardize unsafe_ptr terminology in uapi header comment (Andrii)
  - probe_read_{user,kernel}[_str] naming scheme (Andrii)
  - use global data in last test case, remove relaxed_maps (Andrii)
  - add strict non-pagefault kernel read funcs to avoid warning in
    kernel probe read helpers (Alexei)
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 82 insertions, 40 deletions

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index a6bf19dabaab..df6809a76404 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -563,10 +563,13 @@ union bpf_attr {
  * 	Return
  * 		0 on success, or a negative error in case of failure.
  *
- * int bpf_probe_read(void *dst, u32 size, const void *src)
+ * int bpf_probe_read(void *dst, u32 size, const void *unsafe_ptr)
  * 	Description
  * 		For tracing programs, safely attempt to read *size* bytes from
- * 		address *src* and store the data in *dst*.
+ * 		kernel space address *unsafe_ptr* and store the data in *dst*.
+ *
+ * 		Generally, use bpf_probe_read_user() or bpf_probe_read_kernel()
+ * 		instead.
  * 	Return
  * 		0 on success, or a negative error in case of failure.
  *
@@ -1428,45 +1431,14 @@ union bpf_attr {
  * 	Return
  * 		0 on success, or a negative error in case of failure.
  *
- * int bpf_probe_read_str(void *dst, int size, const void *unsafe_ptr)
+ * int bpf_probe_read_str(void *dst, u32 size, const void *unsafe_ptr)
  * 	Description
- * 		Copy a NUL terminated string from an unsafe address
- * 		*unsafe_ptr* to *dst*. The *size* should include the
- * 		terminating NUL byte. In case the string length is smaller than
- * 		*size*, the target is not padded with further NUL bytes. If the
- * 		string length is larger than *size*, just *size*-1 bytes are
- * 		copied and the last byte is set to NUL.
- *
- * 		On success, the length of the copied string is returned. This
- * 		makes this helper useful in tracing programs for reading
- * 		strings, and more importantly to get its length at runtime. See
- * 		the following snippet:
- *
- * 		::
- *
- * 			SEC("kprobe/sys_open")
- * 			void bpf_sys_open(struct pt_regs *ctx)
- * 			{
- * 			        char buf[PATHLEN]; // PATHLEN is defined to 256
- * 			        int res = bpf_probe_read_str(buf, sizeof(buf),
- * 				                             ctx->di);
- *
- * 				// Consume buf, for example push it to
- * 				// userspace via bpf_perf_event_output(); we
- * 				// can use res (the string length) as event
- * 				// size, after checking its boundaries.
- * 			}
- *
- * 		In comparison, using **bpf_probe_read()** helper here instead
- * 		to read the string would require to estimate the length at
- * 		compile time, and would often result in copying more memory
- * 		than necessary.
+ * 		Copy a NUL terminated string from an unsafe kernel address
+ * 		*unsafe_ptr* to *dst*. See bpf_probe_read_kernel_str() for
+ * 		more details.
  *
- * 		Another useful use case is when parsing individual process
- * 		arguments or individual environment variables navigating
- * 		*current*\ **->mm->arg_start** and *current*\
- * 		**->mm->env_start**: using this helper and the return value,
- * 		one can quickly iterate at the right offset of the memory area.
+ * 		Generally, use bpf_probe_read_user_str() or bpf_probe_read_kernel_str()
+ * 		instead.
  * 	Return
  * 		On success, the strictly positive length of the string,
  * 		including the trailing NUL character. On error, a negative
@@ -2777,6 +2749,72 @@ union bpf_attr {
  * 		restricted to raw_tracepoint bpf programs.
  * 	Return
  * 		0 on success, or a negative error in case of failure.
+ *
+ * int bpf_probe_read_user(void *dst, u32 size, const void *unsafe_ptr)
+ * 	Description
+ * 		Safely attempt to read *size* bytes from user space address
+ * 		*unsafe_ptr* and store the data in *dst*.
+ * 	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
+ * int bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
+ * 	Description
+ * 		Safely attempt to read *size* bytes from kernel space address
+ * 		*unsafe_ptr* and store the data in *dst*.
+ * 	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
+ * int bpf_probe_read_user_str(void *dst, u32 size, const void *unsafe_ptr)
+ * 	Description
+ * 		Copy a NUL terminated string from an unsafe user address
+ * 		*unsafe_ptr* to *dst*. The *size* should include the
+ * 		terminating NUL byte. In case the string length is smaller than
+ * 		*size*, the target is not padded with further NUL bytes. If the
+ * 		string length is larger than *size*, just *size*-1 bytes are
+ * 		copied and the last byte is set to NUL.
+ *
+ * 		On success, the length of the copied string is returned. This
+ * 		makes this helper useful in tracing programs for reading
+ * 		strings, and more importantly to get its length at runtime. See
+ * 		the following snippet:
+ *
+ * 		::
+ *
+ * 			SEC("kprobe/sys_open")
+ * 			void bpf_sys_open(struct pt_regs *ctx)
+ * 			{
+ * 			        char buf[PATHLEN]; // PATHLEN is defined to 256
+ * 			        int res = bpf_probe_read_user_str(buf, sizeof(buf),
+ * 				                                  ctx->di);
+ *
+ * 				// Consume buf, for example push it to
+ * 				// userspace via bpf_perf_event_output(); we
+ * 				// can use res (the string length) as event
+ * 				// size, after checking its boundaries.
+ * 			}
+ *
+ * 		In comparison, using **bpf_probe_read_user()** helper here
+ * 		instead to read the string would require to estimate the length
+ * 		at compile time, and would often result in copying more memory
+ * 		than necessary.
+ *
+ * 		Another useful use case is when parsing individual process
+ * 		arguments or individual environment variables navigating
+ * 		*current*\ **->mm->arg_start** and *current*\
+ * 		**->mm->env_start**: using this helper and the return value,
+ * 		one can quickly iterate at the right offset of the memory area.
+ * 	Return
+ * 		On success, the strictly positive length of the string,
+ * 		including the trailing NUL character. On error, a negative
+ * 		value.
+ *
+ * int bpf_probe_read_kernel_str(void *dst, u32 size, const void *unsafe_ptr)
+ * 	Description
+ * 		Copy a NUL terminated string from an unsafe kernel address *unsafe_ptr*
+ * 		to *dst*. Same semantics as with bpf_probe_read_user_str() apply.
+ * 	Return
+ * 		On success, the strictly positive length of the string,	including
+ * 		the trailing NUL character. On error, a negative value.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -2890,7 +2928,11 @@ union bpf_attr {
 	FN(sk_storage_delete),		\
 	FN(send_signal),		\
 	FN(tcp_gen_syncookie),		\
-	FN(skb_output),
+	FN(skb_output),			\
+	FN(probe_read_user),		\
+	FN(probe_read_kernel),		\
+	FN(probe_read_user_str),	\
+	FN(probe_read_kernel_str),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call