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| author |   Alexei Starovoitov <ast@kernel.org> | 2020-05-15 08:10:36 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-05-15 08:15:07 -0700 |
| commit | 59df9f1fb4977b40cfad8d07b0d5baeb3a07e22c (patch) | |
| tree | bb520b4c58247f567a586756c98ab5840d21f8f8 /Documentation | |
| parent | selftests/bpf: Enforce returning 0 for fentry/fexit programs (diff) | |
| parent | bpf: Restrict bpf_trace_printk()'s %s usage and add %pks, %pus specifier (diff) | |
| download | linux-dev-59df9f1fb4977b40cfad8d07b0d5baeb3a07e22c.tar.xz linux-dev-59df9f1fb4977b40cfad8d07b0d5baeb3a07e22c.zip | |
Merge branch 'restrict-bpf_probe_read'
Daniel Borkmann says:
====================
Small set of fixes in order to restrict BPF helpers for tracing which are
broken on archs with overlapping address ranges as per discussion in [0].
I've targetted this for -bpf tree so they can be routed as fixes. Thanks!
v1 -> v2:
- switch to reusable %pks, %pus format specifiers (Yonghong)
- fixate %s on kernel_ds probing for archs with overlapping addr space
[0] https://lore.kernel.org/bpf/CAHk-=wjJKo0GVixYLmqPn-Q22WFu0xHaBSjKEo7e7Yw72y5SPQ@mail.gmail.com/T/
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/core-api/printk-formats.rst | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 8ebe46b1af39..5dfcc4592b23 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -112,6 +112,20 @@ used when printing stack backtraces. The specifier takes into consideration the effect of compiler optimisations which may occur when tail-calls are used and marked with the noreturn GCC attribute. +Probed Pointers from BPF / tracing +---------------------------------- + +:: + + %pks kernel string + %pus user string + +The ``k`` and ``u`` specifiers are used for printing prior probed memory from +either kernel memory (k) or user memory (u). The subsequent ``s`` specifier +results in printing a string. For direct use in regular vsnprintf() the (k) +and (u) annotation is ignored, however, when used out of BPF's bpf_trace_printk(), +for example, it reads the memory it is pointing to without faulting. + Kernel Pointers --------------- |