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Diffstat (limited to 'Documentation/core-api/printk-formats.rst')
| -rw-r--r-- | Documentation/core-api/printk-formats.rst | 38 |
1 files changed, 28 insertions, 10 deletions
diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 8ebe46b1af39..8c9aba262b1e 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -2,6 +2,8 @@ How to get printk format specifiers right ========================================= +.. _printk-specifiers: + :Author: Randy Dunlap <rdunlap@infradead.org> :Author: Andrew Murray <amurray@mpc-data.co.uk> @@ -112,6 +114,20 @@ 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 --------------- @@ -468,21 +484,23 @@ Examples (OF):: %pfwf /ocp@68000000/i2c@48072000/camera@10/port/endpoint - Full name %pfwP endpoint - Node name -Time and date (struct rtc_time) -------------------------------- +Time and date +------------- :: - %ptR YYYY-mm-ddTHH:MM:SS - %ptRd YYYY-mm-dd - %ptRt HH:MM:SS - %ptR[dt][r] + %pt[RT] YYYY-mm-ddTHH:MM:SS + %pt[RT]d YYYY-mm-dd + %pt[RT]t HH:MM:SS + %pt[RT][dt][r] -For printing date and time as represented by struct rtc_time structure in -human readable format. +For printing date and time as represented by + R struct rtc_time structure + T time64_t type +in human readable format. -By default year will be incremented by 1900 and month by 1. Use %ptRr (raw) -to suppress this behaviour. +By default year will be incremented by 1900 and month by 1. +Use %pt[RT]r (raw) to suppress this behaviour. Passed by reference. |