diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt index 619cdffa5d44..65ea5915178b 100644 --- a/Documentation/printk-formats.txt +++ b/Documentation/printk-formats.txt @@ -1,5 +1,18 @@ -If variable is of Type, use printk format specifier: ---------------------------------------------------------- +========================================= +How to get printk format specifiers right +========================================= + +:Author: Randy Dunlap +:Author: Andrew Murray + + +Integer types +============= + +:: + + If variable is of Type, use printk format specifier: + ------------------------------------------------------------ int %d or %x unsigned int %u or %x long %ld or %lx @@ -13,25 +26,29 @@ If variable is of Type, use printk format specifier: s64 %lld or %llx u64 %llu or %llx -If is dependent on a config option for its size (e.g., sector_t, -blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a -format specifier of its largest possible type and explicitly cast to it. -Example: +If is dependent on a config option for its size (e.g., ``sector_t``, +``blkcnt_t``) or is architecture-dependent for its size (e.g., ``tcflag_t``), +use a format specifier of its largest possible type and explicitly cast to it. + +Example:: printk("test: sector number/total blocks: %llu/%llu\n", (unsigned long long)sector, (unsigned long long)blockcount); -Reminder: sizeof() result is of type size_t. +Reminder: ``sizeof()`` result is of type ``size_t``. -The kernel's printf does not support %n. For obvious reasons, floating -point formats (%e, %f, %g, %a) are also not recognized. Use of any +The kernel's printf does not support ``%n``. For obvious reasons, floating +point formats (``%e, %f, %g, %a``) are also not recognized. Use of any unsupported specifier or length qualifier results in a WARN and early return from vsnprintf. Raw pointer value SHOULD be printed with %p. The kernel supports the following extended format specifiers for pointer types: -Symbols/Function Pointers: +Symbols/Function Pointers +========================= + +:: %pF versatile_init+0x0/0x110 %pf versatile_init @@ -41,99 +58,122 @@ Symbols/Function Pointers: %ps versatile_init %pB prev_fn_of_versatile_init+0x88/0x88 - For printing symbols and function pointers. The 'S' and 's' specifiers - result in the symbol name with ('S') or without ('s') offsets. Where - this is used on a kernel without KALLSYMS - the symbol address is - printed instead. +For printing symbols and function pointers. The ``S`` and ``s`` specifiers +result in the symbol name with (``S``) or without (``s``) offsets. Where +this is used on a kernel without KALLSYMS - the symbol address is +printed instead. - The 'B' specifier results in the symbol name with offsets and should be - used when printing stack backtraces. The specifier takes into - consideration the effect of compiler optimisations which may occur - when tail-call's are used and marked with the noreturn GCC attribute. +The ``B`` specifier results in the symbol name with offsets and should be +used when printing stack backtraces. The specifier takes into +consideration the effect of compiler optimisations which may occur +when tail-call``s are used and marked with the noreturn GCC attribute. - On ia64, ppc64 and parisc64 architectures function pointers are - actually function descriptors which must first be resolved. The 'F' and - 'f' specifiers perform this resolution and then provide the same - functionality as the 'S' and 's' specifiers. +On ia64, ppc64 and parisc64 architectures function pointers are +actually function descriptors which must first be resolved. The ``F`` and +``f`` specifiers perform this resolution and then provide the same +functionality as the ``S`` and ``s`` specifiers. -Kernel Pointers: +Kernel Pointers +=============== + +:: %pK 0x01234567 or 0x0123456789abcdef - For printing kernel pointers which should be hidden from unprivileged - users. The behaviour of %pK depends on the kptr_restrict sysctl - see - Documentation/sysctl/kernel.txt for more details. +For printing kernel pointers which should be hidden from unprivileged +users. The behaviour of ``%pK`` depends on the ``kptr_restrict sysctl`` - see +Documentation/sysctl/kernel.txt for more details. -Struct Resources: +Struct Resources +================ + +:: %pr [mem 0x60000000-0x6fffffff flags 0x2200] or [mem 0x0000000060000000-0x000000006fffffff flags 0x2200] %pR [mem 0x60000000-0x6fffffff pref] or [mem 0x0000000060000000-0x000000006fffffff pref] - For printing struct resources. The 'R' and 'r' specifiers result in a - printed resource with ('R') or without ('r') a decoded flags member. - Passed by reference. +For printing struct resources. The ``R`` and ``r`` specifiers result in a +printed resource with (``R``) or without (``r``) a decoded flags member. +Passed by reference. -Physical addresses types phys_addr_t: +Physical addresses types ``phys_addr_t`` +======================================== + +:: %pa[p] 0x01234567 or 0x0123456789abcdef - For printing a phys_addr_t type (and its derivatives, such as - resource_size_t) which can vary based on build options, regardless of - the width of the CPU data path. Passed by reference. +For printing a ``phys_addr_t`` type (and its derivatives, such as +``resource_size_t``) which can vary based on build options, regardless of +the width of the CPU data path. Passed by reference. -DMA addresses types dma_addr_t: +DMA addresses types ``dma_addr_t`` +================================== + +:: %pad 0x01234567 or 0x0123456789abcdef - For printing a dma_addr_t type which can vary based on build options, - regardless of the width of the CPU data path. Passed by reference. +For printing a ``dma_addr_t`` type which can vary based on build options, +regardless of the width of the CPU data path. Passed by reference. -Raw buffer as an escaped string: +Raw buffer as an escaped string +=============================== + +:: %*pE[achnops] - For printing raw buffer as an escaped string. For the following buffer +For printing raw buffer as an escaped string. For the following buffer:: 1b 62 20 5c 43 07 22 90 0d 5d - few examples show how the conversion would be done (the result string - without surrounding quotes): +few examples show how the conversion would be done (the result string +without surrounding quotes):: %*pE "\eb \C\a"\220\r]" %*pEhp "\x1bb \C\x07"\x90\x0d]" %*pEa "\e\142\040\\\103\a\042\220\r\135" - The conversion rules are applied according to an optional combination - of flags (see string_escape_mem() kernel documentation for the - details): - a - ESCAPE_ANY - c - ESCAPE_SPECIAL - h - ESCAPE_HEX - n - ESCAPE_NULL - o - ESCAPE_OCTAL - p - ESCAPE_NP - s - ESCAPE_SPACE - By default ESCAPE_ANY_NP is used. +The conversion rules are applied according to an optional combination +of flags (see :c:func:`string_escape_mem` kernel documentation for the +details): - ESCAPE_ANY_NP is the sane choice for many cases, in particularly for - printing SSIDs. + - ``a`` - ESCAPE_ANY + - ``c`` - ESCAPE_SPECIAL + - ``h`` - ESCAPE_HEX + - ``n`` - ESCAPE_NULL + - ``o`` - ESCAPE_OCTAL + - ``p`` - ESCAPE_NP + - ``s`` - ESCAPE_SPACE - If field width is omitted the 1 byte only will be escaped. +By default ESCAPE_ANY_NP is used. -Raw buffer as a hex string: +ESCAPE_ANY_NP is the sane choice for many cases, in particularly for +printing SSIDs. + +If field width is omitted the 1 byte only will be escaped. + +Raw buffer as a hex string +========================== + +:: %*ph 00 01 02 ... 3f %*phC 00:01:02: ... :3f %*phD 00-01-02- ... -3f %*phN 000102 ... 3f - For printing a small buffers (up to 64 bytes long) as a hex string with - certain separator. For the larger buffers consider to use - print_hex_dump(). +For printing a small buffers (up to 64 bytes long) as a hex string with +certain separator. For the larger buffers consider to use +:c:func:`print_hex_dump`. -MAC/FDDI addresses: +MAC/FDDI addresses +================== + +:: %pM 00:01:02:03:04:05 %pMR 05:04:03:02:01:00 @@ -141,53 +181,62 @@ MAC/FDDI addresses: %pm 000102030405 %pmR 050403020100 - For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm' - specifiers result in a printed address with ('M') or without ('m') byte - separators. The default byte separator is the colon (':'). +For printing 6-byte MAC/FDDI addresses in hex notation. The ``M`` and ``m`` +specifiers result in a printed address with (``M``) or without (``m``) byte +separators. The default byte separator is the colon (``:``). - Where FDDI addresses are concerned the 'F' specifier can be used after - the 'M' specifier to use dash ('-') separators instead of the default - separator. +Where FDDI addresses are concerned the ``F`` specifier can be used after +the ``M`` specifier to use dash (``-``) separators instead of the default +separator. - For Bluetooth addresses the 'R' specifier shall be used after the 'M' - specifier to use reversed byte order suitable for visual interpretation - of Bluetooth addresses which are in the little endian order. +For Bluetooth addresses the ``R`` specifier shall be used after the ``M`` +specifier to use reversed byte order suitable for visual interpretation +of Bluetooth addresses which are in the little endian order. - Passed by reference. +Passed by reference. -IPv4 addresses: +IPv4 addresses +============== + +:: %pI4 1.2.3.4 %pi4 001.002.003.004 %p[Ii]4[hnbl] - For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4' - specifiers result in a printed address with ('i4') or without ('I4') - leading zeros. +For printing IPv4 dot-separated decimal addresses. The ``I4`` and ``i4`` +specifiers result in a printed address with (``i4``) or without (``I4``) +leading zeros. - The additional 'h', 'n', 'b', and 'l' specifiers are used to specify - host, network, big or little endian order addresses respectively. Where - no specifier is provided the default network/big endian order is used. +The additional ``h``, ``n``, ``b``, and ``l`` specifiers are used to specify +host, network, big or little endian order addresses respectively. Where +no specifier is provided the default network/big endian order is used. - Passed by reference. +Passed by reference. -IPv6 addresses: +IPv6 addresses +============== + +:: %pI6 0001:0002:0003:0004:0005:0006:0007:0008 %pi6 00010002000300040005000600070008 %pI6c 1:2:3:4:5:6:7:8 - For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6' - specifiers result in a printed address with ('I6') or without ('i6') - colon-separators. Leading zeros are always used. +For printing IPv6 network-order 16-bit hex addresses. The ``I6`` and ``i6`` +specifiers result in a printed address with (``I6``) or without (``i6``) +colon-separators. Leading zeros are always used. - The additional 'c' specifier can be used with the 'I' specifier to - print a compressed IPv6 address as described by - http://tools.ietf.org/html/rfc5952 +The additional ``c`` specifier can be used with the ``I`` specifier to +print a compressed IPv6 address as described by +http://tools.ietf.org/html/rfc5952 - Passed by reference. +Passed by reference. -IPv4/IPv6 addresses (generic, with port, flowinfo, scope): +IPv4/IPv6 addresses (generic, with port, flowinfo, scope) +========================================================= + +:: %pIS 1.2.3.4 or 0001:0002:0003:0004:0005:0006:0007:0008 %piS 001.002.003.004 or 00010002000300040005000600070008 @@ -195,87 +244,103 @@ IPv4/IPv6 addresses (generic, with port, flowinfo, scope): %pISpc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345 %p[Ii]S[pfschnbl] - For printing an IP address without the need to distinguish whether it's - of type AF_INET or AF_INET6, a pointer to a valid 'struct sockaddr', - specified through 'IS' or 'iS', can be passed to this format specifier. +For printing an IP address without the need to distinguish whether it``s +of type AF_INET or AF_INET6, a pointer to a valid ``struct sockaddr``, +specified through ``IS`` or ``iS``, can be passed to this format specifier. - The additional 'p', 'f', and 's' specifiers are used to specify port - (IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ':' prefix, - flowinfo a '/' and scope a '%', each followed by the actual value. +The additional ``p``, ``f``, and ``s`` specifiers are used to specify port +(IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ``:`` prefix, +flowinfo a ``/`` and scope a ``%``, each followed by the actual value. - In case of an IPv6 address the compressed IPv6 address as described by - http://tools.ietf.org/html/rfc5952 is being used if the additional - specifier 'c' is given. The IPv6 address is surrounded by '[', ']' in - case of additional specifiers 'p', 'f' or 's' as suggested by - https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07 +In case of an IPv6 address the compressed IPv6 address as described by +http://tools.ietf.org/html/rfc5952 is being used if the additional +specifier ``c`` is given. The IPv6 address is surrounded by ``[``, ``]`` in +case of additional specifiers ``p``, ``f`` or ``s`` as suggested by +https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07 - In case of IPv4 addresses, the additional 'h', 'n', 'b', and 'l' - specifiers can be used as well and are ignored in case of an IPv6 - address. +In case of IPv4 addresses, the additional ``h``, ``n``, ``b``, and ``l`` +specifiers can be used as well and are ignored in case of an IPv6 +address. - Passed by reference. +Passed by reference. - Further examples: +Further examples:: %pISfc 1.2.3.4 or [1:2:3:4:5:6:7:8]/123456789 %pISsc 1.2.3.4 or [1:2:3:4:5:6:7:8]%1234567890 %pISpfc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345/123456789 -UUID/GUID addresses: +UUID/GUID addresses +=================== + +:: %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F - For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L', - 'b' and 'B' specifiers are used to specify a little endian order in - lower ('l') or upper case ('L') hex characters - and big endian order - in lower ('b') or upper case ('B') hex characters. +For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L', +'b' and 'B' specifiers are used to specify a little endian order in +lower ('l') or upper case ('L') hex characters - and big endian order +in lower ('b') or upper case ('B') hex characters. - Where no additional specifiers are used the default big endian - order with lower case hex characters will be printed. +Where no additional specifiers are used the default big endian +order with lower case hex characters will be printed. - Passed by reference. +Passed by reference. -dentry names: +dentry names +============ + +:: %pd{,2,3,4} %pD{,2,3,4} - For printing dentry name; if we race with d_move(), the name might be - a mix of old and new ones, but it won't oops. %pd dentry is a safer - equivalent of %s dentry->d_name.name we used to use, %pd prints - n last components. %pD does the same thing for struct file. +For printing dentry name; if we race with :c:func:`d_move`, the name might be +a mix of old and new ones, but it won't oops. ``%pd`` dentry is a safer +equivalent of ``%s`` ``dentry->d_name.name`` we used to use, ``%pd`` prints +``n`` last components. ``%pD`` does the same thing for struct file. - Passed by reference. +Passed by reference. -block_device names: +block_device names +================== + +:: %pg sda, sda1 or loop0p1 - For printing name of block_device pointers. +For printing name of block_device pointers. -struct va_format: +struct va_format +================ + +:: %pV - For printing struct va_format structures. These contain a format string - and va_list as follows: +For printing struct va_format structures. These contain a format string +and va_list as follows:: struct va_format { const char *fmt; va_list *va; }; - Implements a "recursive vsnprintf". +Implements a "recursive vsnprintf". - Do not use this feature without some mechanism to verify the - correctness of the format string and va_list arguments. +Do not use this feature without some mechanism to verify the +correctness of the format string and va_list arguments. - Passed by reference. +Passed by reference. + +kobjects +======== + +:: -kobjects: %pO Base specifier for kobject based structs. Must be followed with @@ -311,61 +376,70 @@ kobjects: Passed by reference. -struct clk: + +struct clk +========== + +:: %pC pll1 %pCn pll1 %pCr 1560000000 - For printing struct clk structures. '%pC' and '%pCn' print the name - (Common Clock Framework) or address (legacy clock framework) of the - structure; '%pCr' prints the current clock rate. +For printing struct clk structures. ``%pC`` and ``%pCn`` print the name +(Common Clock Framework) or address (legacy clock framework) of the +structure; ``%pCr`` prints the current clock rate. - Passed by reference. +Passed by reference. -bitmap and its derivatives such as cpumask and nodemask: +bitmap and its derivatives such as cpumask and nodemask +======================================================= + +:: %*pb 0779 %*pbl 0,3-6,8-10 - For printing bitmap and its derivatives such as cpumask and nodemask, - %*pb output the bitmap with field width as the number of bits and %*pbl - output the bitmap as range list with field width as the number of bits. +For printing bitmap and its derivatives such as cpumask and nodemask, +``%*pb`` output the bitmap with field width as the number of bits and ``%*pbl`` +output the bitmap as range list with field width as the number of bits. - Passed by reference. +Passed by reference. -Flags bitfields such as page flags, gfp_flags: +Flags bitfields such as page flags, gfp_flags +============================================= + +:: %pGp referenced|uptodate|lru|active|private %pGg GFP_USER|GFP_DMA32|GFP_NOWARN %pGv read|exec|mayread|maywrite|mayexec|denywrite - For printing flags bitfields as a collection of symbolic constants that - would construct the value. The type of flags is given by the third - character. Currently supported are [p]age flags, [v]ma_flags (both - expect unsigned long *) and [g]fp_flags (expects gfp_t *). The flag - names and print order depends on the particular type. +For printing flags bitfields as a collection of symbolic constants that +would construct the value. The type of flags is given by the third +character. Currently supported are [p]age flags, [v]ma_flags (both +expect ``unsigned long *``) and [g]fp_flags (expects ``gfp_t *``). The flag +names and print order depends on the particular type. - Note that this format should not be used directly in TP_printk() part - of a tracepoint. Instead, use the show_*_flags() functions from - . +Note that this format should not be used directly in :c:func:`TP_printk()` part +of a tracepoint. Instead, use the ``show_*_flags()`` functions from +. - Passed by reference. +Passed by reference. -Network device features: +Network device features +======================= + +:: %pNF 0x000000000000c000 - For printing netdev_features_t. +For printing netdev_features_t. - Passed by reference. +Passed by reference. -If you add other %p extensions, please extend lib/test_printf.c with +If you add other ``%p`` extensions, please extend lib/test_printf.c with one or more test cases, if at all feasible. Thank you for your cooperation and attention. - - -By Randy Dunlap and -Andrew Murray