From eb0385a00804004b7dda37aa83645987bea71d77 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Tue, 6 Feb 2024 11:29:23 +0000 Subject: [PATCH 1/2] libstapsdt: support system-wide probing By adding a USDT probe for stapsdt-created probe firings, we can enable tools and tracers that understand USDT but do not support tracing in the dynamically-created shared library, allowing them to catch dynamic probe firings. For example, using libbpf, we could write a BPF program as follows: SEC("usdt//usr/lib/libstapsdt.so:stapsdt:probe") int BPF_USDT(args, const char *provider, const char *probename, const char *str, int val) { __bpf_printk("%s/%s fired\n", provider, probename); __bpf_printk("got %s, %d args\n", str, val); return 0; } When attached to the stapsdt:probe in /usr/lib/libstapsdt.so as above, we can trace events system-wide. For example, with the above BPF program attached - and running the example.py from python stapsdt, we see: $ cat /sys/kernel/debug/tracing/trace_pipe python3-496195 [003] ...11 345760.365976: bpf_trace_printk: pythonapp/firstProbe fired python3-496195 [003] ...11 345760.365979: bpf_trace_printk: got My little probe, 42 args And we will see firings across all processes that utilize libstapsdt. Is-enabled support is added via a semaphore for the stapsdt probe - if the semaphore has a value > 0, it is being traced and all probes should be considered enabled. Signed-off-by: Alan Maguire --- Makefile | 1 + src/libstapsdt.c | 12 ++ src/sdt-config.h | 6 + src/sdt.h | 513 ++++++++++++++++++++++++++++++++++++++++++++ src/stapsdt-probe.c | 41 ++++ src/stapsdt-probe.h | 5 + 6 files changed, 578 insertions(+) create mode 100644 src/sdt-config.h create mode 100644 src/sdt.h create mode 100644 src/stapsdt-probe.c create mode 100644 src/stapsdt-probe.h diff --git a/Makefile b/Makefile index c9d81e2..4958a6e 100644 --- a/Makefile +++ b/Makefile @@ -19,6 +19,7 @@ install: mkdir -p $(DESTDIR)$(PREFIX)/include cp out/$(SONAME) $(DESTDIR)$(PREFIX)/lib/$(SONAME) cp src/libstapsdt.h $(DESTDIR)$(PREFIX)/include/ + rm -f $(DESTDIR)$(PREFIX)/lib/$(SOLINK) ln -s $(DESTDIR)$(PREFIX)/lib/$(SONAME) $(DESTDIR)$(PREFIX)/lib/$(SOLINK) uninstall: diff --git a/src/libstapsdt.c b/src/libstapsdt.c index 4cff164..27398bc 100644 --- a/src/libstapsdt.c +++ b/src/libstapsdt.c @@ -17,6 +17,7 @@ #include "shared-lib.h" #include "util.h" #include "libstapsdt.h" +#include "stapsdt-probe.h" #include "errors.h" #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0) @@ -227,6 +228,12 @@ void probeFire(SDTProbe_t *probe, ...) { arg[i] = va_arg(vl, uint64_t); } + /* fire static probe for libstapsdt signifying a dynamic probe has + * fired; tracers can attach to libstapsdt to see all dynamic probe + * firings system-wide. + */ + stapsdtProbeFire(probe, arg); + switch(probe->argCount) { case 0: ((void (*)())probe->_fire) (); @@ -259,6 +266,11 @@ int probeIsEnabled(SDTProbe_t *probe) { if(probe->_fire == NULL) { return 0; } + /* tracers can attach to stapsdt/probe to see probe firings across + * libstapsdt. + */ + if (stapsdtProbeIsEnabled(probe)) + return 1; if(((*(char *)probe->_fire) & 0x90) == 0x90) { return 0; } diff --git a/src/sdt-config.h b/src/sdt-config.h new file mode 100644 index 0000000..733045a --- /dev/null +++ b/src/sdt-config.h @@ -0,0 +1,6 @@ +/* includes/sys/sdt-config.h. Generated from sdt-config.h.in by configure. + + This file just defines _SDT_ASM_SECTION_AUTOGROUP_SUPPORT to 0 or 1 to + indicate whether the assembler supports "?" in .pushsection directives. */ + +#define _SDT_ASM_SECTION_AUTOGROUP_SUPPORT 1 diff --git a/src/sdt.h b/src/sdt.h new file mode 100644 index 0000000..ca0162b --- /dev/null +++ b/src/sdt.h @@ -0,0 +1,513 @@ +/* - Systemtap static probe definition macros. + + This file is dedicated to the public domain, pursuant to CC0 + (https://creativecommons.org/publicdomain/zero/1.0/) +*/ + +#ifndef _SYS_SDT_H +#define _SYS_SDT_H 1 + +/* + This file defines a family of macros + + STAP_PROBEn(op1, ..., opn) + + that emit a nop into the instruction stream, and some data into an auxiliary + note section. The data in the note section describes the operands, in terms + of size and location. Each location is encoded as assembler operand string. + Consumer tools such as gdb or systemtap insert breakpoints on top of + the nop, and decode the location operand-strings, like an assembler, + to find the values being passed. + + The operand strings are selected by the compiler for each operand. + They are constrained by gcc inline-assembler codes. The default is: + + #define STAP_SDT_ARG_CONSTRAINT nor + + This is a good default if the operands tend to be integral and + moderate in number (smaller than number of registers). In other + cases, the compiler may report "'asm' requires impossible reload" or + similar. In this case, consider simplifying the macro call (fewer + and simpler operands), reduce optimization, or override the default + constraints string via: + + #define STAP_SDT_ARG_CONSTRAINT g + #include + + See also: + https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation + https://gcc.gnu.org/onlinedocs/gcc/Constraints.html + */ + + + +#ifdef __ASSEMBLER__ +# define _SDT_PROBE(provider, name, n, arglist) \ + _SDT_ASM_BODY(provider, name, _SDT_ASM_SUBSTR_1, (_SDT_DEPAREN_##n arglist)) \ + _SDT_ASM_BASE +# define _SDT_ASM_1(x) x; +# define _SDT_ASM_2(a, b) a,b; +# define _SDT_ASM_3(a, b, c) a,b,c; +# define _SDT_ASM_5(a, b, c, d, e) a,b,c,d,e; +# define _SDT_ASM_STRING_1(x) .asciz #x; +# define _SDT_ASM_SUBSTR_1(x) .ascii #x; +# define _SDT_DEPAREN_0() /* empty */ +# define _SDT_DEPAREN_1(a) a +# define _SDT_DEPAREN_2(a,b) a b +# define _SDT_DEPAREN_3(a,b,c) a b c +# define _SDT_DEPAREN_4(a,b,c,d) a b c d +# define _SDT_DEPAREN_5(a,b,c,d,e) a b c d e +# define _SDT_DEPAREN_6(a,b,c,d,e,f) a b c d e f +# define _SDT_DEPAREN_7(a,b,c,d,e,f,g) a b c d e f g +# define _SDT_DEPAREN_8(a,b,c,d,e,f,g,h) a b c d e f g h +# define _SDT_DEPAREN_9(a,b,c,d,e,f,g,h,i) a b c d e f g h i +# define _SDT_DEPAREN_10(a,b,c,d,e,f,g,h,i,j) a b c d e f g h i j +# define _SDT_DEPAREN_11(a,b,c,d,e,f,g,h,i,j,k) a b c d e f g h i j k +# define _SDT_DEPAREN_12(a,b,c,d,e,f,g,h,i,j,k,l) a b c d e f g h i j k l +#else +#if defined _SDT_HAS_SEMAPHORES +#define _SDT_NOTE_SEMAPHORE_USE(provider, name) \ + __asm__ __volatile__ ("" :: "m" (provider##_##name##_semaphore)); +#else +#define _SDT_NOTE_SEMAPHORE_USE(provider, name) +#endif + +# define _SDT_PROBE(provider, name, n, arglist) \ + do { \ + _SDT_NOTE_SEMAPHORE_USE(provider, name); \ + __asm__ __volatile__ (_SDT_ASM_BODY(provider, name, _SDT_ASM_ARGS, (n)) \ + :: _SDT_ASM_OPERANDS_##n arglist); \ + __asm__ __volatile__ (_SDT_ASM_BASE); \ + } while (0) +# define _SDT_S(x) #x +# define _SDT_ASM_1(x) _SDT_S(x) "\n" +# define _SDT_ASM_2(a, b) _SDT_S(a) "," _SDT_S(b) "\n" +# define _SDT_ASM_3(a, b, c) _SDT_S(a) "," _SDT_S(b) "," \ + _SDT_S(c) "\n" +# define _SDT_ASM_5(a, b, c, d, e) _SDT_S(a) "," _SDT_S(b) "," \ + _SDT_S(c) "," _SDT_S(d) "," \ + _SDT_S(e) "\n" +# define _SDT_ASM_ARGS(n) _SDT_ASM_TEMPLATE_##n +# define _SDT_ASM_STRING_1(x) _SDT_ASM_1(.asciz #x) +# define _SDT_ASM_SUBSTR_1(x) _SDT_ASM_1(.ascii #x) + +# define _SDT_ARGFMT(no) _SDT_ASM_1(_SDT_SIGN %n[_SDT_S##no]) \ + _SDT_ASM_1(_SDT_SIZE %n[_SDT_S##no]) \ + _SDT_ASM_1(_SDT_TYPE %n[_SDT_S##no]) \ + _SDT_ASM_SUBSTR(_SDT_ARGTMPL(_SDT_A##no)) + + +# ifndef STAP_SDT_ARG_CONSTRAINT +# if defined __powerpc__ +# define STAP_SDT_ARG_CONSTRAINT nZr +# elif defined __arm__ +# define STAP_SDT_ARG_CONSTRAINT g +# else +# define STAP_SDT_ARG_CONSTRAINT nor +# endif +# endif + +# define _SDT_STRINGIFY(x) #x +# define _SDT_ARG_CONSTRAINT_STRING(x) _SDT_STRINGIFY(x) +/* _SDT_S encodes the size and type as 0xSSTT which is decoded by the assembler + macros _SDT_SIZE and _SDT_TYPE */ +# define _SDT_ARG(n, x) \ + [_SDT_S##n] "n" ((_SDT_ARGSIGNED (x) ? (int)-1 : 1) * (-(((int) _SDT_ARGSIZE (x)) << 8) + (-(0x7f & __builtin_classify_type (x))))), \ + [_SDT_A##n] _SDT_ARG_CONSTRAINT_STRING (STAP_SDT_ARG_CONSTRAINT) (_SDT_ARGVAL (x)) +#endif +#define _SDT_ASM_STRING(x) _SDT_ASM_STRING_1(x) +#define _SDT_ASM_SUBSTR(x) _SDT_ASM_SUBSTR_1(x) + +#define _SDT_ARGARRAY(x) (__builtin_classify_type (x) == 14 \ + || __builtin_classify_type (x) == 5) + +#ifdef __cplusplus +# define _SDT_ARGSIGNED(x) (!_SDT_ARGARRAY (x) \ + && __sdt_type<__typeof (x)>::__sdt_signed) +# define _SDT_ARGSIZE(x) (_SDT_ARGARRAY (x) \ + ? sizeof (void *) : sizeof (x)) +# define _SDT_ARGVAL(x) (x) + +# include + +template +struct __sdt_type +{ + static const bool __sdt_signed = false; +}; + +#define __SDT_ALWAYS_SIGNED(T) \ +template<> struct __sdt_type { static const bool __sdt_signed = true; }; +#define __SDT_COND_SIGNED(T,CT) \ +template<> struct __sdt_type { static const bool __sdt_signed = ((CT)(-1) < 1); }; +__SDT_ALWAYS_SIGNED(signed char) +__SDT_ALWAYS_SIGNED(short) +__SDT_ALWAYS_SIGNED(int) +__SDT_ALWAYS_SIGNED(long) +__SDT_ALWAYS_SIGNED(long long) +__SDT_ALWAYS_SIGNED(volatile signed char) +__SDT_ALWAYS_SIGNED(volatile short) +__SDT_ALWAYS_SIGNED(volatile int) +__SDT_ALWAYS_SIGNED(volatile long) +__SDT_ALWAYS_SIGNED(volatile long long) +__SDT_ALWAYS_SIGNED(const signed char) +__SDT_ALWAYS_SIGNED(const short) +__SDT_ALWAYS_SIGNED(const int) +__SDT_ALWAYS_SIGNED(const long) +__SDT_ALWAYS_SIGNED(const long long) +__SDT_ALWAYS_SIGNED(const volatile signed char) +__SDT_ALWAYS_SIGNED(const volatile short) +__SDT_ALWAYS_SIGNED(const volatile int) +__SDT_ALWAYS_SIGNED(const volatile long) +__SDT_ALWAYS_SIGNED(const volatile long long) +__SDT_COND_SIGNED(char, char) +__SDT_COND_SIGNED(wchar_t, wchar_t) +__SDT_COND_SIGNED(volatile char, char) +__SDT_COND_SIGNED(volatile wchar_t, wchar_t) +__SDT_COND_SIGNED(const char, char) +__SDT_COND_SIGNED(const wchar_t, wchar_t) +__SDT_COND_SIGNED(const volatile char, char) +__SDT_COND_SIGNED(const volatile wchar_t, wchar_t) +#if defined (__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)) +/* __SDT_COND_SIGNED(char16_t) */ +/* __SDT_COND_SIGNED(char32_t) */ +#endif + +template +struct __sdt_type<__sdt_E[]> : public __sdt_type<__sdt_E *> {}; + +template +struct __sdt_type<__sdt_E[__sdt_N]> : public __sdt_type<__sdt_E *> {}; + +#elif !defined(__ASSEMBLER__) +__extension__ extern unsigned long long __sdt_unsp; +# define _SDT_ARGINTTYPE(x) \ + __typeof (__builtin_choose_expr (((__builtin_classify_type (x) \ + + 3) & -4) == 4, (x), 0U)) +# define _SDT_ARGSIGNED(x) \ + (!__extension__ \ + (__builtin_constant_p ((((unsigned long long) \ + (_SDT_ARGINTTYPE (x)) __sdt_unsp) \ + & ((unsigned long long)1 << (sizeof (unsigned long long) \ + * __CHAR_BIT__ - 1))) == 0) \ + || (_SDT_ARGINTTYPE (x)) -1 > (_SDT_ARGINTTYPE (x)) 0)) +# define _SDT_ARGSIZE(x) \ + (_SDT_ARGARRAY (x) ? sizeof (void *) : sizeof (x)) +# define _SDT_ARGVAL(x) (x) +#endif + +#if defined __powerpc__ || defined __powerpc64__ +# define _SDT_ARGTMPL(id) %I[id]%[id] +#elif defined __i386__ +# define _SDT_ARGTMPL(id) %k[id] /* gcc.gnu.org/PR80115 sourceware.org/PR24541 */ +#else +# define _SDT_ARGTMPL(id) %[id] +#endif + +/* NB: gdb PR24541 highlighted an unspecified corner of the sdt.h + operand note format. + + The named register may be a longer or shorter (!) alias for the + storage where the value in question is found. For example, on + i386, 64-bit value may be put in register pairs, and the register + name stored would identify just one of them. Previously, gcc was + asked to emit the %w[id] (16-bit alias of some registers holding + operands), even when a wider 32-bit value was used. + + Bottom line: the byte-width given before the @ sign governs. If + there is a mismatch between that width and that of the named + register, then a sys/sdt.h note consumer may need to employ + architecture-specific heuristics to figure out where the compiler + has actually put the complete value. +*/ + +#ifdef __LP64__ +# define _SDT_ASM_ADDR .8byte +#else +# define _SDT_ASM_ADDR .4byte +#endif + +/* The ia64 and s390 nop instructions take an argument. */ +#if defined(__ia64__) || defined(__s390__) || defined(__s390x__) +#define _SDT_NOP nop 0 +#else +#define _SDT_NOP nop +#endif + +#define _SDT_NOTE_NAME "stapsdt" +#define _SDT_NOTE_TYPE 3 + +/* If the assembler supports the necessary feature, then we can play + nice with code in COMDAT sections, which comes up in C++ code. + Without that assembler support, some combinations of probe placements + in certain kinds of C++ code may produce link-time errors. */ +#include "sdt-config.h" +#if _SDT_ASM_SECTION_AUTOGROUP_SUPPORT +# define _SDT_ASM_AUTOGROUP "?" +#else +# define _SDT_ASM_AUTOGROUP "" +#endif + +#define _SDT_DEF_MACROS \ + _SDT_ASM_1(.altmacro) \ + _SDT_ASM_1(.macro _SDT_SIGN x) \ + _SDT_ASM_3(.pushsection .note.stapsdt,"","note") \ + _SDT_ASM_1(.iflt \\x) \ + _SDT_ASM_1(.ascii "-") \ + _SDT_ASM_1(.endif) \ + _SDT_ASM_1(.popsection) \ + _SDT_ASM_1(.endm) \ + _SDT_ASM_1(.macro _SDT_SIZE_ x) \ + _SDT_ASM_3(.pushsection .note.stapsdt,"","note") \ + _SDT_ASM_1(.ascii "\x") \ + _SDT_ASM_1(.popsection) \ + _SDT_ASM_1(.endm) \ + _SDT_ASM_1(.macro _SDT_SIZE x) \ + _SDT_ASM_1(_SDT_SIZE_ %%((-(-\\x*((-\\x>0)-(-\\x<0))))>>8)) \ + _SDT_ASM_1(.endm) \ + _SDT_ASM_1(.macro _SDT_TYPE_ x) \ + _SDT_ASM_3(.pushsection .note.stapsdt,"","note") \ + _SDT_ASM_2(.ifc 8,\\x) \ + _SDT_ASM_1(.ascii "f") \ + _SDT_ASM_1(.endif) \ + _SDT_ASM_1(.ascii "@") \ + _SDT_ASM_1(.popsection) \ + _SDT_ASM_1(.endm) \ + _SDT_ASM_1(.macro _SDT_TYPE x) \ + _SDT_ASM_1(_SDT_TYPE_ %%((\\x)&(0xff))) \ + _SDT_ASM_1(.endm) + +#define _SDT_UNDEF_MACROS \ + _SDT_ASM_1(.purgem _SDT_SIGN) \ + _SDT_ASM_1(.purgem _SDT_SIZE_) \ + _SDT_ASM_1(.purgem _SDT_SIZE) \ + _SDT_ASM_1(.purgem _SDT_TYPE_) \ + _SDT_ASM_1(.purgem _SDT_TYPE) + +#define _SDT_ASM_BODY(provider, name, pack_args, args, ...) \ + _SDT_DEF_MACROS \ + _SDT_ASM_1(990: _SDT_NOP) \ + _SDT_ASM_3( .pushsection .note.stapsdt,_SDT_ASM_AUTOGROUP,"note") \ + _SDT_ASM_1( .balign 4) \ + _SDT_ASM_3( .4byte 992f-991f, 994f-993f, _SDT_NOTE_TYPE) \ + _SDT_ASM_1(991: .asciz _SDT_NOTE_NAME) \ + _SDT_ASM_1(992: .balign 4) \ + _SDT_ASM_1(993: _SDT_ASM_ADDR 990b) \ + _SDT_ASM_1( _SDT_ASM_ADDR _.stapsdt.base) \ + _SDT_SEMAPHORE(provider,name) \ + _SDT_ASM_STRING(provider) \ + _SDT_ASM_STRING(name) \ + pack_args args \ + _SDT_ASM_SUBSTR(\x00) \ + _SDT_UNDEF_MACROS \ + _SDT_ASM_1(994: .balign 4) \ + _SDT_ASM_1( .popsection) + +#define _SDT_ASM_BASE \ + _SDT_ASM_1(.ifndef _.stapsdt.base) \ + _SDT_ASM_5( .pushsection .stapsdt.base,"aG","progbits", \ + .stapsdt.base,comdat) \ + _SDT_ASM_1( .weak _.stapsdt.base) \ + _SDT_ASM_1( .hidden _.stapsdt.base) \ + _SDT_ASM_1( _.stapsdt.base: .space 1) \ + _SDT_ASM_2( .size _.stapsdt.base, 1) \ + _SDT_ASM_1( .popsection) \ + _SDT_ASM_1(.endif) + +#if defined _SDT_HAS_SEMAPHORES +#define _SDT_SEMAPHORE(p,n) \ + _SDT_ASM_1( _SDT_ASM_ADDR p##_##n##_semaphore) +#else +#define _SDT_SEMAPHORE(p,n) _SDT_ASM_1( _SDT_ASM_ADDR 0) +#endif + +#define _SDT_ASM_BLANK _SDT_ASM_SUBSTR(\x20) +#define _SDT_ASM_TEMPLATE_0 /* no arguments */ +#define _SDT_ASM_TEMPLATE_1 _SDT_ARGFMT(1) +#define _SDT_ASM_TEMPLATE_2 _SDT_ASM_TEMPLATE_1 _SDT_ASM_BLANK _SDT_ARGFMT(2) +#define _SDT_ASM_TEMPLATE_3 _SDT_ASM_TEMPLATE_2 _SDT_ASM_BLANK _SDT_ARGFMT(3) +#define _SDT_ASM_TEMPLATE_4 _SDT_ASM_TEMPLATE_3 _SDT_ASM_BLANK _SDT_ARGFMT(4) +#define _SDT_ASM_TEMPLATE_5 _SDT_ASM_TEMPLATE_4 _SDT_ASM_BLANK _SDT_ARGFMT(5) +#define _SDT_ASM_TEMPLATE_6 _SDT_ASM_TEMPLATE_5 _SDT_ASM_BLANK _SDT_ARGFMT(6) +#define _SDT_ASM_TEMPLATE_7 _SDT_ASM_TEMPLATE_6 _SDT_ASM_BLANK _SDT_ARGFMT(7) +#define _SDT_ASM_TEMPLATE_8 _SDT_ASM_TEMPLATE_7 _SDT_ASM_BLANK _SDT_ARGFMT(8) +#define _SDT_ASM_TEMPLATE_9 _SDT_ASM_TEMPLATE_8 _SDT_ASM_BLANK _SDT_ARGFMT(9) +#define _SDT_ASM_TEMPLATE_10 _SDT_ASM_TEMPLATE_9 _SDT_ASM_BLANK _SDT_ARGFMT(10) +#define _SDT_ASM_TEMPLATE_11 _SDT_ASM_TEMPLATE_10 _SDT_ASM_BLANK _SDT_ARGFMT(11) +#define _SDT_ASM_TEMPLATE_12 _SDT_ASM_TEMPLATE_11 _SDT_ASM_BLANK _SDT_ARGFMT(12) +#define _SDT_ASM_OPERANDS_0() [__sdt_dummy] "g" (0) +#define _SDT_ASM_OPERANDS_1(arg1) _SDT_ARG(1, arg1) +#define _SDT_ASM_OPERANDS_2(arg1, arg2) \ + _SDT_ASM_OPERANDS_1(arg1), _SDT_ARG(2, arg2) +#define _SDT_ASM_OPERANDS_3(arg1, arg2, arg3) \ + _SDT_ASM_OPERANDS_2(arg1, arg2), _SDT_ARG(3, arg3) +#define _SDT_ASM_OPERANDS_4(arg1, arg2, arg3, arg4) \ + _SDT_ASM_OPERANDS_3(arg1, arg2, arg3), _SDT_ARG(4, arg4) +#define _SDT_ASM_OPERANDS_5(arg1, arg2, arg3, arg4, arg5) \ + _SDT_ASM_OPERANDS_4(arg1, arg2, arg3, arg4), _SDT_ARG(5, arg5) +#define _SDT_ASM_OPERANDS_6(arg1, arg2, arg3, arg4, arg5, arg6) \ + _SDT_ASM_OPERANDS_5(arg1, arg2, arg3, arg4, arg5), _SDT_ARG(6, arg6) +#define _SDT_ASM_OPERANDS_7(arg1, arg2, arg3, arg4, arg5, arg6, arg7) \ + _SDT_ASM_OPERANDS_6(arg1, arg2, arg3, arg4, arg5, arg6), _SDT_ARG(7, arg7) +#define _SDT_ASM_OPERANDS_8(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8) \ + _SDT_ASM_OPERANDS_7(arg1, arg2, arg3, arg4, arg5, arg6, arg7), \ + _SDT_ARG(8, arg8) +#define _SDT_ASM_OPERANDS_9(arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9) \ + _SDT_ASM_OPERANDS_8(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8), \ + _SDT_ARG(9, arg9) +#define _SDT_ASM_OPERANDS_10(arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9,arg10) \ + _SDT_ASM_OPERANDS_9(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9), \ + _SDT_ARG(10, arg10) +#define _SDT_ASM_OPERANDS_11(arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9,arg10,arg11) \ + _SDT_ASM_OPERANDS_10(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10), \ + _SDT_ARG(11, arg11) +#define _SDT_ASM_OPERANDS_12(arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9,arg10,arg11,arg12) \ + _SDT_ASM_OPERANDS_11(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11), \ + _SDT_ARG(12, arg12) + +/* These macros can be used in C, C++, or assembly code. + In assembly code the arguments should use normal assembly operand syntax. */ + +#define STAP_PROBE(provider, name) \ + _SDT_PROBE(provider, name, 0, ()) +#define STAP_PROBE1(provider, name, arg1) \ + _SDT_PROBE(provider, name, 1, (arg1)) +#define STAP_PROBE2(provider, name, arg1, arg2) \ + _SDT_PROBE(provider, name, 2, (arg1, arg2)) +#define STAP_PROBE3(provider, name, arg1, arg2, arg3) \ + _SDT_PROBE(provider, name, 3, (arg1, arg2, arg3)) +#define STAP_PROBE4(provider, name, arg1, arg2, arg3, arg4) \ + _SDT_PROBE(provider, name, 4, (arg1, arg2, arg3, arg4)) +#define STAP_PROBE5(provider, name, arg1, arg2, arg3, arg4, arg5) \ + _SDT_PROBE(provider, name, 5, (arg1, arg2, arg3, arg4, arg5)) +#define STAP_PROBE6(provider, name, arg1, arg2, arg3, arg4, arg5, arg6) \ + _SDT_PROBE(provider, name, 6, (arg1, arg2, arg3, arg4, arg5, arg6)) +#define STAP_PROBE7(provider, name, arg1, arg2, arg3, arg4, arg5, arg6, arg7) \ + _SDT_PROBE(provider, name, 7, (arg1, arg2, arg3, arg4, arg5, arg6, arg7)) +#define STAP_PROBE8(provider,name,arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8) \ + _SDT_PROBE(provider, name, 8, (arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8)) +#define STAP_PROBE9(provider,name,arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9)\ + _SDT_PROBE(provider, name, 9, (arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9)) +#define STAP_PROBE10(provider,name,arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9,arg10) \ + _SDT_PROBE(provider, name, 10, \ + (arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9,arg10)) +#define STAP_PROBE11(provider,name,arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9,arg10,arg11) \ + _SDT_PROBE(provider, name, 11, \ + (arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9,arg10,arg11)) +#define STAP_PROBE12(provider,name,arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9,arg10,arg11,arg12) \ + _SDT_PROBE(provider, name, 12, \ + (arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9,arg10,arg11,arg12)) + +/* This STAP_PROBEV macro can be used in variadic scenarios, where the + number of probe arguments is not known until compile time. Since + variadic macro support may vary with compiler options, you must + pre-#define SDT_USE_VARIADIC to enable this type of probe. + + The trick to count __VA_ARGS__ was inspired by this post by + Laurent Deniau : + http://groups.google.com/group/comp.std.c/msg/346fc464319b1ee5 + + Note that our _SDT_NARG is called with an extra 0 arg that's not + counted, so we don't have to worry about the behavior of macros + called without any arguments. */ + +#define _SDT_NARG(...) __SDT_NARG(__VA_ARGS__, 12,11,10,9,8,7,6,5,4,3,2,1,0) +#define __SDT_NARG(_0,_1,_2,_3,_4,_5,_6,_7,_8,_9,_10,_11,_12, N, ...) N +#ifdef SDT_USE_VARIADIC +#define _SDT_PROBE_N(provider, name, N, ...) \ + _SDT_PROBE(provider, name, N, (__VA_ARGS__)) +#define STAP_PROBEV(provider, name, ...) \ + _SDT_PROBE_N(provider, name, _SDT_NARG(0, ##__VA_ARGS__), ##__VA_ARGS__) +#endif + +/* These macros are for use in asm statements. You must compile + with -std=gnu99 or -std=c99 to use the STAP_PROBE_ASM macro. + + The STAP_PROBE_ASM macro generates a quoted string to be used in the + template portion of the asm statement, concatenated with strings that + contain the actual assembly code around the probe site. + + For example: + + asm ("before\n" + STAP_PROBE_ASM(provider, fooprobe, %eax 4(%esi)) + "after"); + + emits the assembly code for "before\nafter", with a probe in between. + The probe arguments are the %eax register, and the value of the memory + word located 4 bytes past the address in the %esi register. Note that + because this is a simple asm, not a GNU C extended asm statement, these + % characters do not need to be doubled to generate literal %reg names. + + In a GNU C extended asm statement, the probe arguments can be specified + using the macro STAP_PROBE_ASM_TEMPLATE(n) for n arguments. The paired + macro STAP_PROBE_ASM_OPERANDS gives the C values of these probe arguments, + and appears in the input operand list of the asm statement. For example: + + asm ("someinsn %0,%1\n" // %0 is output operand, %1 is input operand + STAP_PROBE_ASM(provider, fooprobe, STAP_PROBE_ASM_TEMPLATE(3)) + "otherinsn %[namedarg]" + : "r" (outvar) + : "g" (some_value), [namedarg] "i" (1234), + STAP_PROBE_ASM_OPERANDS(3, some_value, some_ptr->field, 1234)); + + This is just like writing: + + STAP_PROBE3(provider, fooprobe, some_value, some_ptr->field, 1234)); + + but the probe site is right between "someinsn" and "otherinsn". + + The probe arguments in STAP_PROBE_ASM can be given as assembly + operands instead, even inside a GNU C extended asm statement. + Note that these can use operand templates like %0 or %[name], + and likewise they must write %%reg for a literal operand of %reg. */ + +#define _SDT_ASM_BODY_1(p,n,...) _SDT_ASM_BODY(p,n,_SDT_ASM_SUBSTR,(__VA_ARGS__)) +#define _SDT_ASM_BODY_2(p,n,...) _SDT_ASM_BODY(p,n,/*_SDT_ASM_STRING */,__VA_ARGS__) +#define _SDT_ASM_BODY_N2(p,n,no,...) _SDT_ASM_BODY_ ## no(p,n,__VA_ARGS__) +#define _SDT_ASM_BODY_N1(p,n,no,...) _SDT_ASM_BODY_N2(p,n,no,__VA_ARGS__) +#define _SDT_ASM_BODY_N(p,n,...) _SDT_ASM_BODY_N1(p,n,_SDT_NARG(0, __VA_ARGS__),__VA_ARGS__) + +#if __STDC_VERSION__ >= 199901L +# define STAP_PROBE_ASM(provider, name, ...) \ + _SDT_ASM_BODY_N(provider, name, __VA_ARGS__) \ + _SDT_ASM_BASE +# define STAP_PROBE_ASM_OPERANDS(n, ...) _SDT_ASM_OPERANDS_##n(__VA_ARGS__) +#else +# define STAP_PROBE_ASM(provider, name, args) \ + _SDT_ASM_BODY(provider, name, /* _SDT_ASM_STRING */, (args)) \ + _SDT_ASM_BASE +#endif +#define STAP_PROBE_ASM_TEMPLATE(n) _SDT_ASM_TEMPLATE_##n,"use _SDT_ASM_TEMPLATE_" + + +/* DTrace compatible macro names. */ +#define DTRACE_PROBE(provider,probe) \ + STAP_PROBE(provider,probe) +#define DTRACE_PROBE1(provider,probe,parm1) \ + STAP_PROBE1(provider,probe,parm1) +#define DTRACE_PROBE2(provider,probe,parm1,parm2) \ + STAP_PROBE2(provider,probe,parm1,parm2) +#define DTRACE_PROBE3(provider,probe,parm1,parm2,parm3) \ + STAP_PROBE3(provider,probe,parm1,parm2,parm3) +#define DTRACE_PROBE4(provider,probe,parm1,parm2,parm3,parm4) \ + STAP_PROBE4(provider,probe,parm1,parm2,parm3,parm4) +#define DTRACE_PROBE5(provider,probe,parm1,parm2,parm3,parm4,parm5) \ + STAP_PROBE5(provider,probe,parm1,parm2,parm3,parm4,parm5) +#define DTRACE_PROBE6(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6) \ + STAP_PROBE6(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6) +#define DTRACE_PROBE7(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7) \ + STAP_PROBE7(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7) +#define DTRACE_PROBE8(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8) \ + STAP_PROBE8(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8) +#define DTRACE_PROBE9(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8,parm9) \ + STAP_PROBE9(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8,parm9) +#define DTRACE_PROBE10(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8,parm9,parm10) \ + STAP_PROBE10(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8,parm9,parm10) +#define DTRACE_PROBE11(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8,parm9,parm10,parm11) \ + STAP_PROBE11(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8,parm9,parm10,parm11) +#define DTRACE_PROBE12(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8,parm9,parm10,parm11,parm12) \ + STAP_PROBE12(provider,probe,parm1,parm2,parm3,parm4,parm5,parm6,parm7,parm8,parm9,parm10,parm11,parm12) + + +#endif /* sys/sdt.h */ diff --git a/src/stapsdt-probe.c b/src/stapsdt-probe.c new file mode 100644 index 0000000..bf69116 --- /dev/null +++ b/src/stapsdt-probe.c @@ -0,0 +1,41 @@ +#include +#include +#include +#include + +#include "libstapsdt.h" +#define _SDT_HAS_SEMAPHORES 1 + +#include "sdt.h" + +#define SEC(name) __attribute__((section(name), used)) + +/* USDT probe firing is used as a mechanism to support system-wide + * tracing of libstapsdt probe firings; we define provider/probe + * stapsdt/probe and pass it the provider and probe names along + * with up to 6 arguments. Tracers can then attach to libstapsdt.so + * and catch dynamic probe firings system-wide. For example, + * in a libbpf-based program: + * + * SEC("usdt/libstapsdt.so::stapsdt:probe") + * int BPF_USDT(myprobe, char *provider, char *probe) + * { + * __bpf_printk("%s/%s fired!\n"); + * } + * + * To support is-enabled functionality, we specify an associated + * semaphore with the probe; its count is bumped up for each + * tracer attached. + */ +unsigned short stapsdt_probe_semaphore SEC(".probes"); + +void stapsdtProbeFire(SDTProbe_t *probe, uint64_t *args) +{ + STAP_PROBE8(stapsdt, probe, probe->provider->name, probe->name, + args[0], args[1], args[2], args[3], args[4], args[5]); +} + +int stapsdtProbeIsEnabled(void) +{ + return stapsdt_probe_semaphore > 0; +} diff --git a/src/stapsdt-probe.h b/src/stapsdt-probe.h new file mode 100644 index 0000000..6471fbc --- /dev/null +++ b/src/stapsdt-probe.h @@ -0,0 +1,5 @@ +#include "libstapsdt.h" + +void stapsdtProbeFire(SDTProbe_t *probe, uint64_t *args); + +int stapsdtProbeIsEnabled(SDTProbe_t *probe); From e23d194633925c030fde54ee34f77456b4331989 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Tue, 6 Feb 2024 11:42:35 +0000 Subject: [PATCH 2/2] libstapsdt: document internal USDT probe for stapsdt probe firing ...and provide a BPF C example of tracing using it. Signed-off-by: Alan Maguire --- README.md | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/README.md b/README.md index 0c30f7b..2098135 100644 --- a/README.md +++ b/README.md @@ -94,6 +94,24 @@ Here's an example using [eBPF/bcc](https://github.com/iovisor/bcc) trace tool sudo /usr/share/bcc/tools/trace -p $(pgrep demo) 'u::PROBE_NAME' ``` +Other tracing tools that do not support tracing of the libstapsdt-created +libraries can trace the USDT stapsdt/probe. It will fire when a +libstapsdt probe fires. It is passed the provider and probe names +along with arguments. For example, the following BPF C program could +be used to show probe firing: + +``` +SEC("usdt//usr/lib/libstapsdt.so:stapsdt:probe") +int BPF_USDT(args, const char *provider, const char *probename) +{ + __bpf_printk("%s/%s fired\n", provider, probename); + return 0; +} +``` + +One benefit of this form of tracing is that by tracing libstapsdt.so +itself, we can trace libstapsdt probe firings system-wide. + ## Run tests To run tests, just run the command below. Please be aware that there are only