* Re: Capturing User-Level Function Calls/Returns [not found] <e9c7400ff0075f3beba2863c4432a905@ut.ac.ir> @ 2020-07-15 18:28 ` Steven Rostedt 2020-07-15 18:28 ` [lttng-dev] " Steven Rostedt via lttng-dev ` (2 more replies) 0 siblings, 3 replies; 24+ messages in thread From: Steven Rostedt @ 2020-07-15 18:28 UTC (permalink / raw) To: ahmadkhorrami Cc: Linux-trace Users, lttng-dev, Mathieu Desnoyers, Jérémie Galarneau, Namhyung Kim On Wed, 15 Jul 2020 20:37:16 +0430 ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > Hi, > What is the most efficient way to capture occurrence of a function > call/return of a binary program in userspace? > It seems the answer is Uprobes. 1) Am I right? > But Uprobes use "int" instruction which leads to a switch into kernel > mode. 2) Wouldn't it be better to avoid this transition? > I'm looking forward to your reply and will be happy to read your > opinions. > Regards. Hi, I believe LTTng has utilities that can help you trace user space programs. I think there's also a users ftrace like utility that Namhyung was working on. But I don't know where in the development that is. -- Steve ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-15 18:28 ` Capturing User-Level Function Calls/Returns Steven Rostedt @ 2020-07-15 18:28 ` Steven Rostedt via lttng-dev 2020-07-15 18:45 ` Mathieu Desnoyers 2020-07-16 1:04 ` Namhyung Kim 2 siblings, 0 replies; 24+ messages in thread From: Steven Rostedt via lttng-dev @ 2020-07-15 18:28 UTC (permalink / raw) To: ahmadkhorrami; +Cc: Linux-trace Users, lttng-dev, Namhyung Kim On Wed, 15 Jul 2020 20:37:16 +0430 ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > Hi, > What is the most efficient way to capture occurrence of a function > call/return of a binary program in userspace? > It seems the answer is Uprobes. 1) Am I right? > But Uprobes use "int" instruction which leads to a switch into kernel > mode. 2) Wouldn't it be better to avoid this transition? > I'm looking forward to your reply and will be happy to read your > opinions. > Regards. Hi, I believe LTTng has utilities that can help you trace user space programs. I think there's also a users ftrace like utility that Namhyung was working on. But I don't know where in the development that is. -- Steve _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: Capturing User-Level Function Calls/Returns 2020-07-15 18:28 ` Capturing User-Level Function Calls/Returns Steven Rostedt 2020-07-15 18:28 ` [lttng-dev] " Steven Rostedt via lttng-dev @ 2020-07-15 18:45 ` Mathieu Desnoyers 2020-07-15 18:45 ` [lttng-dev] " Mathieu Desnoyers via lttng-dev 2020-07-15 21:39 ` ahmadkhorrami 2020-07-16 1:04 ` Namhyung Kim 2 siblings, 2 replies; 24+ messages in thread From: Mathieu Desnoyers @ 2020-07-15 18:45 UTC (permalink / raw) To: ahmadkhorrami Cc: linux-trace-users, lttng-dev, Jeremie Galarneau, Namhyung Kim, rostedt ----- On Jul 15, 2020, at 2:28 PM, rostedt rostedt@goodmis.org wrote: > On Wed, 15 Jul 2020 20:37:16 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > >> Hi, >> What is the most efficient way to capture occurrence of a function >> call/return of a binary program in userspace? >> It seems the answer is Uprobes. 1) Am I right? >> But Uprobes use "int" instruction which leads to a switch into kernel >> mode. 2) Wouldn't it be better to avoid this transition? >> I'm looking forward to your reply and will be happy to read your >> opinions. >> Regards. > > > Hi, I believe LTTng has utilities that can help you trace user space > programs. Indeed, it is documented here: https://lttng.org/docs/#doc-liblttng-ust-cyg-profile If your program is generating function entry/exit at a very high rate (which goes beyond your available I/O throughput and lasts longer than the memory you have available for ring buffers), you will also probably want to use the "blocking-timeout" option documented at: https://lttng.org/docs/#doc-enabling-disabling-channels Thanks, Mathieu > > I think there's also a users ftrace like utility that Namhyung was > working on. But I don't know where in the development that is. > > -- Steve -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-15 18:45 ` Mathieu Desnoyers @ 2020-07-15 18:45 ` Mathieu Desnoyers via lttng-dev 2020-07-15 21:39 ` ahmadkhorrami 1 sibling, 0 replies; 24+ messages in thread From: Mathieu Desnoyers via lttng-dev @ 2020-07-15 18:45 UTC (permalink / raw) To: ahmadkhorrami; +Cc: linux-trace-users, lttng-dev, rostedt, Namhyung Kim ----- On Jul 15, 2020, at 2:28 PM, rostedt rostedt@goodmis.org wrote: > On Wed, 15 Jul 2020 20:37:16 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > >> Hi, >> What is the most efficient way to capture occurrence of a function >> call/return of a binary program in userspace? >> It seems the answer is Uprobes. 1) Am I right? >> But Uprobes use "int" instruction which leads to a switch into kernel >> mode. 2) Wouldn't it be better to avoid this transition? >> I'm looking forward to your reply and will be happy to read your >> opinions. >> Regards. > > > Hi, I believe LTTng has utilities that can help you trace user space > programs. Indeed, it is documented here: https://lttng.org/docs/#doc-liblttng-ust-cyg-profile If your program is generating function entry/exit at a very high rate (which goes beyond your available I/O throughput and lasts longer than the memory you have available for ring buffers), you will also probably want to use the "blocking-timeout" option documented at: https://lttng.org/docs/#doc-enabling-disabling-channels Thanks, Mathieu > > I think there's also a users ftrace like utility that Namhyung was > working on. But I don't know where in the development that is. > > -- Steve -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: Capturing User-Level Function Calls/Returns 2020-07-15 18:45 ` Mathieu Desnoyers 2020-07-15 18:45 ` [lttng-dev] " Mathieu Desnoyers via lttng-dev @ 2020-07-15 21:39 ` ahmadkhorrami 2020-07-15 21:39 ` [lttng-dev] " ahmadkhorrami via lttng-dev 2020-07-15 21:48 ` Steven Rostedt 1 sibling, 2 replies; 24+ messages in thread From: ahmadkhorrami @ 2020-07-15 21:39 UTC (permalink / raw) To: Mathieu Desnoyers Cc: linux-trace-users, lttng-dev, Jeremie Galarneau, Namhyung Kim, rostedt, linux-trace-users-owner Hi Steven and Mathieu, Firstly, many thanks! This method seems to be the most efficient method. But, IIUC, what you suggest requires source code compilation. I need an efficient dynamic method that, given the function address, captures its occurrence and stores some information from the execution context. Is there anything better than Uprobes perhaps with no trap into the kernel? Why do we need traps? Regards. On 2020-07-15 23:15, Mathieu Desnoyers wrote: > ----- On Jul 15, 2020, at 2:28 PM, rostedt rostedt@goodmis.org wrote: > > On Wed, 15 Jul 2020 20:37:16 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > > Hi, > What is the most efficient way to capture occurrence of a function > call/return of a binary program in userspace? > It seems the answer is Uprobes. 1) Am I right? > But Uprobes use "int" instruction which leads to a switch into kernel > mode. 2) Wouldn't it be better to avoid this transition? > I'm looking forward to your reply and will be happy to read your > opinions. > Regards. > > Hi, I believe LTTng has utilities that can help you trace user space > programs. Indeed, it is documented here: https://lttng.org/docs/#doc-liblttng-ust-cyg-profile If your program is generating function entry/exit at a very high rate (which goes beyond your available I/O throughput and lasts longer than the memory you have available for ring buffers), you will also probably want to use the "blocking-timeout" option documented at: https://lttng.org/docs/#doc-enabling-disabling-channels Thanks, Mathieu > I think there's also a users ftrace like utility that Namhyung was > working on. But I don't know where in the development that is. > > -- Steve ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-15 21:39 ` ahmadkhorrami @ 2020-07-15 21:39 ` ahmadkhorrami via lttng-dev 2020-07-15 21:48 ` Steven Rostedt 1 sibling, 0 replies; 24+ messages in thread From: ahmadkhorrami via lttng-dev @ 2020-07-15 21:39 UTC (permalink / raw) To: Mathieu Desnoyers Cc: linux-trace-users-owner, rostedt, linux-trace-users, lttng-dev, Namhyung Kim Hi Steven and Mathieu, Firstly, many thanks! This method seems to be the most efficient method. But, IIUC, what you suggest requires source code compilation. I need an efficient dynamic method that, given the function address, captures its occurrence and stores some information from the execution context. Is there anything better than Uprobes perhaps with no trap into the kernel? Why do we need traps? Regards. On 2020-07-15 23:15, Mathieu Desnoyers wrote: > ----- On Jul 15, 2020, at 2:28 PM, rostedt rostedt@goodmis.org wrote: > > On Wed, 15 Jul 2020 20:37:16 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > > Hi, > What is the most efficient way to capture occurrence of a function > call/return of a binary program in userspace? > It seems the answer is Uprobes. 1) Am I right? > But Uprobes use "int" instruction which leads to a switch into kernel > mode. 2) Wouldn't it be better to avoid this transition? > I'm looking forward to your reply and will be happy to read your > opinions. > Regards. > > Hi, I believe LTTng has utilities that can help you trace user space > programs. Indeed, it is documented here: https://lttng.org/docs/#doc-liblttng-ust-cyg-profile If your program is generating function entry/exit at a very high rate (which goes beyond your available I/O throughput and lasts longer than the memory you have available for ring buffers), you will also probably want to use the "blocking-timeout" option documented at: https://lttng.org/docs/#doc-enabling-disabling-channels Thanks, Mathieu > I think there's also a users ftrace like utility that Namhyung was > working on. But I don't know where in the development that is. > > -- Steve _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: Capturing User-Level Function Calls/Returns 2020-07-15 21:39 ` ahmadkhorrami 2020-07-15 21:39 ` [lttng-dev] " ahmadkhorrami via lttng-dev @ 2020-07-15 21:48 ` Steven Rostedt 2020-07-15 21:48 ` [lttng-dev] " Steven Rostedt via lttng-dev ` (2 more replies) 1 sibling, 3 replies; 24+ messages in thread From: Steven Rostedt @ 2020-07-15 21:48 UTC (permalink / raw) To: ahmadkhorrami Cc: Mathieu Desnoyers, linux-trace-users, lttng-dev, Jeremie Galarneau, Namhyung Kim, linux-trace-users-owner On Thu, 16 Jul 2020 02:09:50 +0430 ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > Hi Steven and Mathieu, > Firstly, many thanks! This method seems to be the most efficient method. > But, IIUC, what you suggest requires source code compilation. I need an > efficient dynamic method that, given the function address, captures its > occurrence and stores some information from the execution context. Is > there anything better than Uprobes perhaps with no trap into the kernel? > Why do we need traps? > Regards. Without recompiling, how would that be implemented? You would need to insert a jump on top of code, and still be able to preserve that code. What a trap does, is to insert a int3, that will trap into the kernel, it would then emulate the code that the int3 was on, and also call some code that can trace the current state. To do it in user land, you would need to find way to replace the code at the location you want to trace, with a jump to the tracing infrastructure, that will also be able to emulate the code that the jump was inserted on top of. As on x86, that jump will need to be 5 bytes long (covering 5 bytes of text to emulate), where as a int3 is a single byte. Thus, you either recompile and insert nops where you want to place your jumps, or you trap using int3 that can do the work from within the kernel. -- Steve ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-15 21:48 ` Steven Rostedt @ 2020-07-15 21:48 ` Steven Rostedt via lttng-dev 2020-07-15 22:25 ` ahmadkhorrami 2020-07-16 1:06 ` Michel Dagenais via lttng-dev 2 siblings, 0 replies; 24+ messages in thread From: Steven Rostedt via lttng-dev @ 2020-07-15 21:48 UTC (permalink / raw) To: ahmadkhorrami Cc: linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim On Thu, 16 Jul 2020 02:09:50 +0430 ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > Hi Steven and Mathieu, > Firstly, many thanks! This method seems to be the most efficient method. > But, IIUC, what you suggest requires source code compilation. I need an > efficient dynamic method that, given the function address, captures its > occurrence and stores some information from the execution context. Is > there anything better than Uprobes perhaps with no trap into the kernel? > Why do we need traps? > Regards. Without recompiling, how would that be implemented? You would need to insert a jump on top of code, and still be able to preserve that code. What a trap does, is to insert a int3, that will trap into the kernel, it would then emulate the code that the int3 was on, and also call some code that can trace the current state. To do it in user land, you would need to find way to replace the code at the location you want to trace, with a jump to the tracing infrastructure, that will also be able to emulate the code that the jump was inserted on top of. As on x86, that jump will need to be 5 bytes long (covering 5 bytes of text to emulate), where as a int3 is a single byte. Thus, you either recompile and insert nops where you want to place your jumps, or you trap using int3 that can do the work from within the kernel. -- Steve _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: Capturing User-Level Function Calls/Returns 2020-07-15 21:48 ` Steven Rostedt 2020-07-15 21:48 ` [lttng-dev] " Steven Rostedt via lttng-dev @ 2020-07-15 22:25 ` ahmadkhorrami 2020-07-15 22:25 ` [lttng-dev] " ahmadkhorrami via lttng-dev 2020-07-16 1:06 ` Michel Dagenais via lttng-dev 2 siblings, 1 reply; 24+ messages in thread From: ahmadkhorrami @ 2020-07-15 22:25 UTC (permalink / raw) To: Steven Rostedt Cc: Mathieu Desnoyers, linux-trace-users, lttng-dev, Jeremie Galarneau, Namhyung Kim, linux-trace-users-owner So, the only barrier to the user-level implementation is the problem with instruction sizes. That's an enlightening point. Thanks for the detailed answer! Thanks everybody specially Steven and Mathieu. Regards. On 2020-07-16 02:18, Steven Rostedt wrote: > On Thu, 16 Jul 2020 02:09:50 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > >> Hi Steven and Mathieu, >> Firstly, many thanks! This method seems to be the most efficient >> method. >> But, IIUC, what you suggest requires source code compilation. I need >> an >> efficient dynamic method that, given the function address, captures >> its >> occurrence and stores some information from the execution context. Is >> there anything better than Uprobes perhaps with no trap into the >> kernel? >> Why do we need traps? >> Regards. > > Without recompiling, how would that be implemented? > > You would need to insert a jump on top of code, and still be able to > preserve that code. What a trap does, is to insert a int3, that will > trap into the kernel, it would then emulate the code that the int3 was > on, and also call some code that can trace the current state. > > To do it in user land, you would need to find way to replace the code > at the location you want to trace, with a jump to the tracing > infrastructure, that will also be able to emulate the code that the > jump was inserted on top of. As on x86, that jump will need to be 5 > bytes long (covering 5 bytes of text to emulate), where as a int3 is a > single byte. > > Thus, you either recompile and insert nops where you want to place your > jumps, or you trap using int3 that can do the work from within the > kernel. > > -- Steve ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-15 22:25 ` ahmadkhorrami @ 2020-07-15 22:25 ` ahmadkhorrami via lttng-dev 0 siblings, 0 replies; 24+ messages in thread From: ahmadkhorrami via lttng-dev @ 2020-07-15 22:25 UTC (permalink / raw) To: Steven Rostedt Cc: linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim So, the only barrier to the user-level implementation is the problem with instruction sizes. That's an enlightening point. Thanks for the detailed answer! Thanks everybody specially Steven and Mathieu. Regards. On 2020-07-16 02:18, Steven Rostedt wrote: > On Thu, 16 Jul 2020 02:09:50 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > >> Hi Steven and Mathieu, >> Firstly, many thanks! This method seems to be the most efficient >> method. >> But, IIUC, what you suggest requires source code compilation. I need >> an >> efficient dynamic method that, given the function address, captures >> its >> occurrence and stores some information from the execution context. Is >> there anything better than Uprobes perhaps with no trap into the >> kernel? >> Why do we need traps? >> Regards. > > Without recompiling, how would that be implemented? > > You would need to insert a jump on top of code, and still be able to > preserve that code. What a trap does, is to insert a int3, that will > trap into the kernel, it would then emulate the code that the int3 was > on, and also call some code that can trace the current state. > > To do it in user land, you would need to find way to replace the code > at the location you want to trace, with a jump to the tracing > infrastructure, that will also be able to emulate the code that the > jump was inserted on top of. As on x86, that jump will need to be 5 > bytes long (covering 5 bytes of text to emulate), where as a int3 is a > single byte. > > Thus, you either recompile and insert nops where you want to place your > jumps, or you trap using int3 that can do the work from within the > kernel. > > -- Steve _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: Capturing User-Level Function Calls/Returns 2020-07-15 21:48 ` Steven Rostedt 2020-07-15 21:48 ` [lttng-dev] " Steven Rostedt via lttng-dev 2020-07-15 22:25 ` ahmadkhorrami @ 2020-07-16 1:06 ` Michel Dagenais via lttng-dev 2020-07-16 1:06 ` [lttng-dev] " Michel Dagenais via lttng-dev ` (3 more replies) 2 siblings, 4 replies; 24+ messages in thread From: Michel Dagenais via lttng-dev @ 2020-07-16 1:06 UTC (permalink / raw) To: Steven Rostedt Cc: ahmadkhorrami, linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim > Without recompiling, how would that be implemented? As you mentioned, this is possible when "jump patching" 5 bytes instructions. Fast tracepoints in GDB and in kprobe do it. Kprobe goes further and patches sequences of instructions (because the target instruction is less than 5 bytes) if there is no incoming branch into the middle of the sequence. You can go even further, for instance using 3 bytes jumps to a trampoline installed in alignment nops. If you combine different strategies like this, you can eventually reach almost 100% success rate for "jump patching" tracepoints. This gets quite hairy though. However, the short story is that there is currently no tool as far as I know that does that easily and reliably in user space. https://onlinelibrary.wiley.com/doi/abs/10.1002/spe.2746 https://dl.acm.org/doi/pdf/10.1145/3062341.3062344 If you can afford a more invasive tool, that requires a lot of memory and stops your application for quite some time, you can look at approaches like dyninst that decompile the binary, insert instrumentation code and reassemble the code. https://dyninst.org/ > You would need to insert a jump on top of code, and still be able to > preserve that code. What a trap does, is to insert a int3, that will > trap into the kernel, it would then emulate the code that the int3 was > on, and also call some code that can trace the current state. > > To do it in user land, you would need to find way to replace the code > at the location you want to trace, with a jump to the tracing > infrastructure, that will also be able to emulate the code that the > jump was inserted on top of. As on x86, that jump will need to be 5 > bytes long (covering 5 bytes of text to emulate), where as a int3 is a > single byte. > > Thus, you either recompile and insert nops where you want to place your > jumps, or you trap using int3 that can do the work from within the > kernel. > > -- Steve > _______________________________________________ > lttng-dev mailing list > lttng-dev@lists.lttng.org > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 1:06 ` Michel Dagenais via lttng-dev @ 2020-07-16 1:06 ` Michel Dagenais via lttng-dev 2020-07-16 1:49 ` Frank Ch. Eigler ` (2 subsequent siblings) 3 siblings, 0 replies; 24+ messages in thread From: Michel Dagenais via lttng-dev @ 2020-07-16 1:06 UTC (permalink / raw) To: Steven Rostedt Cc: ahmadkhorrami, linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim > Without recompiling, how would that be implemented? As you mentioned, this is possible when "jump patching" 5 bytes instructions. Fast tracepoints in GDB and in kprobe do it. Kprobe goes further and patches sequences of instructions (because the target instruction is less than 5 bytes) if there is no incoming branch into the middle of the sequence. You can go even further, for instance using 3 bytes jumps to a trampoline installed in alignment nops. If you combine different strategies like this, you can eventually reach almost 100% success rate for "jump patching" tracepoints. This gets quite hairy though. However, the short story is that there is currently no tool as far as I know that does that easily and reliably in user space. https://onlinelibrary.wiley.com/doi/abs/10.1002/spe.2746 https://dl.acm.org/doi/pdf/10.1145/3062341.3062344 If you can afford a more invasive tool, that requires a lot of memory and stops your application for quite some time, you can look at approaches like dyninst that decompile the binary, insert instrumentation code and reassemble the code. https://dyninst.org/ > You would need to insert a jump on top of code, and still be able to > preserve that code. What a trap does, is to insert a int3, that will > trap into the kernel, it would then emulate the code that the int3 was > on, and also call some code that can trace the current state. > > To do it in user land, you would need to find way to replace the code > at the location you want to trace, with a jump to the tracing > infrastructure, that will also be able to emulate the code that the > jump was inserted on top of. As on x86, that jump will need to be 5 > bytes long (covering 5 bytes of text to emulate), where as a int3 is a > single byte. > > Thus, you either recompile and insert nops where you want to place your > jumps, or you trap using int3 that can do the work from within the > kernel. > > -- Steve > _______________________________________________ > lttng-dev mailing list > lttng-dev@lists.lttng.org > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 1:06 ` Michel Dagenais via lttng-dev 2020-07-16 1:06 ` [lttng-dev] " Michel Dagenais via lttng-dev @ 2020-07-16 1:49 ` Frank Ch. Eigler 2020-07-16 1:49 ` Frank Ch. Eigler via lttng-dev 2020-07-16 16:26 ` ahmadkhorrami 2020-07-16 16:20 ` ahmadkhorrami 2020-07-16 16:34 ` ahmadkhorrami 3 siblings, 2 replies; 24+ messages in thread From: Frank Ch. Eigler @ 2020-07-16 1:49 UTC (permalink / raw) To: Michel Dagenais Cc: Steven Rostedt, ahmadkhorrami, linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim Hi - > If you can afford a more invasive tool, that requires a lot of > memory and stops your application for quite some time, you can look > at approaches like dyninst that decompile the binary, insert > instrumentation code and reassemble the code. > https://dyninst.org/ For the record, systemtap includes a backend that uses dyninst as a pure userspace backend. % cat foo.c #include <stdio.h> int foo() { printf("foo\n"); return 1; } int main() { foo(); } % gcc -g foo.c % stap --runtime=dyninst -e ' probe process.function("*").{call,return} { println(pp()) } ' -c a.out foo process("/home/fche/a.out").function("main@/home/fche/foo.c:8").call process("/home/fche/a.out").function("foo@/home/fche/foo.c:3").call process("/home/fche/a.out").function("foo@/home/fche/foo.c:3").return process("/home/fche/a.out").function("main@/home/fche/foo.c:8").return - FChE ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 1:49 ` Frank Ch. Eigler @ 2020-07-16 1:49 ` Frank Ch. Eigler via lttng-dev 2020-07-16 16:26 ` ahmadkhorrami 1 sibling, 0 replies; 24+ messages in thread From: Frank Ch. Eigler via lttng-dev @ 2020-07-16 1:49 UTC (permalink / raw) To: Michel Dagenais Cc: Steven Rostedt, ahmadkhorrami, linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim Hi - > If you can afford a more invasive tool, that requires a lot of > memory and stops your application for quite some time, you can look > at approaches like dyninst that decompile the binary, insert > instrumentation code and reassemble the code. > https://dyninst.org/ For the record, systemtap includes a backend that uses dyninst as a pure userspace backend. % cat foo.c #include <stdio.h> int foo() { printf("foo\n"); return 1; } int main() { foo(); } % gcc -g foo.c % stap --runtime=dyninst -e ' probe process.function("*").{call,return} { println(pp()) } ' -c a.out foo process("/home/fche/a.out").function("main@/home/fche/foo.c:8").call process("/home/fche/a.out").function("foo@/home/fche/foo.c:3").call process("/home/fche/a.out").function("foo@/home/fche/foo.c:3").return process("/home/fche/a.out").function("main@/home/fche/foo.c:8").return - FChE _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 1:49 ` Frank Ch. Eigler 2020-07-16 1:49 ` Frank Ch. Eigler via lttng-dev @ 2020-07-16 16:26 ` ahmadkhorrami 2020-07-16 16:26 ` ahmadkhorrami via lttng-dev 1 sibling, 1 reply; 24+ messages in thread From: ahmadkhorrami @ 2020-07-16 16:26 UTC (permalink / raw) To: Frank Ch. Eigler Cc: Michel Dagenais, Steven Rostedt, linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim Hi Frank, Thanks for the point! Regards. On 2020-07-16 06:19, Frank Ch. Eigler wrote: > Hi - > >> If you can afford a more invasive tool, that requires a lot of >> memory and stops your application for quite some time, you can look >> at approaches like dyninst that decompile the binary, insert >> instrumentation code and reassemble the code. > >> https://dyninst.org/ > > For the record, systemtap includes a backend that uses dyninst as a > pure userspace backend. > > % cat foo.c > #include <stdio.h> > > int foo() { > printf("foo\n"); > return 1; > } > > int main() { > foo(); > } > > % gcc -g foo.c > > % stap --runtime=dyninst -e ' > probe process.function("*").{call,return} { println(pp()) } > ' -c a.out > > foo > process("/home/fche/a.out").function("main@/home/fche/foo.c:8").call > process("/home/fche/a.out").function("foo@/home/fche/foo.c:3").call > process("/home/fche/a.out").function("foo@/home/fche/foo.c:3").return > process("/home/fche/a.out").function("main@/home/fche/foo.c:8").return > > - FChE ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 16:26 ` ahmadkhorrami @ 2020-07-16 16:26 ` ahmadkhorrami via lttng-dev 0 siblings, 0 replies; 24+ messages in thread From: ahmadkhorrami via lttng-dev @ 2020-07-16 16:26 UTC (permalink / raw) To: Frank Ch. Eigler Cc: linux-trace-users-owner, linux-trace-users, Steven Rostedt, lttng-dev, Namhyung Kim Hi Frank, Thanks for the point! Regards. On 2020-07-16 06:19, Frank Ch. Eigler wrote: > Hi - > >> If you can afford a more invasive tool, that requires a lot of >> memory and stops your application for quite some time, you can look >> at approaches like dyninst that decompile the binary, insert >> instrumentation code and reassemble the code. > >> https://dyninst.org/ > > For the record, systemtap includes a backend that uses dyninst as a > pure userspace backend. > > % cat foo.c > #include <stdio.h> > > int foo() { > printf("foo\n"); > return 1; > } > > int main() { > foo(); > } > > % gcc -g foo.c > > % stap --runtime=dyninst -e ' > probe process.function("*").{call,return} { println(pp()) } > ' -c a.out > > foo > process("/home/fche/a.out").function("main@/home/fche/foo.c:8").call > process("/home/fche/a.out").function("foo@/home/fche/foo.c:3").call > process("/home/fche/a.out").function("foo@/home/fche/foo.c:3").return > process("/home/fche/a.out").function("main@/home/fche/foo.c:8").return > > - FChE _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 1:06 ` Michel Dagenais via lttng-dev 2020-07-16 1:06 ` [lttng-dev] " Michel Dagenais via lttng-dev 2020-07-16 1:49 ` Frank Ch. Eigler @ 2020-07-16 16:20 ` ahmadkhorrami 2020-07-16 16:20 ` ahmadkhorrami via lttng-dev 2020-07-16 16:34 ` ahmadkhorrami 3 siblings, 1 reply; 24+ messages in thread From: ahmadkhorrami @ 2020-07-16 16:20 UTC (permalink / raw) To: Michel Dagenais Cc: Steven Rostedt, linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim <p>Hi Michel,</p> <p>Thanks for the detailed answer! DBI tools are really interesting but I want to do this during normal execution and on multiple programs running simultaneously. I mean this is not supposed to be conventional tracing with multiple re-executions. I want to extract some information about the execution-state at runtime and inform the lower levels in the software stack to make smarter choices. Fortunately, there are only a few functions that need to be traced. But any reduction in the wasted cycles is helpful, specially if it is caused by privilege level transitions.</p> <p>Regards.</p> <p> </p> <p>On 2020-07-16 05:36, Michel Dagenais wrote:</p> <blockquote><!-- html ignored --><!-- head ignored --><!-- meta ignored --> <div class="pre"><br /> <blockquote>Without recompiling, how would that be implemented?</blockquote> <br /> As you mentioned, this is possible when "jump patching" 5 bytes instructions. Fast tracepoints in GDB and in kprobe do it. Kprobe goes further and patches sequences of instructions (because the target instruction is less than 5 bytes) if there is no incoming branch into the middle of the sequence. You can go even further, for instance using 3 bytes jumps to a trampoline installed in alignment nops. If you combine different strategies like this, you can eventually reach almost 100% success rate for "jump patching" tracepoints. This gets quite hairy though. However, the short story is that there is currently no tool as far as I know that does that easily and reliably in user space.<br /><br /><a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/spe.2746" target="_blank" rel="noopener noreferrer">https://onlinelibrary.wiley.com/doi/abs/10.1002/spe.2746</a><br /><a href="https://dl.acm.org/doi/pdf/10.1145/3062341.3062344" target="_blank" rel="noopener noreferrer">https://dl.acm.org/doi/pdf/10.1145/3062341.3062344</a><br /><br /> If you can afford a more invasive tool, that requires a lot of memory and stops your application for quite some time, you can look at approaches like dyninst that decompile the binary, insert instrumentation code and reassemble the code.<br /><br /><a href="https://dyninst.org/" target="_blank" rel="noopener noreferrer">https://dyninst.org/</a><br /><br /> <blockquote>You would need to insert a jump on top of code, and still be able to<br /> preserve that code. What a trap does, is to insert a int3, that will<br /> trap into the kernel, it would then emulate the code that the int3 was<br /> on, and also call some code that can trace the current state.<br /><br /> To do it in user land, you would need to find way to replace the code<br /> at the location you want to trace, with a jump to the tracing<br /> infrastructure, that will also be able to emulate the code that the<br /> jump was inserted on top of. As on x86, that jump will need to be 5<br /> bytes long (covering 5 bytes of text to emulate), where as a int3 is a<br /> single byte.<br /><br /> Thus, you either recompile and insert nops where you want to place your<br /> jumps, or you trap using int3 that can do the work from within the<br /> kernel.<br /><br /> -- Steve<br /> _______________________________________________<br /> lttng-dev mailing list<br /><a href="mailto:lttng-dev@lists.lttng.org">lttng-dev@lists.lttng.org</a><br /><a href="https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev" target="_blank" rel="noopener noreferrer">https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev</a></blockquote> </div> </blockquote> <p> </p> <div id="_rc_sig"> </div> ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 16:20 ` ahmadkhorrami @ 2020-07-16 16:20 ` ahmadkhorrami via lttng-dev 0 siblings, 0 replies; 24+ messages in thread From: ahmadkhorrami via lttng-dev @ 2020-07-16 16:20 UTC (permalink / raw) To: Michel Dagenais Cc: Steven Rostedt, linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim <p>Hi Michel,</p> <p>Thanks for the detailed answer! DBI tools are really interesting but I want to do this during normal execution and on multiple programs running simultaneously. I mean this is not supposed to be conventional tracing with multiple re-executions. I want to extract some information about the execution-state at runtime and inform the lower levels in the software stack to make smarter choices. Fortunately, there are only a few functions that need to be traced. But any reduction in the wasted cycles is helpful, specially if it is caused by privilege level transitions.</p> <p>Regards.</p> <p> </p> <p>On 2020-07-16 05:36, Michel Dagenais wrote:</p> <blockquote><!-- html ignored --><!-- head ignored --><!-- meta ignored --> <div class="pre"><br /> <blockquote>Without recompiling, how would that be implemented?</blockquote> <br /> As you mentioned, this is possible when "jump patching" 5 bytes instructions. Fast tracepoints in GDB and in kprobe do it. Kprobe goes further and patches sequences of instructions (because the target instruction is less than 5 bytes) if there is no incoming branch into the middle of the sequence. You can go even further, for instance using 3 bytes jumps to a trampoline installed in alignment nops. If you combine different strategies like this, you can eventually reach almost 100% success rate for "jump patching" tracepoints. This gets quite hairy though. However, the short story is that there is currently no tool as far as I know that does that easily and reliably in user space.<br /><br /><a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/spe.2746" target="_blank" rel="noopener noreferrer">https://onlinelibrary.wiley.com/doi/abs/10.1002/spe.2746</a><br /><a href="https://dl.acm.org/doi/pdf/10.1145/3062341.3062344" target="_blank" rel="noopener noreferrer">https://dl.acm.org/doi/pdf/10.1145/3062341.3062344</a><br /><br /> If you can afford a more invasive tool, that requires a lot of memory and stops your application for quite some time, you can look at approaches like dyninst that decompile the binary, insert instrumentation code and reassemble the code.<br /><br /><a href="https://dyninst.org/" target="_blank" rel="noopener noreferrer">https://dyninst.org/</a><br /><br /> <blockquote>You would need to insert a jump on top of code, and still be able to<br /> preserve that code. What a trap does, is to insert a int3, that will<br /> trap into the kernel, it would then emulate the code that the int3 was<br /> on, and also call some code that can trace the current state.<br /><br /> To do it in user land, you would need to find way to replace the code<br /> at the location you want to trace, with a jump to the tracing<br /> infrastructure, that will also be able to emulate the code that the<br /> jump was inserted on top of. As on x86, that jump will need to be 5<br /> bytes long (covering 5 bytes of text to emulate), where as a int3 is a<br /> single byte.<br /><br /> Thus, you either recompile and insert nops where you want to place your<br /> jumps, or you trap using int3 that can do the work from within the<br /> kernel.<br /><br /> -- Steve<br /> _______________________________________________<br /> lttng-dev mailing list<br /><a href="mailto:lttng-dev@lists.lttng.org">lttng-dev@lists.lttng.org</a><br /><a href="https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev" target="_blank" rel="noopener noreferrer">https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev</a></blockquote> </div> </blockquote> <p> </p> <div id="_rc_sig"> </div> _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 1:06 ` Michel Dagenais via lttng-dev ` (2 preceding siblings ...) 2020-07-16 16:20 ` ahmadkhorrami @ 2020-07-16 16:34 ` ahmadkhorrami 2020-07-16 16:34 ` ahmadkhorrami via lttng-dev 3 siblings, 1 reply; 24+ messages in thread From: ahmadkhorrami @ 2020-07-16 16:34 UTC (permalink / raw) To: Michel Dagenais Cc: Steven Rostedt, linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim Hi Michel, Thanks for the detailed answer! DBI tools are really interesting but I want to do this during normal execution and on multiple programs running simultaneously. I mean this is not supposed to be conventional tracing with multiple re-executions. I want to extract some information about the execution-state at runtime and inform the lower levels in the software stack to make smarter choices. Fortunately, there are only a few functions that need to be traced. But any reduction in the wasted cycles is helpful, specially if it is caused by privilege level transitions. Regards. On 2020-07-16 05:36, Michel Dagenais wrote: >> Without recompiling, how would that be implemented? > > As you mentioned, this is possible when "jump patching" 5 bytes > instructions. Fast tracepoints in GDB and in kprobe do it. Kprobe goes > further and patches sequences of instructions (because the target > instruction is less than 5 bytes) if there is no incoming branch into > the middle of the sequence. You can go even further, for instance using > 3 bytes jumps to a trampoline installed in alignment nops. If you > combine different strategies like this, you can eventually reach almost > 100% success rate for "jump patching" tracepoints. This gets quite > hairy though. However, the short story is that there is currently no > tool as far as I know that does that easily and reliably in user space. > > https://onlinelibrary.wiley.com/doi/abs/10.1002/spe.2746 > https://dl.acm.org/doi/pdf/10.1145/3062341.3062344 > > If you can afford a more invasive tool, that requires a lot of memory > and stops your application for quite some time, you can look at > approaches like dyninst that decompile the binary, insert > instrumentation code and reassemble the code. > > https://dyninst.org/ > >> You would need to insert a jump on top of code, and still be able to >> preserve that code. What a trap does, is to insert a int3, that will >> trap into the kernel, it would then emulate the code that the int3 was >> on, and also call some code that can trace the current state. >> >> To do it in user land, you would need to find way to replace the code >> at the location you want to trace, with a jump to the tracing >> infrastructure, that will also be able to emulate the code that the >> jump was inserted on top of. As on x86, that jump will need to be 5 >> bytes long (covering 5 bytes of text to emulate), where as a int3 is a >> single byte. >> >> Thus, you either recompile and insert nops where you want to place >> your >> jumps, or you trap using int3 that can do the work from within the >> kernel. >> >> -- Steve >> _______________________________________________ >> lttng-dev mailing list >> lttng-dev@lists.lttng.org >> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 16:34 ` ahmadkhorrami @ 2020-07-16 16:34 ` ahmadkhorrami via lttng-dev 0 siblings, 0 replies; 24+ messages in thread From: ahmadkhorrami via lttng-dev @ 2020-07-16 16:34 UTC (permalink / raw) To: Michel Dagenais Cc: Steven Rostedt, linux-trace-users-owner, linux-trace-users, lttng-dev, Namhyung Kim Hi Michel, Thanks for the detailed answer! DBI tools are really interesting but I want to do this during normal execution and on multiple programs running simultaneously. I mean this is not supposed to be conventional tracing with multiple re-executions. I want to extract some information about the execution-state at runtime and inform the lower levels in the software stack to make smarter choices. Fortunately, there are only a few functions that need to be traced. But any reduction in the wasted cycles is helpful, specially if it is caused by privilege level transitions. Regards. On 2020-07-16 05:36, Michel Dagenais wrote: >> Without recompiling, how would that be implemented? > > As you mentioned, this is possible when "jump patching" 5 bytes > instructions. Fast tracepoints in GDB and in kprobe do it. Kprobe goes > further and patches sequences of instructions (because the target > instruction is less than 5 bytes) if there is no incoming branch into > the middle of the sequence. You can go even further, for instance using > 3 bytes jumps to a trampoline installed in alignment nops. If you > combine different strategies like this, you can eventually reach almost > 100% success rate for "jump patching" tracepoints. This gets quite > hairy though. However, the short story is that there is currently no > tool as far as I know that does that easily and reliably in user space. > > https://onlinelibrary.wiley.com/doi/abs/10.1002/spe.2746 > https://dl.acm.org/doi/pdf/10.1145/3062341.3062344 > > If you can afford a more invasive tool, that requires a lot of memory > and stops your application for quite some time, you can look at > approaches like dyninst that decompile the binary, insert > instrumentation code and reassemble the code. > > https://dyninst.org/ > >> You would need to insert a jump on top of code, and still be able to >> preserve that code. What a trap does, is to insert a int3, that will >> trap into the kernel, it would then emulate the code that the int3 was >> on, and also call some code that can trace the current state. >> >> To do it in user land, you would need to find way to replace the code >> at the location you want to trace, with a jump to the tracing >> infrastructure, that will also be able to emulate the code that the >> jump was inserted on top of. As on x86, that jump will need to be 5 >> bytes long (covering 5 bytes of text to emulate), where as a int3 is a >> single byte. >> >> Thus, you either recompile and insert nops where you want to place >> your >> jumps, or you trap using int3 that can do the work from within the >> kernel. >> >> -- Steve >> _______________________________________________ >> lttng-dev mailing list >> lttng-dev@lists.lttng.org >> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: Capturing User-Level Function Calls/Returns 2020-07-15 18:28 ` Capturing User-Level Function Calls/Returns Steven Rostedt 2020-07-15 18:28 ` [lttng-dev] " Steven Rostedt via lttng-dev 2020-07-15 18:45 ` Mathieu Desnoyers @ 2020-07-16 1:04 ` Namhyung Kim 2020-07-16 1:04 ` [lttng-dev] " Namhyung Kim via lttng-dev 2020-07-16 16:07 ` ahmadkhorrami 2 siblings, 2 replies; 24+ messages in thread From: Namhyung Kim @ 2020-07-16 1:04 UTC (permalink / raw) To: Steven Rostedt Cc: ahmadkhorrami, Linux-trace Users, lttng-dev, Mathieu Desnoyers, Jérémie Galarneau Hi all, On Thu, Jul 16, 2020 at 3:28 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > On Wed, 15 Jul 2020 20:37:16 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > > > Hi, > > What is the most efficient way to capture occurrence of a function > > call/return of a binary program in userspace? > > It seems the answer is Uprobes. 1) Am I right? > > But Uprobes use "int" instruction which leads to a switch into kernel > > mode. 2) Wouldn't it be better to avoid this transition? > > I'm looking forward to your reply and will be happy to read your > > opinions. > > Regards. > > > Hi, I believe LTTng has utilities that can help you trace user space > programs. > > I think there's also a users ftrace like utility that Namhyung was > working on. But I don't know where in the development that is. It's in https://github.com/namhyung/uftrace Basically it also requires recompilation to add mcount calls for each function. But it now also supports dynamic tracing without any recompilation.. :) It's still experimental and has some limitation, but the idea is to copy first 5 bytes (on x86_64) somewhere and replace it to a call instruction. Thanks Namhyung ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 1:04 ` Namhyung Kim @ 2020-07-16 1:04 ` Namhyung Kim via lttng-dev 2020-07-16 16:07 ` ahmadkhorrami 1 sibling, 0 replies; 24+ messages in thread From: Namhyung Kim via lttng-dev @ 2020-07-16 1:04 UTC (permalink / raw) To: Steven Rostedt; +Cc: ahmadkhorrami, Linux-trace Users, lttng-dev Hi all, On Thu, Jul 16, 2020 at 3:28 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > On Wed, 15 Jul 2020 20:37:16 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > > > Hi, > > What is the most efficient way to capture occurrence of a function > > call/return of a binary program in userspace? > > It seems the answer is Uprobes. 1) Am I right? > > But Uprobes use "int" instruction which leads to a switch into kernel > > mode. 2) Wouldn't it be better to avoid this transition? > > I'm looking forward to your reply and will be happy to read your > > opinions. > > Regards. > > > Hi, I believe LTTng has utilities that can help you trace user space > programs. > > I think there's also a users ftrace like utility that Namhyung was > working on. But I don't know where in the development that is. It's in https://github.com/namhyung/uftrace Basically it also requires recompilation to add mcount calls for each function. But it now also supports dynamic tracing without any recompilation.. :) It's still experimental and has some limitation, but the idea is to copy first 5 bytes (on x86_64) somewhere and replace it to a call instruction. Thanks Namhyung _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: Capturing User-Level Function Calls/Returns 2020-07-16 1:04 ` Namhyung Kim 2020-07-16 1:04 ` [lttng-dev] " Namhyung Kim via lttng-dev @ 2020-07-16 16:07 ` ahmadkhorrami 2020-07-16 16:07 ` [lttng-dev] " ahmadkhorrami via lttng-dev 1 sibling, 1 reply; 24+ messages in thread From: ahmadkhorrami @ 2020-07-16 16:07 UTC (permalink / raw) To: Namhyung Kim Cc: Steven Rostedt, Linux-trace Users, lttng-dev, Mathieu Desnoyers, Jérémie Galarneau, linux-trace-users-owner Hi Namhyung, This seems really interesting and is what I am looking for. Can it capture all function entries/exits? I mean does it fully handle variable instruction sizes in dynamic mode? In any case, thanks! and I hope that it becomes stable as soon as possible, so that everyone can use it. Regards. On 2020-07-16 05:34, Namhyung Kim wrote: > Hi all, > > On Thu, Jul 16, 2020 at 3:28 AM Steven Rostedt <rostedt@goodmis.org> > wrote: > On Wed, 15 Jul 2020 20:37:16 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > > Hi, > What is the most efficient way to capture occurrence of a function > call/return of a binary program in userspace? > It seems the answer is Uprobes. 1) Am I right? > But Uprobes use "int" instruction which leads to a switch into kernel > mode. 2) Wouldn't it be better to avoid this transition? > I'm looking forward to your reply and will be happy to read your > opinions. > Regards. > > Hi, I believe LTTng has utilities that can help you trace user space > programs. > > I think there's also a users ftrace like utility that Namhyung was > working on. But I don't know where in the development that is. It's in https://github.com/namhyung/uftrace Basically it also requires recompilation to add mcount calls for each function. But it now also supports dynamic tracing without any recompilation.. :) It's still experimental and has some limitation, but the idea is to copy first 5 bytes (on x86_64) somewhere and replace it to a call instruction. Thanks Namhyung ^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [lttng-dev] Capturing User-Level Function Calls/Returns 2020-07-16 16:07 ` ahmadkhorrami @ 2020-07-16 16:07 ` ahmadkhorrami via lttng-dev 0 siblings, 0 replies; 24+ messages in thread From: ahmadkhorrami via lttng-dev @ 2020-07-16 16:07 UTC (permalink / raw) To: Namhyung Kim Cc: linux-trace-users-owner, Steven Rostedt, Linux-trace Users, lttng-dev Hi Namhyung, This seems really interesting and is what I am looking for. Can it capture all function entries/exits? I mean does it fully handle variable instruction sizes in dynamic mode? In any case, thanks! and I hope that it becomes stable as soon as possible, so that everyone can use it. Regards. On 2020-07-16 05:34, Namhyung Kim wrote: > Hi all, > > On Thu, Jul 16, 2020 at 3:28 AM Steven Rostedt <rostedt@goodmis.org> > wrote: > On Wed, 15 Jul 2020 20:37:16 +0430 > ahmadkhorrami <ahmadkhorrami@ut.ac.ir> wrote: > > Hi, > What is the most efficient way to capture occurrence of a function > call/return of a binary program in userspace? > It seems the answer is Uprobes. 1) Am I right? > But Uprobes use "int" instruction which leads to a switch into kernel > mode. 2) Wouldn't it be better to avoid this transition? > I'm looking forward to your reply and will be happy to read your > opinions. > Regards. > > Hi, I believe LTTng has utilities that can help you trace user space > programs. > > I think there's also a users ftrace like utility that Namhyung was > working on. But I don't know where in the development that is. It's in https://github.com/namhyung/uftrace Basically it also requires recompilation to add mcount calls for each function. But it now also supports dynamic tracing without any recompilation.. :) It's still experimental and has some limitation, but the idea is to copy first 5 bytes (on x86_64) somewhere and replace it to a call instruction. Thanks Namhyung _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ^ permalink raw reply [flat|nested] 24+ messages in thread
end of thread, other threads:[~2020-07-16 16:34 UTC | newest] Thread overview: 24+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- [not found] <e9c7400ff0075f3beba2863c4432a905@ut.ac.ir> 2020-07-15 18:28 ` Capturing User-Level Function Calls/Returns Steven Rostedt 2020-07-15 18:28 ` [lttng-dev] " Steven Rostedt via lttng-dev 2020-07-15 18:45 ` Mathieu Desnoyers 2020-07-15 18:45 ` [lttng-dev] " Mathieu Desnoyers via lttng-dev 2020-07-15 21:39 ` ahmadkhorrami 2020-07-15 21:39 ` [lttng-dev] " ahmadkhorrami via lttng-dev 2020-07-15 21:48 ` Steven Rostedt 2020-07-15 21:48 ` [lttng-dev] " Steven Rostedt via lttng-dev 2020-07-15 22:25 ` ahmadkhorrami 2020-07-15 22:25 ` [lttng-dev] " ahmadkhorrami via lttng-dev 2020-07-16 1:06 ` Michel Dagenais via lttng-dev 2020-07-16 1:06 ` [lttng-dev] " Michel Dagenais via lttng-dev 2020-07-16 1:49 ` Frank Ch. Eigler 2020-07-16 1:49 ` Frank Ch. Eigler via lttng-dev 2020-07-16 16:26 ` ahmadkhorrami 2020-07-16 16:26 ` ahmadkhorrami via lttng-dev 2020-07-16 16:20 ` ahmadkhorrami 2020-07-16 16:20 ` ahmadkhorrami via lttng-dev 2020-07-16 16:34 ` ahmadkhorrami 2020-07-16 16:34 ` ahmadkhorrami via lttng-dev 2020-07-16 1:04 ` Namhyung Kim 2020-07-16 1:04 ` [lttng-dev] " Namhyung Kim via lttng-dev 2020-07-16 16:07 ` ahmadkhorrami 2020-07-16 16:07 ` [lttng-dev] " ahmadkhorrami via lttng-dev
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