kernel/linux.git/tools/perf/util/jitdump.c, branch v5.9.2

perf inject jit: Remove //anon mmap events

2020-07-08T16:51:12+00:00

**perf-.map and jit-.dump designs: When a JIT generates code to be executed, it must allocate memory and mark it executable using an mmap call. *** perf-.map design The perf-.map assumes that any sample recorded in an anonymous memory page is JIT code. It then tries to resolve the symbol name by looking at the process' perf-.map. *** jit-.dump design The jit-.dump mechanism takes a different approach. It requires a JIT to write a `/jit-.dump` file. This file must also be mmapped so that perf inject -jit can find the file. The JIT must also add JIT_CODE_LOAD records for any functions it generates. The records are timestamped using a clock which can be correlated to the perf record clock. After perf record, the `perf inject -jit` pass parses the recording looking for a `/jit-.dump` file. When it finds the file, it parses it and for each JIT_CODE_LOAD record: * creates an elf file `/jitted--.so * injects a new mmap record mapping the new elf file into the process. *** Coexistence design The kernel and perf support both of these mechanisms. We need to make sure perf works on an app supporting either or both of these mechanisms. Both designs rely on mmap records to determine how to resolve an ip address. The mmap records of both techniques by definition overlap. When the JIT compiles a method, it must: * allocate memory (mmap) * add execution privilege (mprotect or mmap. either will generate an mmap event form the kernel to perf) * compile code into memory * add a function record to perf-.map and/or jit-.dump Because the jit-.dump mechanism supports greater capabilities, perf prefers the symbols from jit-.dump. It implements this based on timestamp ordering of events. There is an implicit ASSUMPTION that the JIT_CODE_LOAD record timestamp will be after the // anon mmap event that was generated during memory allocation or adding the execution privilege setting. *** Problems with the ASSUMPTION The ASSUMPTION made in the Coexistence design section above is violated in the following scenario. *** Scenario While a JIT is jitting code it will eventually need to commit more pages and change these pages to executable permissions. Typically the JIT will want these collocated to minimize branch displacements. The kernel will coalesce these anonymous mapping with identical permissions before sending an MMAP event for the new pages. The address range of the new mmap will not be just the most recently mmap pages. It will include the entire coalesced mmap region. See mm/mmap.c unsigned long mmap_region(struct file *file, unsigned long addr, unsigned long len, vm_flags_t vm_flags, unsigned long pgoff, struct list_head *uf) { ... /* * Can we just expand an old mapping? */ ... perf_event_mmap(vma); ... } *** Symptoms The coalesced // anon mmap event will be timestamped after the JIT_CODE_LOAD records. This means it will be used as the most recent mapping for that entire address range. For remaining events it will look at the inferior perf-.map for symbols. If both mechanisms are supported, the symbol will appear twice with different module names. This causes weird behavior in reporting. If only jit-.dump is supported, the symbol will no longer be resolved. ** Implemented solution This patch solves the issue by removing // anon mmap events for any process which has a valid jit-.dump file. It tracks on a per process basis to handle the case where some running apps support jit-.dump, but some only support perf-.map. It adds new assumptions: * // anon mmap events are only required for perf-.map support. * An app that uses jit-.dump, no longer needs perf-.map support. It assumes that any perf-.map info is inferior. *** Details Use thread->priv to store whether a jitdump file has been processed During "perf inject --jit", discard "//anon*" mmap events for any pid which has sucessfully processed a jitdump file. ** Testing: // jitdump case perf record perf inject --jit --input perf.data --output perfjit.data // verify mmap "//anon" events present initially perf script --input perf.data --show-mmap-events | grep '//anon' // verify mmap "//anon" events removed perf script --input perfjit.data --show-mmap-events | grep '//anon' // no jitdump case perf record perf inject --jit --input perf.data --output perfjit.data // verify mmap "//anon" events present initially perf script --input perf.data --show-mmap-events | grep '//anon' // verify mmap "//anon" events not removed perf script --input perfjit.data --show-mmap-events | grep '//anon' ** Repro: This issue was discovered while testing the initial CoreCLR jitdump implementation. https://github.com/dotnet/coreclr/pull/26897. ** Alternate solutions considered These were also briefly considered: * Change kernel to not coalesce mmap regions. * Change kernel reporting of coalesced mmap regions to perf. Only include newly mapped memory. * Only strip parts of // anon mmap events overlapping existing jitted--.so mmap events. Signed-off-by: Steve MacLean Acked-by: Ian Rogers Cc: Alexander Shishkin Cc: Jiri Olsa Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stephane Eranian Link: http://lore.kernel.org/lkml/1590544271-125795-1-git-send-email-steve.maclean@linux.microsoft.com Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Replace zero-length array with flexible-array

2020-05-28T13:03:27+00:00

The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Gustavo A. R. Silva Cc: Ian Rogers Cc: Jiri Olsa Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/20200515172926.GA31976@embeddedor Signed-off-by: Arnaldo Carvalho de Melo

perf inject jit: Fix JIT_CODE_MOVE filename

2019-09-30T20:29:49+00:00

During perf inject --jit, JIT_CODE_MOVE records were injecting MMAP records with an incorrect filename. Specifically it was missing the ".so" suffix. Further the JIT_CODE_LOAD record were silently truncating the jr->load.code_index field to 32 bits before generating the filename. Make both records emit the same filename based on the full 64 bit code_index field. Fixes: 9b07e27f88b9 ("perf inject: Add jitdump mmap injection support") Cc: stable@vger.kernel.org # v4.6+ Signed-off-by: Steve MacLean Acked-by: Jiri Olsa Cc: Alexander Shishkin Cc: Andi Kleen Cc: Brian Robbins Cc: Davidlohr Bueso Cc: Eric Saint-Etienne Cc: John Keeping Cc: John Salem Cc: Leo Yan Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Song Liu Cc: Stephane Eranian Cc: Tom McDonald Link: http://lore.kernel.org/lkml/BN8PR21MB1362FF8F127B31DBF4121528F7800@BN8PR21MB1362.namprd21.prod.outlook.com Signed-off-by: Arnaldo Carvalho de Melo

libperf: Add perf_evlist__first()/last() functions

2019-09-25T12:51:48+00:00

Add perf_evlist__first()/last() functions to libperf, as internal functions and rename perf's origins to evlist__first/last. Signed-off-by: Jiri Olsa Cc: Alexander Shishkin Cc: Michael Petlan Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/20190913132355.21634-29-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Remove util.h from where it is not needed

2019-09-20T12:19:20+00:00

Check that it is not needed and remove, fixing up some fallout for places where it was only serving to get something else. Cc: Adrian Hunter Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lkml.kernel.org/n/tip-9h6dg6lsqe2usyqjh5rrues4@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Remove needless builtin.h include directives

2019-09-20T12:19:20+00:00

Now that builtin.h isn't included by any other header, we can check where it is really needed, i.e. we can remove it and be sure that it isn't being obtained indirectly. Cc: Adrian Hunter Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lkml.kernel.org/n/tip-mn7jheex85iw9qo6tlv26hb2@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf dsos: Move the dsos struct and its methods to separate source files

2019-09-01T01:24:10+00:00

So that we can reduce the header dependency tree further, in the process noticed that lots of places were getting even things like build-id routines and 'struct perf_tool' definition indirectly, so fix all those too. Cc: Adrian Hunter Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lkml.kernel.org/n/tip-ti0btma9ow5ndrytyoqdk62j@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

libperf: Move perf_event_attr field from perf's evsel to libperf's perf_evsel

2019-07-29T21:34:45+00:00

Move the perf_event_attr struct fron 'struct evsel' to 'struct perf_evsel'. Committer notes: Fixed up these: tools/perf/arch/arm/util/auxtrace.c tools/perf/arch/arm/util/cs-etm.c tools/perf/arch/arm64/util/arm-spe.c tools/perf/arch/s390/util/auxtrace.c tools/perf/util/cs-etm.c Also cc1: warnings being treated as errors tests/sample-parsing.c: In function 'do_test': tests/sample-parsing.c:162: error: missing initializer tests/sample-parsing.c:162: error: (near initialization for 'evsel.core.cpus') struct evsel evsel = { .needs_swap = false, - .core.attr = { - .sample_type = sample_type, - .read_format = read_format, + .core = { + . attr = { + .sample_type = sample_type, + .read_format = read_format, + }, [perfbuilder@a70e4eeb5549 /]$ gcc --version |& head -1 gcc (GCC) 4.4.7 Also we don't need to include perf_event.h in tools/perf/lib/include/perf/evsel.h, forward declaring 'struct perf_event_attr' is enough. And this even fixes the build in some systems where things are used somewhere down the include path from perf_event.h without defining __always_inline. Signed-off-by: Jiri Olsa Cc: Alexander Shishkin Cc: Alexey Budankov Cc: Andi Kleen Cc: Michael Petlan Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20190721112506.12306-43-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf evsel: Rename struct perf_evsel to struct evsel

2019-07-29T21:34:42+00:00

Rename struct perf_evsel to struct evsel, so we don't have a name clash when we add struct perf_evsel in libperf. Committer notes: Added fixes for arm64, provided by Jiri. Signed-off-by: Jiri Olsa Cc: Alexander Shishkin Cc: Alexey Budankov Cc: Andi Kleen Cc: Michael Petlan Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20190721112506.12306-5-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Use zfree() where applicable

2019-07-09T13:13:27+00:00

In places where the equivalent was already being done, i.e.: free(a); a = NULL; And in placs where struct members are being freed so that if we have some erroneous reference to its struct, then accesses to freed members will result in segfaults, which we can detect faster than use after free to areas that may still have something seemingly valid. Cc: Adrian Hunter Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lkml.kernel.org/n/tip-jatyoofo5boc1bsvoig6bb6i@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo