- 08 Oct, 2021 27 commits
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Yucong Sun authored
bpf_get_current_pid_tgid() returns u64, whose upper 32 bits are the same as userspace getpid() return value. Signed-off-by:
Yucong Sun <sunyucong@gmail.com> Signed-off-by:
Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20211006185619.364369-13-fallentree@fb.com
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Yucong Sun authored
This make atomics test able to run in parallel with other tests. Signed-off-by:
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Yucong Sun authored
This patch change cgroup_v1v2 use a different port, avoid conflict with other tests. Signed-off-by:
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Yucong Sun authored
In parallel execution mode, this test now need to use atomic operation to avoid race condition. Signed-off-by:
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Yucong Sun authored
This patch make each worker use a unique cgroup base directory, thus allowing tests that uses cgroups to run concurrently. Signed-off-by:
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Yucong Sun authored
This patch allows tests to define serial_test_name() instead of test_name(), and this will make test_progs execute those in sequence after all other tests finished executing concurrently. Signed-off-by:
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Yucong Sun authored
This patch adds "-j" mode to test_progs, executing tests in multiple process. "-j" mode is optional, and works with all existing test selection mechanism, as well as "-v", "-l" etc. In "-j" mode, main process use UDS/SEQPACKET to communicate to each forked worker, commanding it to run tests and collect logs. After all tests are finished, a summary is printed. main process use multiple competing threads to dispatch work to worker, trying to keep them all busy. The test status will be printed as soon as it is finished, if there are error logs, it will be printed after the final summary line. By specifying "--debug", additional debug information on server/worker communication will be printed. Example output: > ./test_progs -n 15-20 -j [ 12.801730] bpf_testmod: loading out-of-tree module taints kernel. Launching 8 workers. #20 btf_split:OK #16 btf_endian:OK #18 btf_module:OK #17 btf_map_in_map:OK #19 btf_skc_cls_ingress:OK #15 btf_dump:OK Summary: 6/20 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by:
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Andrii Nakryiko authored
Hou Tao says: ==================== From: Hou Tao <houtao1@huawei.com> Hi, The patchset series supports writable context for bare tracepoint. The main idea comes from patchset "writable contexts for bpf raw tracepoints" [1], but it only supports normal tracepoint with associated trace event under tracefs. Now we have one use case in which we add bare tracepoint in VFS layer, and update file::f_mode for specific files. The reason using bare tracepoint is that it doesn't form a ABI and we can change it freely. So add support for it in BPF. Comments are always welcome. [1]: https://lore.kernel.org/lkml/20190426184951.21812-1-mmullins@fb.com Change log: v5: * rebased on bpf-next * patch 1: add Acked-by tag * patch 2: handle invalid section name, make prefixes array being const v4: https://www.spinics.net/lists/bpf/msg47021.html * rebased on bpf-next * update patch 2 to add support for writable raw tracepoint attachment in attach_raw_tp(). * update patch 3 to add Acked-by tag v3: https://www.spinics.net/lists/bpf/msg46824.html * use raw_tp.w instead of raw_tp_writable as section name of writable tp * use ASSERT_XXX() instead of CHECK() * define a common macro for "/sys/kernel/bpf_testmod" v2: https://www.spinics.net/lists/bpf/msg46356.html * rebase on bpf-next tree * address comments from Yonghong Song * rename bpf_testmode_test_writable_ctx::ret as early_ret to reflect its purpose better. v1: https://www.spinics.net/lists/bpf/msg46221.html ==================== Signed-off-by:
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Hou Tao authored
Add a writable bare tracepoint in bpf_testmod module, and trigger its calling when reading /sys/kernel/bpf_testmod with a specific buffer length. The reading will return the value in writable context if the early return flag is enabled in writable context. Signed-off-by:
Hou Tao <houtao1@huawei.com> Signed-off-by:
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Hou Tao authored
Program on writable tracepoint is BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, but its attachment is the same as BPF_PROG_TYPE_RAW_TRACEPOINT. Signed-off-by:
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Hou Tao authored
Commit 9df1c28b ("bpf: add writable context for raw tracepoints") supports writable context for tracepoint, but it misses the support for bare tracepoint which has no associated trace event. Bare tracepoint is defined by DECLARE_TRACE(), so adding a corresponding DECLARE_TRACE_WRITABLE() macro to generate a definition in __bpf_raw_tp_map section for bare tracepoint in a similar way to DEFINE_TRACE_WRITABLE(). Signed-off-by:
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Andrii Nakryiko authored
Quentin Monnet says: ==================== Libbpf is used at several locations in the repository. Most of the time, the tools relying on it build the library in its own directory, and include the headers from there. This works, but this is not the cleanest approach. It generates objects outside of the directory of the tool which is being built, and it also increases the risk that developers include a header file internal to libbpf, which is not supposed to be exposed to user applications. This set adjusts all involved Makefiles to make sure that libbpf is built locally (with respect to the tool's directory or provided build directory), and by ensuring that "make install_headers" is run from libbpf's Makefile to export user headers properly. This comes at a cost: given that the libbpf was so far mostly compiled in its own directory by the different components using it, compiling it once would be enough for all those components. With the new approach, each component compiles its own version. To mitigate this cost, efforts were made to reuse the compiled library when possible: - Make the bpftool version in samples/bpf reuse the library previously compiled for the selftests. - Make the bpftool version in BPF selftests reuse the library previously compiled for the selftests. - Similarly, make resolve_btfids in BPF selftests reuse the same compiled library. - Similarly, make runqslower in BPF selftests reuse the same compiled library; and make it rely on the bpftool version also compiled from the selftests (instead of compiling its own version). - runqslower, when compiled independently, needs its own version of bpftool: make them share the same compiled libbpf. As a result: - Compiling the samples/bpf should compile libbpf just once. - Compiling the BPF selftests should compile libbpf just once. - Compiling the kernel (with BTF support) should now lead to compiling libbpf twice: one for resolve_btfids, one for kernel/bpf/preload. - Compiling runqslower individually should compile libbpf just once. Same thing for bpftool, resolve_btfids, and kernel/bpf/preload/iterators. (Not accounting for the boostrap version of libbpf required by bpftool, which was already placed under a dedicated .../boostrap/libbpf/ directory, and for which the count remains unchanged.) A few commits in the series also contain drive-by clean-up changes for bpftool includes, samples/bpf/.gitignore, or test_bpftool_build.sh. Please refer to individual commit logs for details. v4: - Make the "libbpf_hdrs" dependency an order-only dependency in kernel/bpf/preload/Makefile, samples/bpf/Makefile, and tools/bpf/runqslower/Makefile. This is to avoid to unconditionally recompile the targets. - samples/bpf/.gitignore: prefix objects with a "/" to mark that we ignore them when at the root of the samples/bpf/ directory. - libbpf: add a commit to make "install_headers" depend on the header files, to avoid exporting again if the sources are older than the targets. This ensures that applications relying on those headers are not rebuilt unnecessarily. - bpftool: uncouple the copy of nlattr.h from libbpf target, to have it depend on the source header itself. By avoiding to reinstall this header every time, we avoid unnecessary builds of bpftool. - samples/bpf: Add a new commit to remove the FORCE dependency for libbpf, and replace it with a "$(wildcard ...)" on the .c/.h files in libbpf's directory. This is to avoid always recompiling libbpf/bpftool. - Adjust prefixes in commit subjects. v3: - Remove order-only dependencies on $(LIBBPF_INCLUDE) (or equivalent) directories, given that they are created by libbpf's Makefile. - Add libbpf as a dependency for bpftool/resolve_btfids/runqslower when they are supposed to reuse a libbpf compiled previously. This is to avoid having several libbpf versions being compiled simultaneously in the same directory with parallel builds. Even if this didn't show up during tests, let's remain on the safe side. - kernel/bpf/preload/Makefile: Rename libbpf-hdrs (dash) dependency as libbpf_hdrs. - samples/bpf/.gitignore: Add bpftool/ - samples/bpf/Makefile: Change "/bin/rm -rf" to "$(RM) -r". - samples/bpf/Makefile: Add missing slashes for $(LIBBPF_OUTPUT) and $(LIBBPF_DESTDIR) when buildling bpftool - samples/bpf/Makefile: Add a dependency to libbpf's headers for $(TRACE_HELPERS). - bpftool's Makefile: Use $(LIBBPF) instead of equivalent (but longer) $(LIBBPF_OUTPUT)libbpf.a - BPF iterators' Makefile: build bpftool in .output/bpftool (instead of .output/), add and clean up variables. - runqslower's Makefile: Add an explicit dependency on libbpf's headers to several objects. The dependency is not required (libbpf should have been compiled and so the headers exported through other dependencies for those targets), but they better mark the logical dependency and should help if exporting the headers changed in the future. - New commit to add an "install-bin" target to bpftool, to avoid installing bash completion when buildling BPF iterators and selftests. v2: Declare an additional dependency on libbpf's headers for iterators/iterators.o in kernel/preload/Makefile to make sure that these headers are exported before we compile the object file (and not just before we link it). ==================== Signed-off-by: -
Quentin Monnet authored
With "make install", bpftool installs its binary and its bash completion file. Usually, this is what we want. But a few components in the kernel repository (namely, BPF iterators and selftests) also install bpftool locally before using it. In such a case, bash completion is not necessary and is just a useless build artifact. Let's add an "install-bin" target to bpftool, to offer a way to install the binary only. Signed-off-by:
Quentin Monnet <quentin@isovalent.com> Signed-off-by:
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Quentin Monnet authored
The script test_bpftool_build.sh attempts to build bpftool in the various supported ways, to make sure nothing breaks. One of those ways is to run "make tools/bpf" from the root of the kernel repository. This command builds bpftool, along with the other tools under tools/bpf, and runqslower in particular. After running the command and upon a successful bpftool build, the script attempts to cleanup the generated objects. However, after building with this target and in the case of runqslower, the files are not cleaned up as expected. This is because the "tools/bpf" target sets $(OUTPUT) to .../tools/bpf/runqslower/ when building the tool, causing the object files to be placed directly under the runqslower directory. But when running "cd tools/bpf; make clean", the value for $(OUTPUT) is set to ".output" (relative to the runqslower directory) by runqslower's Makefile, and this is where the Makefile looks for files to clean up. We cannot easily fix in the root Makefile (where "tools/bpf" is defined) or in tools/scripts/Makefile.include (setting $(OUTPUT)), where changing the way the output variables are passed would likely have consequences elsewhere. We could change runqslower's Makefile to build in the repository instead of in a dedicated ".output/", but doing so just to accommodate a test script doesn't sound great. Instead, let's just make sure that we clean up runqslower properly by adding the correct command to the script. This will attempt to clean runqslower twice: the first try with command "cd tools/bpf; make clean" will search for tools/bpf/runqslower/.output and fail to clean it (but will still clean the other tools, in particular bpftool), the second one (added in this commit) sets the $(OUTPUT) variable like for building with the "tool/bpf" target and should succeed. Signed-off-by:
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Quentin Monnet authored
In samples/bpf/Makefile, libbpf has a FORCE dependency that force it to be rebuilt. I read this as a way to keep the library up-to-date, given that we do not have, in samples/bpf, a list of the source files for libbpf itself. However, a better approach would be to use the "$(wildcard ...)" function from make, and to have libbpf depend on all the .c and .h files in its directory. This is what samples/bpf/Makefile does for bpftool, and also what the BPF selftests' Makefile does for libbpf. Let's update the Makefile to avoid rebuilding libbpf all the time (and bpftool on top of it). Signed-off-by:
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Quentin Monnet authored
API headers from libbpf should not be accessed directly from the source directory. Instead, they should be exported with "make install_headers". Make sure that samples/bpf/Makefile installs the headers properly when building. The object compiled from and exported by libbpf are now placed into a subdirectory of sample/bpf/ instead of remaining in tools/lib/bpf/. We attempt to remove this directory on "make clean". However, the "clean" target re-enters the samples/bpf/ directory from the root of the repository ("$(MAKE) -C ../../ M=$(CURDIR) clean"), in such a way that $(srctree) and $(src) are not defined, making it impossible to use $(LIBBPF_OUTPUT) and $(LIBBPF_DESTDIR) in the recipe. So we only attempt to clean $(CURDIR)/libbpf, which is the default value. Add a dependency on libbpf's headers for the $(TRACE_HELPERS). We also change the output directory for bpftool, to place the generated objects under samples/bpf/bpftool/ instead of building in bpftool's directory directly. Doing so, we make sure bpftool reuses the libbpf library previously compiled and installed. Signed-off-by: -
Quentin Monnet authored
Update samples/bpf/.gitignore to ignore files generated when building the samples. Add: - vmlinux.h - the generated skeleton files (*.skel.h) - the samples/bpf/libbpf/ and .../bpftool/ directories, in preparation of a future commit which introduces a local output directory for building libbpf and bpftool. Signed-off-by: -
Quentin Monnet authored
API headers from libbpf should not be accessed directly from the library's source directory. Instead, they should be exported with "make install_headers". Let's make sure that bpf/preload/iterators/Makefile installs the headers properly when building. Signed-off-by:
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Quentin Monnet authored
API headers from libbpf should not be accessed directly from the library's source directory. Instead, they should be exported with "make install_headers". Let's make sure that bpf/preload/Makefile installs the headers properly when building. Note that we declare an additional dependency for iterators/iterators.o: having $(LIBBPF_A) as a dependency to "$(obj)/bpf_preload_umd" is not sufficient, as it makes it required only at the linking step. But we need libbpf to be compiled, and in particular its headers to be exported, before we attempt to compile iterators.o. The issue would not occur before this commit, because libbpf's headers were not exported and were always available under tools/lib/bpf. Signed-off-by:
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Quentin Monnet authored
API headers from libbpf should not be accessed directly from the library's source directory. Instead, they should be exported with "make install_headers". Let's make sure that runqslower installs the headers properly when building. We use a libbpf_hdrs target to mark the logical dependency on libbpf's headers export for a number of object files, even though the headers should have been exported at this time (since bpftool needs them, and is required to generate the skeleton or the vmlinux.h). When descending from a parent Makefile, the specific output directories for building the library and exporting the headers are configurable with BPFOBJ_OUTPUT and BPF_DESTDIR, respectively. This is in addition to OUTPUT, on top of which those variables are constructed by default. Also adjust the Makefile for the BPF selftests. We pass a number of variables to the "make" invocation, because we want to point runqslower to the (target) libbpf shared with other tools, instead of building its own version. In addition, runqslower relies on (target) bpftool, and we also want to pass the proper variables to its Makefile so that bpftool itself reuses the same libbpf. Signed-off-by:
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Quentin Monnet authored
API headers from libbpf should not be accessed directly from the library's source directory. Instead, they should be exported with "make install_headers". Let's make sure that resolve_btfids installs the headers properly when building. When descending from a parent Makefile, the specific output directories for building the library and exporting the headers are configurable with LIBBPF_OUT and LIBBPF_DESTDIR, respectively. This is in addition to OUTPUT, on top of which those variables are constructed by default. Also adjust the Makefile for the BPF selftests in order to point to the (target) libbpf shared with other tools, instead of building a version specific to resolve_btfids. Remove libbpf's order-only dependencies on the include directories (they are created by libbpf and don't need to exist beforehand). Signed-off-by:
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Quentin Monnet authored
Bpftool relies on libbpf, therefore it relies on a number of headers from the library and must be linked against the library. The Makefile for bpftool exposes these objects by adding tools/lib as an include directory ("-I$(srctree)/tools/lib"). This is a working solution, but this is not the cleanest one. The risk is to involuntarily include objects that are not intended to be exposed by the libbpf. The headers needed to compile bpftool should in fact be "installed" from libbpf, with its "install_headers" Makefile target. In addition, there is one header which is internal to the library and not supposed to be used by external applications, but that bpftool uses anyway. Adjust the Makefile in order to install the header files properly before compiling bpftool. Also copy the additional internal header file (nlattr.h), but call it out explicitly. Build (and install headers) in a subdirectory under bpftool/ instead of tools/lib/bpf/. When descending from a parent Makefile, this is configurable by setting the OUTPUT, LIBBPF_OUTPUT and LIBBPF_DESTDIR variables. Also adjust the Makefile for BPF selftests, so as to reuse the (host) libbpf compiled earlier and to avoid compiling a separate version of the library just for bpftool. Signed-off-by: -
Quentin Monnet authored
It seems that the header file was never necessary to compile bpftool, and it is not part of the headers exported from libbpf. Let's remove the includes from prog.c and gen.c. Fixes: d510296d ("bpftool: Use syscall/loader program in "prog load" and "gen skeleton" command.") Signed-off-by:
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Quentin Monnet authored
The "install_headers" target in libbpf's Makefile would unconditionally export all API headers to the target directory. When those headers are installed to compile another application, this means that make always finds newer dependencies for the source files relying on those headers, and deduces that the targets should be rebuilt. Avoid that by making "install_headers" depend on the source header files, and (re-)install them only when necessary. Signed-off-by:
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Yucong Sun authored
New clang version changed ([0]) type name in dwarf from "long int" to "long", this is causing btf_dump tests to fail. [0] https://github.com/llvm/llvm-project/commit/f6a561c4d6754b13165a49990e8365d819f64c86Signed-off-by:
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Dave Marchevsky authored
Since commit 6c4fc209 ("bpf: remove useless version check for prog load") these "version" sections, which result in bpf_attr.kern_version being set, have been unnecessary. Remove them so that it's obvious to folks using selftests as a guide that "modern" BPF progs don't need this section. Signed-off-by:
Dave Marchevsky <davemarchevsky@fb.com> Signed-off-by:
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Song Liu authored
VMs running on upstream 5.12+ kernel support LBR. However, bpf_get_branch_snapshot couldn't stop the LBR before too many entries are flushed. Skip the hit/waste test for VMs before we find a proper fix for LBR in VM. Fixes: 025bd7c7 ("selftests/bpf: Add test for bpf_get_branch_snapshot") Signed-off-by:
Song Liu <songliubraving@fb.com> Signed-off-by:
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- 07 Oct, 2021 4 commits
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Johan Almbladh authored
This patch adds new tests for the two-instruction LD_IMM64. The new tests verify the operation with immediate values of different byte patterns. Mainly intended to cover JITs that want to be clever when loading 64-bit constants. Signed-off-by:
Johan Almbladh <johan.almbladh@anyfinetworks.com> Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20211007143006.634308-1-johan.almbladh@anyfinetworks.com
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Johan Almbladh authored
This patch shaves off a few instructions when loading sparse 64-bit constants to register. The change is covered by additional tests in lib/test_bpf.c. Signed-off-by:
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Johan Almbladh authored
This patch removes a stale Makefile reference to the cBPF JIT that was removed. Fixes: ebcbacfa ("mips, bpf: Remove old BPF JIT implementations") Signed-off-by:
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Jie Meng authored
Introduce a single reg version of maybe_emit_mod() and factor out common code in more cases. Signed-off-by:
Jie Meng <jmeng@fb.com> Signed-off-by:
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- 06 Oct, 2021 9 commits
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Andrii Nakryiko authored
Hengqi Chen says: ==================== bpf_{map,program}__{prev,next} don't follow the libbpf API naming convention. Deprecate them and replace them with a new set of APIs named bpf_object__{prev,next}_{program,map}. v1->v2: [0] * Addressed Andrii's comments [0]: https://patchwork.kernel.org/project/netdevbpf/patch/20210906165456.325999-1-hengqi.chen@gmail.com/ ==================== Signed-off-by: -
Hengqi Chen authored
BPF objects are not reloadable after unload. Users are expected to use bpf_object__close() to unload and free up resources in one operation. No need to expose bpf_object__unload() as a public API, deprecate it ([0]). Add bpf_object__unload() as an alias to internal bpf_object_unload() and replace all bpf_object__unload() uses to avoid compilation errors. [0] Closes: https://github.com/libbpf/libbpf/issues/290Signed-off-by:
Hengqi Chen <hengqi.chen@gmail.com> Signed-off-by:
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Hengqi Chen authored
Replace deprecated bpf_{map,program}__next APIs with newly added bpf_object__next_{map,program} APIs, so that no compilation warnings emit. Signed-off-by: -
Grant Seltzer authored
This adds a section to the documentation for libbpf naming convention which describes how to document API features in libbpf, specifically the format of which API doc comments need to conform to. Signed-off-by:
Grant Seltzer <grantseltzer@gmail.com> Signed-off-by:
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Hengqi Chen authored
Deprecate bpf_{map,program}__{prev,next} APIs. Replace them with a new set of APIs named bpf_object__{prev,next}_{program,map} which follow the libbpf API naming convention ([0]). No functionality changes. [0] Closes: https://github.com/libbpf/libbpf/issues/296Signed-off-by: -
Jiri Olsa authored
Currently the recursion test is hooking __htab_map_lookup_elem function, which is invoked both from bpf_prog and bpf syscall. But in our kernel build, the __htab_map_lookup_elem gets inlined within the htab_map_lookup_elem, so it's not trigered and the test fails. Fixing this by using htab_map_delete_elem, which is not inlined for bpf_prog calls (like htab_map_lookup_elem is) and is used directly as pointer for map_delete_elem, so it won't disappear by inlining. Signed-off-by:
Jiri Olsa <jolsa@kernel.org> Signed-off-by:
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Quentin Monnet authored
Recent-ish versions of make do no longer consider number signs ("#") as comment symbols when they are inserted inside of a macro reference or in a function invocation. In such cases, the symbols should not be escaped. There are a few occurrences of "\#" in libbpf's and samples' Makefiles. In the former, the backslash is harmless, because grep associates no particular meaning to the escaped symbol and reads it as a regular "#". In samples' Makefile, recent versions of make will pass the backslash down to the compiler, making the probe fail all the time and resulting in the display of a warning about "make headers_install" being required, even after headers have been installed. A similar issue has been addressed at some other locations by commit 9564a8cf ("Kbuild: fix # escaping in .cmd files for future Make"). Let's address it for libbpf's and samples' Makefiles in the same fashion, by using a "$(pound)" variable (pulled from tools/scripts/Makefile.include for libbpf, or re-defined for the samples). Reference for the change in make: https://git.savannah.gnu.org/cgit/make.git/commit/?id=c6966b323811c37acedff05b57 Fixes: 2f383041 ("libbpf: Make libbpf_version.h non-auto-generated") Fixes: 07c3bbdb ("samples: bpf: print a warning about headers_install") Signed-off-by: -
Daniel Borkmann authored
The BPF core defines a __weak bpf_jit_compile() dummy function already which should only be overridden by JITs if they actually implement a legacy cBPF JIT. Given arm implements an eBPF JIT, this stub is not needed. Now that MIPS cBPF JIT is finally gone, the only JIT left that is still implementing bpf_jit_compile() is the sparc32 one. Signed-off-by:
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Daniel Borkmann authored
Johan Almbladh says: ==================== This is an implementation of an eBPF JIT for MIPS I-V and MIPS32/64 r1-r6. The new JIT is written from scratch, but uses the same overall structure as other eBPF JITs. Before, the MIPS JIT situation looked like this. - 32-bit: MIPS32, cBPF-only, tests fail - 64-bit: MIPS64r2-r6, eBPF, tests fail, incomplete eBPF ISA support The new JIT implementation raises the bar to the following level. - 32/64-bit: all MIPS ISA, eBPF, all tests pass, full eBPF ISA support Overview -------- The implementation supports all 32-bit and 64-bit eBPF instructions defined as of this writing, including the recently-added atomics. It is intended to provide good performance for native word size operations, while also being complete so the JIT never has to fall back to the interpreter. The new JIT replaces the current cBPF and eBPF JITs for MIPS. The implementation is divided into separate files as follows. The source files contains comments describing internal mechanisms and details on things like eBPF-to-CPU register mappings, so I won't repeat that here. - jit_comp.[ch] code shared between 32-bit and 64-bit JITs - jit_comp32.c 32-bit JIT implementation - jit_comp64.c 64-bit JIT implementation Both the 32-bit and 64-bit versions map all eBPF registers to native MIPS CPU registers. There are also enough unmapped CPU registers available to allow all eBPF operations implemented natively by the JIT to use only CPU registers without having to resort to stack scratch space. Some operations are deemed too complex to implement natively in the JIT. Those are instead implemented as a function call to a helper that performs the operation. This is done in the following cases. - 64-bit div and mod on a 32-bit CPU - 64-bit atomics on a 32-bit CPU - 32-bit atomics on a 32-bit CPU that lacks ll/sc instructions CPU errata workarounds ---------------------- The JIT implements workarounds for R10000, Loongson-2F and Loongson-3 CPU errata. For the Loongson workarounds, I have used the public information available on the matter. Link: https://sourceware.org/legacy-ml/binutils/2009-11/msg00387.html Testing ------- During the development of the JIT, I have added a number of new test cases to the test_bpf.ko test suite to be able to verify correctness of JIT implementations in a more systematic way. The new additions increase the test suite roughly three-fold, with many of the new tests being very extensive and even exhaustive when feasible. Link: https://lore.kernel.org/bpf/20211001130348.3670534-1-johan.almbladh@anyfinetworks.com/ Link: https://lore.kernel.org/bpf/20210914091842.4186267-1-johan.almbladh@anyfinetworks.com/ Link: https://lore.kernel.org/bpf/20210809091829.810076-1-johan.almbladh@anyfinetworks.com/ The JIT has been tested by running the test_bpf.ko test suite in QEMU with the following MIPS ISAs, in both big and little endian mode, with and without JIT hardening enabled. MIPS32r2, MIPS32r6, MIPS64r2, MIPS64r6 For the QEMU r2 targets, the correctness of pre-r2 code emitted has been tested by manually overriding each of the following macros with 0. cpu_has_llsc, cpu_has_mips_2, cpu_has_mips_r1, cpu_has_mips_r2 Similarly, CPU errata workaround code has been tested by enabling the each of the following configurations for the MIPS64r2 targets. CONFIG_WAR_R10000 CONFIG_CPU_LOONGSON3_WORKAROUNDS CONFIG_CPU_NOP_WORKAROUNDS CONFIG_CPU_JUMP_WORKAROUNDS The JIT passes all tests in all configurations. Below is the summary for MIPS32r2 in little endian mode. test_bpf: Summary: 1006 PASSED, 0 FAILED, [994/994 JIT'ed] test_bpf: test_tail_calls: Summary: 8 PASSED, 0 FAILED, [8/8 JIT'ed] test_bpf: test_skb_segment: Summary: 2 PASSED, 0 FAILED According to MIPS ISA reference documentation, the result of a 32-bit ALU arithmetic operation on a 64-bit CPU is unpredictable if an operand register value is not properly sign-extended to 64 bits. To verify the code emitted by the JIT, the code generation engine in QEMU was modifed to flip all low 32 bits if the above condition was not met. With this trip-wire installed, the kernel booted properly in qemu-system-mips64el and all test_bpf.ko tests passed. Remaining features ------------------ While the JIT is complete is terms of eBPF ISA support, this series does not include support for BPF-to-BPF calls and BPF trampolines. Those features are planned to be added in another patch series. The BPF_ST | BPF_NOSPEC instruction currently emits nothing. This is consistent with the behavior if the MIPS interpreter and the existing eBPF JIT. Why not build on the existing eBPF JIT? --------------------------------------- The existing eBPF JIT was originally written for MIPS64. An effort was made to add MIPS32 support to it in commit 716850ab ("MIPS: eBPF: Initial eBPF support for MIPS32 architecture."). That turned out to contain a number of flaws, so eBPF support for MIPS32 was disabled in commit 36366e36 ("MIPS: BPF: Restore MIPS32 cBPF JIT"). Link: https://lore.kernel.org/bpf/5deaa994.1c69fb81.97561.647e@mx.google.com/ The current eBPF JIT for MIPS64 lacks a lot of functionality regarding ALU32, JMP32 and atomic operations. It also lacks 32-bit CPU support on a fundamental level, for example 32-bit CPU register mappings and o32 ABI calling conventions. For optimization purposes, it tracks register usage through the program control flow in order to do zero-extension and sign- extension only when necessary, a static analysis of sorts. In my opinion, having this kind of complexity in JITs, and for which there is not adequate test coverage, is a problem. Such analysis should be done by the verifier, if needed at all. Finally, when I run the BPF test suite test_bpf.ko on the current JIT, there are errors and warnings. I believe that an eBPF JIT should strive to be correct, complete and optimized, and in that order. The JIT runs after the verifer has audited the program and given its approval. If the JIT then emits code that does something else, it will undermine the eBPF security model. A simple implementation is easier to get correct than a complex one. Furthermore, the real performance hit is not an extra CPU instruction here and there, but when the JIT bails on an unimplemented eBPF instruction and cause the whole program to fall back to the interpreter. My reasoning here boils down to the following. * The JIT should not contain a static analyzer that tracks branches. * It is acceptable to emit possibly superfluous sign-/zero-extensions for ALU32 and JMP32 operations on a 64-bit MIPS to guarantee correctness. * The JIT should handle all eBPF instructions on all MIPS CPUs. I conclude that the current eBPF MIPS JIT is complex, incomplete and incorrect. For the reasons stated above, I decided to not use the existing JIT implementation. ==================== Signed-off-by:
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