- Linux-kselftest-mirror - lists.linaro.org

[PATCH v2 1/3] kunit: Add a macro to wrap a deferred action function

by David Gow

KUnit's deferred action API accepts a void(*)(void *) function pointer which is called when the test is exited. However, we very frequently want to use existing functions which accept a single pointer, but which may not be of type void*. While this is probably dodgy enough to be on the wrong side of the C standard, it's been often used for similar callbacks, and gcc's -Wcast-function-type seems to ignore cases where the only difference is the type of the argument, assuming it's compatible (i.e., they're both pointers to data). However, clang 16 has introduced -Wcast-function-type-strict, which no longer permits any deviation in function pointer type. This seems to be because it'd break CFI, which validates the type of function calls. This rather ruins our attempts to cast functions to defer them, and leaves us with a few options. The one we've chosen is to implement a macro which will generate a wrapper function which accepts a void*, and casts the argument to the appropriate type. For example, if you were trying to wrap: void foo_close(struct foo *handle); you could use: KUNIT_DEFINE_ACTION_WRAPPER(kunit_action_foo_close, foo_close, struct foo *); This would create a new kunit_action_foo_close() function, of type kunit_action_t, which could be passed into kunit_add_action() and similar functions. In addition to defining this macro, update KUnit and its tests to use it. Link: https://github.com/ClangBuiltLinux/linux/issues/1750 Reviewed-by: Nathan Chancellor <nathan(a)kernel.org> Tested-by: Nathan Chancellor <nathan(a)kernel.org> Acked-by: Daniel Vetter <daniel(a)ffwll.ch> Reviewed-by: Maxime Ripard <mripard(a)kernel.org> Signed-off-by: David Gow <davidgow(a)google.com> --- Thanks everyone for testing v1 of this: this update only changes documentation. Changes since v1: https://lore.kernel.org/linux-kselftest/20231110200830.1832556-1-davidgow@g… - Update the usage.rst documentation (Thanks, Nathan) - Add a better doc comment for KUNIT_DEFINE_ACTION_WRAPPER() --- Documentation/dev-tools/kunit/usage.rst | 10 +++++++--- include/kunit/resource.h | 21 +++++++++++++++++++++ lib/kunit/kunit-test.c | 5 +---- lib/kunit/test.c | 6 ++++-- 4 files changed, 33 insertions(+), 9 deletions(-) diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst index c27e1646ecd9..9db12e91668e 100644 --- a/Documentation/dev-tools/kunit/usage.rst +++ b/Documentation/dev-tools/kunit/usage.rst @@ -651,12 +651,16 @@ For example: } Note that, for functions like device_unregister which only accept a single -pointer-sized argument, it's possible to directly cast that function to -a ``kunit_action_t`` rather than writing a wrapper function, for example: +pointer-sized argument, it's possible to automatically generate a wrapper +with the ``KUNIT_DEFINE_ACTION_WRAPPER()`` macro, for example: .. code-block:: C - kunit_add_action(test, (kunit_action_t *)&device_unregister, &dev); + KUNIT_DEFINE_ACTION_WRAPPER(device_unregister, device_unregister_wrapper, struct device *); + kunit_add_action(test, &device_unregister_wrapper, &dev); + +You should do this in preference to manually casting to the ``kunit_action_t`` type, +as casting function pointers will break Control Flow Integrity (CFI). ``kunit_add_action`` can fail if, for example, the system is out of memory. You can use ``kunit_add_action_or_reset`` instead which runs the action diff --git a/include/kunit/resource.h b/include/kunit/resource.h index c7383e90f5c9..4ad69a2642a5 100644 --- a/include/kunit/resource.h +++ b/include/kunit/resource.h @@ -390,6 +390,27 @@ void kunit_remove_resource(struct kunit *test, struct kunit_resource *res); /* A 'deferred action' function to be used with kunit_add_action. */ typedef void (kunit_action_t)(void *); +/** + * KUNIT_DEFINE_ACTION_WRAPPER() - Wrap a function for use as a deferred action. + * + * @wrapper: The name of the new wrapper function define. + * @orig: The original function to wrap. + * @arg_type: The type of the argument accepted by @orig. + * + * Defines a wrapper for a function which accepts a single, pointer-sized + * argument. This wrapper can then be passed to kunit_add_action() and + * similar. This should be used in preference to casting a function + * directly to kunit_action_t, as casting function pointers will break + * control flow integrity (CFI), leading to crashes. + */ +#define KUNIT_DEFINE_ACTION_WRAPPER(wrapper, orig, arg_type) \ + static void wrapper(void *in) \ + { \ + arg_type arg = (arg_type)in; \ + orig(arg); \ + } + + /** * kunit_add_action() - Call a function when the test ends. * @test: Test case to associate the action with. diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c index 99d2a3a528e1..3e9c5192d095 100644 --- a/lib/kunit/kunit-test.c +++ b/lib/kunit/kunit-test.c @@ -538,10 +538,7 @@ static struct kunit_suite kunit_resource_test_suite = { #if IS_BUILTIN(CONFIG_KUNIT_TEST) /* This avoids a cast warning if kfree() is passed direct to kunit_add_action(). */ -static void kfree_wrapper(void *p) -{ - kfree(p); -} +KUNIT_DEFINE_ACTION_WRAPPER(kfree_wrapper, kfree, const void *); static void kunit_log_test(struct kunit *test) { diff --git a/lib/kunit/test.c b/lib/kunit/test.c index f2eb71f1a66c..0308865194bb 100644 --- a/lib/kunit/test.c +++ b/lib/kunit/test.c @@ -772,6 +772,8 @@ static struct notifier_block kunit_mod_nb = { }; #endif +KUNIT_DEFINE_ACTION_WRAPPER(kfree_action_wrapper, kfree, const void *) + void *kunit_kmalloc_array(struct kunit *test, size_t n, size_t size, gfp_t gfp) { void *data; @@ -781,7 +783,7 @@ void *kunit_kmalloc_array(struct kunit *test, size_t n, size_t size, gfp_t gfp) if (!data) return NULL; - if (kunit_add_action_or_reset(test, (kunit_action_t *)kfree, data) != 0) + if (kunit_add_action_or_reset(test, kfree_action_wrapper, data) != 0) return NULL; return data; @@ -793,7 +795,7 @@ void kunit_kfree(struct kunit *test, const void *ptr) if (!ptr) return; - kunit_release_action(test, (kunit_action_t *)kfree, (void *)ptr); + kunit_release_action(test, kfree_action_wrapper, (void *)ptr); } EXPORT_SYMBOL_GPL(kunit_kfree); -- 2.43.0.rc1.413.gea7ed67945-goog

2 years

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[PATCH net-next 0/5] selftests: tc-testing: updates and cleanups for tdc

by Pedro Tammela

Address the recommendations from the previous series and cleanup some leftovers. Pedro Tammela (5): selftests: tc-testing: remove buildebpf plugin selftests: tc-testing: remove unnecessary time.sleep selftests: tc-testing: prefix iproute2 functions with "ipr2" selftests: tc-testing: cleanup on Ctrl-C selftests: tc-testing: remove unused import tools/testing/selftests/tc-testing/Makefile | 29 +------- tools/testing/selftests/tc-testing/README | 2 - .../testing/selftests/tc-testing/action-ebpf | Bin 0 -> 856 bytes .../tc-testing/plugin-lib/buildebpfPlugin.py | 67 ------------------ .../tc-testing/plugin-lib/nsPlugin.py | 20 +++--- .../tc-testing/tc-tests/actions/bpf.json | 14 ++-- .../tc-testing/tc-tests/filters/bpf.json | 10 ++- tools/testing/selftests/tc-testing/tdc.py | 11 ++- tools/testing/selftests/tc-testing/tdc.sh | 2 +- 9 files changed, 25 insertions(+), 130 deletions(-) create mode 100644 tools/testing/selftests/tc-testing/action-ebpf delete mode 100644 tools/testing/selftests/tc-testing/plugin-lib/buildebpfPlugin.py -- 2.40.1

2 years

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[PATCH net 0/4] selftests/net: fix a few small compiler warnings

by Willem de Bruijn

From: Willem de Bruijn <willemb(a)google.com> Observed a clang warning when backporting cmsg_sender. Ran the same build against all the .c files under selftests/net. This is clang-14 with -Wall Which is what tools/testing/selftests/net/Makefile also enables. Willem de Bruijn (4): selftests/net: ipsec: fix constant out of range selftests/net: fix a char signedness issue selftests/net: unix: fix unused variable compiler warning selftests/net: mptcp: fix uninitialized variable warnings tools/testing/selftests/net/af_unix/diag_uid.c | 1 - tools/testing/selftests/net/cmsg_sender.c | 2 +- tools/testing/selftests/net/ipsec.c | 4 ++-- tools/testing/selftests/net/mptcp/mptcp_connect.c | 11 ++++------- tools/testing/selftests/net/mptcp/mptcp_inq.c | 11 ++++------- 5 files changed, 11 insertions(+), 18 deletions(-) -- 2.43.0.rc1.413.gea7ed67945-goog

2 years

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[RFC PATCH 0/5] RISC-V: Add dynamic TSO support

by Christoph Muellner

From: Christoph Müllner <christoph.muellner(a)vrull.eu> The upcoming RISC-V Ssdtso specification introduces a bit in the senvcfg CSR to switch the memory consistency model at run-time from RVWMO to TSO (and back). The active consistency model can therefore be switched on a per-hart base and managed by the kernel on a per-process/thread base. This patch implements basic Ssdtso support and adds a prctl API on top so that user-space processes can switch to a stronger memory consistency model (than the kernel was written for) at run-time. I am not sure if other architectures support switching the memory consistency model at run-time, but designing the prctl API in an arch-independent way allows reusing it in the future. The patchset also comes with a short documentation of the prctl API. This series is based on the second draft of the Ssdtso specification which was published recently on an RVI list: https://lists.riscv.org/g/tech-arch-review/message/183 Note, that the Ssdtso specification is in development state (i.e., not frozen or even ratified) which is also the reason why I marked the series as RFC. One aspect that is not covered in this patchset is virtualization. It is planned to add virtualization support in a later version. Hints/suggestions on how to implement this part are very much appreciated. Christoph Müllner (5): RISC-V: Add basic Ssdtso support RISC-V: Expose Ssdtso via hwprobe API uapi: prctl: Add new prctl call to set/get the memory consistency model RISC-V: Implement prctl call to set/get the memory consistency model RISC-V: selftests: Add DTSO tests Documentation/arch/riscv/hwprobe.rst | 3 + .../mm/dynamic-memory-consistency-model.rst | 76 ++++++++++++++++++ arch/riscv/Kconfig | 10 +++ arch/riscv/include/asm/csr.h | 1 + arch/riscv/include/asm/dtso.h | 74 ++++++++++++++++++ arch/riscv/include/asm/hwcap.h | 1 + arch/riscv/include/asm/processor.h | 8 ++ arch/riscv/include/asm/switch_to.h | 3 + arch/riscv/include/uapi/asm/hwprobe.h | 1 + arch/riscv/kernel/Makefile | 1 + arch/riscv/kernel/cpufeature.c | 1 + arch/riscv/kernel/dtso.c | 33 ++++++++ arch/riscv/kernel/process.c | 4 + arch/riscv/kernel/sys_riscv.c | 1 + include/uapi/linux/prctl.h | 5 ++ kernel/sys.c | 12 +++ tools/testing/selftests/riscv/Makefile | 2 +- tools/testing/selftests/riscv/dtso/.gitignore | 1 + tools/testing/selftests/riscv/dtso/Makefile | 11 +++ tools/testing/selftests/riscv/dtso/dtso.c | 77 +++++++++++++++++++ 20 files changed, 324 insertions(+), 1 deletion(-) create mode 100644 Documentation/mm/dynamic-memory-consistency-model.rst create mode 100644 arch/riscv/include/asm/dtso.h create mode 100644 arch/riscv/kernel/dtso.c create mode 100644 tools/testing/selftests/riscv/dtso/.gitignore create mode 100644 tools/testing/selftests/riscv/dtso/Makefile create mode 100644 tools/testing/selftests/riscv/dtso/dtso.c -- 2.41.0

2 years

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lsm_list_modules_test.c:104:22: error: 'LSM_ID_IMA' undeclared (first use in this function); did you mean 'LSM_ID_YAMA'?

by Naresh Kamboju

Following build errors noticed while building selftests lsm tests for x86 with gcc-13 toolchain on Linux next-20231127 tag. Build log: ------ selftest/lsm/lsm_list_modules_test lsm_list_modules_test.c: In function 'correct_lsm_list_modules': lsm_list_modules_test.c:104:22: error: 'LSM_ID_IMA' undeclared (first use in this function); did you mean 'LSM_ID_YAMA'? 104 | case LSM_ID_IMA: | ^~~~~~~~~~ | LSM_ID_YAMA lsm_list_modules_test.c:104:22: note: each undeclared identifier is reported only once for each function it appears in Reported-by: Linux Kernel Functional Testing <lkft(a)linaro.org> Steps to reproduce: ----- tuxmake --runtime podman --target-arch x86_64 --toolchain gcc-13 \ --kconfig https://storage.tuxsuite.com/public/linaro/lkft/builds/2Yk9XptRIQra77bvzZHc… \ debugkernel cpupower headers kernel kselftest modules Links: - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20231127/te… - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20231127/te… - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20231127/te… -- Linaro LKFT https://lkft.linaro.org

2 years

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[PATCH net-next 00/38] Conver all net selftests to run in unique namespace

by Hangbin Liu

As Guillaume pointed, many selftests create namespaces with very common names (like "client" or "server") or even (partially) run directly in init_net. This makes these tests prone to failure if another namespace with the same name already exists. It also makes it impossible to run several instances of these tests in parallel. This patch set conver all the net selftests to run in unique namespace, so we can update the selftest freamwork to run all tests in it's own namespace in parallel. After update, we only need to wait for the test which need longest time. ]# per_test_logging=1 time ./run_kselftest.sh -n -c net TAP version 13 # selftests: net: reuseport_bpf_numa not ok 3 selftests: net: reuseport_bpf_numa # exit=1 # selftests: net: reuseport_bpf_cpu not ok 2 selftests: net: reuseport_bpf_cpu # exit=1 # selftests: net: reuseport_dualstack not ok 4 selftests: net: reuseport_dualstack # exit=1 # selftests: net: reuseaddr_conflict ok 5 selftests: net: reuseaddr_conflict ... # selftests: net: test_vxlan_mdb.sh ok 90 selftests: net: test_vxlan_mdb.sh # selftests: net: fib_nexthops.sh not ok 41 selftests: net: fib_nexthops.sh # exit=1 # selftests: net: fcnal-test.sh not ok 36 selftests: net: fcnal-test.sh # exit=1 real 55m1.238s user 12m10.350s sys 22m17.432s Hangbin Liu (38): selftests/net: add lib.sh selftests/net: arp_ndisc_evict_nocarrier.sh convert to run test in unique namespace selftest: arp_ndisc_untracked_subnets.sh convert to run test in unique namespace selftests/net: convert cmsg tests to make them run in unique namespace selftests/net: convert drop_monitor_tests.sh to run it in unique namespace selftests/net: convert fcnal-test.sh to run it in unique namespace selftests/net: convert fib_nexthop_multiprefix to run it in unique namespace selftests/net: convert fib_nexthop_nongw.sh to run it in unique namespace selftests/net: convert fib_nexthops.sh to run it in unique namespace selftests/net: convert fib-onlink-tests.sh to run it in unique namespace selftests/net: convert fib_rule_tests.sh to run it in unique namespace selftests/net: convert fib_tests.sh to run it in unique namespace selftests/net: convert gre_gso.sh to run it in unique namespace selftests/net: convert icmp_redirect.sh to run it in unique namespace sleftests/net: convert icmp.sh to run it in unique namespace selftests/net: convert ioam6.sh to run it in unique namespace selftests/net: convert l2tp.sh to run it in unique namespace selftests/net: convert ndisc_unsolicited_na_test.sh to run it in unique namespace selftests/net: convert netns-name.sh to run it in unique namespace selftests/net: convert fdb_flush.sh to run it in unique namespace selftests/net: convert rtnetlink.sh to run it in unique namespace selftests/net: convert sctp_vrf.sh to run it in unique namespace selftests/net: use unique netns name for setup_loopback.sh setup_veth.sh selftests/net: convert stress_reuseport_listen.sh to run it in unique namespace selftests/net: convert test_bridge_backup_port.sh to run it in unique namespace selftests/net: convert test_bridge_neigh_suppress.sh to run it in unique namespace selftests/net: convert test_vxlan_mdb.sh to run it in unique namespace selftests/net: convert test_vxlan_nolocalbypass.sh to run it in unique namespace selftests/net: convert test_vxlan_under_vrf.sh to run it in unique namespace selftests/net: convert test_vxlan_vnifiltering.sh to run it in unique namespace selftests/net: convert toeplitz.sh to run it in unique namespace selftests/net: convert unicast_extensions.sh to run it in unique namespace selftests/net: convert vrf_route_leaking.sh to run it in unique namespace selftests/net: convert vrf_strict_mode_test.sh to run it in unique namespace selftests/net: convert vrf-xfrm-tests.sh to run it in unique namespace selftests/net: convert traceroute.sh to run it in unique namespace selftests/net: convert xfrm_policy.sh to run it in unique namespace kselftest/runner.sh: add netns support tools/testing/selftests/kselftest/runner.sh | 26 +- tools/testing/selftests/net/Makefile | 2 +- .../net/arp_ndisc_evict_nocarrier.sh | 46 +-- .../net/arp_ndisc_untracked_subnets.sh | 18 +- tools/testing/selftests/net/cmsg_ipv6.sh | 10 +- tools/testing/selftests/net/cmsg_so_mark.sh | 7 +- tools/testing/selftests/net/cmsg_time.sh | 7 +- .../selftests/net/drop_monitor_tests.sh | 21 +- tools/testing/selftests/net/fcnal-test.sh | 30 +- tools/testing/selftests/net/fdb_flush.sh | 11 +- .../testing/selftests/net/fib-onlink-tests.sh | 7 +- .../selftests/net/fib_nexthop_multiprefix.sh | 104 +++-- .../selftests/net/fib_nexthop_nongw.sh | 34 +- tools/testing/selftests/net/fib_nexthops.sh | 142 ++++--- tools/testing/selftests/net/fib_rule_tests.sh | 36 +- tools/testing/selftests/net/fib_tests.sh | 184 +++++---- tools/testing/selftests/net/gre_gso.sh | 18 +- tools/testing/selftests/net/icmp.sh | 10 +- tools/testing/selftests/net/icmp_redirect.sh | 182 +++++---- tools/testing/selftests/net/ioam6.sh | 247 ++++++------ tools/testing/selftests/net/l2tp.sh | 130 +++---- tools/testing/selftests/net/lib.sh | 98 +++++ .../net/ndisc_unsolicited_na_test.sh | 19 +- tools/testing/selftests/net/netns-name.sh | 44 +-- tools/testing/selftests/net/rtnetlink.sh | 21 +- tools/testing/selftests/net/sctp_vrf.sh | 12 +- tools/testing/selftests/net/settings | 2 +- tools/testing/selftests/net/setup_loopback.sh | 8 +- tools/testing/selftests/net/setup_veth.sh | 9 +- .../selftests/net/stress_reuseport_listen.sh | 6 +- .../selftests/net/test_bridge_backup_port.sh | 368 +++++++++--------- .../net/test_bridge_neigh_suppress.sh | 333 ++++++++-------- tools/testing/selftests/net/test_vxlan_mdb.sh | 202 +++++----- .../selftests/net/test_vxlan_nolocalbypass.sh | 48 ++- .../selftests/net/test_vxlan_under_vrf.sh | 70 ++-- .../selftests/net/test_vxlan_vnifiltering.sh | 154 +++++--- tools/testing/selftests/net/toeplitz.sh | 16 +- tools/testing/selftests/net/traceroute.sh | 82 ++-- .../selftests/net/unicast_extensions.sh | 99 +++-- tools/testing/selftests/net/vrf-xfrm-tests.sh | 77 ++-- .../selftests/net/vrf_route_leaking.sh | 201 +++++----- .../selftests/net/vrf_strict_mode_test.sh | 47 ++- tools/testing/selftests/net/xfrm_policy.sh | 138 +++---- tools/testing/selftests/run_kselftest.sh | 4 + 44 files changed, 1676 insertions(+), 1654 deletions(-) create mode 100644 tools/testing/selftests/net/lib.sh -- 2.41.0

2 years

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Re: [PATCH net-next v2] net: ctnetlink: support filtering by zone

by Pablo Neira Ayuso

Hi, On Mon, Nov 27, 2023 at 11:49:16AM +0000, Felix Huettner wrote: > conntrack zones are heavily used by tools like openvswitch to run > multiple virtual "routers" on a single machine. In this context each > conntrack zone matches to a single router, thereby preventing > overlapping IPs from becoming issues. > In these systems it is common to operate on all conntrack entries of a > given zone, e.g. to delete them when a router is deleted. Previously this > required these tools to dump the full conntrack table and filter out the > relevant entries in userspace potentially causing performance issues. > > To do this we reuse the existing CTA_ZONE attribute. This was previous > parsed but not used during dump and flush requests. Now if CTA_ZONE is > set we filter these operations based on the provided zone. > However this means that users that previously passed CTA_ZONE will > experience a difference in functionality. > > Alternatively CTA_FILTER could have been used for the same > functionality. However it is not yet supported during flush requests and > is only available when using AF_INET or AF_INET6. You mean, AF_UNSPEC cannot be specified in CTA_FILTER? Please, extend libnetfilter_conntrack to support for this feature, there is a filter API that can be used for this purpose. Thanks.

2 years

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Re: [RFC PATCH 0/5] RISC-V: Add dynamic TSO support

by Peter Zijlstra

On Fri, Nov 24, 2023 at 12:04:09PM +0100, Jonas Oberhauser wrote: > > I think ARM64 approached this problem by adding the > > load-acquire/store-release instructions and for TSO based code, > > translate into those (eg. x86 -> arm64 transpilers). > > > Although those instructions have a bit more ordering constraints. > > I have heard rumors that the apple chips also have a register that can be > set at runtime. Oh, I thought they made do with the load-acquire/store-release thingies. But to be fair, I haven't been paying *that* much attention to the apple stuff. I did read about how they fudged some of the x86 flags thing. > And there are some IBM machines that have a setting, but not sure how it is > controlled. Cute, I'm assuming this is the Power series (s390 already being TSO)? I wasn't aware they had this. > > IIRC Risc-V actually has such instructions as well, so *why* are you > > doing this?!?! > > > Unfortunately, at least last time I checked RISC-V still hadn't gotten such > instructions. > What they have is the *semantics* of the instructions, but no actual opcodes > to encode them. Well, that sucks.. > I argued for them in the RISC-V memory group, but it was considered to be > outside the scope of that group. > > Transpiling with sufficient DMB ISH to get the desired ordering is really > bad for performance. Ha!, quite dreadful I would imagine. > That is not to say that linux should support this. Perhaps linux should > pressure RISC-V into supporting implicit barriers instead. I'm not sure I count for much in this regard, but yeah, that sounds like a plan :-)

2 years

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[PATCH 0/3] tools/nolibc: rlimit support

by Thomas Weißschuh

The series adds support for setrlimit/getrlimit. Mainly to avoid spurious coredumps when running the tests under qemu-user. Signed-off-by: Thomas Weißschuh <linux(a)weissschuh.net> --- Thomas Weißschuh (3): tools/nolibc: drop custom definition of struct rusage tools/nolibc: add support for getrlimit/setrlimit selftests/nolibc: disable coredump via setrlimit tools/include/nolibc/sys.h | 38 ++++++++++++++++++++++++++++ tools/include/nolibc/types.h | 21 +-------------- tools/testing/selftests/nolibc/nolibc-test.c | 31 +++++++++++++++++++++++ 3 files changed, 70 insertions(+), 20 deletions(-) --- base-commit: 0dbd4651f3f80151910a36416fa0df28a10c3b0a change-id: 20231122-nolibc-rlimit-bb5b1f264fc4 Best regards, -- Thomas Weißschuh <linux(a)weissschuh.net>

2 years

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[PATCH 0/5] pstore: add tty frontend and multi-backend

by Yuanhe Shu

In public cloud scenario, if kdump service works abnormally, users cannot get vmcore. Without vmcore, user has no idea why the kernel crashed. Meanwhile, there is no additional information to find the reason why the kdump service is abnormal. One way is to obtain console messages through VNC. The drawback is that VNC is real-time, if user missed the timing to get the VNC output, the crash needs to be retriggered. Another way is to enable the console frontend of pstore and record the console messages to the pstore backend. On the one hand, the console logs only contain kernel printk logs and does not cover user-mode print logs. Although we can redirect user-mode logs to the pmsg frontend provided by pstore, user-mode information related to booting and kdump service vary from systemd, kdump.sh, and so on which makes redirection troublesome. So we added a tty frontend and save all logs of tty driver to the pstore backend. Another problem is that currently pstore only supports a single backend. For debugging kdump problems, we hope to save the console logs and tty logs to the ramoops backend of pstore, as it will not be lost after rebooting. If the user has enabled another backend, the ramoops backend will not be registered. To this end, we add the multi-backend function to support simultaneous registration of multiple backends. Based on the above changes, we can enable pstore in the crashdump kernel and save the console logs and tty logs to the ramoops backend of pstore. After rebooting, we can view the relevant logs by mounting the pstore file system. Furthermore, we also modified kexec-tools referring to crash-utils for reading memory, so that pstore ramoops information can be read without enabling pstore in first kernel. As we set the address and size of ramoops, as well as the sizes of console and tty, we can infer the physical address of console logs and tty logs in memory. Referring to the read method of crash-utils, the console logs and tty logs are read from the memory, user can get pstore debug information without affecting the first kernel at all. kexec-tools modification can be seen at https://github.com/shuyuanmen/kexec-tools/blob/main/Add-pstore-segment.patch Yuanhe Shu (5): pstore: add tty frontend pstore: add multi-backends support pstore: add subdirs for multi-backends pstore: remove the module parameter "backend" tools/pstore: update pstore selftests drivers/tty/n_tty.c | 1 + fs/pstore/Kconfig | 23 ++ fs/pstore/Makefile | 2 + fs/pstore/blk.c | 10 + fs/pstore/ftrace.c | 22 +- fs/pstore/inode.c | 86 ++++++- fs/pstore/internal.h | 16 +- fs/pstore/platform.c | 238 ++++++++++++-------- fs/pstore/pmsg.c | 23 +- fs/pstore/ram.c | 40 +++- fs/pstore/tty.c | 56 +++++ fs/pstore/zone.c | 42 +++- include/linux/pstore.h | 33 +++ include/linux/pstore_blk.h | 3 + include/linux/pstore_ram.h | 1 + include/linux/pstore_zone.h | 2 + include/linux/tty.h | 14 ++ tools/testing/selftests/pstore/common_tests | 4 - 18 files changed, 500 insertions(+), 116 deletions(-) create mode 100644 fs/pstore/tty.c -- 2.39.3

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