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[122.63.70.7]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b2d4f431c3sm136809165ad.79.2026.04.14.03.27.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2026 03:27:45 -0700 (PDT) From: Tao Liu To: yamazaki-msmt@nec.com, k-hagio-ab@nec.com, kexec@lists.infradead.org Cc: aravinda@linux.vnet.ibm.com, stephen.s.brennan@oracle.com, Tao Liu Subject: [PATCH v5][makedumpfile 7/9] Add sample extension as an example reference Date: Tue, 14 Apr 2026 22:26:54 +1200 Message-ID: <20260414102656.55200-8-ltao@redhat.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20260414102656.55200-1-ltao@redhat.com> References: <20260414102656.55200-1-ltao@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: N5Bz2TBNYG8oB9V0SBFuv9ZicDFFCdu69_lfAJMdyzc_1776162466 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260414_032749_552859_333B64F4 X-CRM114-Status: GOOD ( 19.75 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org This patch will add a sample.c as an example extension for code reference. The extension will do nothing related to page filtering, but print a few kernel symbol/type information. Suggested-by: Kazuhito Hagio Signed-off-by: Tao Liu --- extensions/Makefile | 2 +- extensions/sample.c | 69 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 70 insertions(+), 1 deletion(-) create mode 100644 extensions/sample.c diff --git a/extensions/Makefile b/extensions/Makefile index b23f346..dbaec4e 100644 --- a/extensions/Makefile +++ b/extensions/Makefile @@ -1,5 +1,5 @@ CC ?= gcc -CONTRIB_SO := +CONTRIB_SO := sample.so all: $(CONTRIB_SO) diff --git a/extensions/sample.c b/extensions/sample.c new file mode 100644 index 0000000..e4938d1 --- /dev/null +++ b/extensions/sample.c @@ -0,0 +1,69 @@ +#include "../makedumpfile.h" +#include "../btf_info.h" +#include "../kallsyms.h" +#include "../extension.h" + +/* + * Declare the kernel symbols/types that will be used by the extension later. + * The btf/kallsyms component of makedumpfile will resolve these requested + * info automatically during extension loading. + * + * The symbol/types declared by non-OPT macros as INIT_MOD_XX are must-have for + * the extension, any missing of these will lead to load-fail of the extension. + * This is useful to skip one extension as early. E.g. exit the amdgpu mm filtering + * extension when filtering against a vmcore dumpped by a machine which have + * no amdgpu hardware. + * + * The symbol/types declared by OPT macros as INIT_OPT_MOD_XX are optional, + * meaning the existence of these are checked during extension runtime. This + * is useful to cover different kernel versions where some of the data structure + * are slightly different. + */ +/* All kernel will have init_task and task_struct.mm */ +INIT_MOD_SYM(vmlinux, init_task); +INIT_MOD_STRUCT_MEMBER(vmlinux, task_struct, mm); +/* + * Older kernels use mm_struct.mm_rb, + * later ones use mm_struct.mm_mt + */ +INIT_OPT_MOD_STRUCT_MEMBER(vmlinux, mm_struct, mm_mt); +INIT_OPT_MOD_STRUCT_MEMBER(vmlinux, mm_struct, mm_rb); + +/* + * Extension callback when makedumpfile is doing page filtering, + * extension should decide whether the given page should be kept(PG_INCLUDE), + * discarded(PG_EXCLUDE) or undecided(PG_UNDECID). Here we simply return + * PG_UNDECID to let every page fallbacks to traditinal page-flags + * check routine or let other extensions make the decision. + */ +int extension_callback(unsigned long pfn, const void *pcache) +{ + return PG_UNDECID; +} + +/* Entry of extension */ +void extension_init(void) +{ + MSG("sample.so: The address of init_task is: %lx\n", + GET_MOD_SYM(vmlinux, init_task)); + MSG("sample.so: The size of task_struct is: %d bytes\n", + GET_MOD_STRUCT_MEMBER_SSIZE(vmlinux, task_struct, mm)); + MSG("sample.so: The offset of member mm within task_struct is: %d bytes\n", + GET_MOD_STRUCT_MEMBER_MOFF(vmlinux, task_struct, mm) / 8 ); + MSG("sample.so: The size of member mm within task_struct is: %d bytes\n", + GET_MOD_STRUCT_MEMBER_MSIZE(vmlinux, task_struct, mm)); + if (MOD_STRUCT_MEMBER_EXIST(vmlinux, mm_struct, mm_mt)) { + MSG("sample.so: Your kernel is using maple tree in mm_struct\n"); + } + if (MOD_STRUCT_MEMBER_EXIST(vmlinux, mm_struct, mm_rb)) { + MSG("sample.so: Your kernel is using rb tree in mm_struct\n"); + } +} + +/* + * This function is called when the extension is unloaded. + * If desired, perform any cleanups here. + */ +__attribute__((destructor)) +void extension_cleanup(void) { } + -- 2.47.0