[Crash-utility] Support for dynamic allocations of 'struct fpu'

Hello, This is a follow-up report of the issue I found in the release test for makedumpfile-1.5.9. The original report was posted in kexec-ML: http://lists.infradead.org/pipermail/kexec/2015-October/014620.html I looked for the cause of this issue and found that it doesn't seem to be an issue of makedumpfile, it seems to be a crash side issue. The size of task_struct is decided dynamically by FPU registers since linux 4.2 due to: commit 5aaeb5c01c5b6c0be7b7aadbf3ace9f3a4458c3d Author: Ingo Molnar <mingo(a)kernel.org&gt; Date: Fri Jul 17 12:28:12 2015 +0200 x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86 and commit 0c8c0f03e3a292e031596484275c14cf39c0ab7a Author: Dave Hansen <dave(a)sr71.net&gt; Date: Fri Jul 17 12:28:11 2015 +0200 86/fpu, sched: Dynamically allocate 'struct fpu' This change will cause a difference between dwarf info and the actual size like below: (This is an example in linux 4.2 on x86_64) - dwarf info $ dwarfdump vmlinux | grep -A 2 task_struct DW_AT_name "task_struct" DW_AT_byte_size 0x00001940 // 6464 byte DW_AT_decl_file 0x0000001a include/linux/sched.h - actual size crash> p arch_task_struct_size arch_task_struct_size = $1 = 2880 crash> I don't think crash handle this change, so crash can read an irrelevant page when trying to read a task_struct. If the dump is filtered by makedumpfile and the page just behind the task_struct is excluded, the message I reported will be shown. To fix the size_table for the crash's initialization is easy, we should just update it by arch_task_struct_size like: diff --git a/task.c b/task.c index 8956fb5..ee94d4e 100755 --- a/task.c +++ b/task.c @@ -284,6 +284,17 @@ task_init(void) MEMBER_OFFSET_INIT(pid_pid_chain, "pid", "pid_chain"); STRUCT_SIZE_INIT(task_struct, "task_struct"); + int task_struct_size; + if (kernel_symbol_exists("arch_task_struct_size") && + readmem(symbol_value("arch_task_struct_size"), KVADDR, + &task_struct_size, sizeof(int), + "arch_task_struct_size", RETURN_ON_ERROR)) { + ASSIGN_SIZE(task_struct) = task_struct_size; + if (CRASHDEBUG(1)) + fprintf(fp, "\downsize_task_struct: %ld to %ld\n", + STRUCT_SIZE("task_struct"), + SIZE(task_struct)); + } However, struct command always refer to dwarf info since it's probably designed for general purpose, I can't come up with good way to fix it. Do you have any comments ? Thanks, Atsushi Kumagai