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sysrq有多种功能，对于ARM Linux这种嵌入式没键盘的系统来说，也可以通过/proc/sysrq-trigger来进行操作。实验平台：QEMU模拟的ARM Linux内核版本： # uname -aLinux (none) 4.0.0-rc1+ #46 SMP Thu Nov 2 20:43:41 CST 2017 armv7l GNU/Linux
一键内核崩溃# cd /proc/# echo c > sysrq-trigger [ 372.703889] sysrq: SysRq : Trigger a crash[ 372.705883] Unable to handle kernel NULL pointer dereference at virtual address 00000000[ 372.707831] pgd = 9ed5c000[ 372.708459] [00000000] *pgd=7f661831, *pte=00000000, *ppte=00000000[ 372.710189] Internal error: Oops: 817 [#1] SMP ARM[ 372.711290] Modules linked in:[ 372.712699] CPU: 0 PID: 705 Comm: sh Not tainted 4.0.0-rc1+ #46[ 372.715446] Hardware name: ARM-Versatile Express[ 372.722231] task: 9ec9b700 ti: 9ed5a000 task.ti: 9ed5a000[ 372.725480] PC is at sysrq_handle_crash+0x30/0x40[ 372.727546] LR is at sysrq_handle_crash+0x28/0x40[ 372.728286] pc : [<802903d8>] lr : [<802903d0>] psr: a0000013[ 372.728286] sp : 9ed5bf18 ip : 00000000 fp : 0016d22c[ 372.729548] r10: 76f55000 r9 : 9ed5a000 r8 : 00000007[ 372.729788] r7 : 00000000 r6 : 00000063 r5 : 80650494 r4 : 80658ea8[ 372.730066] r3 : 00000000 r2 : 00000001 r1 : 00000000 r0 : 00000063[ 372.730394] Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user[ 372.730716] Control: 10c5387d Table: 7ed5c06a DAC: 00000015[ 372.730970] Process sh (pid: 705, stack limit = 0x9ed5a210)[ 372.731239] Stack: (0x9ed5bf18 to 0x9ed5c000)[ 372.731549] bf00: 802903a8 80290ba4[ 372.731887] bf20: 00000002 00000001 00000000 00000000 9eff0d80 80290cb0 00000000 80122bd8[ 372.732299] bf40: 9f5f5000 00000002 76f55000 9ed5bf80 00000002 800da168 0016d22c 800240f0[ 372.732618] bf60: 00000003 00000000 00000000 9f5f5000 9f5f5000 00000002 76f55000 800da488[ 372.732954] bf80: 00000000 00000000 00000000 00000002 76f55000 00166cd8 00000004 8000e7a8[ 372.733286] bfa0: 00000000 8000e5e0 00000002 76f55000 00000001 76f55000 00000002 00000000[ 372.733592] bfc0: 00000002 76f55000 00166cd8 00000004 000c49ae 0016c4c0 00000002 0016d22c[ 372.733928] bfe0: 00000002 7eb2f8c0 000a2235 00008e7c 60000010 00000001 00000000 00000000[ 372.735094] [<802903d8>] (sysrq_handle_crash) from [<80290ba4>] (__handle_sysrq+0x90/0x164)[ 372.735580] [<80290ba4>] (__handle_sysrq) from [<80290cb0>] (write_sysrq_trigger+0x38/0x48)[ 372.736221] [<80290cb0>] (write_sysrq_trigger) from [<80122bd8>] (proc_reg_write+0x5c/0x84)[ 372.738252] [<80122bd8>] (proc_reg_write) from [<800da168>] (vfs_write+0xa0/0x1a8)[ 372.740445] [<800da168>] (vfs_write) from [<800da488>] (SyS_write+0x40/0x8c)[ 372.742670] [<800da488>] (SyS_write) from [<8000e5e0>] (ret_fast_syscall+0x0/0x40)[ 372.745287] Code: 0a000000 e12fff33 e3a03000 e3a02001 (e5c32000) [ 372.748107] ---[ end trace 22610ffc8a0b80b3 ]---[ 372.749418] Kernel panic - not syncing: Fatal exception[ 372.751070] CPU1: stopping[ 372.752136] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G D 4.0.0-rc1+ #46[ 372.752457] Hardware name: ARM-Versatile Express[ 372.753464] [<80015790>] (unwind_backtrace) from [<80011a10>] (show_stack+0x10/0x14)[ 372.753854] [<80011a10>] (show_stack) from [<804842bc>] (dump_stack+0x74/0x90)[ 372.754240] [<804842bc>] (dump_stack) from [<80013b2c>] (handle_IPI+0x134/0x170)[ 372.754632] [<80013b2c>] (handle_IPI) from [<800086a4>] (gic_handle_irq+0x54/0x5c)[ 372.755039] [<800086a4>] (gic_handle_irq) from [<80012500>] (__irq_svc+0x40/0x54)[ 372.755458] Exception stack(0x9f487f90 to 0x9f487fd8)[ 372.755872] 7f80: ffffffed 9f487fe0 ffffffed 8001c020[ 372.756322] 7fa0: 8064a454 00000000 00000000 80647540 80646c08 8064a4a8 00000000 8064a4a0[ 372.756753] 7fc0: 00000000 9f487fd8 8000f7d8 8000f7dc 60000013 ffffffff[ 372.757150] [<80012500>] (__irq_svc) from [<8000f7dc>] (arch_cpu_idle+0x30/0x3c)[ 372.757581] [<8000f7dc>] (arch_cpu_idle) from [<8004f0cc>] (cpu_startup_entry+0x1e4/0x2c4)[ 372.758187] [<8004f0cc>] (cpu_startup_entry) from [<60008744>] (0x60008744)[ 372.778966] CPU2: stopping[ 372.779266] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G D 4.0.0-rc1+ #46
一键导出内存管理信息# echo m > sysrq-trigger [ 137.476259] sysrq: SysRq : Show Memory[ 137.476530] Mem-info:[ 137.476768] Normal per-cpu:[ 137.476893] CPU 0: hi: 186, btch: 31 usd: 67[ 137.477034] CPU 1: hi: 186, btch: 31 usd: 155[ 137.477182] CPU 2: hi: 186, btch: 31 usd: 87[ 137.477422] CPU 3: hi: 186, btch: 31 usd: 56[ 137.477747] active_anon:16 inactive_anon:0 isolated_anon:0[ 137.477747] active_file:308 inactive_file:53 isolated_file:0[ 137.477747] unevictable:0 dirty:1 writeback:0 unstable:0[ 137.477747] free:125418 slab_reclaimable:296 slab_unreclaimable:923[ 137.477747] mapped:274 shmem:0 pagetables:7 bounce:0[ 137.477747] free_cma:0[ 137.478878] Normal free:501672kB min:2864kB low:3580kB high:4296kB active_anon:64kB inactive_anon:0kB active_file:1232kB inactive_file:212kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:524288kB managed:513016kB mlocked:0kB dirty:4kB writeback:0kB mapped:1096kB shmem:0kB slab_reclaimable:1184kB slab_unreclaimable:3692kB kernel_stack:408kB pagetables:28kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no[ 137.479821] lowmem_reserve[]: 0 0[ 137.480035] Normal: 2*4kB (UE) 4*8kB (U) 2*16kB (UM) 1*32kB (M) 1*64kB (E) 0*128kB 1*256kB (U) 1*512kB (E) 3*1024kB (M) 3*2048kB (EM) 120*4096kB (MR) = 501672kB[ 137.480824] 362 total pagecache pages[ 137.480985] 0 pages in swap cache[ 137.481101] Swap cache stats: add 0, delete 0, find 0/0[ 137.481311] Free swap = 0kB[ 137.481393] Total swap = 0kB[ 137.488594] 131072 pages of RAM[ 137.488882] 125849 free pages[ 137.489062] 2818 reserved pages[ 137.489319] 641 slab pages[ 137.489498] 517 pages shared[ 137.489717] 0 pages swap cached
终止除init外的所有进程# echo e > sysrq-trigger [ 104.903722] sysrq: SysRq : Terminate All Tasks
其他的功能还有很多很多，具体的列表：
其他功能通过定位，可以调整模板整体大小和段前后距 echo > sysrq-trigger [ 271.111610] sysrq: SysRq : HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) show-blocked-tasks(w)
一键内核崩溃# cd /proc/# echo c > sysrq-trigger [ 372.703889] sysrq: SysRq : Trigger a crash[ 372.705883] Unable to handle kernel NULL pointer dereference at virtual address 00000000[ 372.707831] pgd = 9ed5c000[ 372.708459] [00000000] *pgd=7f661831, *pte=00000000, *ppte=00000000[ 372.710189] Internal error: Oops: 817 [#1] SMP ARM[ 372.711290] Modules linked in:[ 372.712699] CPU: 0 PID: 705 Comm: sh Not tainted 4.0.0-rc1+ #46[ 372.715446] Hardware name: ARM-Versatile Express[ 372.722231] task: 9ec9b700 ti: 9ed5a000 task.ti: 9ed5a000[ 372.725480] PC is at sysrq_handle_crash+0x30/0x40[ 372.727546] LR is at sysrq_handle_crash+0x28/0x40[ 372.728286] pc : [<802903d8>] lr : [<802903d0>] psr: a0000013[ 372.728286] sp : 9ed5bf18 ip : 00000000 fp : 0016d22c[ 372.729548] r10: 76f55000 r9 : 9ed5a000 r8 : 00000007[ 372.729788] r7 : 00000000 r6 : 00000063 r5 : 80650494 r4 : 80658ea8[ 372.730066] r3 : 00000000 r2 : 00000001 r1 : 00000000 r0 : 00000063[ 372.730394] Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user[ 372.730716] Control: 10c5387d Table: 7ed5c06a DAC: 00000015[ 372.730970] Process sh (pid: 705, stack limit = 0x9ed5a210)[ 372.731239] Stack: (0x9ed5bf18 to 0x9ed5c000)[ 372.731549] bf00: 802903a8 80290ba4[ 372.731887] bf20: 00000002 00000001 00000000 00000000 9eff0d80 80290cb0 00000000 80122bd8[ 372.732299] bf40: 9f5f5000 00000002 76f55000 9ed5bf80 00000002 800da168 0016d22c 800240f0[ 372.732618] bf60: 00000003 00000000 00000000 9f5f5000 9f5f5000 00000002 76f55000 800da488[ 372.732954] bf80: 00000000 00000000 00000000 00000002 76f55000 00166cd8 00000004 8000e7a8[ 372.733286] bfa0: 00000000 8000e5e0 00000002 76f55000 00000001 76f55000 00000002 00000000[ 372.733592] bfc0: 00000002 76f55000 00166cd8 00000004 000c49ae 0016c4c0 00000002 0016d22c[ 372.733928] bfe0: 00000002 7eb2f8c0 000a2235 00008e7c 60000010 00000001 00000000 00000000[ 372.735094] [<802903d8>] (sysrq_handle_crash) from [<80290ba4>] (__handle_sysrq+0x90/0x164)[ 372.735580] [<80290ba4>] (__handle_sysrq) from [<80290cb0>] (write_sysrq_trigger+0x38/0x48)[ 372.736221] [<80290cb0>] (write_sysrq_trigger) from [<80122bd8>] (proc_reg_write+0x5c/0x84)[ 372.738252] [<80122bd8>] (proc_reg_write) from [<800da168>] (vfs_write+0xa0/0x1a8)[ 372.740445] [<800da168>] (vfs_write) from [<800da488>] (SyS_write+0x40/0x8c)[ 372.742670] [<800da488>] (SyS_write) from [<8000e5e0>] (ret_fast_syscall+0x0/0x40)[ 372.745287] Code: 0a000000 e12fff33 e3a03000 e3a02001 (e5c32000) [ 372.748107] ---[ end trace 22610ffc8a0b80b3 ]---[ 372.749418] Kernel panic - not syncing: Fatal exception[ 372.751070] CPU1: stopping[ 372.752136] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G D 4.0.0-rc1+ #46[ 372.752457] Hardware name: ARM-Versatile Express[ 372.753464] [<80015790>] (unwind_backtrace) from [<80011a10>] (show_stack+0x10/0x14)[ 372.753854] [<80011a10>] (show_stack) from [<804842bc>] (dump_stack+0x74/0x90)[ 372.754240] [<804842bc>] (dump_stack) from [<80013b2c>] (handle_IPI+0x134/0x170)[ 372.754632] [<80013b2c>] (handle_IPI) from [<800086a4>] (gic_handle_irq+0x54/0x5c)[ 372.755039] [<800086a4>] (gic_handle_irq) from [<80012500>] (__irq_svc+0x40/0x54)[ 372.755458] Exception stack(0x9f487f90 to 0x9f487fd8)[ 372.755872] 7f80: ffffffed 9f487fe0 ffffffed 8001c020[ 372.756322] 7fa0: 8064a454 00000000 00000000 80647540 80646c08 8064a4a8 00000000 8064a4a0[ 372.756753] 7fc0: 00000000 9f487fd8 8000f7d8 8000f7dc 60000013 ffffffff[ 372.757150] [<80012500>] (__irq_svc) from [<8000f7dc>] (arch_cpu_idle+0x30/0x3c)[ 372.757581] [<8000f7dc>] (arch_cpu_idle) from [<8004f0cc>] (cpu_startup_entry+0x1e4/0x2c4)[ 372.758187] [<8004f0cc>] (cpu_startup_entry) from [<60008744>] (0x60008744)[ 372.778966] CPU2: stopping[ 372.779266] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G D 4.0.0-rc1+ #46一键导出内存管理信息# echo m > sysrq-trigger [ 137.476259] sysrq: SysRq : Show Memory[ 137.476530] Mem-info:[ 137.476768] Normal per-cpu:[ 137.476893] CPU 0: hi: 186, btch: 31 usd: 67[ 137.477034] CPU 1: hi: 186, btch: 31 usd: 155[ 137.477182] CPU 2: hi: 186, btch: 31 usd: 87[ 137.477422] CPU 3: hi: 186, btch: 31 usd: 56[ 137.477747] active_anon:16 inactive_anon:0 isolated_anon:0[ 137.477747] active_file:308 inactive_file:53 isolated_file:0[ 137.477747] unevictable:0 dirty:1 writeback:0 unstable:0[ 137.477747] free:125418 slab_reclaimable:296 slab_unreclaimable:923[ 137.477747] mapped:274 shmem:0 pagetables:7 bounce:0[ 137.477747] free_cma:0[ 137.478878] Normal free:501672kB min:2864kB low:3580kB high:4296kB active_anon:64kB inactive_anon:0kB active_file:1232kB inactive_file:212kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:524288kB managed:513016kB mlocked:0kB dirty:4kB writeback:0kB mapped:1096kB shmem:0kB slab_reclaimable:1184kB slab_unreclaimable:3692kB kernel_stack:408kB pagetables:28kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no[ 137.479821] lowmem_reserve[]: 0 0[ 137.480035] Normal: 2*4kB (UE) 4*8kB (U) 2*16kB (UM) 1*32kB (M) 1*64kB (E) 0*128kB 1*256kB (U) 1*512kB (E) 3*1024kB (M) 3*2048kB (EM) 120*4096kB (MR) = 501672kB[ 137.480824] 362 total pagecache pages[ 137.480985] 0 pages in swap cache[ 137.481101] Swap cache stats: add 0, delete 0, find 0/0[ 137.481311] Free swap = 0kB[ 137.481393] Total swap = 0kB[ 137.488594] 131072 pages of RAM[ 137.488882] 125849 free pages[ 137.489062] 2818 reserved pages[ 137.489319] 641 slab pages[ 137.489498] 517 pages shared[ 137.489717] 0 pages swap cached终止除init外的所有进程# echo e > sysrq-trigger [ 104.903722] sysrq: SysRq : Terminate All Tasks其他的功能还有很多很多，具体的列表：
其他功能通过定位，可以调整模板整体大小和段前后距 echo > sysrq-trigger [ 271.111610] sysrq: SysRq : HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) show-blocked-tasks(w)