kernel 調用uefi的run time service 關機

2019-11-09 15:45:58

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當上層調用reboot命令時，就會調用到arch/arm64/kernel/PRocess.c 中的SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,void __user *, arg){ struct pid_namespace *pid_ns = task_active_pid_ns(current); char buffer[256]; int ret = 0; mutex_lock(&reboot_mutex); switch (cmd) { case linux_REBOOT_CMD_RESTART: kernel_restart(NULL); break; case LINUX_REBOOT_CMD_POWER_OFF: kernel_power_off(); do_exit(0); break;}我們重點開看請參數是LINUX_REBOOT_CMD_RESTART時，會調用kernel_restart->machine_restartvoid machine_restart(char *cmd){ /* Disable interrupts first */ local_irq_disable(); smp_send_stop(); /* * UpdateCapsule() depends on the system being reset via * ResetSystem(). */ if (efi_enabled(EFI_RUNTIME_SERVICES)) efi_reboot(reboot_mode, NULL); /* Now call the architecture specific reboot code. */ if (arm_pm_restart) arm_pm_restart(reboot_mode, cmd); else do_kernel_restart(cmd); /* * Whoops - the architecture was unable to reboot. */ printk("Reboot failed -- System halted/n"); while (1);}在machine_restart 中，可以看到如果kernel可以使用uefi的runtime service的話，就會調用efi_rebootvoid efi_reboot(enum reboot_mode reboot_mode, const char *__unused){ const char *str[] = { "cold", "warm", "shutdown", "platform" }; int efi_mode, cap_reset_mode; if (!efi_enabled(EFI_RUNTIME_SERVICES)) return; switch (reboot_mode) { case REBOOT_WARM: case REBOOT_SOFT: efi_mode = EFI_RESET_WARM; break; default: efi_mode = EFI_RESET_COLD; break; } /* * If a quirk forced an EFI reset mode, always use that. */ if (efi_reboot_quirk_mode != -1) efi_mode = efi_reboot_quirk_mode; if (efi_capsule_pending(&cap_reset_mode)) { if (efi_mode != cap_reset_mode) printk(KERN_CRIT "efi: %s reset requested but pending " "capsule update requires %s reset... Performing " "%s reset./n", str[efi_mode], str[cap_reset_mode], str[cap_reset_mode]); efi_mode = cap_reset_mode; } efi.reset_system(efi_mode, EFI_SUCCESS, 0, NULL);}在efi_reboot 中可以看到reboot分為四中"cold", "warm", "shutdown", "platform"，最終轉成兩種mode EFI_RESET_WARM和 EFI_RESET_COLD最后通過 efi.reset_system(efi_mode, EFI_SUCCESS, 0, NULL);來reboot系統.在reboot命令中如果參數是LINUX_REBOOT_CMD_POWER_OFF的話kernel_power_off->machine_power_offvoid machine_power_off(void){ local_irq_disable(); smp_send_stop(); if (pm_power_off) pm_power_off();}可見最后是調用pm_power_off 來關機的.static int __init efi_shutdown_init(void){ if (!efi_enabled(EFI_RUNTIME_SERVICES)) return -ENODEV; if (efi_poweroff_required()) pm_power_off = efi_power_off; return 0;}late_initcall(efi_shutdown_init);同上肯定是可以使用uefi的runtime service ，而efi_poweroff_required 也是判斷是否可以使用runtime service，這兩者感覺有的重復。bool efi_poweroff_required(void){ return efi_enabled(EFI_RUNTIME_SERVICES);}總之會調用efi_power_off來關機而static void efi_power_off(void){ efi.reset_system(EFI_RESET_SHUTDOWN, EFI_SUCCESS, 0, NULL);}也是調用efi接口來實現關機.

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