From: Vivek Goyal - Kexec on panic functionality allocates memory for saving cpu registers in case of system crash event. Address of this allocated memory needs to be exported to user space, which is used by kexec-tools. - Previously, a single /sys/kernel/crash_notes entry was being exported as memory allocated was a single continuous array. Now memory allocation being dyanmic and per cpu based, address of per cpu buffer is exported through "/sys/devices/system/cpu/cpuX/crash_notes" Signed-off-by: Vivek Goyal Cc: Greg KH Signed-off-by: Andrew Morton --- drivers/base/cpu.c | 32 ++++++++++++++++++++++++++++++++ kernel/ksysfs.c | 13 ------------- 2 files changed, 32 insertions(+), 13 deletions(-) diff -puN drivers/base/cpu.c~kdump-export-per-cpu-crash-notes-pointer-through-sysfs drivers/base/cpu.c --- 25/drivers/base/cpu.c~kdump-export-per-cpu-crash-notes-pointer-through-sysfs Thu Nov 17 14:21:04 2005 +++ 25-akpm/drivers/base/cpu.c Thu Nov 17 14:21:04 2005 @@ -83,6 +83,33 @@ static inline void register_cpu_control( } #endif /* CONFIG_HOTPLUG_CPU */ +#ifdef CONFIG_KEXEC +#include + +static ssize_t show_crash_notes(struct sys_device *dev, char *buf) +{ + struct cpu *cpu = container_of(dev, struct cpu, sysdev); + ssize_t rc; + unsigned long long addr; + int cpunum; + + cpunum = cpu->sysdev.id; + + /* + * Might be reading other cpu's data based on which cpu read thread + * has been scheduled. But cpu data (memory) is allocated once during + * boot up and this data does not change there after. Hence this + * operation should be safe. No locking required. + */ + get_cpu(); + addr = __pa(per_cpu_ptr(crash_notes, cpunum)); + rc = sprintf(buf, "%Lx\n", addr); + put_cpu(); + return rc; +} +static SYSDEV_ATTR(crash_notes, 0400, show_crash_notes, NULL); +#endif + /* * register_cpu - Setup a driverfs device for a CPU. * @cpu - Callers can set the cpu->no_control field to 1, to indicate not to @@ -108,6 +135,11 @@ int __devinit register_cpu(struct cpu *c register_cpu_control(cpu); if (!error) cpu_sys_devices[num] = &cpu->sysdev; + +#ifdef CONFIG_KEXEC + if (!error) + error = sysdev_create_file(&cpu->sysdev, &attr_crash_notes); +#endif return error; } diff -puN kernel/ksysfs.c~kdump-export-per-cpu-crash-notes-pointer-through-sysfs kernel/ksysfs.c --- 25/kernel/ksysfs.c~kdump-export-per-cpu-crash-notes-pointer-through-sysfs Thu Nov 17 14:21:04 2005 +++ 25-akpm/kernel/ksysfs.c Thu Nov 17 14:21:04 2005 @@ -48,16 +48,6 @@ static ssize_t uevent_helper_store(struc KERNEL_ATTR_RW(uevent_helper); #endif -#ifdef CONFIG_KEXEC -#include - -static ssize_t crash_notes_show(struct subsystem *subsys, char *page) -{ - return sprintf(page, "%p\n", (void *)crash_notes); -} -KERNEL_ATTR_RO(crash_notes); -#endif - decl_subsys(kernel, NULL, NULL); EXPORT_SYMBOL_GPL(kernel_subsys); @@ -66,9 +56,6 @@ static struct attribute * kernel_attrs[] &uevent_seqnum_attr.attr, &uevent_helper_attr.attr, #endif -#ifdef CONFIG_KEXEC - &crash_notes_attr.attr, -#endif NULL }; _