From: Michael Holzheu This patch introduces a mechanism that allows architecture backends to remove page tables for the crashkernel memory. This can protect the loaded kdump kernel from being overwritten by broken kernel code. A new function crash_map_pages() is added that can be implemented by architecture code. This function has the following syntax: void crash_map_pages(int enable); "enable" can be 0 for removing or 1 for adding page tables. The function is called before and after the crashkernel segments are loaded. It is also called in crash_shrink_memory() to create new page tables when the crashkernel memory size is reduced. To support architectures that have large pages this patch also introduces a new define KEXEC_CRASH_MEM_ALIGN. The crashkernel start and size must always be aligned with KEXEC_CRASH_MEM_ALIGN. Signed-off-by: Michael Holzheu --- include/linux/kexec.h | 5 +++++ kernel/kexec.c | 16 ++++++++++++++-- 2 files changed, 19 insertions(+), 2 deletions(-) --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -37,6 +37,10 @@ #define KEXEC_CRASH_CONTROL_MEMORY_LIMIT KEXEC_CONTROL_MEMORY_LIMIT #endif +#ifndef KEXEC_CRASH_MEM_ALIGN +#define KEXEC_CRASH_MEM_ALIGN PAGE_SIZE +#endif + #define KEXEC_NOTE_HEAD_BYTES ALIGN(sizeof(struct elf_note), 4) #define KEXEC_CORE_NOTE_NAME "CORE" #define KEXEC_CORE_NOTE_NAME_BYTES ALIGN(sizeof(KEXEC_CORE_NOTE_NAME), 4) @@ -133,6 +137,7 @@ extern void crash_kexec(struct pt_regs * int kexec_should_crash(struct task_struct *); void crash_save_cpu(struct pt_regs *regs, int cpu); void crash_save_vmcoreinfo(void); +void crash_map_pages(int enable); void arch_crash_save_vmcoreinfo(void); void vmcoreinfo_append_str(const char *fmt, ...) __attribute__ ((format (printf, 1, 2))); --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -999,6 +999,7 @@ SYSCALL_DEFINE4(kexec_load, unsigned lon kimage_free(xchg(&kexec_crash_image, NULL)); result = kimage_crash_alloc(&image, entry, nr_segments, segments); + crash_map_pages(1); } if (result) goto out; @@ -1015,6 +1016,8 @@ SYSCALL_DEFINE4(kexec_load, unsigned lon goto out; } kimage_terminate(image); + if (flags & KEXEC_ON_CRASH) + crash_map_pages(0); } /* Install the new kernel, and Uninstall the old */ image = xchg(dest_image, image); @@ -1026,6 +1029,13 @@ out: return result; } +/* + * provide an empty default implementation here -- architecture + * code may override this + */ +void __weak crash_map_pages(int enable) +{} + #ifdef CONFIG_COMPAT asmlinkage long compat_sys_kexec_load(unsigned long entry, unsigned long nr_segments, @@ -1134,14 +1144,16 @@ int crash_shrink_memory(unsigned long ne goto unlock; } - start = roundup(start, PAGE_SIZE); - end = roundup(start + new_size, PAGE_SIZE); + start = roundup(start, KEXEC_CRASH_MEM_ALIGN); + end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN); + crash_map_pages(1); crash_free_reserved_phys_range(end, crashk_res.end); if ((start == end) && (crashk_res.parent != NULL)) release_resource(&crashk_res); crashk_res.end = end - 1; + crash_map_pages(0); unlock: mutex_unlock(&kexec_mutex); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/