On Thu, Sep 08, 2011 at 03:26:10PM +0200, Michael Holzheu wrote: > From: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx> > > 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); CCing Huang Ying. I am not sure if preserve context thing will be impacted by this in anyway. Hyuang, While I am looking at x86 code, I had a question. gitblame tells you changed that code last, so here I go. What is init_transition_pgtable() and why do we need it. I see that init_pgtable() sets up identity mapped page table from 0 to max_pfn. Code running in control page (identity_mapped onwards) will make use of identity mapped page tables. Then I see that init_transition_pgtable() goes ahead and seems to be modifying identity mapped page tables to map address relocate_kernel to control code physical address. Why do we have to do that? Thanks Vivek > > "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 <holzheu@xxxxxxxxxxxxxxxxxx> > --- > 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-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html