From: Xunlei Pang <xlpang@xxxxxxxxxx> Subject: kexec: move vmcoreinfo out of the kernel's .bss section As Eric said, "what we need to do is move the variable vmcoreinfo_note out of the kernel's .bss section. And modify the code to regenerate and keep this information in something like the control page. Definitely something like this needs a page all to itself, and ideally far away from any other kernel data structures. I clearly was not watching closely the data someone decided to keep this silly thing in the kernel's .bss section." This patch allocates extra pages for these vmcoreinfo_XXX variables, one advantage is that it enhances some safety of vmcoreinfo, because vmcoreinfo now is kept far away from other kernel data structures. Link: http://lkml.kernel.org/r/1493281021-20737-1-git-send-email-xlpang@xxxxxxxxxx Signed-off-by: Xunlei Pang <xlpang@xxxxxxxxxx> Tested-by: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx> Reviewed-by: Juergen Gross <jgross@xxxxxxxx> Suggested-by: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Dave Young <dyoung@xxxxxxxxxx> Cc: Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx> Cc: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/ia64/kernel/machine_kexec.c | 5 ----- arch/s390/kernel/machine_kexec.c | 1 + arch/s390/kernel/setup.c | 6 ------ arch/x86/kernel/crash.c | 2 +- arch/x86/xen/mmu_pv.c | 4 ++-- include/linux/crash_core.h | 4 ++-- kernel/crash_core.c | 26 ++++++++++++++++++++++---- kernel/ksysfs.c | 2 +- 8 files changed, 29 insertions(+), 21 deletions(-) diff -puN arch/ia64/kernel/machine_kexec.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section arch/ia64/kernel/machine_kexec.c --- a/arch/ia64/kernel/machine_kexec.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section +++ a/arch/ia64/kernel/machine_kexec.c @@ -163,8 +163,3 @@ void arch_crash_save_vmcoreinfo(void) #endif } -phys_addr_t paddr_vmcoreinfo_note(void) -{ - return ia64_tpa((unsigned long)(char *)&vmcoreinfo_note); -} - diff -puN arch/s390/kernel/machine_kexec.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section arch/s390/kernel/machine_kexec.c --- a/arch/s390/kernel/machine_kexec.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section +++ a/arch/s390/kernel/machine_kexec.c @@ -246,6 +246,7 @@ void arch_crash_save_vmcoreinfo(void) VMCOREINFO_SYMBOL(lowcore_ptr); VMCOREINFO_SYMBOL(high_memory); VMCOREINFO_LENGTH(lowcore_ptr, NR_CPUS); + mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note()); } void machine_shutdown(void) diff -puN arch/s390/kernel/setup.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section arch/s390/kernel/setup.c --- a/arch/s390/kernel/setup.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section +++ a/arch/s390/kernel/setup.c @@ -496,11 +496,6 @@ static void __init setup_memory_end(void pr_notice("The maximum memory size is %luMB\n", memory_end >> 20); } -static void __init setup_vmcoreinfo(void) -{ - mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note()); -} - #ifdef CONFIG_CRASH_DUMP /* @@ -939,7 +934,6 @@ void __init setup_arch(char **cmdline_p) #endif setup_resources(); - setup_vmcoreinfo(); setup_lowcore(); smp_fill_possible_mask(); cpu_detect_mhz_feature(); diff -puN arch/x86/kernel/crash.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section arch/x86/kernel/crash.c --- a/arch/x86/kernel/crash.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section +++ a/arch/x86/kernel/crash.c @@ -457,7 +457,7 @@ static int prepare_elf64_headers(struct bufp += sizeof(Elf64_Phdr); phdr->p_type = PT_NOTE; phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note(); - phdr->p_filesz = phdr->p_memsz = sizeof(vmcoreinfo_note); + phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE; (ehdr->e_phnum)++; #ifdef CONFIG_X86_64 diff -puN arch/x86/xen/mmu_pv.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section arch/x86/xen/mmu_pv.c --- a/arch/x86/xen/mmu_pv.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section +++ a/arch/x86/xen/mmu_pv.c @@ -2693,8 +2693,8 @@ EXPORT_SYMBOL_GPL(xen_destroy_contiguous phys_addr_t paddr_vmcoreinfo_note(void) { if (xen_pv_domain()) - return virt_to_machine(&vmcoreinfo_note).maddr; + return virt_to_machine(vmcoreinfo_note).maddr; else - return __pa_symbol(&vmcoreinfo_note); + return __pa(vmcoreinfo_note); } #endif /* CONFIG_KEXEC_CORE */ diff -puN include/linux/crash_core.h~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section include/linux/crash_core.h --- a/include/linux/crash_core.h~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section +++ a/include/linux/crash_core.h @@ -19,7 +19,7 @@ CRASH_CORE_NOTE_NAME_BYTES + \ CRASH_CORE_NOTE_DESC_BYTES) -#define VMCOREINFO_BYTES (4096) +#define VMCOREINFO_BYTES PAGE_SIZE #define VMCOREINFO_NOTE_NAME "VMCOREINFO" #define VMCOREINFO_NOTE_NAME_BYTES ALIGN(sizeof(VMCOREINFO_NOTE_NAME), 4) #define VMCOREINFO_NOTE_SIZE ((CRASH_CORE_NOTE_HEAD_BYTES * 2) + \ @@ -56,7 +56,7 @@ phys_addr_t paddr_vmcoreinfo_note(void); #define VMCOREINFO_CONFIG(name) \ vmcoreinfo_append_str("CONFIG_%s=y\n", #name) -extern u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4]; +extern u32 *vmcoreinfo_note; extern size_t vmcoreinfo_size; extern size_t vmcoreinfo_max_size; diff -puN kernel/crash_core.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section kernel/crash_core.c --- a/kernel/crash_core.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section +++ a/kernel/crash_core.c @@ -14,10 +14,10 @@ #include <asm/sections.h> /* vmcoreinfo stuff */ -static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES]; -u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4]; +static unsigned char *vmcoreinfo_data; size_t vmcoreinfo_size; -size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data); +size_t vmcoreinfo_max_size = VMCOREINFO_BYTES; +u32 *vmcoreinfo_note; /* * parsing the "crashkernel" commandline @@ -326,6 +326,9 @@ static void update_vmcoreinfo_note(void) void crash_save_vmcoreinfo(void) { + if (!vmcoreinfo_note) + return; + vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds()); update_vmcoreinfo_note(); } @@ -356,11 +359,26 @@ void __weak arch_crash_save_vmcoreinfo(v phys_addr_t __weak paddr_vmcoreinfo_note(void) { - return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note); + return __pa(vmcoreinfo_note); } static int __init crash_save_vmcoreinfo_init(void) { + vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL); + if (!vmcoreinfo_data) { + pr_warn("Memory allocation for vmcoreinfo_data failed\n"); + return -ENOMEM; + } + + vmcoreinfo_note = alloc_pages_exact(VMCOREINFO_NOTE_SIZE, + GFP_KERNEL | __GFP_ZERO); + if (!vmcoreinfo_note) { + free_page((unsigned long)vmcoreinfo_data); + vmcoreinfo_data = NULL; + pr_warn("Memory allocation for vmcoreinfo_note failed\n"); + return -ENOMEM; + } + VMCOREINFO_OSRELEASE(init_uts_ns.name.release); VMCOREINFO_PAGESIZE(PAGE_SIZE); diff -puN kernel/ksysfs.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section kernel/ksysfs.c --- a/kernel/ksysfs.c~kexec-move-vmcoreinfo-out-of-the-kernels-bss-section +++ a/kernel/ksysfs.c @@ -134,7 +134,7 @@ static ssize_t vmcoreinfo_show(struct ko { phys_addr_t vmcore_base = paddr_vmcoreinfo_note(); return sprintf(buf, "%pa %x\n", &vmcore_base, - (unsigned int)sizeof(vmcoreinfo_note)); + (unsigned int)VMCOREINFO_NOTE_SIZE); } KERNEL_ATTR_RO(vmcoreinfo); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
