From 841bd048ea17485fe683859197082e906ed65594 Mon Sep 17 00:00:00 2001 From: HATAYAMA Daisuke Date: Wed, 20 Mar 2013 15:08:37 +1100 Subject: [PATCH] kexec: fill note buffers by NT_VMCORE_PAD notes in page-size boundary Fill both crash_notes and vmcoreinfo_note buffers by NT_VMCORE_PAD note type to make them satisfy mmap()'s page-size boundary requirement. So far, end of note segments has been marked by zero-filled elf header. Instead, this patch writes NT_VMCORE_PAD note in the end of note segments until the offset on page-size boundary. Also, old kernel can treat the ELF segments created without null header because it stops reading ELF segments if real size it reads reachs p_memsz. Signed-off-by: HATAYAMA Daisuke Cc: Zhang Yanfei Cc: Vivek Goyal Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton --- arch/s390/include/asm/kexec.h | 8 +++--- include/linux/kexec.h | 12 +++++---- kernel/kexec.c | 46 ++++++++++++++++++++++------------- 3 files changed, 41 insertions(+), 25 deletions(-) diff --git a/arch/s390/include/asm/kexec.h b/arch/s390/include/asm/kexec.h index 694bcd6bd927..f33ec08ec8d3 100644 --- a/arch/s390/include/asm/kexec.h +++ b/arch/s390/include/asm/kexec.h @@ -41,8 +41,8 @@ /* * Size for s390x ELF notes per CPU * - * Seven notes plus zero note at the end: prstatus, fpregset, timer, - * tod_cmp, tod_reg, control regs, and prefix + * Seven notes plus note with NT_VMCORE_PAD type at the end: prstatus, + * fpregset, timer, tod_cmp, tod_reg, control regs, and prefix */ #define KEXEC_NOTE_BYTES \ (ALIGN(sizeof(struct elf_note), 4) * 8 + \ @@ -53,7 +53,9 @@ ALIGN(sizeof(u64), 4) + \ ALIGN(sizeof(u32), 4) + \ ALIGN(sizeof(u64) * 16, 4) + \ - ALIGN(sizeof(u32), 4) \ + ALIGN(sizeof(u32), 4) + \ + KEXEC_CORE_NOTE_DESC_BYTES + \ + VMCOREINFO_NOTE_NAME_BYTES \ ) /* Provide a dummy definition to avoid build failures. */ diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 5113570f4b4e..6592935f6649 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -47,14 +47,16 @@ #define KEXEC_CORE_NOTE_NAME_BYTES ALIGN(sizeof(KEXEC_CORE_NOTE_NAME), 4) #define KEXEC_CORE_NOTE_DESC_BYTES ALIGN(sizeof(struct elf_prstatus), 4) /* - * The per-cpu notes area is a list of notes terminated by a "NULL" - * note header. For kdump, the code in vmcore.c runs in the context - * of the second kernel to combine them into one note. + * The per-cpu notes area is a list of notes terminated by a note + * header with NT_VMCORE_PAD type. For kdump, the code in vmcore.c + * runs in the context of the second kernel to combine them into one + * note. */ #ifndef KEXEC_NOTE_BYTES #define KEXEC_NOTE_BYTES ( (KEXEC_NOTE_HEAD_BYTES * 2) + \ KEXEC_CORE_NOTE_NAME_BYTES + \ - KEXEC_CORE_NOTE_DESC_BYTES ) + KEXEC_CORE_NOTE_DESC_BYTES + \ + VMCOREINFO_NOTE_NAME_BYTES) #endif /* @@ -187,7 +189,7 @@ extern struct kimage *kexec_crash_image; #define VMCOREINFO_NOTE_NAME_BYTES ALIGN(sizeof(VMCOREINFO_NOTE_NAME), 4) #define VMCOREINFO_NOTE_SIZE ALIGN(KEXEC_NOTE_HEAD_BYTES*2 \ +VMCOREINFO_BYTES \ - +VMCOREINFO_NOTE_NAME_BYTES, \ + +VMCOREINFO_NOTE_NAME_BYTES*2, \ PAGE_SIZE) /* Location of a reserved region to hold the crash kernel. diff --git a/kernel/kexec.c b/kernel/kexec.c index 0ecef8ef2eef..02d19826282c 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -40,6 +40,7 @@ /* Per cpu memory for storing cpu states in case of system crash. */ note_buf_t __percpu *crash_notes; +static size_t crash_notes_size = ALIGN(sizeof(note_buf_t), PAGE_SIZE); /* vmcoreinfo stuff */ static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES]; @@ -1166,6 +1167,7 @@ unlock: return ret; } +/* If @data is NULL, fill @buf with 0 in @data_len bytes. */ static u32 *append_elf_note(u32 *buf, char *name, unsigned type, void *data, size_t data_len) { @@ -1178,26 +1180,36 @@ static u32 *append_elf_note(u32 *buf, char *name, unsigned type, void *data, buf += (sizeof(note) + 3)/4; memcpy(buf, name, note.n_namesz); buf += (note.n_namesz + 3)/4; - memcpy(buf, data, note.n_descsz); + if (data) + memcpy(buf, data, note.n_descsz); + else + memset(buf, 0, note.n_descsz); buf += (note.n_descsz + 3)/4; return buf; } -static void final_note(u32 *buf) +static void final_note(u32 *buf, size_t buf_len, size_t data_len) { - struct elf_note note; + size_t used_bytes, pad_hdr_size; - note.n_namesz = 0; - note.n_descsz = 0; - note.n_type = 0; - memcpy(buf, ¬e, sizeof(note)); + pad_hdr_size = KEXEC_NOTE_HEAD_BYTES + VMCOREINFO_NOTE_NAME_BYTES; + + /* + * keep space for ELF note header and "VMCOREINFO" name to + * terminate ELF segment by NT_VMCORE_PAD note. + */ + BUG_ON(data_len + pad_hdr_size > buf_len); + + used_bytes = data_len + pad_hdr_size; + append_elf_note(buf, VMCOREINFO_NOTE_NAME, NT_VMCORE_PAD, NULL, + roundup(used_bytes, PAGE_SIZE) - used_bytes); } void crash_save_cpu(struct pt_regs *regs, int cpu) { struct elf_prstatus prstatus; - u32 *buf; + u32 *buf, *buf_end; if ((cpu < 0) || (cpu >= nr_cpu_ids)) return; @@ -1215,16 +1227,15 @@ void crash_save_cpu(struct pt_regs *regs, int cpu) memset(&prstatus, 0, sizeof(prstatus)); prstatus.pr_pid = current->pid; elf_core_copy_kernel_regs(&prstatus.pr_reg, regs); - buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_PRSTATUS, - &prstatus, sizeof(prstatus)); - final_note(buf); + buf_end = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_PRSTATUS, + &prstatus, sizeof(prstatus)); + final_note(buf_end, crash_notes_size, (buf_end - buf) * sizeof(u32)); } static int __init crash_notes_memory_init(void) { /* Allocate memory for saving cpu registers. */ - crash_notes = __alloc_percpu(roundup(sizeof(note_buf_t), PAGE_SIZE), - PAGE_SIZE); + crash_notes = __alloc_percpu(crash_notes_size, PAGE_SIZE); if (!crash_notes) { printk("Kexec: Memory allocation for saving cpu register" " states failed\n"); @@ -1423,13 +1434,14 @@ int __init parse_crashkernel_low(char *cmdline, static void update_vmcoreinfo_note(void) { - u32 *buf = vmcoreinfo_note; + u32 *buf = vmcoreinfo_note, *buf_end; if (!vmcoreinfo_size) return; - buf = append_elf_note(buf, VMCOREINFO_NOTE_NAME, NT_VMCORE_DEBUGINFO, - vmcoreinfo_data, vmcoreinfo_size); - final_note(buf); + buf_end = append_elf_note(buf, VMCOREINFO_NOTE_NAME, NT_VMCORE_DEBUGINFO, + vmcoreinfo_data, vmcoreinfo_size); + final_note(buf_end, sizeof(vmcoreinfo_note), + (buf_end - buf) * sizeof(u32)); } void crash_save_vmcoreinfo(void) -- 2.39.5