s390/kdump: Fix elfcorehdr size calculation

Before the memory for the elfcorehdr is allocated the required size is
estimated with

       alloc_size = 0x1000 + get_cpu_cnt() * 0x4a0 +
               mem_chunk_cnt * sizeof(Elf64_Phdr);

Where 0x4a0 is used as size for the ELF notes to store the register
contend. This size is 8 bytes too small. Usually this does not immediately
cause a problem because the page reserved for overhead (Elf_Ehdr,
vmcoreinfo, etc.) is pretty generous. So usually there is enough spare
memory to counter the mis-calculated per cpu size. However, with growing
overhead and/or a huge cpu count the allocated size gets too small for the
elfcorehdr. Ultimately a BUG_ON is triggered causing the crash kernel to
panic.

Fix this by properly calculating the required size instead of relying on
magic numbers.

Fixes: a62bc07392 ("s390/kdump: add support for vector extension")
Signed-off-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Philipp Rudo 2018-07-19 11:13:45 +02:00 committed by Martin Schwidefsky
parent 5223c67167
commit 8cce437fbb
1 changed files with 98 additions and 6 deletions

View File

@ -306,6 +306,15 @@ static void *kzalloc_panic(int len)
return rc;
}
static const char *nt_name(Elf64_Word type)
{
const char *name = "LINUX";
if (type == NT_PRPSINFO || type == NT_PRSTATUS || type == NT_PRFPREG)
name = KEXEC_CORE_NOTE_NAME;
return name;
}
/*
* Initialize ELF note
*/
@ -332,11 +341,26 @@ static void *nt_init_name(void *buf, Elf64_Word type, void *desc, int d_len,
static inline void *nt_init(void *buf, Elf64_Word type, void *desc, int d_len)
{
const char *note_name = "LINUX";
return nt_init_name(buf, type, desc, d_len, nt_name(type));
}
if (type == NT_PRPSINFO || type == NT_PRSTATUS || type == NT_PRFPREG)
note_name = KEXEC_CORE_NOTE_NAME;
return nt_init_name(buf, type, desc, d_len, note_name);
/*
* Calculate the size of ELF note
*/
static size_t nt_size_name(int d_len, const char *name)
{
size_t size;
size = sizeof(Elf64_Nhdr);
size += roundup(strlen(name) + 1, 4);
size += roundup(d_len, 4);
return size;
}
static inline size_t nt_size(Elf64_Word type, int d_len)
{
return nt_size_name(d_len, nt_name(type));
}
/*
@ -374,6 +398,29 @@ static void *fill_cpu_elf_notes(void *ptr, int cpu, struct save_area *sa)
return ptr;
}
/*
* Calculate size of ELF notes per cpu
*/
static size_t get_cpu_elf_notes_size(void)
{
struct save_area *sa = NULL;
size_t size;
size = nt_size(NT_PRSTATUS, sizeof(struct elf_prstatus));
size += nt_size(NT_PRFPREG, sizeof(elf_fpregset_t));
size += nt_size(NT_S390_TIMER, sizeof(sa->timer));
size += nt_size(NT_S390_TODCMP, sizeof(sa->todcmp));
size += nt_size(NT_S390_TODPREG, sizeof(sa->todpreg));
size += nt_size(NT_S390_CTRS, sizeof(sa->ctrs));
size += nt_size(NT_S390_PREFIX, sizeof(sa->prefix));
if (MACHINE_HAS_VX) {
size += nt_size(NT_S390_VXRS_HIGH, sizeof(sa->vxrs_high));
size += nt_size(NT_S390_VXRS_LOW, sizeof(sa->vxrs_low));
}
return size;
}
/*
* Initialize prpsinfo note (new kernel)
*/
@ -429,6 +476,30 @@ static void *nt_vmcoreinfo(void *ptr)
return nt_init_name(ptr, 0, vmcoreinfo, size, "VMCOREINFO");
}
static size_t nt_vmcoreinfo_size(void)
{
const char *name = "VMCOREINFO";
char nt_name[11];
Elf64_Nhdr note;
void *addr;
if (copy_oldmem_kernel(&addr, &S390_lowcore.vmcore_info, sizeof(addr)))
return 0;
if (copy_oldmem_kernel(&note, addr, sizeof(note)))
return 0;
memset(nt_name, 0, sizeof(nt_name));
if (copy_oldmem_kernel(nt_name, addr + sizeof(note),
sizeof(nt_name) - 1))
return 0;
if (strcmp(nt_name, name) != 0)
return 0;
return nt_size_name(note.n_descsz, name);
}
/*
* Initialize final note (needed for /proc/vmcore code)
*/
@ -539,6 +610,27 @@ static void *notes_init(Elf64_Phdr *phdr, void *ptr, u64 notes_offset)
return ptr;
}
static size_t get_elfcorehdr_size(int mem_chunk_cnt)
{
size_t size;
size = sizeof(Elf64_Ehdr);
/* PT_NOTES */
size += sizeof(Elf64_Phdr);
/* nt_prpsinfo */
size += nt_size(NT_PRPSINFO, sizeof(struct elf_prpsinfo));
/* regsets */
size += get_cpu_cnt() * get_cpu_elf_notes_size();
/* nt_vmcoreinfo */
size += nt_vmcoreinfo_size();
/* nt_final */
size += sizeof(Elf64_Nhdr);
/* PT_LOADS */
size += mem_chunk_cnt * sizeof(Elf64_Phdr);
return size;
}
/*
* Create ELF core header (new kernel)
*/
@ -566,8 +658,8 @@ int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
mem_chunk_cnt = get_mem_chunk_cnt();
alloc_size = 0x1000 + get_cpu_cnt() * 0x4a0 +
mem_chunk_cnt * sizeof(Elf64_Phdr);
alloc_size = get_elfcorehdr_size(mem_chunk_cnt);
hdr = kzalloc_panic(alloc_size);
/* Init elf header */
ptr = ehdr_init(hdr, mem_chunk_cnt);