From: HATAYAMA Daisuke Date: Wed, 20 Mar 2013 04:08:33 +0000 (+1100) Subject: vmcore: reference e_phoff member explicitly to get position of program header table X-Git-Tag: next-20130320~2^2~111 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=732ea3703146ab63eca0a8352b83b42987a02191;p=karo-tx-linux.git vmcore: reference e_phoff member explicitly to get position of program header table Currently, read to /proc/vmcore is done by read_oldmem() that uses ioremap/iounmap per a single page. For example, if memory is 1GB, ioremap/iounmap is called (1GB / 4KB)-times, that is, 262144 times. This causes big performance degradation. In particular, the current main user of this mmap() is makedumpfile, which not only reads memory from /proc/vmcore but also does other processing like filtering, compression and IO work. Update of page table and the following TLB flush makes such processing much slow; though I have yet to make patch for makedumpfile and yet to confirm how it's improved. To address the issue, this patch implements mmap() on /proc/vmcore to improve read performance. My simple benchmark shows the improvement from 200 [MiB/sec] to over 50.0 [GiB/sec]. This patch: Currently, the code assumes that position of program header table is next to ELF header. But future change can break the assumption on kexec-tools and the 1st kernel. To avoid worst case, reference e_phoff member explicitly to get position of program header table in file-offset. Signed-off-by: Zhang Yanfei Signed-off-by: HATAYAMA Daisuke Cc: Vivek Goyal Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton --- diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c index b870f740ab5a..163281e1d1b0 100644 --- a/fs/proc/vmcore.c +++ b/fs/proc/vmcore.c @@ -221,8 +221,8 @@ static u64 __init get_vmcore_size_elf64(char *elfptr) Elf64_Phdr *phdr_ptr; ehdr_ptr = (Elf64_Ehdr *)elfptr; - phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); - size = sizeof(Elf64_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr)); + phdr_ptr = (Elf64_Phdr*)(elfptr + ehdr_ptr->e_phoff); + size = ehdr_ptr->e_phoff + ((ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr)); for (i = 0; i < ehdr_ptr->e_phnum; i++) { size += phdr_ptr->p_memsz; phdr_ptr++; @@ -238,8 +238,8 @@ static u64 __init get_vmcore_size_elf32(char *elfptr) Elf32_Phdr *phdr_ptr; ehdr_ptr = (Elf32_Ehdr *)elfptr; - phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr)); - size = sizeof(Elf32_Ehdr) + ((ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr)); + phdr_ptr = (Elf32_Phdr*)(elfptr + ehdr_ptr->e_phoff); + size = ehdr_ptr->e_phoff + ((ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr)); for (i = 0; i < ehdr_ptr->e_phnum; i++) { size += phdr_ptr->p_memsz; phdr_ptr++; @@ -259,7 +259,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, u64 phdr_sz = 0, note_off; ehdr_ptr = (Elf64_Ehdr *)elfptr; - phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); + phdr_ptr = (Elf64_Phdr*)(elfptr + ehdr_ptr->e_phoff); for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) { int j; void *notes_section; @@ -305,7 +305,7 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, /* Prepare merged PT_NOTE program header. */ phdr.p_type = PT_NOTE; phdr.p_flags = 0; - note_off = sizeof(Elf64_Ehdr) + + note_off = ehdr_ptr->e_phoff + (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf64_Phdr); phdr.p_offset = note_off; phdr.p_vaddr = phdr.p_paddr = 0; @@ -313,14 +313,14 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, phdr.p_align = 0; /* Add merged PT_NOTE program header*/ - tmp = elfptr + sizeof(Elf64_Ehdr); + tmp = elfptr + ehdr_ptr->e_phoff; memcpy(tmp, &phdr, sizeof(phdr)); tmp += sizeof(phdr); /* Remove unwanted PT_NOTE program headers. */ i = (nr_ptnote - 1) * sizeof(Elf64_Phdr); *elfsz = *elfsz - i; - memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf64_Ehdr)-sizeof(Elf64_Phdr))); + memmove(tmp, tmp+i, ((*elfsz)-ehdr_ptr->e_phoff-sizeof(Elf64_Phdr))); /* Modify e_phnum to reflect merged headers. */ ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1; @@ -340,7 +340,7 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz, u64 phdr_sz = 0, note_off; ehdr_ptr = (Elf32_Ehdr *)elfptr; - phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr)); + phdr_ptr = (Elf32_Phdr*)(elfptr + ehdr_ptr->e_phoff); for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) { int j; void *notes_section; @@ -386,7 +386,7 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz, /* Prepare merged PT_NOTE program header. */ phdr.p_type = PT_NOTE; phdr.p_flags = 0; - note_off = sizeof(Elf32_Ehdr) + + note_off = ehdr_ptr->e_phoff + (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf32_Phdr); phdr.p_offset = note_off; phdr.p_vaddr = phdr.p_paddr = 0; @@ -394,14 +394,14 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz, phdr.p_align = 0; /* Add merged PT_NOTE program header*/ - tmp = elfptr + sizeof(Elf32_Ehdr); + tmp = elfptr + ehdr_ptr->e_phoff; memcpy(tmp, &phdr, sizeof(phdr)); tmp += sizeof(phdr); /* Remove unwanted PT_NOTE program headers. */ i = (nr_ptnote - 1) * sizeof(Elf32_Phdr); *elfsz = *elfsz - i; - memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf32_Ehdr)-sizeof(Elf32_Phdr))); + memmove(tmp, tmp+i, ((*elfsz)-ehdr_ptr->e_phoff-sizeof(Elf32_Phdr))); /* Modify e_phnum to reflect merged headers. */ ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1; @@ -422,10 +422,10 @@ static int __init process_ptload_program_headers_elf64(char *elfptr, struct vmcore *new; ehdr_ptr = (Elf64_Ehdr *)elfptr; - phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); /* PT_NOTE hdr */ + phdr_ptr = (Elf64_Phdr*)(elfptr + ehdr_ptr->e_phoff); /* PT_NOTE hdr */ /* First program header is PT_NOTE header. */ - vmcore_off = sizeof(Elf64_Ehdr) + + vmcore_off = ehdr_ptr->e_phoff + (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr) + phdr_ptr->p_memsz; /* Note sections */ @@ -459,10 +459,10 @@ static int __init process_ptload_program_headers_elf32(char *elfptr, struct vmcore *new; ehdr_ptr = (Elf32_Ehdr *)elfptr; - phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr)); /* PT_NOTE hdr */ + phdr_ptr = (Elf32_Phdr*)(elfptr + ehdr_ptr->e_phoff); /* PT_NOTE hdr */ /* First program header is PT_NOTE header. */ - vmcore_off = sizeof(Elf32_Ehdr) + + vmcore_off = ehdr_ptr->e_phoff + (ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr) + phdr_ptr->p_memsz; /* Note sections */ @@ -496,7 +496,7 @@ static void __init set_vmcore_list_offsets_elf64(char *elfptr, ehdr_ptr = (Elf64_Ehdr *)elfptr; /* Skip Elf header and program headers. */ - vmcore_off = sizeof(Elf64_Ehdr) + + vmcore_off = ehdr_ptr->e_phoff + (ehdr_ptr->e_phnum) * sizeof(Elf64_Phdr); list_for_each_entry(m, vc_list, list) { @@ -516,7 +516,7 @@ static void __init set_vmcore_list_offsets_elf32(char *elfptr, ehdr_ptr = (Elf32_Ehdr *)elfptr; /* Skip Elf header and program headers. */ - vmcore_off = sizeof(Elf32_Ehdr) + + vmcore_off = ehdr_ptr->e_phoff + (ehdr_ptr->e_phnum) * sizeof(Elf32_Phdr); list_for_each_entry(m, vc_list, list) { @@ -558,11 +558,19 @@ static int __init parse_crash_elf64_headers(void) if (!elfcorebuf) return -ENOMEM; addr = elfcorehdr_addr; - rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz, &addr, 0); + rc = read_from_oldmem(elfcorebuf, sizeof(Elf64_Ehdr), &addr, 0); if (rc < 0) { kfree(elfcorebuf); return rc; } + addr = elfcorehdr_addr + ehdr.e_phoff; + rc = read_from_oldmem(elfcorebuf + sizeof(Elf64_Ehdr), + ehdr.e_phnum * sizeof(Elf64_Phdr), &addr, 0); + if (rc < 0) { + kfree(elfcorebuf); + return rc; + } + ((Elf64_Ehdr *)elfcorebuf)->e_phoff = sizeof(Elf64_Ehdr); /* Merge all PT_NOTE headers into one. */ rc = merge_note_headers_elf64(elfcorebuf, &elfcorebuf_sz, &vmcore_list); @@ -613,11 +621,19 @@ static int __init parse_crash_elf32_headers(void) if (!elfcorebuf) return -ENOMEM; addr = elfcorehdr_addr; - rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz, &addr, 0); + rc = read_from_oldmem(elfcorebuf, sizeof(Elf32_Ehdr), &addr, 0); + if (rc < 0) { + kfree(elfcorebuf); + return rc; + } + addr = elfcorehdr_addr + ehdr.e_phoff; + rc = read_from_oldmem(elfcorebuf + sizeof(Elf32_Ehdr), + ehdr.e_phnum * sizeof(Elf32_Phdr), &addr, 0); if (rc < 0) { kfree(elfcorebuf); return rc; } + ((Elf32_Ehdr *)elfcorebuf)->e_phoff = sizeof(Elf32_Ehdr); /* Merge all PT_NOTE headers into one. */ rc = merge_note_headers_elf32(elfcorebuf, &elfcorebuf_sz, &vmcore_list);