| /* Reconstruct an ELF file by reading the segments out of remote memory. |
| Copyright (C) 2005 Red Hat, Inc. |
| |
| This program is Open Source software; you can redistribute it and/or |
| modify it under the terms of the Open Software License version 1.0 as |
| published by the Open Source Initiative. |
| |
| You should have received a copy of the Open Software License along |
| with this program; if not, you may obtain a copy of the Open Software |
| License version 1.0 from http://www.opensource.org/licenses/osl.php or |
| by writing the Open Source Initiative c/o Lawrence Rosen, Esq., |
| 3001 King Ranch Road, Ukiah, CA 95482. */ |
| |
| #include <config.h> |
| #include "../libelf/libelfP.h" |
| #undef _ |
| |
| #include "libdwflP.h" |
| |
| #include <gelf.h> |
| #include <sys/types.h> |
| #include <stdbool.h> |
| #include <stdlib.h> |
| #include <string.h> |
| |
| /* Reconstruct an ELF file by reading the segments out of remote memory |
| based on the ELF file header at EHDR_VMA and the ELF program headers it |
| points to. If not null, *LOADBASEP is filled in with the difference |
| between the addresses from which the segments were read, and the |
| addresses the file headers put them at. |
| |
| The function READ_MEMORY is called to copy at least MINREAD and at most |
| MAXREAD bytes from the remote memory at target address ADDRESS into the |
| local buffer at DATA; it should return -1 for errors (with code in |
| `errno'), 0 if it failed to read at least MINREAD bytes due to EOF, or |
| the number of bytes read if >= MINREAD. ARG is passed through. */ |
| |
| Elf * |
| elf_from_remote_memory (GElf_Addr ehdr_vma, |
| GElf_Addr *loadbasep, |
| ssize_t (*read_memory) (void *arg, void *data, |
| GElf_Addr address, |
| size_t minread, |
| size_t maxread), |
| void *arg) |
| { |
| /* First read in the file header and check its sanity. */ |
| |
| const size_t initial_bufsize = 256; |
| unsigned char *buffer = malloc (initial_bufsize); |
| if (buffer == NULL) |
| { |
| no_memory: |
| __libdwfl_seterrno (DWFL_E_NOMEM); |
| return NULL; |
| } |
| |
| ssize_t nread = (*read_memory) (arg, buffer, ehdr_vma, |
| sizeof (Elf32_Ehdr), initial_bufsize); |
| if (nread <= 0) |
| { |
| read_error: |
| free (buffer); |
| __libdwfl_seterrno (nread < 0 ? DWFL_E_ERRNO : DWFL_E_TRUNCATED); |
| return NULL; |
| } |
| |
| if (memcmp (buffer, ELFMAG, SELFMAG) != 0) |
| { |
| bad_elf: |
| __libdwfl_seterrno (DWFL_E_BADELF); |
| return NULL; |
| } |
| |
| /* Extract the information we need from the file header. */ |
| |
| union |
| { |
| Elf32_Ehdr e32; |
| Elf64_Ehdr e64; |
| } ehdr; |
| Elf_Data xlatefrom = |
| { |
| .d_type = ELF_T_EHDR, |
| .d_buf = buffer, |
| .d_version = EV_CURRENT, |
| }; |
| Elf_Data xlateto = |
| { |
| .d_type = ELF_T_EHDR, |
| .d_buf = &ehdr, |
| .d_size = sizeof ehdr, |
| .d_version = EV_CURRENT, |
| }; |
| |
| GElf_Off phoff; |
| uint_fast16_t phnum; |
| uint_fast16_t phentsize; |
| GElf_Off shdrs_end; |
| |
| switch (buffer[EI_CLASS]) |
| { |
| case ELFCLASS32: |
| xlatefrom.d_size = sizeof (Elf32_Ehdr); |
| if (elf32_xlatetom (&xlateto, &xlatefrom, buffer[EI_DATA]) == NULL) |
| { |
| libelf_error: |
| __libdwfl_seterrno (DWFL_E_LIBELF); |
| return NULL; |
| } |
| phoff = ehdr.e32.e_phoff; |
| phnum = ehdr.e32.e_phnum; |
| phentsize = ehdr.e32.e_phentsize; |
| if (phentsize != sizeof (Elf32_Phdr) || phnum == 0) |
| goto bad_elf; |
| shdrs_end = ehdr.e32.e_shoff + ehdr.e32.e_shnum * ehdr.e32.e_shentsize; |
| break; |
| |
| case ELFCLASS64: |
| xlatefrom.d_size = sizeof (Elf64_Ehdr); |
| if (elf32_xlatetom (&xlateto, &xlatefrom, buffer[EI_DATA]) == NULL) |
| goto libelf_error; |
| phoff = ehdr.e64.e_phoff; |
| phnum = ehdr.e64.e_phnum; |
| phentsize = ehdr.e64.e_phentsize; |
| if (phentsize != sizeof (Elf64_Phdr) || phnum == 0) |
| goto bad_elf; |
| shdrs_end = ehdr.e64.e_shoff + ehdr.e64.e_shnum * ehdr.e64.e_shentsize; |
| break; |
| |
| default: |
| goto bad_elf; |
| } |
| |
| |
| /* The file header tells where to find the program headers. |
| These are what we use to actually choose what to read. */ |
| |
| xlatefrom.d_type = xlateto.d_type = ELF_T_PHDR; |
| xlatefrom.d_size = phnum * phentsize; |
| |
| if ((size_t) nread >= phoff + phnum * phentsize) |
| /* We already have all the phdrs from the initial read. */ |
| xlatefrom.d_buf = buffer + phoff; |
| else |
| { |
| /* Read in the program headers. */ |
| |
| if (initial_bufsize < phnum * phentsize) |
| { |
| unsigned char *newbuf = realloc (buffer, phnum * phentsize); |
| if (newbuf == NULL) |
| { |
| free (buffer); |
| goto no_memory; |
| } |
| buffer = newbuf; |
| } |
| nread = (*read_memory) (arg, buffer, ehdr_vma + phoff, |
| phnum * phentsize, phnum * phentsize); |
| if (nread <= 0) |
| goto read_error; |
| |
| xlatefrom.d_buf = buffer; |
| } |
| |
| union |
| { |
| Elf32_Phdr p32[phnum]; |
| Elf64_Phdr p64[phnum]; |
| } phdrs; |
| |
| xlateto.d_buf = &phdrs; |
| xlateto.d_size = sizeof phdrs; |
| |
| /* Scan for PT_LOAD segments to find the total size of the file image. */ |
| size_t contents_size = 0; |
| GElf_Off segments_end = 0; |
| GElf_Addr loadbase = ehdr_vma; |
| switch (ehdr.e32.e_ident[EI_CLASS]) |
| { |
| inline void handle_segment (GElf_Addr vaddr, GElf_Off offset, |
| GElf_Xword filesz, GElf_Xword align) |
| { |
| GElf_Off segment_end = ((offset + filesz + align - 1) & -align); |
| |
| if (segment_end > (GElf_Off) contents_size) |
| contents_size = segment_end; |
| |
| if ((offset & -align) == 0 && loadbase == ehdr_vma) |
| loadbase = ehdr_vma - (vaddr & -align); |
| |
| segments_end = offset + filesz; |
| } |
| |
| case ELFCLASS32: |
| if (elf32_xlatetom (&xlateto, &xlatefrom, |
| ehdr.e32.e_ident[EI_DATA]) == NULL) |
| goto libelf_error; |
| for (uint_fast16_t i = 0; i < phnum; ++i) |
| if (phdrs.p32[i].p_type == PT_LOAD) |
| handle_segment (phdrs.p32[i].p_vaddr, phdrs.p32[i].p_offset, |
| phdrs.p32[i].p_filesz, phdrs.p32[i].p_align); |
| break; |
| |
| case ELFCLASS64: |
| if (elf32_xlatetom (&xlateto, &xlatefrom, |
| ehdr.e32.e_ident[EI_DATA]) == NULL) |
| goto libelf_error; |
| for (uint_fast16_t i = 0; i < phnum; ++i) |
| if (phdrs.p32[i].p_type == PT_LOAD) |
| handle_segment (phdrs.p64[i].p_vaddr, phdrs.p64[i].p_offset, |
| phdrs.p64[i].p_filesz, phdrs.p64[i].p_align); |
| break; |
| |
| default: |
| abort (); |
| break; |
| } |
| |
| /* Trim the last segment so we don't bother with zeros in the last page |
| that are off the end of the file. However, if the extra bit in that |
| page includes the section headers, keep them. */ |
| if ((GElf_Off) contents_size > segments_end |
| && (GElf_Off) contents_size >= shdrs_end) |
| { |
| contents_size = segments_end; |
| if ((GElf_Off) contents_size < shdrs_end) |
| contents_size = shdrs_end; |
| } |
| else |
| contents_size = segments_end; |
| |
| free (buffer); |
| |
| /* Now we know the size of the whole image we want read in. */ |
| buffer = calloc (1, contents_size); |
| if (buffer == NULL) |
| goto no_memory; |
| |
| switch (ehdr.e32.e_ident[EI_CLASS]) |
| { |
| inline bool handle_segment (GElf_Addr vaddr, GElf_Off offset, |
| GElf_Xword filesz, GElf_Xword align) |
| { |
| GElf_Off start = offset & -align; |
| GElf_Off end = (offset + filesz + align - 1) & -align; |
| if (end > (GElf_Off) contents_size) |
| end = contents_size; |
| nread = (*read_memory) (arg, buffer + start, |
| (loadbase + vaddr) & -align, |
| end - start, end - start); |
| return nread <= 0; |
| } |
| |
| case ELFCLASS32: |
| for (uint_fast16_t i = 0; i < phnum; ++i) |
| if (phdrs.p32[i].p_type == PT_LOAD) |
| if (handle_segment (phdrs.p32[i].p_vaddr, phdrs.p32[i].p_offset, |
| phdrs.p32[i].p_filesz, phdrs.p32[i].p_align)) |
| goto read_error; |
| |
| /* If the segments visible in memory didn't include the section |
| headers, then clear them from the file header. */ |
| if (contents_size < shdrs_end) |
| { |
| ehdr.e32.e_shoff = 0; |
| ehdr.e32.e_shnum = 0; |
| ehdr.e32.e_shstrndx = 0; |
| } |
| |
| /* This will normally have been in the first PT_LOAD segment. But it |
| conceivably could be missing, and we might have just changed it. */ |
| xlatefrom.d_type = xlateto.d_type = ELF_T_EHDR; |
| xlatefrom.d_size = xlateto.d_size = sizeof ehdr.e32; |
| xlatefrom.d_buf = &ehdr.e32; |
| xlateto.d_buf = buffer; |
| if (elf32_xlatetof (&xlateto, &xlatefrom, |
| ehdr.e32.e_ident[EI_DATA]) == NULL) |
| goto libelf_error; |
| break; |
| |
| case ELFCLASS64: |
| for (uint_fast16_t i = 0; i < phnum; ++i) |
| if (phdrs.p32[i].p_type == PT_LOAD) |
| if (handle_segment (phdrs.p64[i].p_vaddr, phdrs.p64[i].p_offset, |
| phdrs.p64[i].p_filesz, phdrs.p64[i].p_align)) |
| goto read_error; |
| |
| /* If the segments visible in memory didn't include the section |
| headers, then clear them from the file header. */ |
| if (contents_size < shdrs_end) |
| { |
| ehdr.e64.e_shoff = 0; |
| ehdr.e64.e_shnum = 0; |
| ehdr.e64.e_shstrndx = 0; |
| } |
| |
| /* This will normally have been in the first PT_LOAD segment. But it |
| conceivably could be missing, and we might have just changed it. */ |
| xlatefrom.d_type = xlateto.d_type = ELF_T_EHDR; |
| xlatefrom.d_size = xlateto.d_size = sizeof ehdr.e64; |
| xlatefrom.d_buf = &ehdr.e64; |
| xlateto.d_buf = buffer; |
| if (elf32_xlatetof (&xlateto, &xlatefrom, |
| ehdr.e64.e_ident[EI_DATA]) == NULL) |
| goto libelf_error; |
| break; |
| |
| default: |
| abort (); |
| break; |
| } |
| |
| /* Now we have the image. Open libelf on it. */ |
| |
| Elf *elf = elf_memory ((char *) buffer, contents_size); |
| if (elf == NULL) |
| { |
| free (buffer); |
| return NULL; |
| } |
| |
| elf->flags |= ELF_F_MALLOCED; |
| if (loadbasep != NULL) |
| *loadbasep = loadbase; |
| return elf; |
| } |