Adjust for monotone.

1 files changed, 328 insertions, 0 deletions

diff --git a/libdwfl/elf-from-memory.c b/libdwfl/elf-from-memory.c
new file mode 100644
index 00000000..3175ab16
--- /dev/null
+++ b/libdwfl/elf-from-memory.c
@@ -0,0 +1,328 @@
+/* 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;
+}