libdwfl: elf_from_remote_memory should use pagesize, not p_align.
elf_from_remote_memory would use the actual p_align of the PT_LOAD segments
to calculate the loadbase, end and start of a segment. But the dynamic
loader aligns the segments using the pagesize and only sanity checks the
p_align values. So we should do the same to get accurate segment addresses.
Also fixes a small memory leak in case the ELF image appears to be bad.
Signed-off-by: Mark Wielaard <mjw@redhat.com>
diff --git a/libdwfl/elf-from-memory.c b/libdwfl/elf-from-memory.c
index 7d35df6..602614b 100644
--- a/libdwfl/elf-from-memory.c
+++ b/libdwfl/elf-from-memory.c
@@ -1,5 +1,5 @@
/* Reconstruct an ELF file by reading the segments out of remote memory.
- Copyright (C) 2005-2011 Red Hat, Inc.
+ Copyright (C) 2005-2011, 2014 Red Hat, Inc.
This file is part of elfutils.
This file is free software; you can redistribute it and/or modify
@@ -48,10 +48,14 @@
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. */
+ the number of bytes read if >= MINREAD. ARG is passed through.
+
+ PAGESIZE is the minimum page size and alignment used for the PT_LOAD
+ segments. */
Elf *
elf_from_remote_memory (GElf_Addr ehdr_vma,
+ GElf_Xword pagesize,
GElf_Addr *loadbasep,
ssize_t (*read_memory) (void *arg, void *data,
GElf_Addr address,
@@ -83,6 +87,7 @@
if (memcmp (buffer, ELFMAG, SELFMAG) != 0)
{
bad_elf:
+ free (buffer);
__libdwfl_seterrno (DWFL_E_BADELF);
return NULL;
}
@@ -195,21 +200,32 @@
bool found_base = false;
switch (ehdr.e32.e_ident[EI_CLASS])
{
- inline void handle_segment (GElf_Addr vaddr, GElf_Off offset,
- GElf_Xword filesz, GElf_Xword align)
+ /* Sanity checks segments and calculates segment_end,
+ segments_end, segments_end_mem and loadbase (if not
+ found_base yet). Returns true if sanity checking failed,
+ false otherwise. */
+ inline bool handle_segment (GElf_Addr vaddr, GElf_Off offset,
+ GElf_Xword filesz, GElf_Xword palign)
{
- GElf_Off segment_end = ((offset + filesz + align - 1) & -align);
+ /* Sanity check the alignment requirements. */
+ if ((palign & (pagesize - 1)) != 0
+ || ((vaddr - offset) & (palign - 1)) != 0)
+ return true;
+
+ GElf_Off segment_end = ((offset + filesz + pagesize - 1)
+ & -pagesize);
if (segment_end > (GElf_Off) contents_size)
contents_size = segment_end;
- if (!found_base && (offset & -align) == 0)
+ if (!found_base && (offset & -pagesize) == 0)
{
- loadbase = ehdr_vma - (vaddr & -align);
+ loadbase = ehdr_vma - (vaddr & -pagesize);
found_base = true;
}
segments_end = offset + filesz;
+ return false;
}
case ELFCLASS32:
@@ -218,8 +234,9 @@
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);
+ if (handle_segment (phdrs.p32[i].p_vaddr, phdrs.p32[i].p_offset,
+ phdrs.p32[i].p_filesz, phdrs.p32[i].p_align))
+ goto bad_elf;
break;
case ELFCLASS64:
@@ -228,8 +245,9 @@
goto libelf_error;
for (uint_fast16_t i = 0; i < phnum; ++i)
if (phdrs.p64[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);
+ if (handle_segment (phdrs.p64[i].p_vaddr, phdrs.p64[i].p_offset,
+ phdrs.p64[i].p_filesz, phdrs.p64[i].p_align))
+ goto bad_elf;
break;
default:
@@ -259,15 +277,17 @@
switch (ehdr.e32.e_ident[EI_CLASS])
{
+ /* Reads the given segment. Returns true if reading fails,
+ false otherwise. */
inline bool handle_segment (GElf_Addr vaddr, GElf_Off offset,
- GElf_Xword filesz, GElf_Xword align)
+ GElf_Xword filesz)
{
- GElf_Off start = offset & -align;
- GElf_Off end = (offset + filesz + align - 1) & -align;
+ GElf_Off start = offset & -pagesize;
+ GElf_Off end = (offset + filesz + pagesize - 1) & -pagesize;
if (end > (GElf_Off) contents_size)
end = contents_size;
nread = (*read_memory) (arg, buffer + start,
- (loadbase + vaddr) & -align,
+ (loadbase + vaddr) & -pagesize,
end - start, end - start);
return nread <= 0;
}
@@ -276,7 +296,7 @@
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))
+ phdrs.p32[i].p_filesz))
goto read_error;
/* If the segments visible in memory didn't include the section
@@ -303,7 +323,7 @@
for (uint_fast16_t i = 0; i < phnum; ++i)
if (phdrs.p64[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))
+ phdrs.p64[i].p_filesz))
goto read_error;
/* If the segments visible in memory didn't include the section