[patch] Fix bfd_elf_bfd_from_remote_memory() loadbase
Jan Kratochvil
jan.kratochvil@redhat.com
Mon Aug 13 21:28:00 GMT 2007
On Mon, 13 Aug 2007 05:56:54 +0200, Alan Modra wrote:
...
> - remove the nonsense PF_R tests.
> - set loadbase using the first header with (p_offset & -p_align) == 0
On Mon, 13 Aug 2007 06:14:30 +0200, Roland McGrath wrote:
...
> It is probably also appropriate to change how the later part of the function
> works (the actual data reading). Removing the PF_R check from the second
> loop in the existing code
[attached]
GDB testsuite ran on x86_64; vDSO manually tested on IA-64.
On Mon, 13 Aug 2007 03:15:44 +0200, Roland McGrath wrote:
...
> Jan's new comment explaining the PF_R check is incorrect. It may once
> have been the case in Linux that the debugger was unable to read memory
> mapped without read permission, but that has certainly not been true
> recently.
While it is Linux kernel dependent (kernel-2.6.21-1.3228.fc7.x86_64) I have
made a test [attached] of this behavior with the results you describe.
Still some segments / segments parts may be missing if using a core file
backend but it is the responsibility of the TARGET_READ_MEMORY callback to
never report error - or possibly a fix out of scope of this patch.
Regards,
Jan
prot: @address self-Read(requested)->(permitted) self-Write self-eXecute ptrace-Read(permitted) ptrace-Write
00: @0x2aaaaaaae000 R(-)->(-) W(-)->(-) X(-)->(-) pR(+) pW(+)
01: @0x2aaaaaab0000 R(-)->(+) W(-)->(-) X(+)->(-) pR(+) pW(+)
02: @0x2aaaaaab2000 R(-)->(+) W(+)->(+) X(-)->(-) pR(+) pW(+)
03: @0x2aaaaaab4000 R(-)->(+) W(+)->(+) X(+)->(-) pR(+) pW(+)
04: @0x2aaaaaab6000 R(+)->(+) W(-)->(-) X(-)->(+) pR(+) pW(+)
05: @0x2aaaaaab8000 R(+)->(+) W(-)->(-) X(+)->(+) pR(+) pW(+)
06: @0x2aaaaaaba000 R(+)->(+) W(+)->(+) X(-)->(+) pR(+) pW(+)
07: @0x2aaaaaabc000 R(+)->(+) W(+)->(+) X(+)->(+) pR(+) pW(+)
/proc/PID/maps:
2aaaaaaae000-2aaaaaaaf000 ---p 2aaaaaaae000 00:00 0
2aaaaaab0000-2aaaaaab1000 r--p 2aaaaaab0000 00:00 0
2aaaaaab2000-2aaaaaab3000 -w-p 2aaaaaab2000 00:00 0
2aaaaaab4000-2aaaaaab5000 rw-p 2aaaaaab4000 00:00 0
2aaaaaab6000-2aaaaaab7000 --xp 2aaaaaab6000 00:00 0
2aaaaaab8000-2aaaaaab9000 r-xp 2aaaaaab8000 00:00 0
2aaaaaaba000-2aaaaaabb000 -wxp 2aaaaaaba000 00:00 0
2aaaaaabc000-2aaaaaabd000 rwxp 2aaaaaabc000 00:00 0
core:
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000010000 0x00002aaaaaaae000 0x0000000000000000
0x0000000000001000 0x0000000000001000 1000
LOAD 0x0000000000011000 0x00002aaaaaab0000 0x0000000000000000
0x0000000000001000 0x0000000000001000 R 1000
LOAD 0x0000000000012000 0x00002aaaaaab2000 0x0000000000000000
0x0000000000001000 0x0000000000001000 W 1000
LOAD 0x0000000000013000 0x00002aaaaaab4000 0x0000000000000000
0x0000000000001000 0x0000000000001000 RW 1000
LOAD 0x0000000000014000 0x00002aaaaaab6000 0x0000000000000000
0x0000000000001000 0x0000000000001000 E 1000
LOAD 0x0000000000015000 0x00002aaaaaab8000 0x0000000000000000
0x0000000000001000 0x0000000000001000 R E 1000
LOAD 0x0000000000016000 0x00002aaaaaaba000 0x0000000000000000
0x0000000000001000 0x0000000000001000 WE 1000
LOAD 0x0000000000017000 0x00002aaaaaabc000 0x0000000000000000
0x0000000000001000 0x0000000000001000 RWE 1000
-------------- next part --------------
2007-08-13 Jan Kratochvil <jan.kratochvil@redhat.com>
* elfcode.h (NAME(_bfd_elf,bfd_from_remote_memory)): LOADBASE is now
initialized only on the first PT_LOAD. New variable LOADBASE_SET.
Removed PF_R checking for IA-64 vDSOs as redundant now.
Code advisory: Roland McGrath
--- bfd/elfcode.h 4 Aug 2007 16:31:00 -0000 1.85
+++ bfd/elfcode.h 13 Aug 2007 20:52:25 -0000
@@ -1635,6 +1635,7 @@ NAME(_bfd_elf,bfd_from_remote_memory)
int err;
unsigned int i;
bfd_vma loadbase;
+ bfd_boolean loadbase_set;
/* Read in the ELF header in external format. */
err = target_read_memory (ehdr_vma, (bfd_byte *) &x_ehdr, sizeof x_ehdr);
@@ -1711,13 +1712,11 @@ NAME(_bfd_elf,bfd_from_remote_memory)
contents_size = 0;
last_phdr = NULL;
loadbase = ehdr_vma;
+ loadbase_set = FALSE;
for (i = 0; i < i_ehdr.e_phnum; ++i)
{
elf_swap_phdr_in (templ, &x_phdrs[i], &i_phdrs[i]);
- /* IA-64 vDSO may have two mappings for one segment, where one mapping
- is executable only, and one is read only. We must not use the
- executable one. */
- if (i_phdrs[i].p_type == PT_LOAD && (i_phdrs[i].p_flags & PF_R))
+ if (i_phdrs[i].p_type == PT_LOAD)
{
bfd_vma segment_end;
segment_end = (i_phdrs[i].p_offset + i_phdrs[i].p_filesz
@@ -1725,8 +1724,14 @@ NAME(_bfd_elf,bfd_from_remote_memory)
if (segment_end > (bfd_vma) contents_size)
contents_size = segment_end;
- if ((i_phdrs[i].p_offset & -i_phdrs[i].p_align) == 0)
- loadbase = ehdr_vma - (i_phdrs[i].p_vaddr & -i_phdrs[i].p_align);
+ /* LOADADDR is the `Base address' from the gELF specification:
+ `lowest p_vaddr value for a PT_LOAD segment' is P_VADDR from the
+ first PT_LOAD as PT_LOADs are ordered by P_VADDR. */
+ if (!loadbase_set && (i_phdrs[i].p_offset & -i_phdrs[i].p_align) == 0)
+ {
+ loadbase = ehdr_vma - (i_phdrs[i].p_vaddr & -i_phdrs[i].p_align);
+ loadbase_set = TRUE;
+ }
last_phdr = &i_phdrs[i];
}
@@ -1764,10 +1769,7 @@ NAME(_bfd_elf,bfd_from_remote_memory)
}
for (i = 0; i < i_ehdr.e_phnum; ++i)
- /* IA-64 vDSO may have two mappings for one segment, where one mapping
- is executable only, and one is read only. We must not use the
- executable one. */
- if (i_phdrs[i].p_type == PT_LOAD && (i_phdrs[i].p_flags & PF_R))
+ if (i_phdrs[i].p_type == PT_LOAD)
{
bfd_vma start = i_phdrs[i].p_offset & -i_phdrs[i].p_align;
bfd_vma end = (i_phdrs[i].p_offset + i_phdrs[i].p_filesz
-------------- next part --------------
#include <sys/mman.h>
#include <stdlib.h>
#include <assert.h>
#include <asm/page.h>
#include <stdio.h>
#include <unistd.h>
#include <setjmp.h>
#include <signal.h>
#include <string.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <errno.h>
#include <limits.h>
static sigjmp_buf env;
static void sigsegv (int signo)
{
assert (signo == SIGSEGV);
siglongjmp (env, 1);
assert (0);
}
static void funcret (void)
{
}
static void funcafter (void)
{
}
int main (void)
{
unsigned prot;
char command[LINE_MAX];
int status;
puts ("prot: @address self-Read(requested)->(permitted) self-Write self-eXecute ptrace-Read(permitted) ptrace-Write");
signal (SIGSEGV, sigsegv);
for (prot = 0; prot < 010; prot++)
{
void *p;
volatile int prep;
pid_t child;
int i;
p = mmap (NULL, 2 * PAGE_SIZE,
0
| (prot & 04 ? PROT_READ : 0)
| (prot & 02 ? PROT_WRITE : 0)
| (prot & 01 ? PROT_EXEC : 0),
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (p == MAP_FAILED)
{
printf ("0%o failed\n", prot);
continue;
}
i = munmap (p, PAGE_SIZE);
assert (i == 0);
p += PAGE_SIZE;
printf ("0%o: @%p", prot, p);
printf (" R(%c)->", prot & 04 ? '+' : '-');
if (!sigsetjmp (env, 1))
{
volatile long v = *((volatile long *) p);
v;
fputs ("(+)", stdout);
}
else
fputs ("(-)", stdout);
printf (" W(%c)->", prot & 02 ? '+' : '-');
if (!sigsetjmp (env, 1))
{
*((volatile long *) p) = 1;
fputs ("(+)", stdout);
}
else
fputs ("(-)", stdout);
printf (" X(%c)->", prot & 01 ? '+' : '-');
if (!sigsetjmp (env, 1))
{
prep = 1;
i = mprotect (p, PAGE_SIZE, PROT_WRITE);
assert (i == 0);
memcpy (p, funcret, (char *) funcafter - (char *) funcret);
i = mprotect (p, PAGE_SIZE, prot);
assert (i == 0);
prep = 0;
((void (*) (void)) p) ();
fputs ("(+)", stdout);
}
else
{
if (prep)
fputs ("(*)", stdout);
else
fputs ("(-)", stdout);
}
child = fork ();
switch (child)
{
case -1: assert (0);
case 0:
{
long l;
l = ptrace (PTRACE_TRACEME, 0, NULL, NULL);
assert (l == 0);
raise (SIGSTOP);
_exit (0);
}
default:
{
long l;
pid_t pid_got;
pid_got = waitpid (child, &status, 0);
assert (pid_got == child);
assert (WIFSTOPPED (status));
assert (WSTOPSIG (status) == SIGSTOP);
errno = 0;
l = ptrace (PTRACE_PEEKDATA, child, p, NULL);
printf (" pR(%c)", errno == 0 ? '+' : '-');
l = ptrace (PTRACE_POKEDATA, child, p, 1);
printf (" pW(%c)", l == 0 ? '+' : '-');
l = ptrace (PTRACE_DETACH, child, NULL, NULL);
assert (l == 0);
pid_got = waitpid (child, &status, 0);
assert (pid_got == child);
assert (WIFEXITED (status));
assert (WEXITSTATUS (status) == 0);
}
}
putchar ('\n');
}
snprintf (command, sizeof command, "cat /proc/%d/maps", (int) getpid ());
status = system (command);
assert (WIFEXITED (status));
assert (WEXITSTATUS (status) == 0);
abort ();
return 0;
}
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