[patch] Fix 64-bit->32-bit vDSO reporting
Jan Kratochvil
jan.kratochvil at redhat.com
Thu Oct 11 06:22:10 UTC 2012
Hi Roland,
jankratochvil/auxv32
On Thu, 11 Oct 2012 00:27:35 +0200, Roland McGrath wrote:
> The problem is indeed obvious. I really wish there were a better way to
> detect the bit-width of the process than looking at /proc/PID/exe, but
> perhaps there really isn't.
>
> What about just looking at the first 8 bytes of the auxv data? The first
> element is never AT_NULL, so it will have a nonzero a_type. No a_type
> value will ever be more than UINT32_MAX. So for big-endian, the first four
> bytes being zero says it's 64-bit. For little-endian, it's not so easy
> without assuming that the first a_val is nonzero. That's actually reliable
> enough in practice, but it feels wrong. Maybe there is something better
> for little-endian that I'm not thinking of.
I had similar concerns.
Done the other changes.
Thanks,
Jan
commit 6c7496074e45f285312ceb076c08091652998dfb
Author: Jan Kratochvil <jan.kratochvil at redhat.com>
Date: Wed Oct 10 20:42:30 2012 +0200
libdwfl/
linux-proc-maps.c: Include system.h.
(PROCEXEFMT, get_pid_class): New.
(grovel_auxv): New parameter pid_class. Use it.
(dwfl_linux_proc_report): New variable pid_class, initialize it by
get_pid_class, use it for grovel_auxv.
Signed-off-by: Jan Kratochvil <jan.kratochvil at redhat.com>
diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 189d3b7..c18362c 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,11 @@
+2012-10-11 Jan Kratochvil <jan.kratochvil at redhat.com>
+
+ * linux-proc-maps.c: Include system.h.
+ (PROCEXEFMT, get_pid_class): New.
+ (grovel_auxv): New parameter pid_class. Use it.
+ (dwfl_linux_proc_report): New variable pid_class, initialize it by
+ get_pid_class, use it for grovel_auxv.
+
2012-10-10 Jan Kratochvil <jan.kratochvil at redhat.com>
* dwfl_segment_report_module.c (dwfl_segment_report_module):
diff --git a/libdwfl/linux-proc-maps.c b/libdwfl/linux-proc-maps.c
index 4fbe90d..2ac0e3e 100644
--- a/libdwfl/linux-proc-maps.c
+++ b/libdwfl/linux-proc-maps.c
@@ -39,17 +39,47 @@
#include <unistd.h>
#include <assert.h>
#include <endian.h>
+#include "system.h"
#define PROCMAPSFMT "/proc/%d/maps"
#define PROCMEMFMT "/proc/%d/mem"
#define PROCAUXVFMT "/proc/%d/auxv"
+#define PROCEXEFMT "/proc/%d/exe"
+/* Return ELFCLASS64 or ELFCLASS32 for the main ELF executable. Return
+ ELFCLASSNONE for an error. */
+
+static unsigned char
+get_pid_class (pid_t pid)
+{
+ char *fname;
+ if (asprintf (&fname, PROCEXEFMT, pid) < 0)
+ return ELFCLASSNONE;
+
+ int fd = open64 (fname, O_RDONLY);
+ free (fname);
+ if (fd < 0)
+ return ELFCLASSNONE;
+
+ unsigned char buf[EI_CLASS + 1];
+ ssize_t nread = pread_retry (fd, &buf, sizeof buf, 0);
+ close (fd);
+ if (nread != sizeof (buf) || buf[EI_MAG0] != ELFMAG0
+ || buf[EI_MAG1] != ELFMAG1 || buf[EI_MAG2] != ELFMAG2
+ || buf[EI_MAG3] != ELFMAG3
+ || (buf[EI_CLASS] != ELFCLASS64 && buf[EI_CLASS] != ELFCLASS32))
+ return ELFCLASSNONE;
+
+ return buf[EI_CLASS];
+}
+
/* Search /proc/PID/auxv for the AT_SYSINFO_EHDR tag. */
static int
-grovel_auxv (pid_t pid, Dwfl *dwfl, GElf_Addr *sysinfo_ehdr)
+grovel_auxv (pid_t pid, Dwfl *dwfl, unsigned char pid_class,
+ GElf_Addr *sysinfo_ehdr)
{
char *fname;
if (asprintf (&fname, PROCAUXVFMT, pid) < 0)
@@ -72,9 +102,9 @@ grovel_auxv (pid_t pid, Dwfl *dwfl, GElf_Addr *sysinfo_ehdr)
nread = read (fd, &d, sizeof d);
if (nread > 0)
{
- switch (sizeof (long int))
+ switch (pid_class)
{
- case 4:
+ case ELFCLASS32:
for (size_t i = 0; (char *) &d.a32[i] < &d.buffer[nread]; ++i)
if (d.a32[i].a_type == AT_SYSINFO_EHDR)
{
@@ -89,7 +119,7 @@ grovel_auxv (pid_t pid, Dwfl *dwfl, GElf_Addr *sysinfo_ehdr)
&& dwfl->segment_align <= 1)
dwfl->segment_align = d.a32[i].a_un.a_val;
break;
- case 8:
+ case ELFCLASS64:
for (size_t i = 0; (char *) &d.a64[i] < &d.buffer[nread]; ++i)
if (d.a64[i].a_type == AT_SYSINFO_EHDR)
{
@@ -227,9 +257,13 @@ dwfl_linux_proc_report (Dwfl *dwfl, pid_t pid)
if (dwfl == NULL)
return -1;
+ unsigned char pid_class = get_pid_class (pid);
+ if (pid_class == ELFCLASSNONE)
+ return -1;
+
/* We'll notice the AT_SYSINFO_EHDR address specially when we hit it. */
GElf_Addr sysinfo_ehdr = 0;
- int result = grovel_auxv (pid, dwfl, &sysinfo_ehdr);
+ int result = grovel_auxv (pid, dwfl, pid_class, &sysinfo_ehdr);
if (result != 0)
return result;
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