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Re: [PATCH 2/3] Use PTRACE_PEEKUSER to get fs_base/gs_base for x32
- From: "H.J. Lu" <hongjiu dot lu at intel dot com>
- To: GDB <gdb-patches at sourceware dot org>, Mark Kettenis <kettenis at gnu dot org>
- Date: Thu, 21 Jun 2012 11:59:36 -0700
- Subject: Re: [PATCH 2/3] Use PTRACE_PEEKUSER to get fs_base/gs_base for x32
- References: <20120621181529.GA23439@intel.com>
- Reply-to: "H.J. Lu" <hjl dot tools at gmail dot com>
On Thu, Jun 21, 2012 at 11:15:29AM -0700, H.J. Lu wrote:
> PTRACE_ARCH_PRCTL is obsolete since 2.6.25, where the fs_base and gs_base
> fields of user_regs_struct can be used directly. Since x32 support was
> added to kernel 3.4.0 and PTRACE_ARCH_PRCTL support was removed for x32,
> we should always use fs_base/gs_base for x32. OK to install? We
>
> Thanks.
Here is a better patch to use the fs_base and gs_base fields of
struct user_regs_struct to get fs/gs base. OK to install?
Thanks.
H.J.
---
2012-06-16 Roland McGrath <roland@hack.frob.com>
H.J. Lu <hongjiu.lu@intel.com>
* amd64-linux-nat.c: Include <sys/user.h> if
HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE or
HAVE_STRUCT_USER_REGS_STRUCT_GS_BASE is defined.
(ps_get_thread_area): Use PTRACE_PEEKUSER to get fs_base/gs_base
if HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE or
HAVE_STRUCT_USER_REGS_STRUCT_GS_BASE is defined.
* configure.ac: Check if the fs_base and gs_base members of
`struct user_regs_struct' exist.
* config.in: Regenerated.
* configure: Likewise.
diff --git a/gdb/amd64-linux-nat.c b/gdb/amd64-linux-nat.c
index 23eadbd..781456f 100644
--- a/gdb/amd64-linux-nat.c
+++ b/gdb/amd64-linux-nat.c
@@ -34,6 +34,10 @@
#include <sys/debugreg.h>
#include <sys/syscall.h>
#include <sys/procfs.h>
+#if defined HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE \
+ || defined HAVE_STRUCT_USER_REGS_STRUCT_GS_BASE
+#include <sys/user.h>
+#endif
#include <asm/prctl.h>
/* FIXME ezannoni-2003-07-09: we need <sys/reg.h> to be included after
<asm/ptrace.h> because the latter redefines FS and GS for no apparent
@@ -479,10 +483,39 @@ ps_get_thread_area (const struct ps_prochandle *ph,
switch (idx)
{
case FS:
+#ifdef HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE
+ {
+ /* PTRACE_ARCH_PRCTL is obsolete since 2.6.25, where the
+ fs_base and gs_base fields of user_regs_struct can be
+ used directly. */
+ unsigned long fs;
+ errno = 0;
+ fs = ptrace (PTRACE_PEEKUSER, lwpid,
+ offsetof (struct user_regs_struct, fs_base), 0);
+ if (errno == 0)
+ {
+ *base = (void *) fs;
+ return PS_OK;
+ }
+ }
+#endif
if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_FS) == 0)
return PS_OK;
break;
case GS:
+#ifdef HAVE_STRUCT_USER_REGS_STRUCT_GS_BASE
+ {
+ unsigned long gs;
+ errno = 0;
+ gs = ptrace (PTRACE_PEEKUSER, lwpid,
+ offsetof (struct user_regs_struct, gs_base), 0);
+ if (errno == 0)
+ {
+ *base = (void *) gs;
+ return PS_OK;
+ }
+ }
+#endif
if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_GS) == 0)
return PS_OK;
break;
diff --git a/gdb/config.in b/gdb/config.in
index 5767773..74f5888 100644
--- a/gdb/config.in
+++ b/gdb/config.in
@@ -447,6 +447,12 @@
/* Define to 1 if `struct thread' is a member of `td_pcb'. */
#undef HAVE_STRUCT_THREAD_TD_PCB
+/* Define to 1 if `struct user_regs_struct' is a member of `fs_base'. */
+#undef HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE
+
+/* Define to 1 if `struct user_regs_struct' is a member of `gs_base'. */
+#undef HAVE_STRUCT_USER_REGS_STRUCT_GS_BASE
+
/* Define to 1 if you have the `syscall' function. */
#undef HAVE_SYSCALL
diff --git a/gdb/configure b/gdb/configure
index 1d03188..91381f1 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -10612,6 +10612,31 @@ _ACEOF
fi
+# See if <sys/user.h> supports the %fs_base and %gs_bas amd64 segment registers.
+# Older amd64 Linux's don't have the fs_base and gs_base members of
+# `struct user_regs_struct'.
+ac_fn_c_check_member "$LINENO" "struct user_regs_struct" "fs_base" "ac_cv_member_struct_user_regs_struct_fs_base" "#include <sys/user.h>
+"
+if test "x$ac_cv_member_struct_user_regs_struct_fs_base" = x""yes; then :
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE 1
+_ACEOF
+
+
+fi
+ac_fn_c_check_member "$LINENO" "struct user_regs_struct" "gs_base" "ac_cv_member_struct_user_regs_struct_gs_base" "#include <sys/user.h>
+"
+if test "x$ac_cv_member_struct_user_regs_struct_gs_base" = x""yes; then :
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_STRUCT_USER_REGS_STRUCT_GS_BASE 1
+_ACEOF
+
+
+fi
+
+
# See if <sys/ptrace.h> provides the PTRACE_GETREGS request.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for PTRACE_GETREGS" >&5
$as_echo_n "checking for PTRACE_GETREGS... " >&6; }
diff --git a/gdb/configure.ac b/gdb/configure.ac
index e48ec05..f3c8b26 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -1274,6 +1274,12 @@ fi
AC_CHECK_MEMBERS([struct reg.r_fs, struct reg.r_gs], [], [],
[#include <machine/reg.h>])
+# See if <sys/user.h> supports the %fs_base and %gs_bas amd64 segment registers.
+# Older amd64 Linux's don't have the fs_base and gs_base members of
+# `struct user_regs_struct'.
+AC_CHECK_MEMBERS([struct user_regs_struct.fs_base, struct user_regs_struct.gs_base],
+ [], [], [#include <sys/user.h>])
+
# See if <sys/ptrace.h> provides the PTRACE_GETREGS request.
AC_MSG_CHECKING(for PTRACE_GETREGS)
AC_CACHE_VAL(gdb_cv_have_ptrace_getregs,