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S390: Enable re-attaching with native-extended-gdbserver 

On s390x, when running attach.exp with native-extended-gdbserver,
gdbserver crashes in find_regno like this:

  .../regcache.c:252: A problem internal to GDBserver has been detected.
  Unknown register tdb0 requested

On the GDB side it looks like this:

  (gdb) attach 31568
  Attaching to process 31568
  Remote connection closed

The test case attempts to attach to a new process via the already running
gdbserver.  Thus s390_arch_setup is called a second time, and that's where
the problem occurs.  In order to determine the word width (32 or 64 bits),
s390_arch_setup reads the pswm register through the regcache.  For that it
uses a temporary tdesc which is supposed to work for all s390 targets,
since the actual tdesc has not been determined yet.  But in this second
round this doesn't work, because s390_regsets has been updated already and
now contains regsets not described by the temporary tdesc, such as the one
containing tdb0.

This is fixed by rearranging the logic in s390_arch_setup.

gdb/gdbserver/ChangeLog:

	* linux-s390-low.c (s390_get_hwcap): Replace tdesc parameter by
	the word size.  Add comment.
	(s390_get_wordsize): New function.
	(s390_arch_setup): No longer select a temporary tdesc to fetch the
	pswm with it.  Instead, use s390_get_wordsize to determine the
	word size first and derive the correct tdesc from that directly.
This commit is contained in:
Andreas Arnez 2018-03-21 17:41:44 +01:00
parent 0ccf57bd81
commit 7edb9bd32b
2 changed files with 62 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
gdb/gdbserver/ChangeLog
View File

@ -1,3 +1,12 @@
2018-03-21 Andreas Arnez <arnez@linux.vnet.ibm.com>
* linux-s390-low.c (s390_get_hwcap): Replace tdesc parameter by
the word size. Add comment.
(s390_get_wordsize): New function.
(s390_arch_setup): No longer select a temporary tdesc to fetch the
pswm with it. Instead, use s390_get_wordsize to determine the
word size first and derive the correct tdesc from that directly.
2018-03-16 Simon Marchi <simon.marchi@polymtl.ca>
* Makefile.in: Include silent-rules.mk.

97
gdb/gdbserver/linux-s390-low.c
View File

@ -486,10 +486,12 @@ s390_set_pc (struct regcache *regcache, CORE_ADDR newpc)
}
}
/* Get HWCAP from AUXV, using the given WORDSIZE. Return the HWCAP, or
zero if not found. */
static unsigned long
s390_get_hwcap (const struct target_desc *tdesc)
s390_get_hwcap (int wordsize)
{
int wordsize = register_size (tdesc, 0);
gdb_byte *data = (gdb_byte *) alloca (2 * wordsize);
int offset = 0;
@ -514,6 +516,27 @@ s390_get_hwcap (const struct target_desc *tdesc)
return 0;
}
/* Determine the word size for the given PID, in bytes. */
#ifdef __s390x__
static int
s390_get_wordsize (int pid)
{
errno = 0;
PTRACE_XFER_TYPE pswm = ptrace (PTRACE_PEEKUSER, pid,
(PTRACE_TYPE_ARG3) 0,
(PTRACE_TYPE_ARG4) 0);
if (errno != 0) {
warning (_("Couldn't determine word size, assuming 64-bit.\n"));
return 8;
}
/* Derive word size from extended addressing mode (PSW bit 31). */
return pswm & (1L << 32) ? 8 : 4;
}
#else
#define s390_get_wordsize(pid) 4
#endif
static int
s390_check_regset (int pid, int regset, int regsize)
{
@ -540,49 +563,32 @@ s390_arch_setup (void)
const struct target_desc *tdesc;
struct regset_info *regset;
/* Check whether the kernel supports extra register sets. */
/* Determine word size and HWCAP. */
int pid = pid_of (current_thread);
int wordsize = s390_get_wordsize (pid);
unsigned long hwcap = s390_get_hwcap (wordsize);
/* Check whether the kernel supports extra register sets. */
int have_regset_last_break
= s390_check_regset (pid, NT_S390_LAST_BREAK, 8);
int have_regset_system_call
= s390_check_regset (pid, NT_S390_SYSTEM_CALL, 4);
int have_regset_tdb = s390_check_regset (pid, NT_S390_TDB, 256);
int have_regset_vxrs = s390_check_regset (pid, NT_S390_VXRS_LOW, 128)
&& s390_check_regset (pid, NT_S390_VXRS_HIGH, 256);
int have_regset_gs = s390_check_regset (pid, NT_S390_GS_CB, 32)
&& s390_check_regset (pid, NT_S390_GS_BC, 32);
int have_regset_tdb
= (s390_check_regset (pid, NT_S390_TDB, 256)
&& (hwcap & HWCAP_S390_TE) != 0);
int have_regset_vxrs
= (s390_check_regset (pid, NT_S390_VXRS_LOW, 128)
&& s390_check_regset (pid, NT_S390_VXRS_HIGH, 256)
&& (hwcap & HWCAP_S390_VX) != 0);
int have_regset_gs
= (s390_check_regset (pid, NT_S390_GS_CB, 32)
&& s390_check_regset (pid, NT_S390_GS_BC, 32)
&& (hwcap & HWCAP_S390_GS) != 0);
/* Assume 31-bit inferior process. */
if (have_regset_system_call)
tdesc = tdesc_s390_linux32v2;
else if (have_regset_last_break)
tdesc = tdesc_s390_linux32v1;
else
tdesc = tdesc_s390_linux32;
/* On a 64-bit host, check the low bit of the (31-bit) PSWM
-- if this is one, we actually have a 64-bit inferior. */
{
#ifdef __s390x__
unsigned int pswm;
struct regcache *regcache = new_register_cache (tdesc);
fetch_inferior_registers (regcache, find_regno (tdesc, "pswm"));
collect_register_by_name (regcache, "pswm", &pswm);
free_register_cache (regcache);
if (pswm & 1)
if (wordsize == 8)
{
if (have_regset_tdb)
have_regset_tdb =
(s390_get_hwcap (tdesc_s390x_linux64v2) & HWCAP_S390_TE) != 0;
if (have_regset_vxrs)
have_regset_vxrs =
(s390_get_hwcap (tdesc_s390x_linux64v2) & HWCAP_S390_VX) != 0;
if (have_regset_gs)
have_regset_gs =
(s390_get_hwcap (tdesc_s390x_linux64v2) & HWCAP_S390_GS) != 0;
if (have_regset_gs)
tdesc = tdesc_s390x_gs_linux64;
else if (have_regset_vxrs)
@ -602,16 +608,9 @@ s390_arch_setup (void)
using the full 64-bit GPRs. */
else
#endif
if (s390_get_hwcap (tdesc) & HWCAP_S390_HIGH_GPRS)
if (hwcap & HWCAP_S390_HIGH_GPRS)
{
have_hwcap_s390_high_gprs = 1;
if (have_regset_tdb)
have_regset_tdb = (s390_get_hwcap (tdesc) & HWCAP_S390_TE) != 0;
if (have_regset_vxrs)
have_regset_vxrs = (s390_get_hwcap (tdesc) & HWCAP_S390_VX) != 0;
if (have_regset_gs)
have_regset_gs = (s390_get_hwcap (tdesc) & HWCAP_S390_GS) != 0;
if (have_regset_gs)
tdesc = tdesc_s390_gs_linux64;
else if (have_regset_vxrs)
@ -626,6 +625,16 @@ s390_arch_setup (void)
else
tdesc = tdesc_s390_linux64;
}
else
{
/* Assume 31-bit inferior process. */
if (have_regset_system_call)
tdesc = tdesc_s390_linux32v2;
else if (have_regset_last_break)
tdesc = tdesc_s390_linux32v1;
else
tdesc = tdesc_s390_linux32;
}
have_hwcap_s390_vx = have_regset_vxrs;
}