[PATCH 0/3] S390: Some gdbserver fixes

[PATCH 0/3] S390: Some gdbserver fixes

[Andreas Arnez]

Some fixes for test suite FAILs on s390(x) with native-gdbserver or
native-extended-gdbserver.

Andreas Arnez (3):
  S390: Enable re-attaching with native-extended-gdbserver
  S390: gdbserver: Don't write guarded storage registers
  S390: Make IPA recognize tdescs with guarded storage

 gdb/gdbserver/linux-s390-ipa.c |  13 ++++-
 gdb/gdbserver/linux-s390-low.c | 130 ++++++++++++++++++++---------------------
 2 files changed, 73 insertions(+), 70 deletions(-)

-- 
2.14.3

[PATCH 1/3] S390: Enable re-attaching with native-extended-gdbserver

[Andreas Arnez]

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.
---
 gdb/gdbserver/linux-s390-low.c | 97 +++++++++++++++++++++++-------------------
 1 file changed, 53 insertions(+), 44 deletions(-)

diff --git a/gdb/gdbserver/linux-s390-low.c b/gdb/gdbserver/linux-s390-low.c
index 451f42c7c9..203accdaaa 100644
--- a/gdb/gdbserver/linux-s390-low.c
+++ b/gdb/gdbserver/linux-s390-low.c
@@ -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);
-
-  /* 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;
+  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);
 
-  /* 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;
   }
-- 
2.14.3

Re: [PATCH 1/3] S390: Enable re-attaching with native-extended-gdbserver

[Simon Marchi]

I am just looking through this to have an idea of what's happening
and found one nit:

> +/* 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;
> +  }

GNU-style curly braces.

Simon

Re: [PATCH 1/3] S390: Enable re-attaching with native-extended-gdbserver

[Andreas Arnez]

On Wed, Mar 21 2018, Simon Marchi wrote:

> I am just looking through this to have an idea of what's happening
> and found one nit:
>
>> +/* 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;
>> +  }
>
> GNU-style curly braces.

Oops...

Thanks, pushed a fix.

--
Andreas

[PATCH 2/3] S390: gdbserver: Don't write guarded storage registers

[Andreas Arnez]

On S390, the guarded storage register set is only valid if guarded storage
is active.  Reading/writing the register set yields errors if this is not
the case.  Then gdbserver emits warnings like these:

  Warning: ptrace(regsets_store_inferior_registers): No data available

Apart from confusing the user, this can also lead to test case failures
due to unexpected output.  To suppress this, make the guarded storage
regsets read-only for now.

gdb/gdbserver/ChangeLog:

	* linux-s390-low.c (s390_fill_gs): Remove function.
	(s390_fill_gsbc): Remove function.
	(s390_regsets): Set fill functions for the guarded storage regsets
	to NULL.
---
 gdb/gdbserver/linux-s390-low.c | 29 +++++------------------------
 1 file changed, 5 insertions(+), 24 deletions(-)

diff --git a/gdb/gdbserver/linux-s390-low.c b/gdb/gdbserver/linux-s390-low.c
index 203accdaaa..7de70f3a38 100644
--- a/gdb/gdbserver/linux-s390-low.c
+++ b/gdb/gdbserver/linux-s390-low.c
@@ -374,16 +374,6 @@ s390_store_vxrs_high (struct regcache *regcache, const void *buf)
     supply_register (regcache, v16 + i, (const char *) buf + 16 * i);
 }
 
-static void
-s390_fill_gs (struct regcache *regcache, void *buf)
-{
-  int gsd = find_regno (regcache->tdesc, "gsd");
-  int i;
-
-  for (i = 0; i < 3; i++)
-    collect_register (regcache, gsd + i, (char *) buf + 8 * (i + 1));
-}
-
 static void
 s390_store_gs (struct regcache *regcache, const void *buf)
 {
@@ -394,16 +384,6 @@ s390_store_gs (struct regcache *regcache, const void *buf)
     supply_register (regcache, gsd + i, (const char *) buf + 8 * (i + 1));
 }
 
-static void
-s390_fill_gsbc (struct regcache *regcache, void *buf)
-{
-  int bc_gsd = find_regno (regcache->tdesc, "bc_gsd");
-  int i;
-
-  for (i = 0; i < 3; i++)
-    collect_register (regcache, bc_gsd + i, (char *) buf + 8 * (i + 1));
-}
-
 static void
 s390_store_gsbc (struct regcache *regcache, const void *buf)
 {
@@ -432,10 +412,11 @@ static struct regset_info s390_regsets[] = {
     EXTENDED_REGS, s390_fill_vxrs_low, s390_store_vxrs_low },
   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_S390_VXRS_HIGH, 0,
     EXTENDED_REGS, s390_fill_vxrs_high, s390_store_vxrs_high },
-  { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_S390_GS_CB, 0,
-    EXTENDED_REGS, s390_fill_gs, s390_store_gs },
-  { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_S390_GS_BC, 0,
-    EXTENDED_REGS, s390_fill_gsbc, s390_store_gsbc },
+  /* Guarded storage registers are read-only.  */
+  { PTRACE_GETREGSET, -1, NT_S390_GS_CB, 0, EXTENDED_REGS,
+    NULL, s390_store_gs },
+  { PTRACE_GETREGSET, -1, NT_S390_GS_BC, 0, EXTENDED_REGS,
+    NULL, s390_store_gsbc },
   NULL_REGSET
 };
 
-- 
2.14.3

[PATCH 3/3] S390: Make IPA recognize tdescs with guarded storage

[Andreas Arnez]

The in-process agent does not handle tdescs with guarded storage yet.
This is fixed.

gdb/gdbserver/ChangeLog:

	* linux-s390-ipa.c (get_ipa_tdesc): Add handling for
	S390_TDESC_GS.
	* linux-s390-low.c (s390_get_ipa_tdesc_idx): Likewise.
	(initialize_low_tracepoint): Call init_registers_s390x_gs_linux64
	and init_registers_s390_gs_linux64.
---
 gdb/gdbserver/linux-s390-ipa.c | 13 +++++++++++--
 gdb/gdbserver/linux-s390-low.c |  4 ++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/gdb/gdbserver/linux-s390-ipa.c b/gdb/gdbserver/linux-s390-ipa.c
index 707d3384f0..bf9addb17a 100644
--- a/gdb/gdbserver/linux-s390-ipa.c
+++ b/gdb/gdbserver/linux-s390-ipa.c
@@ -119,7 +119,7 @@ static const int s390_linux64_ft_collect_regmap[] = {
   FT_VR (28), FT_VR (29), FT_VR (30), FT_VR (31),
 };
 
-/* Used for s390-te-linux64, s390-tevx-linux64.  */
+/* Used for s390-te-linux64, s390-tevx-linux64, and s390-gs-linux64.  */
 
 static const int s390_te_linux64_ft_collect_regmap[] = {
   /* 32-bit PSWA and PSWM.  */
@@ -207,7 +207,8 @@ static const int s390x_ft_collect_regmap[] = {
   FT_VR (28), FT_VR (29), FT_VR (30), FT_VR (31),
 };
 
-/* Used for s390x-te-linux64, s390x-tevx-linux64.  */
+/* Used for s390x-te-linux64, s390x-tevx-linux64, and
+   s390x-gs-linux64.  */
 
 static const int s390x_te_ft_collect_regmap[] = {
   /* 64-bit PSWA and PSWM.  */
@@ -335,6 +336,9 @@ get_ipa_tdesc (int idx)
     case S390_TDESC_TEVX:
       SET_REGMAP(s390x_te_ft_collect_regmap, 0);
       return tdesc_s390x_tevx_linux64;
+    case S390_TDESC_GS:
+      SET_REGMAP(s390x_te_ft_collect_regmap, 0);
+      return tdesc_s390x_gs_linux64;
 #else
     case S390_TDESC_32:
       SET_REGMAP(s390_linux32_ft_collect_regmap, 0);
@@ -363,6 +367,9 @@ get_ipa_tdesc (int idx)
     case S390_TDESC_TEVX:
       SET_REGMAP(s390_te_linux64_ft_collect_regmap, 0);
       return tdesc_s390_tevx_linux64;
+    case S390_TDESC_GS:
+      SET_REGMAP(s390_te_ft_collect_regmap, 0);
+      return tdesc_s390_gs_linux64;
 #endif
     default:
       internal_error (__FILE__, __LINE__,
@@ -440,6 +447,7 @@ initialize_low_tracepoint (void)
   init_registers_s390x_te_linux64 ();
   init_registers_s390x_vx_linux64 ();
   init_registers_s390x_tevx_linux64 ();
+  init_registers_s390x_gs_linux64 ();
 #else
   init_registers_s390_linux32 ();
   init_registers_s390_linux32v1 ();
@@ -450,5 +458,6 @@ initialize_low_tracepoint (void)
   init_registers_s390_te_linux64 ();
   init_registers_s390_vx_linux64 ();
   init_registers_s390_tevx_linux64 ();
+  init_registers_s390_gs_linux64 ();
 #endif
 }
diff --git a/gdb/gdbserver/linux-s390-low.c b/gdb/gdbserver/linux-s390-low.c
index 7de70f3a38..cc219e2ba9 100644
--- a/gdb/gdbserver/linux-s390-low.c
+++ b/gdb/gdbserver/linux-s390-low.c
@@ -1431,6 +1431,8 @@ s390_get_ipa_tdesc_idx (void)
     return S390_TDESC_VX;
   if (tdesc == tdesc_s390x_tevx_linux64)
     return S390_TDESC_TEVX;
+  if (tdesc == tdesc_s390x_gs_linux64)
+    return S390_TDESC_GS;
 #endif
 
   if (tdesc == tdesc_s390_linux32)
@@ -1451,6 +1453,8 @@ s390_get_ipa_tdesc_idx (void)
     return S390_TDESC_VX;
   if (tdesc == tdesc_s390_tevx_linux64)
     return S390_TDESC_TEVX;
+  if (tdesc == tdesc_s390_gs_linux64)
+    return S390_TDESC_GS;
 
   return 0;
 }
-- 
2.14.3

Re: [PATCH 0/3] S390: Some gdbserver fixes

[Andreas Arnez]

On Mon, Mar 19 2018, Andreas Arnez wrote:

> Some fixes for test suite FAILs on s390(x) with native-gdbserver or
> native-extended-gdbserver.
>
> Andreas Arnez (3):
>   S390: Enable re-attaching with native-extended-gdbserver
>   S390: gdbserver: Don't write guarded storage registers
>   S390: Make IPA recognize tdescs with guarded storage
>
>  gdb/gdbserver/linux-s390-ipa.c |  13 ++++-
>  gdb/gdbserver/linux-s390-low.c | 130 ++++++++++++++++++++---------------------
>  2 files changed, 73 insertions(+), 70 deletions(-)

I've pushed these now.

--
Andreas