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Re: [RFC 7/7] Add S390 support for linux-kernel target

From: Luis Machado <lgustavo at codesourcery dot com>
To: Philipp Rudo <prudo at linux dot vnet dot ibm dot com>, <gdb-patches at sourceware dot org>
Cc: <peter dot griffin at linaro dot org>, <yao dot qi at arm dot com>, <arnez at linux dot vnet dot ibm dot com>
Date: Thu, 12 Jan 2017 11:08:59 -0600
Subject: Re: [RFC 7/7] Add S390 support for linux-kernel target
Authentication-results: sourceware.org; auth=none
References: <20170112113217.48852-1-prudo@linux.vnet.ibm.com> <20170112113217.48852-8-prudo@linux.vnet.ibm.com>
Reply-to: Luis Machado <lgustavo at codesourcery dot com>

On 01/12/2017 05:32 AM, Philipp Rudo wrote:

Implement functions for the linux-kernel target hooks.

gdb/ChangeLog:

	* s390-linux-tdep.h: Define macros for address translation.
	* s390-linux-tdep.c: Include gdbthread.h and lk-low.h.
	(s390_gregmap_lk): New array.
	(s390_gregset_lk): New type.
	(s390_lk_get_registers, s390_lk_get_percpu_offset)
	(s390_lk_map_running_task_to_cpu, s390_lk_is_kvaddr)
	(s390_lk_read_table_entry, s390_lk_vtop, s390_lk_init_private): New
	function.
	(s390_gdbarch_init): Adjust.
---
 gdb/s390-linux-tdep.c | 270 ++++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/s390-linux-tdep.h |  62 ++++++++++++
 2 files changed, 332 insertions(+)

diff --git a/gdb/s390-linux-tdep.c b/gdb/s390-linux-tdep.c
index 054c6d5..f436a74 100644
--- a/gdb/s390-linux-tdep.c
+++ b/gdb/s390-linux-tdep.c

I wonder if we should put the new lk-specific code in its own file, likes390-lk-tdep.c or something. It would make thing a bit more clear andwould pollute the current s390-linux-tdep.c file?

@@ -29,6 +29,7 @@
 #include "target.h"
 #include "gdbcore.h"
 #include "gdbcmd.h"
+#include "gdbthread.h"
 #include "objfiles.h"
 #include "floatformat.h"
 #include "regcache.h"
@@ -49,6 +50,8 @@
 #include "auxv.h"
 #include "xml-syscall.h"

+#include "lk-low.h"
+
 #include "stap-probe.h"
 #include "ax.h"
 #include "ax-gdb.h"
@@ -783,6 +786,14 @@ static const struct regcache_map_entry s390_gregmap[] =
     { 0 }
   };

+static const struct regcache_map_entry s390_gregmap_lk[] =
+  {
+    { 10, S390_R6_REGNUM }, /* r0-r5 volatile */
+    { -2, REGCACHE_MAP_SKIP, 8 },
+    { 1, S390_PSWA_REGNUM }, /* Use r14 for PSWA.  */
+    { 0 }
+  };
+
 static const struct regcache_map_entry s390_regmap_cr [] =
   {
     { 16, S390_CR0_REGNUM, 8 },
@@ -891,6 +902,12 @@ const struct regset s390_gregset = {
   regcache_collect_regset
 };

+const struct regset s390_gregset_lk = {
+  s390_gregmap_lk,
+  regcache_supply_regset,
+  regcache_collect_regset
+};
+
 const struct regset s390_cr_regset = {
   s390_regmap_cr,
   regcache_supply_regset,
@@ -1080,6 +1097,256 @@ s390_core_read_description (struct gdbarch *gdbarch,
     }
 }

+/* Funktion for Linux kernel target get_registers hook.  Supplies gprs for


"Function..."

+   task TASK to REGCACHE.  Uses r14 (back jump address) as current pswa.  */
+
+void
+s390_lk_get_registers (CORE_ADDR task, struct target_ops *target,
+		       struct regcache *regcache, int regnum)
+{
+  const struct regset *regset;
+  CORE_ADDR ksp, gprs, pswa;
+  gdb_byte *buf;
+  size_t size;
+  struct cleanup *old_chain;
+
+  regset = &s390_gregset_lk;
+
+  ksp = lk_read_addr (task + LK_OFFSET (task_struct, thread)
+		      + LK_OFFSET (thread_struct, ksp));
+  gprs = ksp + LK_OFFSET (stack_frame, gprs);
+  size = FIELD_SIZE (LK_FIELD (stack_frame, gprs));
+

Do we have a reasonable MAX for this size? If so, we may try to have astatic array instead of allocating and deallocating in such a shorttime. Just a suggestion.

+  buf = XCNEWVEC (gdb_byte, size);
+  old_chain = make_cleanup (xfree, buf);
+  read_memory (gprs, buf, size);
+  regset->supply_regset (regset, regcache, -1, buf, size);
+  do_cleanups (old_chain);
+}
+
+/* Function for Linux kernel target get_percpu_offset hook. Returns the


Two spaces after period.

+   percpu_offset from lowcore for cpu CPU.  */
+
+CORE_ADDR
+s390_lk_get_percpu_offset (int cpu)


Is cpu ever negative? If not, make it unsigned?

+{
+  CORE_ADDR lowcore_ptr, lowcore;
+  int ptr_len = lk_builtin_type_size (unsigned_long);
+
+  lowcore_ptr = LK_ADDR (lowcore_ptr) + (ptr_len * cpu);
+  lowcore = lk_read_addr (lowcore_ptr);
+
+  return lk_read_addr (lowcore + LK_OFFSET (lowcore, percpu_offset));
+}
+
+/* Function for Linux kernel target map_running_task_to_cpu hook.  */
+
+int
+s390_lk_map_running_task_to_cpu (struct thread_info *ti)
+{
+  struct regcache *regcache;
+  enum register_status reg_status;
+  CORE_ADDR lowcore;
+  int cpu;
+
+  regcache = get_thread_regcache (ti->ptid);
+  reg_status = regcache_raw_read_unsigned (regcache, S390_PREFIX_REGNUM,
+					   (ULONGEST *) &lowcore);
+  if (reg_status != REG_VALID)
+    error (_("Could not find prefix register for thread with pid %d, lwp %li."),
+	   ti->ptid.pid, ti->ptid.lwp);
+
+  cpu = lk_read_int (lowcore + LK_OFFSET (lowcore, cpu_nr));
+
+  return cpu;
+}
+
+/* Funktion for Linux kernel target is_kvaddr hook.  */


"Function..."

+
+int
+s390_lk_is_kvaddr (CORE_ADDR addr)
+{
+  return addr >= LK_ADDR (high_memory);
+}
+
+/* Read table entry from TABLE at offset OFFSET.  Helper for s390_lk_vtop.  */
+
+static inline ULONGEST
+s390_lk_read_table_entry (CORE_ADDR table, ULONGEST offset)
+{
+  return lk_read_ulong (table + offset * lk_builtin_type_size (unsigned_long));
+}
+
+/* Function for Linux kernel target vtop hook.  Assume 64 bit addresses.  */
+
+CORE_ADDR
+s390_lk_vtop (CORE_ADDR table, CORE_ADDR vaddr)
+{
+  ULONGEST entry, offset;
+  CORE_ADDR paddr;
+  int table_type;
+
+  /* Read first entry in table to get its type.  As the Table-Type bits are
+     the same in every table assume Region1-Table.  */
+  entry = s390_lk_read_table_entry (table, 0);
+  table_type = (entry & S390_LK_RFTE_TT) >> 2;
+
+  switch (table_type)
+    {
+      case S390_LK_DAT_TT_REGION1:
+	{
+	  offset = (vaddr & S390_LK_VADDR_RFX) >> 53;
+	  entry = s390_lk_read_table_entry (table, offset);
+
+	  /* Do sanity checks.  */
+	  if (!entry)
+	    warning (_("Trying to translate address %#lx with empty region-first-table entry."),
+		   vaddr);

Use paddress (...) to print the hex address of vaddr or phex (...). Moreoccurrences of this throughout the patch.

+	  else if ((entry & S390_LK_RFTE_TT) >> 2 != S390_LK_DAT_TT_REGION1)
+	    warning (_("Trying to translate address %#lx with corrupt table type in region-first-table entry."),
+		     vaddr);
+	  else if (entry & S390_LK_RFTE_I)
+	    warning (_("Translating address %#lx with invalid bit set at region-first-table entry."),
+		     vaddr);
+
+	  table = entry & S390_LK_RFTE_O;
+	}
+	/* fall through */
+      case S390_LK_DAT_TT_REGION2:
+	{
+	  offset = (vaddr & S390_LK_VADDR_RSX) >> 42;
+	  entry = s390_lk_read_table_entry (table, offset);
+
+	  /* Do sanity checks.  */
+	  if (!entry)
+	    warning (_("Trying to translate address %#lx with empty region-second-table entry."),
+		   vaddr);
+	  else if ((entry & S390_LK_RSTE_TT) >> 2 != S390_LK_DAT_TT_REGION2)
+	    warning (_("Trying to translate address %#lx with corrupt table type in region-second-table entry."),
+		     vaddr);
+	  else if (entry & S390_LK_RSTE_I)
+	    warning (_("Translating address %#lx with invalid bit set at region-second-table entry."),
+		     vaddr);
+
+	  table = entry & S390_LK_RSTE_O;
+	}
+	/* fall through */
+      case S390_LK_DAT_TT_REGION3:
+	{
+	  offset = (vaddr & S390_LK_VADDR_RTX) >> 31;
+	  entry = s390_lk_read_table_entry (table, offset);
+
+	  /* Do sanity checks.  */
+	  if (!entry)
+	    warning (_("Trying to translate address %#lx with empty region-third-table entry."),
+		   vaddr);
+	  else if ((entry & S390_LK_RTTE_TT) >> 2 != S390_LK_DAT_TT_REGION3)
+	    warning (_("Trying to translate address %#lx with corrupt table type in region-third-table entry."),
+		     vaddr);
+	  else if (entry & S390_LK_RTTE_I)
+	    warning (_("Translating address %#lx with invalid bit set at region-third-table entry."),
+		     vaddr);
+
+	  /* Check for huge page.  */
+	  if (entry & S390_LK_RTTE_FC)
+	    {
+	      paddr = ((entry & S390_LK_RTTE_RFAA)
+		       + (vaddr & ~S390_LK_RTTE_RFAA));
+	      return paddr;
+	    }
+
+	  table = entry & S390_LK_RTTE_O;
+	}
+	/* fall through */
+      case S390_LK_DAT_TT_SEGMENT:
+	{
+	  offset = (vaddr & S390_LK_VADDR_SX) >> 20;
+	  entry = s390_lk_read_table_entry (table, offset);
+
+	  /* Do sanity checks.  */
+	  if (!entry)
+	    warning (_("Trying to translate address %#lx with empty segment-table entry."),
+		   vaddr);
+	  else if ((entry & S390_LK_STE_TT) >> 2 != S390_LK_DAT_TT_SEGMENT)
+	    warning (_("Trying to translate address %#lx with corrupt table type in segment-table entry."),
+		     vaddr);
+	  else if (entry & S390_LK_STE_I)
+	    warning (_("Translating address %#lx with invalid bit set at segment-table entry."),
+		     vaddr);
+
+	  /* Check for large page.  */


Is large different from huge?

+	  if (entry & S390_LK_STE_FC)
+	    {
+	      paddr = ((entry & S390_LK_STE_SFAA)
+		       + (vaddr & ~S390_LK_STE_SFAA));
+	      return paddr;
+	    }
+
+	  table = entry & S390_LK_STE_O;
+	  break;
+	}
+    } /* switch (table_type) */
+
+  offset = (vaddr & S390_LK_VADDR_PX) >> 12;
+  entry = s390_lk_read_table_entry (table, offset);
+
+  /* Do sanity checks.  */
+  if (!entry)
+    warning (_("Trying to translate address %#lx with empty page-table entry."),
+	     vaddr);
+  else if (entry & S390_LK_PTE_I)
+    warning (_("Translating address %#lx with invalid bit set at page-table entry."),
+	     vaddr);
+
+  paddr = ((entry & S390_LK_PTE_PFAA) + (vaddr & ~S390_LK_PTE_PFAA));
+
+  return paddr;
+}
+
+/* Function for Linux kernel target get_module_text_offset hook.  */
+
+CORE_ADDR
+s390_lk_get_module_text_offset (CORE_ADDR mod)
+{
+  CORE_ADDR offset, mod_arch;
+
+  mod_arch = mod + LK_OFFSET (module, arch);
+  offset = lk_read_ulong (mod_arch + LK_OFFSET (mod_arch_specific, got_size));
+  offset += lk_read_ulong (mod_arch + LK_OFFSET (mod_arch_specific, plt_size));
+
+  return offset;
+}
+
+/* Initialize s390 dependent private data for linux kernel target.  */


Newline between comment and function declaration.

+void
+s390_lk_init_private (struct gdbarch *gdbarch)
+{
+  LK_DECLARE_FIELD (stack_frame, gprs);
+
+  LK_DECLARE_FIELD (thread_struct, ksp);
+
+  LK_DECLARE_STRUCT_ALIAS (_lowcore, lowcore); /* linux -4.4 */
+  LK_DECLARE_STRUCT_ALIAS (lowcore, lowcore); /* linux 4.5+ */
+  if (LK_STRUCT (lowcore) == NULL)
+    error (_("Could not find struct lowcore. Abort."));


Two spaces after period. Also, "Aborting" instead of "Abort"?

+  LK_DECLARE_FIELD (lowcore, percpu_offset);
+  LK_DECLARE_FIELD (lowcore, current_pid);
+  LK_DECLARE_FIELD (lowcore, cpu_nr);
+
+  LK_DECLARE_FIELD (mod_arch_specific, got_size);
+  LK_DECLARE_FIELD (mod_arch_specific, plt_size);
+
+  LK_DECLARE_ADDR (lowcore_ptr);
+  LK_DECLARE_ADDR (high_memory);
+
+  LK_HOOK->get_registers = s390_lk_get_registers;
+  LK_HOOK->is_kvaddr = s390_lk_is_kvaddr;
+  LK_HOOK->vtop = s390_lk_vtop;
+  LK_HOOK->get_percpu_offset = s390_lk_get_percpu_offset;
+  LK_HOOK->map_running_task_to_cpu = s390_lk_map_running_task_to_cpu;
+  LK_HOOK->get_module_text_offset = s390_lk_get_module_text_offset;
+}
+

 /* Decoding S/390 instructions.  */

@@ -8220,6 +8487,9 @@ s390_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   set_gdbarch_process_record (gdbarch, s390_process_record);
   set_gdbarch_process_record_signal (gdbarch, s390_linux_record_signal);

+  /* Support linux kernel debugging.  */
+  set_gdbarch_lk_init_private (gdbarch, s390_lk_init_private);
+
   s390_init_linux_record_tdep (&s390_linux_record_tdep, ABI_LINUX_S390);
   s390_init_linux_record_tdep (&s390x_linux_record_tdep, ABI_LINUX_ZSERIES);

diff --git a/gdb/s390-linux-tdep.h b/gdb/s390-linux-tdep.h
index fdb3c3d..8a16b0b 100644
--- a/gdb/s390-linux-tdep.h
+++ b/gdb/s390-linux-tdep.h
@@ -238,4 +238,66 @@ extern struct target_desc *tdesc_s390x_te_linux64;
 extern struct target_desc *tdesc_s390x_vx_linux64;
 extern struct target_desc *tdesc_s390x_tevx_linux64;

+/* Definitions for address translation.  */
+/* DAT Table types.  */
+#define S390_LK_DAT_TT_REGION1  3
+#define S390_LK_DAT_TT_REGION2  2
+#define S390_LK_DAT_TT_REGION3  1
+#define S390_LK_DAT_TT_SEGMENT  0
+
+/* Region-First-Table */
+#define S390_LK_RFTE_TL  0x3ULL		/* Table-Length */
+#define S390_LK_RFTE_TT  0xcULL		/* Table-Type */
+#define S390_LK_RFTE_I   0x20ULL	/* Region-Invalid Bit */
+#define S390_LK_RFTE_TF  0xc0ULL	/* Table Offset */
+#define S390_LK_RFTE_P   0x200ULL	/* DAT-Protection Bit */
+#define S390_LK_RFTE_O  ~0xfffULL	/* Region-Second-Table Origin */
+
+/* Region-Second-Table flags.  */
+#define S390_LK_RSTE_TL  0x3ULL		/* Table-Length */
+#define S390_LK_RSTE_TT  0xcULL		/* Table-Type */
+#define S390_LK_RSTE_I   0x20ULL	/* Region-Invalid Bit */
+#define S390_LK_RSTE_TF  0xc0ULL	/* Table Offset */
+#define S390_LK_RSTE_P   0x200ULL	/* DAT-Protection Bit */
+#define S390_LK_RSTE_O  ~0xfffULL	/* Region-Third-Table Origin */
+
+/* Region-Third-Table flags.  */
+#define S390_LK_RTTE_TL    0x3ULL	  /* Table-Length */
+#define S390_LK_RTTE_TT    0xcULL	  /* Table-Type */
+#define S390_LK_RTTE_CR    0x10ULL	  /* Common-Region Bit */
+#define S390_LK_RTTE_I     0x20ULL	  /* Region-Invalid Bit */
+#define S390_LK_RTTE_TF    0xc0ULL	  /* Table Offset */
+#define S390_LK_RTTE_P     0x200ULL	  /* DAT-Protection Bit */
+#define S390_LK_RTTE_FC    0x400ULL	  /* Format-Control Bit */
+#define S390_LK_RTTE_F     0x800ULL	  /* Fetch-Protection Bit */
+#define S390_LK_RTTE_ACC   0xf000ULL	  /* Access-Control Bits */
+#define S390_LK_RTTE_AV    0x10000ULL	  /* ACCF-Validy Control */


"Validy" or "Validity"?

+#define S390_LK_RTTE_O    ~0xfffULL	  /* Segment-Table Origin */
+#define S390_LK_RTTE_RFAA ~0x7fffffffULL  /* Region-Frame Absolute Address */
+
+/* Segment-Table flags.  */
+#define S390_LK_STE_TT    0xcULL	/* Table-Type */
+#define S390_LK_STE_I     0x20ULL	/* Segment-Invalid Bit */
+#define S390_LK_STE_TF    0xc0ULL	/* Table Offset */
+#define S390_LK_STE_P     0x200ULL	/* DAT-Protection Bit */
+#define S390_LK_STE_FC    0x400ULL	/* Format-Control Bit */
+#define S390_LK_STE_F     0x800ULL	/* Fetch-Protection Bit */
+#define S390_LK_STE_ACC   0xf000ULL	/* Access-Control Bits */
+#define S390_LK_STE_AV    0x10000ULL	/* ACCF-Validy Control */
+#define S390_LK_STE_O    ~0x7ffULL	/* Page-Table Origin */
+#define S390_LK_STE_SFAA ~0xfffffULL	/* Segment-Frame Absolute Address */
+
+/* Page-Table flags.  */
+#define S390_LK_PTE_P     0x200ULL	/* DAT-Protection Bit */
+#define S390_LK_PTE_I     0x400ULL	/* Page-Invalid Bit */
+#define S390_LK_PTE_PFAA ~0xfffULL	/* Page-Frame Absolute Address */
+
+/* Virtual Address Fields.  */
+#define S390_LK_VADDR_RFX 0xffe0000000000000ULL
+#define S390_LK_VADDR_RSX 0x001ffc0000000000ULL
+#define S390_LK_VADDR_RTX 0x000003ff80000000ULL
+#define S390_LK_VADDR_SX  0x000000007ff00000ULL
+#define S390_LK_VADDR_PX  0x00000000000ff000ULL
+#define S390_LK_VADDR_BX  0x0000000000000fffULL
+
 #endif

Follow-Ups:
- Re: [RFC 7/7] Add S390 support for linux-kernel target
  - From: Philipp Rudo

References:
- [RFC 0/7] Support for Linux kernel debugging
  - From: Philipp Rudo
- [RFC 7/7] Add S390 support for linux-kernel target
  - From: Philipp Rudo

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