gdb: make displaced stepping implementation capable of managing multiple buffers

The displaced_step_buffer class, introduced in the previous patch,
manages access to a single displaced step buffer.  Change it into
displaced_step_buffers (note the plural), which manages access to
multiple displaced step buffers.

When preparing a displaced step for a thread, it looks for an unused
buffer.

For now, all users still pass a single displaced step buffer, so no real
behavior change is expected here.  The following patch makes a user pass
more than one buffer, so the functionality introduced by this patch is
going to be useful in the next one.

gdb/ChangeLog:

	* displaced-stepping.h (struct displaced_step_buffer): Rename
	to...
	(struct displaced_step_buffers): ... this.
	<m_addr, m_current_thread, m_copy_insn_closure>: Remove.
	<struct displaced_step_buffer>: New inner class.
	<m_buffers>: New.
	* displaced-stepping.c (displaced_step_buffer::prepare): Rename
	to...
	(displaced_step_buffers::prepare): ... this, adjust for multiple
	buffers.
	(displaced_step_buffer::finish):  Rename to...
	(displaced_step_buffers::finish): ... this, adjust for multiple
	buffers.
	(displaced_step_buffer::copy_insn_closure_by_addr): Rename to...
	(displaced_step_buffers::copy_insn_closure_by_addr): ... this,
	adjust for multiple buffers.
	(displaced_step_buffer::restore_in_ptid): Rename to...
	(displaced_step_buffers::restore_in_ptid): ... this, adjust for
	multiple buffers.
	* linux-tdep.h (linux_init_abi): Change supports_displaced_step
	for num_disp_step_buffers.
	* linux-tdep.c (struct linux_gdbarch_data)
	<num_disp_step_buffers>: New field.
	(struct linux_info) <disp_step_buf>: Rename to...
	<disp_step_bufs>: ... this, change type to
	displaced_step_buffers.
	(linux_displaced_step_prepare): Use
	linux_gdbarch_data::num_disp_step_buffers to create that number
	of buffers.
	(linux_displaced_step_finish): Adjust.
	(linux_displaced_step_copy_insn_closure_by_addr): Adjust.
	(linux_displaced_step_restore_all_in_ptid): Adjust.
	(linux_init_abi): Change supports_displaced_step parameter for
	num_disp_step_buffers, save it in linux_gdbarch_data.
	* aarch64-linux-tdep.c (aarch64_linux_init_abi): Adjust.
	* alpha-linux-tdep.c (alpha_linux_init_abi): Adjust.
	* amd64-linux-tdep.c (amd64_linux_init_abi_common): Change
	supports_displaced_step parameter for num_disp_step_buffers.
	(amd64_linux_init_abi): Adjust.
	(amd64_x32_linux_init_abi): Adjust.
	* arc-linux-tdep.c (arc_linux_init_osabi): Adjust.
	* arm-linux-tdep.c (arm_linux_init_abi): Adjust.
	* bfin-linux-tdep.c (bfin_linux_init_abi): Adjust.
	* cris-linux-tdep.c (cris_linux_init_abi): Adjust.
	* csky-linux-tdep.c (csky_linux_init_abi): Adjust.
	* frv-linux-tdep.c (frv_linux_init_abi): Adjust.
	* hppa-linux-tdep.c (hppa_linux_init_abi): Adjust.
	* i386-linux-tdep.c (i386_linux_init_abi): Adjust.
	* ia64-linux-tdep.c (ia64_linux_init_abi): Adjust.
	* m32r-linux-tdep.c (m32r_linux_init_abi): Adjust.
	* m68k-linux-tdep.c (m68k_linux_init_abi):
	* microblaze-linux-tdep.c (microblaze_linux_init_abi):
	* mips-linux-tdep.c (mips_linux_init_abi): Adjust.
	* mn10300-linux-tdep.c (am33_linux_init_osabi): Adjust.
	* nios2-linux-tdep.c (nios2_linux_init_abi): Adjust.
	* or1k-linux-tdep.c (or1k_linux_init_abi): Adjust.
	* ppc-linux-tdep.c (ppc_linux_init_abi): Adjust.
	* riscv-linux-tdep.c (riscv_linux_init_abi): Adjust.
	* rs6000-tdep.c (struct ppc_inferior_data) <disp_step_buf>:
	Change type to displaced_step_buffers.
	* s390-linux-tdep.c (s390_linux_init_abi_any): Adjust.
	* sh-linux-tdep.c (sh_linux_init_abi): Adjust.
	* sparc-linux-tdep.c (sparc32_linux_init_abi): Adjust.
	* sparc64-linux-tdep.c (sparc64_linux_init_abi): Adjust.
	* tic6x-linux-tdep.c (tic6x_uclinux_init_abi): Adjust.
	* tilegx-linux-tdep.c (tilegx_linux_init_abi): Adjust.
	* xtensa-linux-tdep.c (xtensa_linux_init_abi): Adjust.

Change-Id: Ia9c02f207da2c9e1d9188020139619122392bb70

1 files changed, 36 insertions, 18 deletions

diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index 57ea45cf6b6..5ae28d826c1 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -166,9 +166,10 @@ enum
 static struct gdbarch_data *linux_gdbarch_data_handle;
 
 struct linux_gdbarch_data
-  {
-    struct type *siginfo_type;
-  };
+{
+  struct type *siginfo_type;
+  int num_disp_step_buffers;
+};
 
 static void *
 init_linux_gdbarch_data (struct obstack *obstack)
@@ -200,8 +201,8 @@ struct linux_info
      if we tried looking it up but failed.  */
   int vsyscall_range_p = 0;
 
-  /* Inferior's displaced step buffer.  */
-  gdb::optional<displaced_step_buffer> disp_step_buf;
+  /* Inferior's displaced step buffers.  */
+  gdb::optional<displaced_step_buffers> disp_step_bufs;
 };
 
 /* Per-inferior data key.  */
@@ -2540,15 +2541,25 @@ linux_displaced_step_prepare (gdbarch *arch, thread_info *thread,
 {
   linux_info *per_inferior = get_linux_inferior_data (thread->inf);
 
-  if (!per_inferior->disp_step_buf.has_value ())
+  if (!per_inferior->disp_step_bufs.has_value ())
     {
+      /* Figure out the location of the buffers.  They are contiguous, starting
+	 at DISP_STEP_BUF_ADDR.  They are all of size BUF_LEN.  */
       CORE_ADDR disp_step_buf_addr
 	= linux_displaced_step_location (thread->inf->gdbarch);
+      int buf_len = gdbarch_max_insn_length (arch);
 
-      per_inferior->disp_step_buf.emplace (disp_step_buf_addr);
+      linux_gdbarch_data *gdbarch_data = get_linux_gdbarch_data (arch);
+      gdb_assert (gdbarch_data->num_disp_step_buffers > 0);
+
+      std::vector<CORE_ADDR> buffers;
+      for (int i = 0; i < gdbarch_data->num_disp_step_buffers; i++)
+	buffers.push_back (disp_step_buf_addr + i * buf_len);
+
+      per_inferior->disp_step_bufs.emplace (buffers);
     }
 
-  return per_inferior->disp_step_buf->prepare (thread, displaced_pc);
+  return per_inferior->disp_step_bufs->prepare (thread, displaced_pc);
 }
 
 /* See linux-tdep.h.  */
@@ -2558,9 +2569,9 @@ linux_displaced_step_finish (gdbarch *arch, thread_info *thread, gdb_signal sig)
 {
   linux_info *per_inferior = get_linux_inferior_data (thread->inf);
 
-  gdb_assert (per_inferior->disp_step_buf.has_value ());
+  gdb_assert (per_inferior->disp_step_bufs.has_value ());
 
-  return per_inferior->disp_step_buf->finish (arch, thread, sig);
+  return per_inferior->disp_step_bufs->finish (arch, thread, sig);
 }
 
 /* See linux-tdep.h.  */
@@ -2571,10 +2582,10 @@ linux_displaced_step_copy_insn_closure_by_addr (inferior *inf, CORE_ADDR addr)
   linux_info *per_inferior = linux_inferior_data.get (inf);
 
   if (per_inferior == nullptr
-      || !per_inferior->disp_step_buf.has_value ())
+      || !per_inferior->disp_step_bufs.has_value ())
     return nullptr;
 
-  return per_inferior->disp_step_buf->copy_insn_closure_by_addr (addr);
+  return per_inferior->disp_step_bufs->copy_insn_closure_by_addr (addr);
 }
 
 /* See linux-tdep.h.  */
@@ -2585,10 +2596,10 @@ linux_displaced_step_restore_all_in_ptid (inferior *parent_inf, ptid_t ptid)
   linux_info *per_inferior = linux_inferior_data.get (parent_inf);
 
   if (per_inferior == nullptr
-      || !per_inferior->disp_step_buf.has_value ())
+      || !per_inferior->disp_step_bufs.has_value ())
     return;
 
-  per_inferior->disp_step_buf->restore_in_ptid (ptid);
+  per_inferior->disp_step_bufs->restore_in_ptid (ptid);
 }
 
 /* See linux-tdep.h.  */
@@ -2636,15 +2647,22 @@ show_dump_excluded_mappings (struct ui_file *file, int from_tty,
 }
 
 /* To be called from the various GDB_OSABI_LINUX handlers for the
-   various GNU/Linux architectures and machine types.  */
+   various GNU/Linux architectures and machine types.
+
+   NUM_DISP_STEP_BUFFERS is the number of displaced step buffers to use.  If 0,
+   displaced stepping is not supported. */
 
 void
 linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch,
-		bool supports_displaced_step)
+		int num_disp_step_buffers)
 {
-  if (supports_displaced_step)
+  if (num_disp_step_buffers > 0)
     {
-      set_gdbarch_displaced_step_prepare (gdbarch, linux_displaced_step_prepare);
+      linux_gdbarch_data *gdbarch_data = get_linux_gdbarch_data (gdbarch);
+      gdbarch_data->num_disp_step_buffers = num_disp_step_buffers;
+
+      set_gdbarch_displaced_step_prepare (gdbarch,
+					  linux_displaced_step_prepare);
       set_gdbarch_displaced_step_finish (gdbarch, linux_displaced_step_finish);
       set_gdbarch_displaced_step_copy_insn_closure_by_addr
 	(gdbarch, linux_displaced_step_copy_insn_closure_by_addr);