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, 37 insertions, 16 deletions

diff --git a/gdb/displaced-stepping.h b/gdb/displaced-stepping.h
index a2d80aeda4f..d1a1cebb93e 100644
--- a/gdb/displaced-stepping.h
+++ b/gdb/displaced-stepping.h
@@ -20,6 +20,7 @@
 #ifndef DISPLACED_STEPPING_H
 #define DISPLACED_STEPPING_H
 
+#include "gdbsupport/array-view.h"
 #include "gdbsupport/byte-vector.h"
 
 struct gdbarch;
@@ -154,13 +155,19 @@ private:
   gdbarch *m_original_gdbarch = nullptr;
 };
 
-/* Manage access to a single displaced stepping buffer.  */
+/* Control access to multiple displaced stepping buffers at fixed addresses.  */
 
-struct displaced_step_buffer
+struct displaced_step_buffers
 {
-  explicit displaced_step_buffer (CORE_ADDR buffer_addr)
-    : m_addr (buffer_addr)
-  {}
+  explicit displaced_step_buffers (gdb::array_view<CORE_ADDR> buffer_addrs)
+  {
+    gdb_assert (buffer_addrs.size () > 0);
+
+    m_buffers.reserve (buffer_addrs.size ());
+
+    for (CORE_ADDR buffer_addr : buffer_addrs)
+      m_buffers.emplace_back (buffer_addr);
+  }
 
   displaced_step_prepare_status prepare (thread_info *thread,
 					 CORE_ADDR &displaced_pc);
@@ -174,21 +181,35 @@ struct displaced_step_buffer
   void restore_in_ptid (ptid_t ptid);
 
 private:
-  /* Original PC of the instruction being displaced-stepped in this buffer.  */
-  CORE_ADDR m_original_pc = 0;
 
-  /* Address of the buffer.  */
-  const CORE_ADDR m_addr;
+  /* State of a single buffer.  */
+
+  struct displaced_step_buffer
+  {
+    explicit displaced_step_buffer (CORE_ADDR addr)
+      : addr (addr)
+    {}
+
+    /* Address of the buffer.  */
+    const CORE_ADDR addr;
+
+    /* The original PC of the instruction currently being stepped.  */
+    CORE_ADDR original_pc = 0;
+
+    /* If set, the thread currently using the buffer.  If unset, the buffer is not
+       used.  */
+    thread_info *current_thread = nullptr;
 
-  /* If set, the thread currently using the buffer.  */
-  thread_info *m_current_thread = nullptr;
+    /* Saved copy of the bytes in the displaced buffer, to be restored once the
+       buffer is no longer used.  */
+    gdb::byte_vector saved_copy;
 
-  /* Saved contents of copy area.  */
-  gdb::byte_vector m_saved_copy;
+    /* Closure obtained from gdbarch_displaced_step_copy_insn, to be passed to
+       gdbarch_displaced_step_fixup_insn.  */
+    displaced_step_copy_insn_closure_up copy_insn_closure;
+  };
 
-  /* The closure provided gdbarch_displaced_step_copy_insn, to be used
-     for post-step cleanup.  */
-  displaced_step_copy_insn_closure_up m_copy_insn_closure;
+  std::vector<displaced_step_buffer> m_buffers;
 };
 
 #endif /* DISPLACED_STEPPING_H */