diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
index 0000b498f8959b44ed20404c834a4ad77fcea8d4..b183a3c9a380da866c41b31321c28f0e0bdd467f 100644
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -2240,7 +2240,9 @@ aarch64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
set_gdbarch_get_syscall_number (gdbarch, aarch64_linux_get_syscall_number);
/* Displaced stepping. */
- set_gdbarch_max_insn_length (gdbarch, 4 * AARCH64_DISPLACED_MODIFIED_INSNS);
+ set_gdbarch_max_insn_length (gdbarch, 4);
+ set_gdbarch_displaced_step_buffer_length
+ (gdbarch, 4 * AARCH64_DISPLACED_MODIFIED_INSNS);
set_gdbarch_displaced_step_copy_insn (gdbarch,
aarch64_displaced_step_copy_insn);
set_gdbarch_displaced_step_fixup (gdbarch, aarch64_displaced_step_fixup);
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 70d77452e93dc383c71707f36b3cefc1e130a418..883f8be296b9a61e4b0564fd3b8b45b402f9a303 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -10662,7 +10662,9 @@ arm_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
/* Note: for displaced stepping, this includes the breakpoint, and one word
of additional scratch space. This setting isn't used for anything beside
displaced stepping at present. */
- set_gdbarch_max_insn_length (gdbarch, 4 * ARM_DISPLACED_MODIFIED_INSNS);
+ set_gdbarch_displaced_step_buffer_length
+ (gdbarch, 4 * ARM_DISPLACED_MODIFIED_INSNS);
+ set_gdbarch_max_insn_length (gdbarch, 4);
/* This should be low enough for everything. */
tdep->lowest_pc = 0x20;
diff --git a/gdb/displaced-stepping.c b/gdb/displaced-stepping.c
index 06b32a80f6a0ec54284aff2ddd456ea1e2625ecf..9f98ea8c35bd4dcf698e2775b5dab2194c99a3fb 100644
--- a/gdb/displaced-stepping.c
+++ b/gdb/displaced-stepping.c
@@ -55,7 +55,7 @@ displaced_step_buffers::prepare (thread_info *thread, CORE_ADDR &displaced_pc)
regcache *regcache = get_thread_regcache (thread);
const address_space *aspace = regcache->aspace ();
gdbarch *arch = regcache->arch ();
- ULONGEST len = gdbarch_max_insn_length (arch);
+ ULONGEST len = gdbarch_displaced_step_buffer_length (arch);
/* Search for an unused buffer. */
displaced_step_buffer *buffer = nullptr;
@@ -243,7 +243,7 @@ displaced_step_buffers::finish (gdbarch *arch, thread_info *thread,
below. */
thread->inf->displaced_step_state.unavailable = false;
- ULONGEST len = gdbarch_max_insn_length (arch);
+ ULONGEST len = gdbarch_displaced_step_buffer_length (arch);
/* Restore memory of the buffer. */
write_memory_ptid (thread->ptid, buffer->addr,
@@ -302,7 +302,7 @@ displaced_step_buffers::restore_in_ptid (ptid_t ptid)
regcache *regcache = get_thread_regcache (buffer.current_thread);
gdbarch *arch = regcache->arch ();
- ULONGEST len = gdbarch_max_insn_length (arch);
+ ULONGEST len = gdbarch_displaced_step_buffer_length (arch);
write_memory_ptid (ptid, buffer.addr, buffer.saved_copy.data (), len);
diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h
index ddb97f60315f515487dea21fc4c58087a4f395b5..76d12a15317ffb892a52046b74b1bab85379eda8 100644
--- a/gdb/gdbarch-gen.h
+++ b/gdb/gdbarch-gen.h
@@ -1039,8 +1039,8 @@ extern void set_gdbarch_max_insn_length (struct gdbarch *gdbarch, ULONGEST max_i
see the comments in infrun.c.
The TO area is only guaranteed to have space for
- gdbarch_max_insn_length (arch) bytes, so this function must not
- write more bytes than that to that area.
+ gdbarch_displaced_step_buffer_length (arch) octets, so this
+ function must not write more octets than that to this area.
If you do not provide this function, GDB assumes that the
architecture does not support displaced stepping.
@@ -1122,6 +1122,14 @@ typedef void (gdbarch_displaced_step_restore_all_in_ptid_ftype) (inferior *paren
extern void gdbarch_displaced_step_restore_all_in_ptid (struct gdbarch *gdbarch, inferior *parent_inf, ptid_t child_ptid);
extern void set_gdbarch_displaced_step_restore_all_in_ptid (struct gdbarch *gdbarch, gdbarch_displaced_step_restore_all_in_ptid_ftype *displaced_step_restore_all_in_ptid);
+/* The maximum length in octets required for a displaced-step instruction
+ buffer. By default this will be the same as gdbarch::max_insn_length,
+ but should be overridden for architectures that might expand a
+ displaced-step instruction to multiple replacement instructions. */
+
+extern ULONGEST gdbarch_displaced_step_buffer_length (struct gdbarch *gdbarch);
+extern void set_gdbarch_displaced_step_buffer_length (struct gdbarch *gdbarch, ULONGEST displaced_step_buffer_length);
+
/* Relocate an instruction to execute at a different address. OLDLOC
is the address in the inferior memory where the instruction to
relocate is currently at. On input, TO points to the destination
diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
index 84f6a481885249a83185350243e1615481a32d06..b4763aa6bf4fe26a5bfe537a3cf363c265f33af8 100644
--- a/gdb/gdbarch.c
+++ b/gdb/gdbarch.c
@@ -192,6 +192,7 @@ struct gdbarch
gdbarch_displaced_step_finish_ftype *displaced_step_finish = NULL;
gdbarch_displaced_step_copy_insn_closure_by_addr_ftype *displaced_step_copy_insn_closure_by_addr = nullptr;
gdbarch_displaced_step_restore_all_in_ptid_ftype *displaced_step_restore_all_in_ptid = nullptr;
+ ULONGEST displaced_step_buffer_length = 0;
gdbarch_relocate_instruction_ftype *relocate_instruction = NULL;
gdbarch_overlay_update_ftype *overlay_update = nullptr;
gdbarch_core_read_description_ftype *core_read_description = nullptr;
@@ -451,6 +452,10 @@ verify_gdbarch (struct gdbarch *gdbarch)
log.puts ("\n\tdisplaced_step_finish");
/* Skip verify of displaced_step_copy_insn_closure_by_addr, has predicate. */
/* Skip verify of displaced_step_restore_all_in_ptid, invalid_p == 0 */
+ if (gdbarch->displaced_step_buffer_length == 0)
+ gdbarch->displaced_step_buffer_length = gdbarch->max_insn_length;
+ if (gdbarch->displaced_step_buffer_length < gdbarch->max_insn_length)
+ log.puts ("\n\tdisplaced_step_buffer_length");
/* Skip verify of relocate_instruction, has predicate. */
/* Skip verify of overlay_update, has predicate. */
/* Skip verify of core_read_description, has predicate. */
@@ -1109,6 +1114,9 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
gdb_printf (file,
"gdbarch_dump: displaced_step_restore_all_in_ptid = <%s>\n",
host_address_to_string (gdbarch->displaced_step_restore_all_in_ptid));
+ gdb_printf (file,
+ "gdbarch_dump: displaced_step_buffer_length = %s\n",
+ plongest (gdbarch->displaced_step_buffer_length));
gdb_printf (file,
"gdbarch_dump: gdbarch_relocate_instruction_p() = %d\n",
gdbarch_relocate_instruction_p (gdbarch));
@@ -4157,6 +4165,24 @@ set_gdbarch_displaced_step_restore_all_in_ptid (struct gdbarch *gdbarch,
gdbarch->displaced_step_restore_all_in_ptid = displaced_step_restore_all_in_ptid;
}
+ULONGEST
+gdbarch_displaced_step_buffer_length (struct gdbarch *gdbarch)
+{
+ gdb_assert (gdbarch != NULL);
+ /* Check variable is valid. */
+ gdb_assert (!(gdbarch->displaced_step_buffer_length < gdbarch->max_insn_length));
+ if (gdbarch_debug >= 2)
+ gdb_printf (gdb_stdlog, "gdbarch_displaced_step_buffer_length called\n");
+ return gdbarch->displaced_step_buffer_length;
+}
+
+void
+set_gdbarch_displaced_step_buffer_length (struct gdbarch *gdbarch,
+ ULONGEST displaced_step_buffer_length)
+{
+ gdbarch->displaced_step_buffer_length = displaced_step_buffer_length;
+}
+
bool
gdbarch_relocate_instruction_p (struct gdbarch *gdbarch)
{
diff --git a/gdb/gdbarch_components.py b/gdb/gdbarch_components.py
index 6cdf15b391026efa84b2d7a7afc640514c30f146..92c501d2a722caef59545ec42c05217b6791f065 100644
--- a/gdb/gdbarch_components.py
+++ b/gdb/gdbarch_components.py
@@ -1735,8 +1735,8 @@ For a general explanation of displaced stepping and how GDB uses it,
see the comments in infrun.c.
The TO area is only guaranteed to have space for
-gdbarch_max_insn_length (arch) bytes, so this function must not
-write more bytes than that to that area.
+gdbarch_displaced_step_buffer_length (arch) octets, so this
+function must not write more octets than that to this area.
If you do not provide this function, GDB assumes that the
architecture does not support displaced stepping.
@@ -1844,6 +1844,20 @@ contents of all displaced step buffers in the child's address space.
invalid=False,
)
+Value(
+ comment="""
+The maximum length in octets required for a displaced-step instruction
+buffer. By default this will be the same as gdbarch::max_insn_length,
+but should be overridden for architectures that might expand a
+displaced-step instruction to multiple replacement instructions.
+""",
+ type="ULONGEST",
+ name="displaced_step_buffer_length",
+ predefault="0",
+ postdefault="gdbarch->max_insn_length",
+ invalid="gdbarch->displaced_step_buffer_length < gdbarch->max_insn_length",
+)
+
Method(
comment="""
Relocate an instruction to execute at a different address. OLDLOC
diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index e6ce13a1c672d4f326a6d5df9609d03d38f61ff2..3eaa5f3358484a7837f86c2b74d164a3c8fe6984 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -2603,7 +2603,7 @@ linux_displaced_step_prepare (gdbarch *arch, thread_info *thread,
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);
+ int buf_len = gdbarch_displaced_step_buffer_length (arch);
linux_gdbarch_data *gdbarch_data = get_linux_gdbarch_data (arch);
gdb_assert (gdbarch_data->num_disp_step_buffers > 0);
diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
index 6ba56527a22f9c627cb0494908fd752d46b1fa18..9859a7d8b85a8cb8e7f578e157adc8b96b1bd0be 100644
--- a/gdb/rs6000-tdep.c
+++ b/gdb/rs6000-tdep.c
@@ -889,7 +889,8 @@ ppc_displaced_step_copy_insn (struct gdbarch *gdbarch,
CORE_ADDR from, CORE_ADDR to,
struct regcache *regs)
{
- size_t len = gdbarch_max_insn_length (gdbarch);
+ size_t len = gdbarch_displaced_step_buffer_length (gdbarch);
+ gdb_assert (len > PPC_INSN_SIZE);
std::unique_ptr<ppc_displaced_step_copy_insn_closure> closure
(new ppc_displaced_step_copy_insn_closure (len));
gdb_byte *buf = closure->buf.data ();
@@ -8363,8 +8364,9 @@ rs6000_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
set_gdbarch_displaced_step_finish (gdbarch, ppc_displaced_step_finish);
set_gdbarch_displaced_step_restore_all_in_ptid
(gdbarch, ppc_displaced_step_restore_all_in_ptid);
+ set_gdbarch_displaced_step_buffer_length (gdbarch, 2 * PPC_INSN_SIZE);
- set_gdbarch_max_insn_length (gdbarch, 2 * PPC_INSN_SIZE);
+ set_gdbarch_max_insn_length (gdbarch, PPC_INSN_SIZE);
/* Hook in ABI-specific overrides, if they have been registered. */
info.target_desc = tdesc;