[PATCH 17/24] gdb: add gdbarch_pseudo_register_write that takes a frame

Simon Marchi
2023-11-08T05:17:03Z

From: Simon Marchi <simon.marchi@efficios.com>

Add a new variant of gdbarch_pseudo_register_write that takes a
frame_info in order to write raw registers. Use this new method when
available:

- in put_frame_register, when trying to write a pseudo register to a given frame
- in regcache::cooked_write

No implementation is migrated to use this new method (that will come in
subsequent patches), so no behavior change is expected here.

The objective is to fix writing pseudo registers to non-current
frames. See previous commit "gdb: read pseudo register through
frame" for a more detailed explanation.

Change-Id: Ie7fe364a15a4d86c2ecb09de2b4baa08c45555ac
---
gdb/frame.c | 9 +++++-
gdb/gdbarch-gen.h | 15 +++++++++-
gdb/gdbarch.c | 32 ++++++++++++++++++++
gdb/gdbarch_components.py | 19 ++++++++++++
gdb/regcache.c | 4 +++
gdb/value.c | 63 +++++++++++++++++++++++++++++++++++++++
gdb/value.h | 22 ++++++++++++++
7 files changed, 162 insertions(+), 2 deletions(-)

diff --git a/gdb/frame.c b/gdb/frame.c
index 3035f87369ca..81836d6d5357 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -1452,7 +1452,14 @@ put_frame_register (frame_info_ptr next_frame, int regnum,
break;
}
case lval_register:
- get_current_regcache ()->cooked_write (realnum, buf, 1.0f);
+ /* Not sure if that's always true... but we have a problem if not. */
+ gdb_assert (size == register_size (gdbarch, realnum));
+
+ if (realnum < gdbarch_num_regs (gdbarch)
+ || !gdbarch_pseudo_register_write_p (gdbarch))
+ get_current_regcache ()->cooked_write (realnum, buf, 1.0f);
+ else
+ gdbarch_pseudo_register_write (gdbarch, next_frame, realnum, buf);
break;
default:
error (_("Attempt to assign to an unmodifiable value."));
diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h
index 3160aa8a9613..9cf58490d0b6 100644
--- a/gdb/gdbarch-gen.h
+++ b/gdb/gdbarch-gen.h
@@ -200,12 +200,25 @@ typedef struct value * (gdbarch_pseudo_register_read_value_ftype) (struct gdbarc
extern struct value * gdbarch_pseudo_register_read_value (struct gdbarch *gdbarch, frame_info_ptr next_frame, int cookednum);
extern void set_gdbarch_pseudo_register_read_value (struct gdbarch *gdbarch, gdbarch_pseudo_register_read_value_ftype *pseudo_register_read_value);

+/* Write bytes in BUF to pseudo register with number PSEUDO_REG_NUM.
+
+ Raw registers backing the pseudo register should be written to using
+ NEXT_FRAME. */
+
+extern bool gdbarch_pseudo_register_write_p (struct gdbarch *gdbarch);
+
+typedef void (gdbarch_pseudo_register_write_ftype) (struct gdbarch *gdbarch, frame_info_ptr next_frame, int pseudo_reg_num, gdb::array_view<const gdb_byte> buf);
+extern void gdbarch_pseudo_register_write (struct gdbarch *gdbarch, frame_info_ptr next_frame, int pseudo_reg_num, gdb::array_view<const gdb_byte> buf);
+extern void set_gdbarch_pseudo_register_write (struct gdbarch *gdbarch, gdbarch_pseudo_register_write_ftype *pseudo_register_write);
+
/* Write bytes to a pseudo register.

This is marked as deprecated because it gets passed a regcache for
implementations to write raw registers in. This doesn't work for unwound
frames, where the raw registers backing the pseudo registers may have been
- saved elsewhere. */
+ saved elsewhere.
+
+ Implementations should be migrated to implement pseudo_register_write instead. */

extern bool gdbarch_deprecated_pseudo_register_write_p (struct gdbarch *gdbarch);

diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
index e198d339f6ba..d584305fefb2 100644
--- a/gdb/gdbarch.c
+++ b/gdb/gdbarch.c
@@ -74,6 +74,7 @@ struct gdbarch
gdbarch_virtual_frame_pointer_ftype *virtual_frame_pointer = legacy_virtual_frame_pointer;
gdbarch_pseudo_register_read_ftype *pseudo_register_read = nullptr;
gdbarch_pseudo_register_read_value_ftype *pseudo_register_read_value = nullptr;
+ gdbarch_pseudo_register_write_ftype *pseudo_register_write = nullptr;
gdbarch_deprecated_pseudo_register_write_ftype *deprecated_pseudo_register_write = nullptr;
int num_regs = -1;
int num_pseudo_regs = 0;
@@ -330,6 +331,7 @@ verify_gdbarch (struct gdbarch *gdbarch)
/* Skip verify of virtual_frame_pointer, invalid_p == 0 */
/* Skip verify of pseudo_register_read, has predicate. */
/* Skip verify of pseudo_register_read_value, has predicate. */
+ /* Skip verify of pseudo_register_write, has predicate. */
/* Skip verify of deprecated_pseudo_register_write, has predicate. */
if (gdbarch->num_regs == -1)
log.puts ("\n\tnum_regs");
@@ -649,6 +651,12 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
gdb_printf (file,
"gdbarch_dump: pseudo_register_read_value = <%s>\n",
host_address_to_string (gdbarch->pseudo_register_read_value));
+ gdb_printf (file,
+ "gdbarch_dump: gdbarch_pseudo_register_write_p() = %d\n",
+ gdbarch_pseudo_register_write_p (gdbarch));
+ gdb_printf (file,
+ "gdbarch_dump: pseudo_register_write = <%s>\n",
+ host_address_to_string (gdbarch->pseudo_register_write));
gdb_printf (file,
"gdbarch_dump: gdbarch_deprecated_pseudo_register_write_p() = %d\n",
gdbarch_deprecated_pseudo_register_write_p (gdbarch));
@@ -1902,6 +1910,30 @@ set_gdbarch_pseudo_register_read_value (struct gdbarch *gdbarch,
gdbarch->pseudo_register_read_value = pseudo_register_read_value;
}

+bool
+gdbarch_pseudo_register_write_p (struct gdbarch *gdbarch)
+{
+ gdb_assert (gdbarch != NULL);
+ return gdbarch->pseudo_register_write != NULL;
+}
+
+void
+gdbarch_pseudo_register_write (struct gdbarch *gdbarch, frame_info_ptr next_frame, int pseudo_reg_num, gdb::array_view<const gdb_byte> buf)
+{
+ gdb_assert (gdbarch != NULL);
+ gdb_assert (gdbarch->pseudo_register_write != NULL);
+ if (gdbarch_debug >= 2)
+ gdb_printf (gdb_stdlog, "gdbarch_pseudo_register_write called\n");
+ gdbarch->pseudo_register_write (gdbarch, next_frame, pseudo_reg_num, buf);
+}
+
+void
+set_gdbarch_pseudo_register_write (struct gdbarch *gdbarch,
+ gdbarch_pseudo_register_write_ftype pseudo_register_write)
+{
+ gdbarch->pseudo_register_write = pseudo_register_write;
+}
+
bool
gdbarch_deprecated_pseudo_register_write_p (struct gdbarch *gdbarch)
{
diff --git a/gdb/gdbarch_components.py b/gdb/gdbarch_components.py
index 1100da160550..ce8169b19a57 100644
--- a/gdb/gdbarch_components.py
+++ b/gdb/gdbarch_components.py
@@ -418,6 +418,23 @@ never be called.
predicate=True,
)

+Method(
+ comment="""
+Write bytes in BUF to pseudo register with number PSEUDO_REG_NUM.
+
+Raw registers backing the pseudo register should be written to using
+NEXT_FRAME.
+""",
+ type="void",
+ name="pseudo_register_write",
+ params=[
+ ("frame_info_ptr", "next_frame"),
+ ("int", "pseudo_reg_num"),
+ ("gdb::array_view<const gdb_byte>", "buf"),
+ ],
+ predicate=True,
+)
+
Method(
comment="""
Write bytes to a pseudo register.
@@ -426,6 +443,8 @@ This is marked as deprecated because it gets passed a regcache for
implementations to write raw registers in. This doesn't work for unwound
frames, where the raw registers backing the pseudo registers may have been
saved elsewhere.
+
+Implementations should be migrated to implement pseudo_register_write instead.
""",
type="void",
name="deprecated_pseudo_register_write",
diff --git a/gdb/regcache.c b/gdb/regcache.c
index dadc949434ee..16b117e767be 100644
--- a/gdb/regcache.c
+++ b/gdb/regcache.c
@@ -929,6 +929,10 @@ regcache::cooked_write (int regnum, gdb::array_view<const gdb_byte> src, float)

if (regnum < num_raw_registers ())
raw_write (regnum, src, 1.0f);
+ else if (gdbarch_pseudo_register_write_p (m_descr->gdbarch))
+ gdbarch_pseudo_register_write
+ (m_descr->gdbarch, get_next_frame_sentinel_okay (get_current_frame ()),
+ regnum, src);
else
gdbarch_deprecated_pseudo_register_write (m_descr->gdbarch, this, regnum,
src.data ());
diff --git a/gdb/value.c b/gdb/value.c
index 27a79dc62fc1..51dca972a587 100644
--- a/gdb/value.c
+++ b/gdb/value.c
@@ -4057,6 +4057,22 @@ pseudo_from_raw_part (frame_info_ptr next_frame, int pseudo_reg_num,

/* See value.h. */

+void
+pseudo_to_raw_part (frame_info_ptr next_frame,
+ gdb::array_view<const gdb_byte> pseudo_buf,
+ int raw_reg_num, int raw_offset)
+{
+ int raw_reg_size = register_size (get_frame_arch (next_frame), raw_reg_num);
+
+ /* When overflowing a register, put_frame_register_bytes writes to the
+ subsequent registers. We don't want that behavior here, so make sure
+ the write is wholly within register RAW_REG_NUM. */
+ gdb_assert (raw_offset + pseudo_buf.size () <= raw_reg_size);
+ put_frame_register_bytes (next_frame, raw_reg_num, raw_offset, pseudo_buf);
+}
+
+/* See value.h. */
+
value *
pseudo_from_concat_raw (frame_info_ptr next_frame, int pseudo_reg_num,
int raw_reg_1_num, int raw_reg_2_num)
@@ -4080,6 +4096,27 @@ pseudo_from_concat_raw (frame_info_ptr next_frame, int pseudo_reg_num,
return pseudo_reg_val;
}

+void
+pseudo_to_concat_raw (frame_info_ptr next_frame,
+ gdb::array_view<const gdb_byte> pseudo_buf,
+ int raw_reg_1_num, int raw_reg_2_num)
+{
+ int src_offset = 0;
+ gdbarch *arch = frame_unwind_arch (next_frame);
+
+ int raw_reg_1_size = register_size (arch, raw_reg_1_num);
+ put_frame_register_bytes (next_frame, raw_reg_1_num, 0,
+ pseudo_buf.slice (src_offset, raw_reg_1_size));
+ src_offset += raw_reg_1_size;
+
+ int raw_reg_2_size = register_size (arch, raw_reg_2_num);
+ put_frame_register_bytes (next_frame, raw_reg_2_num, 0,
+ pseudo_buf.slice (src_offset, raw_reg_2_size));
+ src_offset += raw_reg_2_size;
+
+ gdb_assert (src_offset == pseudo_buf.size ());
+}
+
/* See value.h. */

value *
@@ -4111,6 +4148,32 @@ pseudo_from_concat_raw (frame_info_ptr next_frame, int pseudo_reg_num,
return pseudo_reg_val;
}

+void
+pseudo_to_concat_raw (frame_info_ptr next_frame,
+ gdb::array_view<const gdb_byte> pseudo_buf,
+ int raw_reg_1_num, int raw_reg_2_num, int raw_reg_3_num)
+{
+ int src_offset = 0;
+ gdbarch *arch = frame_unwind_arch (next_frame);
+
+ int raw_reg_1_size = register_size (arch, raw_reg_1_num);
+ put_frame_register_bytes (next_frame, raw_reg_1_num, 0,
+ pseudo_buf.slice (src_offset, raw_reg_1_size));
+ src_offset += raw_reg_1_size;
+
+ int raw_reg_2_size = register_size (arch, raw_reg_2_num);
+ put_frame_register_bytes (next_frame, raw_reg_2_num, 0,
+ pseudo_buf.slice (src_offset, raw_reg_2_size));
+ src_offset += raw_reg_2_size;
+
+ int raw_reg_3_size = register_size (arch, raw_reg_3_num);
+ put_frame_register_bytes (next_frame, raw_reg_3_num, 0,
+ pseudo_buf.slice (src_offset, raw_reg_3_size));
+ src_offset += raw_reg_3_size;
+
+ gdb_assert (src_offset == pseudo_buf.size ());
+}
+
/* Implementation of the convenience function $_isvoid. */

static struct value *
diff --git a/gdb/value.h b/gdb/value.h
index b5c097ad58bf..6a74d4e2c2ee 100644
--- a/gdb/value.h
+++ b/gdb/value.h
@@ -1661,6 +1661,13 @@ struct scoped_array_length_limiting
value *pseudo_from_raw_part (frame_info_ptr next_frame, int pseudo_reg_num,
int raw_reg_num, int raw_offset);

+/* Write PSEUDO_BUF, the contents of a pseudo register, to part of raw register
+ RAW_REG_NUM starting at RAW_OFFSET. */
+
+void pseudo_to_raw_part (frame_info_ptr this_frame,
+ gdb::array_view<const gdb_byte> pseudo_buf,
+ int raw_reg_num, int raw_offset);
+
/* Create a value for pseudo register PSEUDO_REG_NUM by concatenating raw
registers RAW_REG_1_NUM and RAW_REG_2_NUM.

@@ -1670,10 +1677,25 @@ value *pseudo_from_raw_part (frame_info_ptr next_frame, int pseudo_reg_num,
value *pseudo_from_concat_raw (frame_info_ptr next_frame, int pseudo_reg_num,
int raw_reg_1_num, int raw_reg_2_num);

+/* Write PSEUDO_BUF, the contents of a pseudo register, to the two raw registers
+ RAW_REG_1_NUM and RAW_REG_2_NUM. */
+
+void pseudo_to_concat_raw (frame_info_ptr this_frame,
+ gdb::array_view<const gdb_byte> pseudo_buf,
+ int raw_reg_1_num, int raw_reg_2_num);
+
/* Same as the above, but with three raw registers. */

value *pseudo_from_concat_raw (frame_info_ptr next_frame, int pseudo_reg_num,
int raw_reg_1_num, int raw_reg_2_num,
int raw_reg_3_num);

+/* Write PSEUDO_BUF, the contents of a pseudo register, to the tthreewo raw
+ registers RAW_REG_1_NUM, RAW_REG_2_NUM and RAW_REG_3_NUM. */
+
+void pseudo_to_concat_raw (frame_info_ptr this_frame,
+ gdb::array_view<const gdb_byte> pseudo_buf,
+ int raw_reg_1_num, int raw_reg_2_num,
+ int raw_reg_3_num);
+
#endif /* !defined (VALUE_H) */
--
2.42.1