[PATCH 11/15] Class reg_buffer_rw

Yao Qi
2017-12-01T10:48:41Z

jit.c uses the regcache in a slightly different way, the regcache dosn't
write through to target, but it has read and write methods. If I apply
regcache in record-full.c, it has the similar use pattern. This patch
adds a new class reg_buffer_rw, which is a register buffer, but can be
red and written.

Since jit.c doesn't want to write registers through to target, it uses
regcache as a readonly regcache (because only readonly regcache
disconnects from the target), but it adds a hole in regcache
(raw_set_cached_value) in order to modify a readonly regcache. This patch
fixes this hole completely.

regcache inherits reg_buffer_rw, and reg_buffer_rw inherits regcache_read.
The ideal design is that both reg_buffer_rw and regcache_read inherit
reg_buffer, and regcache inherit reg_buffer_rw and regcache_read (virtual
inheritance). I concern about the performance overhead of virtual
inheritance, so I don't do it in the patch.

gdb:

2017-11-28 Yao Qi <yao.qi@linaro.org>

* jit.c (struct jit_unwind_private) <regcache>: Change its type to
reg_buffer_rw *.
(jit_unwind_reg_set_impl): Call raw_supply.
(jit_frame_sniffer): Use reg_buffer_rw.
* record-full.c (record_full_core_regbuf): Change its type.
(record_full_core_open_1): Use reg_buffer_rw.
(record_full_close): Likewise.
(record_full_core_fetch_registers): Use regcache->raw_supply.
(record_full_core_store_registers): Likewise.
* regcache.c (regcache::get_register_status): Move it to
reg_buffer.
(regcache_raw_set_cached_value): Remove.
(regcache::raw_set_cached_value): Remove.
(regcache::raw_write): Call raw_supply.
(regcache::raw_supply): Move it to reg_buffer_rw.
* regcache.h (regcache_raw_set_cached_value): Remove.
(reg_buffer_rw): New class.
---
gdb/jit.c | 10 ++++------
gdb/record-full.c | 21 +++++++++------------
gdb/regcache.c | 32 +++++---------------------------
gdb/regcache.h | 42 ++++++++++++++++++++++++++----------------
4 files changed, 44 insertions(+), 61 deletions(-)

diff --git a/gdb/jit.c b/gdb/jit.c
index 36aaefc..602aec9 100644
--- a/gdb/jit.c
+++ b/gdb/jit.c
@@ -1097,7 +1097,7 @@ struct jit_unwind_private
{
/* Cached register values. See jit_frame_sniffer to see how this
works. */
- struct regcache *regcache;
+ reg_buffer_rw *regcache;

/* The frame being unwound. */
struct frame_info *this_frame;
@@ -1126,7 +1126,7 @@ jit_unwind_reg_set_impl (struct gdb_unwind_callbacks *cb, int dwarf_regnum,
return;
}

- regcache_raw_set_cached_value (priv->regcache, gdb_reg, value->value);
+ priv->regcache->raw_supply (gdb_reg, value->value);
value->free (value);
}

@@ -1188,7 +1188,6 @@ jit_frame_sniffer (const struct frame_unwind *self,
struct jit_unwind_private *priv_data;
struct gdb_unwind_callbacks callbacks;
struct gdb_reader_funcs *funcs;
- struct gdbarch *gdbarch;

callbacks.reg_get = jit_unwind_reg_get_impl;
callbacks.reg_set = jit_unwind_reg_set_impl;
@@ -1201,11 +1200,10 @@ jit_frame_sniffer (const struct frame_unwind *self,

gdb_assert (!*cache);

- gdbarch = get_frame_arch (this_frame);
-
*cache = XCNEW (struct jit_unwind_private);
priv_data = (struct jit_unwind_private *) *cache;
- priv_data->regcache = new regcache (gdbarch);
+ /* Take a snapshot of current regcache. */
+ priv_data->regcache = new reg_buffer_rw (get_frame_arch (this_frame), true);
priv_data->this_frame = this_frame;

callbacks.priv_data = priv_data;
diff --git a/gdb/record-full.c b/gdb/record-full.c
index ec6fc69..65a2bfb 100644
--- a/gdb/record-full.c
+++ b/gdb/record-full.c
@@ -168,7 +168,7 @@ struct record_full_core_buf_entry
};

/* Record buf with core target. */
-static gdb_byte *record_full_core_regbuf = NULL;
+static reg_buffer_rw *record_full_core_regbuf = NULL;
static struct target_section *record_full_core_start;
static struct target_section *record_full_core_end;
static struct record_full_core_buf_entry *record_full_core_buf_list = NULL;
@@ -780,16 +780,16 @@ record_full_core_open_1 (const char *name, int from_tty)

/* Get record_full_core_regbuf. */
target_fetch_registers (regcache, -1);
- record_full_core_regbuf = (gdb_byte *) xmalloc (MAX_REGISTER_SIZE * regnum);
+ record_full_core_regbuf = new reg_buffer_rw (regcache->arch (), false);
+
for (i = 0; i < regnum; i ++)
- regcache_raw_collect (regcache, i,
- record_full_core_regbuf + MAX_REGISTER_SIZE * i);
+ record_full_core_regbuf->raw_supply (i, *regcache);

/* Get record_full_core_start and record_full_core_end. */
if (build_section_table (core_bfd, &record_full_core_start,
&record_full_core_end))
{
- xfree (record_full_core_regbuf);
+ delete record_full_core_regbuf;
record_full_core_regbuf = NULL;
error (_("\"%s\": Can't find sections: %s"),
bfd_get_filename (core_bfd), bfd_errmsg (bfd_get_error ()));
@@ -871,7 +871,7 @@ record_full_close (struct target_ops *self)
/* Release record_full_core_regbuf. */
if (record_full_core_regbuf)
{
- xfree (record_full_core_regbuf);
+ delete record_full_core_regbuf;
record_full_core_regbuf = NULL;
}

@@ -2032,12 +2032,10 @@ record_full_core_fetch_registers (struct target_ops *ops,
int i;

for (i = 0; i < num; i ++)
- regcache_raw_supply (regcache, i,
- record_full_core_regbuf + MAX_REGISTER_SIZE * i);
+ regcache->raw_supply (i, *record_full_core_regbuf);
}
else
- regcache_raw_supply (regcache, regno,
- record_full_core_regbuf + MAX_REGISTER_SIZE * regno);
+ regcache->raw_supply (regno, *record_full_core_regbuf);
}

/* "to_prepare_to_store" method for prec over corefile. */
@@ -2056,8 +2054,7 @@ record_full_core_store_registers (struct target_ops *ops,
int regno)
{
if (record_full_gdb_operation_disable)
- regcache_raw_collect (regcache, regno,
- record_full_core_regbuf + MAX_REGISTER_SIZE * regno);
+ record_full_core_regbuf->raw_supply (regno, *regcache);
else
error (_("You can't do that without a process to debug."));
}
diff --git a/gdb/regcache.c b/gdb/regcache.c
index 4174a8c..9b5b02e 100644
--- a/gdb/regcache.c
+++ b/gdb/regcache.c
@@ -205,7 +205,7 @@ regcache::regcache (gdbarch *gdbarch, const address_space *aspace_,
/* The register buffers. A read-only register cache can hold the
full [0 .. gdbarch_num_regs + gdbarch_num_pseudo_regs) while a
read/write register cache can only hold [0 .. gdbarch_num_regs). */
- : regcache_read (gdbarch, readonly_p_),
+ : reg_buffer_rw (gdbarch, readonly_p_),
m_aspace (aspace_), m_readonly_p (readonly_p_)
{
m_ptid = minus_one_ptid;
@@ -353,13 +353,9 @@ regcache_register_status (const struct regcache *regcache, int regnum)
}

enum register_status
-regcache::get_register_status (int regnum) const
+reg_buffer::get_register_status (int regnum) const
{
- gdb_assert (regnum >= 0);
- if (m_readonly_p)
- gdb_assert (regnum < m_descr->nr_cooked_registers);
- else
- gdb_assert (regnum < num_raw_registers ());
+ assert_regnum (regnum);

return (enum register_status) m_register_status[regnum];
}
@@ -802,23 +798,6 @@ regcache_cooked_write_unsigned (struct regcache *regcache, int regnum,
regcache->cooked_write (regnum, val);
}

-/* See regcache.h. */
-
-void
-regcache_raw_set_cached_value (struct regcache *regcache, int regnum,
- const gdb_byte *buf)
-{
- regcache->raw_set_cached_value (regnum, buf);
-}
-
-void
-regcache::raw_set_cached_value (int regnum, const gdb_byte *buf)
-{
- memcpy (register_buffer (regnum), buf,
- m_descr->sizeof_register[regnum]);
- m_register_status[regnum] = REG_VALID;
-}
-
void
regcache_raw_write (struct regcache *regcache, int regnum,
const gdb_byte *buf)
@@ -848,7 +827,7 @@ regcache::raw_write (int regnum, const gdb_byte *buf)
return;

target_prepare_to_store (this);
- raw_set_cached_value (regnum, buf);
+ raw_supply (regnum, buf);

/* Invalidate the register after it is written, in case of a
failure. */
@@ -1024,13 +1003,12 @@ regcache_raw_supply (struct regcache *regcache, int regnum, const void *buf)
}

void
-regcache::raw_supply (int regnum, const void *buf)
+reg_buffer_rw::raw_supply (int regnum, const void *buf)
{
void *regbuf;
size_t size;

assert_regnum (regnum);
- gdb_assert (!m_readonly_p);

regbuf = register_buffer (regnum);
size = m_descr->sizeof_register[regnum];
diff --git a/gdb/regcache.h b/gdb/regcache.h
index bd91bc6..3de5d80 100644
--- a/gdb/regcache.h
+++ b/gdb/regcache.h
@@ -68,14 +68,6 @@ extern void regcache_raw_write_unsigned (struct regcache *regcache,
extern LONGEST regcache_raw_get_signed (struct regcache *regcache,
int regnum);

-/* Set a raw register's value in the regcache's buffer. Unlike
- regcache_raw_write, this is not write-through. The intention is
- allowing to change the buffer contents of a read-only regcache
- allocated with new. */
-
-extern void regcache_raw_set_cached_value
- (struct regcache *regcache, int regnum, const gdb_byte *buf);
-
/* Partial transfer of raw registers. These perform read, modify,
write style operations. The read variant returns the status of the
register. */
@@ -229,12 +221,13 @@ public:
/* Return regcache's architecture. */
gdbarch *arch () const;

+ enum register_status get_register_status (int regnum) const;
+
virtual ~reg_buffer ()
{
xfree (m_registers);
xfree (m_register_status);
}
-
protected:
/* Assert on the range of REGNUM. */
void assert_regnum (int regnum) const;
@@ -257,6 +250,7 @@ protected:
signed char *m_register_status;

friend class regcache;
+ friend class reg_buffer_rw;
};

class regcache_read : public reg_buffer
@@ -289,11 +283,33 @@ protected:
bool is_raw);
};

+/* Buffer of registers, can be red and written. */
+
+class reg_buffer_rw : public regcache_read
+{
+public:
+ reg_buffer_rw (gdbarch *gdbarch, bool has_pseudo)
+ : regcache_read (gdbarch, has_pseudo)
+ {}
+
+ void raw_supply (int regnum, const void *buf);
+
+ void raw_supply (int regnum, const reg_buffer &src)
+ {
+ raw_supply (regnum, src.register_buffer (regnum));
+ }
+
+ void raw_update (int regnum) override
+ {}
+
+ DISABLE_COPY_AND_ASSIGN (reg_buffer_rw);
+};
+
class regcache_readonly;

/* The register cache for storing raw register values. */

-class regcache : public regcache_read
+class regcache : public reg_buffer_rw
{
public:
regcache (gdbarch *gdbarch)
@@ -337,17 +353,11 @@ public:
void raw_collect_integer (int regnum, gdb_byte *addr, int addr_len,
bool is_signed) const;

- void raw_supply (int regnum, const void *buf);
-
void raw_supply_integer (int regnum, const gdb_byte *addr, int addr_len,
bool is_signed);

void raw_supply_zeroed (int regnum);

- enum register_status get_register_status (int regnum) const;
-
- void raw_set_cached_value (int regnum, const gdb_byte *buf);
-
void invalidate (int regnum);

void raw_write_part (int regnum, int offset, int len, const gdb_byte *buf);
--
1.9.1