[PATCH v2 09/11] gdbserver: define and use regcache::reset

Tankut Baris Aktemur
2024-12-30T10:58:45Z

Define a `reset` method for a regcache and use it for code
simplification. This patch allows further simplification in the next
patch.

The reset method fills the register data with zeroes. For the use in
get_thread_regcache, this is added behavior, making the patch not a
pure refactoring, and may look like extra overhead. However, it is
better to avoid having arbitrary values left in the data buffer.
Hence, it is considered a behavioral improvement.
---
gdbserver/regcache.cc | 30 ++++++++++++++++--------------
gdbserver/regcache.h | 4 ++++
2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/gdbserver/regcache.cc b/gdbserver/regcache.cc
index 03e975dc00154d01798765273534ca9cdcdc7eb7..7e1a722b0f80b9e5641bddfbbe95cbcf2b228df8 100644
--- a/gdbserver/regcache.cc
+++ b/gdbserver/regcache.cc
@@ -52,8 +52,7 @@ get_thread_regcache (thread_info *thread, bool fetch)

switch_to_thread (thread);
/* Invalidate all registers, to prevent stale left-overs. */
- memset (regcache->register_status, REG_UNKNOWN,
- regcache->tdesc->reg_defs.size ());
+ regcache->reset (REG_UNKNOWN);
fetch_inferior_registers (regcache, -1);
regcache->registers_fetched = true;
}
@@ -138,12 +137,11 @@ regcache::regcache (const target_desc *tdesc)
garbage. */
this->tdesc = tdesc;
this->registers
- = (unsigned char *) xcalloc (1, tdesc->registers_size);
+ = (unsigned char *) xmalloc (tdesc->registers_size);
this->registers_owned = true;
this->register_status
= (unsigned char *) xmalloc (tdesc->reg_defs.size ());
- memset ((void *) this->register_status, REG_UNKNOWN,
- tdesc->reg_defs.size ());
+ reset (REG_UNKNOWN);
}

regcache::~regcache ()
@@ -155,6 +153,18 @@ regcache::~regcache ()

#endif

+void
+regcache::reset (enum register_status status)
+{
+ /* Zero-initialize the register cache, in case there are registers
+ the target never fetches. This way they'll read as zero instead
+ of garbage. */
+ memset (this->registers, 0, this->tdesc->registers_size);
+#ifndef IN_PROCESS_AGENT
+ memset (this->register_status, status, this->tdesc->reg_defs.size ());
+#endif
+}
+
void
regcache::copy_from (regcache *src)
{
@@ -370,15 +380,7 @@ supply_regblock (struct regcache *regcache, const void *buf)
#endif
}
else
- {
- const struct target_desc *tdesc = regcache->tdesc;
-
- memset (regcache->registers, 0, tdesc->registers_size);
-#ifndef IN_PROCESS_AGENT
- for (int i = 0; i < tdesc->reg_defs.size (); i++)
- regcache->set_register_status (i, REG_UNAVAILABLE);
-#endif
- }
+ regcache->reset (REG_UNAVAILABLE);
}

#ifndef IN_PROCESS_AGENT
diff --git a/gdbserver/regcache.h b/gdbserver/regcache.h
index f3e99de443b884e13b02c8d858ea9e6ee668700f..b5a0b85982515dd545c6f79688ba7a4fd177b3d6 100644
--- a/gdbserver/regcache.h
+++ b/gdbserver/regcache.h
@@ -56,6 +56,10 @@ struct regcache : public reg_buffer_common

DISABLE_COPY_AND_ASSIGN (regcache);

+ /* Clear the register values to all zeros and set the register
+ statuses to STATUS. */
+ void reset (enum register_status status);
+
/* See gdbsupport/common-regcache.h. */
enum register_status get_register_status (int regnum) const override;

--
2.34.1

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