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[binutils-gdb] Use partial register read/writes in transfer_regset


https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=8e7767e3f782c46451a548d708f5582669d7a6d7

commit 8e7767e3f782c46451a548d708f5582669d7a6d7
Author: Alan Hayward <alan.hayward@arm.com>
Date:   Wed Jun 20 18:19:05 2018 +0100

    Use partial register read/writes in transfer_regset
    
    This avoids assert failures when the register is bigger than the
    slot size. This happens on Aarch64 when truncating Z registers
    into an fpsimd structure. This can be triggered by running
    gdb command "generate-core-file".
    
    Also, when the register is smaller then the slot size, then
    zero pad when writing to the slot, and truncate when writing
    to the regcache. This happens on Aarch64 with the CPSR register.
    
    Continue to ensure registers are invalidated when both buffers
    are null.
    
    gdb/
    	* regcache.c (readable_regcache::read_part): Fix asserts.
    	(reg_buffer::raw_collect_part): New function.
    	(regcache::write_part): Fix asserts.
    	(reg_buffer::raw_supply_part): New function.
    	(regcache::transfer_regset_register): New helper function.
    	(regcache::transfer_regset): Call new functions.
    	(regcache_supply_regset): Use gdb_byte*.
    	(regcache::supply_regset): Likewise.
    	(regcache_collect_regset): Likewise.
    	(regcache::collect_regset): Likewise.
    	* regcache.h (reg_buffer::raw_collect_part): New declaration.
    	(reg_buffer::raw_supply_part): Likewise.
    	(regcache::transfer_regset_register): Likewise.
    	(regcache::transfer_regset): Use gdb_byte*.

Diff:
---
 gdb/ChangeLog  |  17 ++++++++
 gdb/regcache.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++----------
 gdb/regcache.h |  20 ++++++++-
 3 files changed, 142 insertions(+), 25 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index de9127f..9539c87 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,22 @@
 2018-06-22  Alan Hayward  <alan.hayward@arm.com>
 
+	* regcache.c (readable_regcache::read_part): Fix asserts.
+	(reg_buffer::raw_collect_part): New function.
+	(regcache::write_part): Fix asserts.
+	(reg_buffer::raw_supply_part): New function.
+	(regcache::transfer_regset_register): New helper function.
+	(regcache::transfer_regset): Call new functions.
+	(regcache_supply_regset): Use gdb_byte*.
+	(regcache::supply_regset): Likewise.
+	(regcache_collect_regset): Likewise.
+	(regcache::collect_regset): Likewise.
+	* regcache.h (reg_buffer::raw_collect_part): New declaration.
+	(reg_buffer::raw_supply_part): Likewise.
+	(regcache::transfer_regset_register): Likewise.
+	(regcache::transfer_regset): Use gdb_byte*.
+
+2018-06-22  Alan Hayward  <alan.hayward@arm.com>
+
 	* nat/aarch64-sve-linux-ptrace.h (HAS_SVE_STATE): Use &.
 
 2018-06-21  Pedro Alves  <palves@redhat.com>
diff --git a/gdb/regcache.c b/gdb/regcache.c
index 1bc4f0d..1e241de 100644
--- a/gdb/regcache.c
+++ b/gdb/regcache.c
@@ -801,7 +801,8 @@ readable_regcache::read_part (int regnum, int offset, int len,
   int reg_size = register_size (arch (), regnum);
 
   gdb_assert (out != NULL);
-  gdb_assert (offset >= 0 && len >= 0 && offset + len <= reg_size);
+  gdb_assert (offset >= 0 && offset <= reg_size);
+  gdb_assert (len >= 0 && offset + len <= reg_size);
 
   if (offset == 0 && len == 0)
     {
@@ -830,6 +831,36 @@ readable_regcache::read_part (int regnum, int offset, int len,
 
 /* See regcache.h.  */
 
+void
+reg_buffer::raw_collect_part (int regnum, int offset, int len,
+			      gdb_byte *out) const
+{
+  int reg_size = register_size (arch (), regnum);
+
+  gdb_assert (out != nullptr);
+  gdb_assert (offset >= 0 && offset <= reg_size);
+  gdb_assert (len >= 0 && offset + len <= reg_size);
+
+  if (offset == 0 && len == 0)
+    {
+      /* Nothing to do.  */
+      return;
+    }
+
+  if (offset == 0 && len == reg_size)
+    {
+      /* Collect the full register.  */
+      return raw_collect (regnum, out);
+    }
+
+  /* Read to buffer, then write out.  */
+  gdb_byte *reg = (gdb_byte *) alloca (reg_size);
+  raw_collect (regnum, reg);
+  memcpy (out, reg + offset, len);
+}
+
+/* See regcache.h.  */
+
 enum register_status
 regcache::write_part (int regnum, int offset, int len,
 		      const gdb_byte *in, bool is_raw)
@@ -837,7 +868,8 @@ regcache::write_part (int regnum, int offset, int len,
   int reg_size = register_size (arch (), regnum);
 
   gdb_assert (in != NULL);
-  gdb_assert (offset >= 0 && len >= 0 && offset + len <= reg_size);
+  gdb_assert (offset >= 0 && offset <= reg_size);
+  gdb_assert (len >= 0 && offset + len <= reg_size);
 
   if (offset == 0 && len == 0)
     {
@@ -868,6 +900,38 @@ regcache::write_part (int regnum, int offset, int len,
 
 /* See regcache.h.  */
 
+void
+reg_buffer::raw_supply_part (int regnum, int offset, int len,
+			     const gdb_byte *in)
+{
+  int reg_size = register_size (arch (), regnum);
+
+  gdb_assert (in != nullptr);
+  gdb_assert (offset >= 0 && offset <= reg_size);
+  gdb_assert (len >= 0 && offset + len <= reg_size);
+
+  if (offset == 0 && len == 0)
+    {
+      /* Nothing to do.  */
+      return;
+    }
+
+  if (offset == 0 && len == reg_size)
+    {
+      /* Supply the full register.  */
+      return raw_supply (regnum, in);
+    }
+
+  gdb_byte *reg = (gdb_byte *) alloca (reg_size);
+
+  /* Read existing value to buffer.  */
+  raw_collect (regnum, reg);
+
+  /* Write to buffer, then write out.  */
+  memcpy (reg + offset, in, len);
+  raw_supply (regnum, reg);
+}
+
 enum register_status
 readable_regcache::raw_read_part (int regnum, int offset, int len,
 				  gdb_byte *buf)
@@ -1006,15 +1070,43 @@ reg_buffer::raw_collect_integer (int regnum, gdb_byte *addr, int addr_len,
 			byte_order);
 }
 
-/* Transfer a single or all registers belonging to a certain register
-   set to or from a buffer.  This is the main worker function for
-   regcache_supply_regset and regcache_collect_regset.  */
+/* See regcache.h.  */
+
+void
+regcache::transfer_regset_register (struct regcache *out_regcache, int regnum,
+				    const gdb_byte *in_buf, gdb_byte *out_buf,
+				    int slot_size, int offs) const
+{
+  struct gdbarch *gdbarch = arch ();
+  int reg_size = std::min (register_size (gdbarch, regnum), slot_size);
+
+  /* Use part versions and reg_size to prevent possible buffer overflows when
+     accessing the regcache.  */
+
+  if (out_buf != nullptr)
+    {
+      raw_collect_part (regnum, 0, reg_size, out_buf + offs);
+
+      /* Ensure any additional space is cleared.  */
+      if (slot_size > reg_size)
+	memset (out_buf + offs + reg_size, 0, slot_size - reg_size);
+    }
+  else if (in_buf != nullptr)
+    out_regcache->raw_supply_part (regnum, 0, reg_size, in_buf + offs);
+  else
+    {
+      /* Invalidate the register.  */
+      out_regcache->raw_supply (regnum, nullptr);
+    }
+}
+
+/* See regcache.h.  */
 
 void
 regcache::transfer_regset (const struct regset *regset,
 			   struct regcache *out_regcache,
-			   int regnum, const void *in_buf,
-			   void *out_buf, size_t size) const
+			   int regnum, const gdb_byte *in_buf,
+			   gdb_byte *out_buf, size_t size) const
 {
   const struct regcache_map_entry *map;
   int offs = 0, count;
@@ -1040,12 +1132,8 @@ regcache::transfer_regset (const struct regset *regset,
 	    if (offs + slot_size > size)
 	      break;
 
-	    if (out_buf)
-	      raw_collect (regno, (gdb_byte *) out_buf + offs);
-	    else
-	      out_regcache->raw_supply (regno, in_buf
-					? (const gdb_byte *) in_buf + offs
-					: NULL);
+	    transfer_regset_register (out_regcache, regno, in_buf, out_buf,
+				      slot_size, offs);
 	  }
       else
 	{
@@ -1054,12 +1142,8 @@ regcache::transfer_regset (const struct regset *regset,
 	  if (offs + slot_size > size)
 	    return;
 
-	  if (out_buf)
-	    raw_collect (regnum, (gdb_byte *) out_buf + offs);
-	  else
-	    out_regcache->raw_supply (regnum, in_buf
-				      ? (const gdb_byte *) in_buf + offs
-				      : NULL);
+	  transfer_regset_register (out_regcache, regnum, in_buf, out_buf,
+				    slot_size, offs);
 	  return;
 	}
     }
@@ -1074,14 +1158,14 @@ regcache_supply_regset (const struct regset *regset,
 			struct regcache *regcache,
 			int regnum, const void *buf, size_t size)
 {
-  regcache->supply_regset (regset, regnum, buf, size);
+  regcache->supply_regset (regset, regnum, (const gdb_byte *) buf, size);
 }
 
 void
 regcache::supply_regset (const struct regset *regset,
 			 int regnum, const void *buf, size_t size)
 {
-  transfer_regset (regset, this, regnum, buf, NULL, size);
+  transfer_regset (regset, this, regnum, (const gdb_byte *) buf, nullptr, size);
 }
 
 /* Collect register REGNUM from REGCACHE to BUF, using the register
@@ -1093,14 +1177,14 @@ regcache_collect_regset (const struct regset *regset,
 			 const struct regcache *regcache,
 			 int regnum, void *buf, size_t size)
 {
-  regcache->collect_regset (regset, regnum, buf, size);
+  regcache->collect_regset (regset, regnum, (gdb_byte *) buf, size);
 }
 
 void
 regcache::collect_regset (const struct regset *regset,
 			 int regnum, void *buf, size_t size) const
 {
-  transfer_regset (regset, NULL, regnum, NULL, buf, size);
+  transfer_regset (regset, nullptr, regnum, nullptr, (gdb_byte *) buf, size);
 }
 
 /* See common/common-regcache.h.  */
diff --git a/gdb/regcache.h b/gdb/regcache.h
index 983137f..ea692f3 100644
--- a/gdb/regcache.h
+++ b/gdb/regcache.h
@@ -166,6 +166,10 @@ public:
   void raw_collect_integer (int regnum, gdb_byte *addr, int addr_len,
 			    bool is_signed) const;
 
+  /* Collect register REGNUM from REGCACHE, starting at OFFSET in register,
+     reading only LEN.  */
+  void raw_collect_part (int regnum, int offset, int len, gdb_byte *out) const;
+
   /* See common/common-regcache.h.  */
   void raw_supply (int regnum, const void *buf) override;
 
@@ -187,6 +191,10 @@ public:
      unavailable).  */
   void raw_supply_zeroed (int regnum);
 
+  /* Supply register REGNUM to REGCACHE, starting at OFFSET in register, writing
+     only LEN, without editing the rest of the register.  */
+  void raw_supply_part (int regnum, int offset, int len, const gdb_byte *in);
+
   void invalidate (int regnum);
 
   virtual ~reg_buffer () = default;
@@ -358,10 +366,18 @@ protected:
 
 private:
 
+  /* Helper function for transfer_regset.  Copies across a single register.  */
+  void transfer_regset_register (struct regcache *out_regcache, int regnum,
+				 const gdb_byte *in_buf, gdb_byte *out_buf,
+				 int slot_size, int offs) const;
+
+  /* Transfer a single or all registers belonging to a certain register
+     set to or from a buffer.  This is the main worker function for
+     regcache_supply_regset and regcache_collect_regset.  */
   void transfer_regset (const struct regset *regset,
 			struct regcache *out_regcache,
-			int regnum, const void *in_buf,
-			void *out_buf, size_t size) const;
+			int regnum, const gdb_byte *in_buf,
+			gdb_byte *out_buf, size_t size) const;
 
   /* Perform a partial register transfer using a read, modify, write
      operation.  */


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