Return target_xfer_status in to_xfer_partial

This patch does the conversion of to_xfer_partial from

    LONGEST (*to_xfer_partial) (struct target_ops *ops,
				enum target_object object, const char *annex,
				gdb_byte *readbuf, const gdb_byte *writebuf,
				ULONGEST offset, ULONGEST len);

to

    enum target_xfer_status (*to_xfer_partial) (struct target_ops *ops,
				enum target_object object, const char *annex,
				gdb_byte *readbuf, const gdb_byte *writebuf,
				ULONGEST offset, ULONGEST len, ULONGEST *xfered_len);

It changes to_xfer_partial return the transfer status and the transfered
length by *XFERED_LEN.  Generally, the return status has three stats,

 - TARGET_XFER_OK,
 - TARGET_XFER_EOF,
 - TARGET_XFER_E_XXXX,

See the comments to them in 'enum target_xfer_status'.  Note that
Pedro suggested not name TARGET_XFER_DONE, as it is confusing,
compared with "TARGET_XFER_OK".  We finally name it TARGET_XFER_EOF.

With this change, GDB core can handle unavailable data in a convenient
way.

The rationale behind this change was mentioned here
https://sourceware.org/ml/gdb-patches/2013-10/msg00761.html

Consider an object/value like this:

  0          100      150        200           512
  DDDDDDDDDDDxxxxxxxxxDDDDDD...DDIIIIIIIIIIII..III

where D is valid data, and xxx is unavailable data, and I is beyond
the end of the object (Invalid).  Currently, if we start the
xfer at 0, requesting, say 512 bytes, we'll first get back 100 bytes.
The xfer machinery then retries fetching [100,512), and gets back
TARGET_XFER_E_UNAVAILABLE.  That's sufficient when you're either
interested in either having the whole of the 512 bytes available,
or erroring out.  But, in this scenario, we're interested in
the data at [150,512).  The problem is that the last
TARGET_XFER_E_UNAVAILABLE gives us no indication where to
start the read next.  We'd need something like:

get me [0,512) >>>
     <<< here's [0,100), *xfered_len is 100, returns TARGET_XFER_OK

get me [100,512)  >>> (**1)
     <<< [100,150) is unavailable, *xfered_len is 50, return TARGET_XFER_E_UNAVAILABLE.

get me [150,512) >>>
     <<< here's [150,200), *xfered_len is 50, return TARGET_XFER_OK.

get me [200,512) >>>
     <<< no more data, return TARGET_XFER_EOF.

This naturally implies pushing down the decision of whether
to return TARGET_XFER_E_UNAVAILABLE or something else
down to the target.  (Which kinds of leads back to tfile
itself reading from RO memory from file (though we could
export a function in exec.c for that that tfile delegates to,
instead of re-adding the old code).

Beside this change, we also add a macro TARGET_XFER_STATUS_ERROR_P to
check whether a status is an error or not, to stop using "status < 0".
This patch also eliminates the comparison between status and 0.

No target implementations to to_xfer_partial adapts this new
interface.  The interface still behaves as before.

gdb:

2014-02-11  Yao Qi  <yao@codesourcery.com>

	* target.h (enum target_xfer_error): Rename to ...
	(enum target_xfer_status): ... it.  New.  All users updated.
	(enum target_xfer_status) <TARGET_XFER_OK>, <TARGET_XFER_EOF>:
	New.
	(TARGET_XFER_STATUS_ERROR_P): New macro.
	(target_xfer_error_to_string): Remove declaration.
	(target_xfer_status_to_string): Declare.
	(target_xfer_partial_ftype): Adjust it.
	(struct target_ops) <to_xfer_partial>: Return
	target_xfer_status.  Add argument xfered_len.  Update
	comments.
	* target.c (target_xfer_error_to_string): Rename to ...
	(target_xfer_status_to_string): ... it.  New.  All callers
	updated.
	(target_read_live_memory): Likewise.  Call target_xfer_partial
	instead of target_read.
	(memory_xfer_live_readonly_partial): Return
	target_xfer_status.  Add argument xfered_len.
	(raw_memory_xfer_partial): Likewise.
	(memory_xfer_partial_1): Likewise.
	(memory_xfer_partial): Likewise.
	(target_xfer_partial): Likewise.  Check *XFERED_LEN is set
	properly.  Update debug message.
	(default_xfer_partial, current_xfer_partial): Likewise.
	(target_write_partial): Likewise.
	(target_read_partial): Likewise.  All callers updated.
	(read_whatever_is_readable): Likewise.
	(target_write_with_progress): Likewise.
	(target_read_alloc_1): Likewise.

	* aix-thread.c (aix_thread_xfer_partial): Likewise.
	* auxv.c (procfs_xfer_auxv): Likewise.
	(ld_so_xfer_auxv, memory_xfer_auxv): Likewise.
	* bfd-target.c (target_bfd_xfer_partial): Likewise.
	* bsd-kvm.c (bsd_kvm_xfer_partial): Likewise.
	* bsd-uthread.c (bsd_uthread_xfer_partia): Likewise.
	* corefile.c (read_memory): Adjust.
	* corelow.c (core_xfer_partial): Likewise.
	* ctf.c (ctf_xfer_partial): Likewise.
	* darwin-nat.c (darwin_read_dyld_info): Likewise.  All callers
	updated.
	(darwin_xfer_partial): Likewise.
	* exec.c (section_table_xfer_memory_partial): Likewise.  All
	callers updated.
	(exec_xfer_partial): Likewise.
	* exec.h (section_table_xfer_memory_partial): Update
	declaration.
	* gnu-nat.c (gnu_xfer_memory): Likewise.  Assert 'res' is not
	negative.
	(gnu_xfer_partial): Likewise.
	* ia64-hpux-nat.c (ia64_hpux_xfer_memory_no_bs): Likewise.
	(ia64_hpux_xfer_memory, ia64_hpux_xfer_uregs): Likewise.
	(ia64_hpux_xfer_solib_got): Likewise.
	* inf-ptrace.c (inf_ptrace_xfer_partial): Likewise.  Change
	type of 'partial_len' to ULONGEST.
	* inf-ttrace.c (inf_ttrace_xfer_partial): Likewise.
	* linux-nat.c (linux_xfer_siginfo ): Likewise.
	(linux_nat_xfer_partial): Likewise.
	(linux_proc_xfer_partial, linux_xfer_partial): Likewise.
	(linux_proc_xfer_spu, linux_nat_xfer_osdata): Likewise.
	* monitor.c (monitor_xfer_memory): Likewise.
	(monitor_xfer_partial): Likewise.
	* procfs.c (procfs_xfer_partial): Likewise.
	* record-btrace.c (record_btrace_xfer_partial): Likewise.
	* record-full.c (record_full_xfer_partial): Likewise.
	(record_full_core_xfer_partial): Likewise.
	* remote-sim.c (gdbsim_xfer_memory): Likewise.
	(gdbsim_xfer_partial): Likewise.
	* remote.c (remote_write_bytes_aux): Likewise.  All callers
	updated.
	(remote_write_bytes, remote_read_bytes): Likewise.  All
	callers updated.
	(remote_flash_erase): Likewise.  All callers updated.
	(remote_write_qxfer): Likewise.  All callers updated.
	(remote_read_qxfer): Likewise.  All callers updated.
	(remote_xfer_partial): Likewise.
	* rs6000-nat.c (rs6000_xfer_partial): Likewise.
	(rs6000_xfer_shared_libraries): Likewise.
	* sol-thread.c (sol_thread_xfer_partial): Likewise.
	(sol_thread_xfer_partial): Likewise.
	* sparc-nat.c (sparc_xfer_wcookie): Likewise.
	(sparc_xfer_partial): Likewise.
	* spu-linux-nat.c (spu_proc_xfer_spu): Likewise.  All callers
	updated.
	(spu_xfer_partial): Likewise.
	* spu-multiarch.c (spu_xfer_partial): Likewise.
	* tracepoint.c (tfile_xfer_partial): Likewise.
	* windows-nat.c (windows_xfer_memory): Likewise.
	(windows_xfer_shared_libraries): Likewise.
	(windows_xfer_partial): Likewise.
	* valprint.c: Replace 'target_xfer_error' with
	'target_xfer_status' in comments.

1 files changed, 33 insertions, 25 deletions

diff --git a/gdb/ia64-hpux-nat.c b/gdb/ia64-hpux-nat.c
index b783c99..9e6516d 100644
--- a/gdb/ia64-hpux-nat.c
+++ b/gdb/ia64-hpux-nat.c
@@ -342,10 +342,11 @@ static target_xfer_partial_ftype *super_xfer_partial;
 /* The "xfer_partial" routine for a memory region that is completely
    outside of the backing-store region.  */
 
-static LONGEST
+static enum target_xfer_status
 ia64_hpux_xfer_memory_no_bs (struct target_ops *ops, const char *annex,
 			     gdb_byte *readbuf, const gdb_byte *writebuf,
-			     CORE_ADDR addr, LONGEST len)
+			     CORE_ADDR addr, LONGEST len,
+			     ULONGEST *xfered_len)
 {
   /* Memory writes need to be aligned on 16byte boundaries, at least
      when writing in the text section.  On the other hand, the size
@@ -367,17 +368,17 @@ ia64_hpux_xfer_memory_no_bs (struct target_ops *ops, const char *annex,
 				   NULL /* write */,
 				   aligned_addr, addr - aligned_addr);
       if (status <= 0)
-	return 0;
+	return TARGET_XFER_EOF;
       memcpy (aligned_buf + (addr - aligned_addr), writebuf, len);
 
       return super_xfer_partial (ops, TARGET_OBJECT_MEMORY, annex,
 				 NULL /* read */, aligned_buf /* write */,
-				 aligned_addr, aligned_len);
+				 aligned_addr, aligned_len, xfered_len);
     }
   else
     /* Memory read or properly aligned memory write.  */
     return super_xfer_partial (ops, TARGET_OBJECT_MEMORY, annex, readbuf,
-			       writebuf, addr, len);
+			       writebuf, addr, len, xfered_len);
 }
 
 /* Read LEN bytes at ADDR from memory, and store it in BUF.  This memory
@@ -517,10 +518,10 @@ ia64_hpux_get_register_from_save_state_t (int regnum, int reg_size)
 /* The "xfer_partial" target_ops routine for ia64-hpux, in the case
    where the requested object is TARGET_OBJECT_MEMORY.  */
 
-static LONGEST
+static enum target_xfer_status
 ia64_hpux_xfer_memory (struct target_ops *ops, const char *annex,
 		       gdb_byte *readbuf, const gdb_byte *writebuf,
-		       CORE_ADDR addr, ULONGEST len)
+		       CORE_ADDR addr, ULONGEST len, ULONGEST *xfered_len)
 {
   CORE_ADDR bsp, bspstore;
   CORE_ADDR start_addr, short_len;
@@ -563,7 +564,7 @@ ia64_hpux_xfer_memory (struct target_ops *ops, const char *annex,
       status = ia64_hpux_xfer_memory_no_bs (ops, annex, readbuf, writebuf,
 					    addr, short_len);
       if (status <= 0)
-        return 0;
+        return TARGET_XFER_EOF;
     }
 
   /* 2. Memory region after BSP.  */
@@ -581,7 +582,7 @@ ia64_hpux_xfer_memory (struct target_ops *ops, const char *annex,
 		 writebuf ? writebuf + (start_addr - addr) : NULL,
 		 start_addr, short_len);
       if (status <= 0)
-	return 0;
+	return TARGET_XFER_EOF;
     }
 
   /* 3. Memory region between BSPSTORE and BSP.  */
@@ -606,10 +607,11 @@ ia64_hpux_xfer_memory (struct target_ops *ops, const char *annex,
 		  writebuf ? writebuf + (start_addr - addr) : NULL,
 		  start_addr, short_len);
       if (status < 0)
-	return 0;
+	return TARGET_XFER_EOF;
     }
 
-  return len;
+  *xfered_len = len;
+  return TARGET_XFER_OK;
 }
 
 /* Handle the transfer of TARGET_OBJECT_HPUX_UREGS objects on ia64-hpux.
@@ -619,10 +621,10 @@ ia64_hpux_xfer_memory (struct target_ops *ops, const char *annex,
    we do not currently do not need these transfers), and will raise
    a failed assertion if WRITEBUF is not NULL.  */
 
-static LONGEST
+static enum target_xfer_status
 ia64_hpux_xfer_uregs (struct target_ops *ops, const char *annex,
 		      gdb_byte *readbuf, const gdb_byte *writebuf,
-		      ULONGEST offset, LONGEST len)
+		      ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
 {
   int status;
 
@@ -631,7 +633,9 @@ ia64_hpux_xfer_uregs (struct target_ops *ops, const char *annex,
   status = ia64_hpux_read_register_from_save_state_t (offset, readbuf, len);
   if (status < 0)
     return TARGET_XFER_E_IO;
-  return len;
+
+  *xfered_len = (ULONGEST) len;
+  return TARGET_XFER_OK;
 }
 
 /* Handle the transfer of TARGET_OBJECT_HPUX_SOLIB_GOT objects on ia64-hpux.
@@ -640,10 +644,10 @@ ia64_hpux_xfer_uregs (struct target_ops *ops, const char *annex,
    we do not currently do not need these transfers), and will raise
    a failed assertion if WRITEBUF is not NULL.  */
 
-static LONGEST
+static enum target_xfer_status
 ia64_hpux_xfer_solib_got (struct target_ops *ops, const char *annex,
 			  gdb_byte *readbuf, const gdb_byte *writebuf,
-			  ULONGEST offset, ULONGEST len)
+			  ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
 {
   CORE_ADDR fun_addr;
   /* The linkage pointer.  We use a uint64_t to make sure that the size
@@ -656,7 +660,7 @@ ia64_hpux_xfer_solib_got (struct target_ops *ops, const char *annex,
   gdb_assert (writebuf == NULL);
 
   if (offset > sizeof (got))
-    return 0;
+    return TARGET_XFER_EOF;
 
   fun_addr = string_to_core_addr (annex);
   got = ia64_hpux_get_solib_linkage_addr (fun_addr);
@@ -665,28 +669,32 @@ ia64_hpux_xfer_solib_got (struct target_ops *ops, const char *annex,
     len = sizeof (got) - offset;
   memcpy (readbuf, &got + offset, len);
 
-  return len;
+  *xfered_len = (ULONGEST) len;
+  return TARGET_XFER_OK;
 }
 
 /* The "to_xfer_partial" target_ops routine for ia64-hpux.  */
 
-static LONGEST
+static enum target_xfer_status
 ia64_hpux_xfer_partial (struct target_ops *ops, enum target_object object,
 			const char *annex, gdb_byte *readbuf,
-			const gdb_byte *writebuf, ULONGEST offset, ULONGEST len)
+			const gdb_byte *writebuf, ULONGEST offset, ULONGEST len,
+			ULONGEST *xfered_len)
 {
-  LONGEST val;
+  enum target_xfer_status val;
 
   if (object == TARGET_OBJECT_MEMORY)
-    val = ia64_hpux_xfer_memory (ops, annex, readbuf, writebuf, offset, len);
+    val = ia64_hpux_xfer_memory (ops, annex, readbuf, writebuf, offset, len,
+				 xfered_len);
   else if (object == TARGET_OBJECT_HPUX_UREGS)
-    val = ia64_hpux_xfer_uregs (ops, annex, readbuf, writebuf, offset, len);
+    val = ia64_hpux_xfer_uregs (ops, annex, readbuf, writebuf, offset, len,
+				xfered_len);
   else if (object == TARGET_OBJECT_HPUX_SOLIB_GOT)
     val = ia64_hpux_xfer_solib_got (ops, annex, readbuf, writebuf, offset,
-				    len);
+				    len, xfered_len);
   else
     val = super_xfer_partial (ops, object, annex, readbuf, writebuf, offset,
-			      len);
+			      len, xfered_len);
 
   return val;
 }