Re: [PATCH 2/3] (patch 2/4, v2) [nto] Implement TARGET_OBJECT_AUXV.

[Aleksandar Ristovski <aristovski@qnx.com>]

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On 15-10-20 11:20 AM, Pedro Alves wrote:
> Does this result in any visible improvement?  I assume that
> at least, "info auxv" now works [1] [2].  It'd be really nice to have a
> blurb in the commit log mentioning what motivated this.

Yes, info auxv works on a live process. For the core I have other
patches that need to go in first, but the mechanism of getting auxv
remains the same; only determining initial stack changes.

I will add something to the commit log.
"Fix 'info auxv' for nto."


> 
> [1] - BTW, if you enable gdb.base/auxv.exp on NTO, does it pass?
> 

It fails since we have AT_* entries that are specific to nto, and get
printed as ??? which causes regex to not match. I have it patched
internally and print them out, but didn't think it would be acceptable
upstream.

(gdb) PASS: gdb.base/auxv.exp: continue
info auxv^M
3    AT_PHDR              Program headers for program    0x8048034^M
4    AT_PHENT             Size of program header entry   32^M
5    AT_PHNUM             Number of program headers      8^M
9    AT_ENTRY             Entry point of program         0x8048668^M
6    AT_PAGESZ            System page size               4096^M
7    AT_BASE              Base address of interpreter    0xb0300000^M
12   AT_EUID              Effective user ID              2050^M
13   AT_GID               Real group ID                  3221225482^M
47   ???                                                 0x8047f7d^M
WARNING: Unrecognized tag value: 47   ???
                  0x8047f7d^M

(gdb) FAIL: gdb.base/auxv.exp: info auxv on live process


> On 10/20/2015 03:28 PM, Aleksandar Ristovski wrote:
>> gdb/ChangeLog:
>>
>> 	* nto-procfs.c (sys/auxv.h): Include.
>> 	(procfs_xfer_partial): Implement TARGET_OBJECT_AUXV.
>> 	* gdb/nto-tdep.c (nto_read_auxv_from_initial_stack): New function.
>> 	* gdb/nto-tdep.h (nto_read_auxv_from_initial_stack): New declaration.
> 
> Drop the "gdb/" in the file paths.
> 

Ok, sorry. Used 'mklog' script and didn't remove gdb/.

>> @@ -885,6 +887,40 @@ procfs_xfer_partial (struct target_ops *ops, enum target_object object,
>>      {
...
>> +	  /* Similar as in the case of a core file, we read auxv from
>> +	     initial_stack.  */
> 
> Hmm, where's this "similar" you refer to?  AFAICS, for cores, BFD
> extracts it from the NT_AUVX note.

We don't dump it in the note, we dump initial stack page containing it.

> 
>> +	  initial_stack = procinfo.initial_stack;
>> +
>> +	  /* procfs is always 'self-hosted', no byte-order manipulation. */
> 
> Double-space after period.
> 

Ok.

> Otherwise looks OK.
> 

Attaching the patch with double-space fix and added "what was fixed" in
commit message.


Thank you,

Aleksandar Ristovski

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From 37c288bf9c2c945c63ab89eff6da459ee274c083 Mon Sep 17 00:00:00 2001
From: Aleksandar Ristovski <aristovski@qnx.com>
Date: Tue, 20 Oct 2015 10:01:04 -0400
Subject: [PATCH] [nto] Implement TARGET_OBJECT_AUXV.

Fix 'info auxv' for nto.

gdb/ChangeLog:

	* nto-procfs.c (sys/auxv.h): Include.
	(procfs_xfer_partial): Implement TARGET_OBJECT_AUXV.
	* nto-tdep.c (nto_read_auxv_from_initial_stack): New function.
	* nto-tdep.h (nto_read_auxv_from_initial_stack): New declaration.
---
 gdb/nto-procfs.c | 36 ++++++++++++++++++++++++
 gdb/nto-tdep.c   | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/nto-tdep.h   |  3 ++
 3 files changed, 122 insertions(+)

diff --git a/gdb/nto-procfs.c b/gdb/nto-procfs.c
index 264d88b..df8a344 100644
--- a/gdb/nto-procfs.c
+++ b/gdb/nto-procfs.c
@@ -30,6 +30,8 @@
 #include <sys/syspage.h>
 #include <dirent.h>
 #include <sys/netmgr.h>
+#include <sys/auxv.h>
+
 #include "gdbcore.h"
 #include "inferior.h"
 #include "target.h"
@@ -885,6 +887,40 @@ procfs_xfer_partial (struct target_ops *ops, enum target_object object,
     {
     case TARGET_OBJECT_MEMORY:
       return procfs_xfer_memory (readbuf, writebuf, offset, len, xfered_len);
+    case TARGET_OBJECT_AUXV:
+      if (readbuf != NULL)
+	{
+	  int err;
+	  CORE_ADDR initial_stack;
+	  debug_process_t procinfo;
+	  /* For 32-bit architecture, size of auxv_t is 8 bytes.  */
+	  const unsigned int sizeof_auxv_t = sizeof (auxv_t);
+	  const unsigned int sizeof_tempbuf = 20 * sizeof_auxv_t;
+	  int tempread;
+	  gdb_byte *const tempbuf = alloca (sizeof_tempbuf);
+
+	  if (tempbuf == NULL)
+	    return TARGET_XFER_E_IO;
+
+	  err = devctl (ctl_fd, DCMD_PROC_INFO, &procinfo,
+		        sizeof procinfo, 0);
+	  if (err != EOK)
+	    return TARGET_XFER_E_IO;
+
+	  /* Similar as in the case of a core file, we read auxv from
+	     initial_stack.  */
+	  initial_stack = procinfo.initial_stack;
+
+	  /* procfs is always 'self-hosted', no byte-order manipulation.  */
+	  tempread = nto_read_auxv_from_initial_stack (initial_stack, tempbuf,
+						       sizeof_tempbuf,
+						       sizeof (auxv_t));
+	  tempread = min (tempread, len) - offset;
+	  memcpy (readbuf, tempbuf + offset, tempread);
+	  *xfered_len = tempread;
+	  return tempread ? TARGET_XFER_OK : TARGET_XFER_EOF;
+	}
+	/* Fallthru */
     default:
       return ops->beneath->to_xfer_partial (ops->beneath, object, annex,
 					    readbuf, writebuf, offset, len,
diff --git a/gdb/nto-tdep.c b/gdb/nto-tdep.c
index 81ee7fb..62eb88a 100644
--- a/gdb/nto-tdep.c
+++ b/gdb/nto-tdep.c
@@ -394,3 +394,86 @@ nto_initialize_signals (void)
   signal_pass_update (SIGPHOTON, 1);
 #endif
 }
+
+/* Read AUXV from initial_stack.  */
+LONGEST
+nto_read_auxv_from_initial_stack (CORE_ADDR initial_stack, gdb_byte *readbuf,
+                                  LONGEST len, size_t sizeof_auxv_t)
+{
+  gdb_byte targ32[4]; /* For 32 bit target values.  */
+  gdb_byte targ64[8]; /* For 64 bit target values.  */
+  CORE_ADDR data_ofs = 0;
+  ULONGEST anint;
+  LONGEST len_read = 0;
+  gdb_byte *buff;
+  enum bfd_endian byte_order;
+  int ptr_size;
+
+  if (sizeof_auxv_t == 16)
+    ptr_size = 8;
+  else
+    ptr_size = 4;
+
+  /* Skip over argc, argv and envp... Comment from ldd.c:
+
+     The startup frame is set-up so that we have:
+     auxv
+     NULL
+     ...
+     envp2
+     envp1 <----- void *frame + (argc + 2) * sizeof(char *)
+     NULL
+     ...
+     argv2
+     argv1
+     argc  <------ void * frame
+
+     On entry to ldd, frame gives the address of argc on the stack.  */
+  /* Read argc. 4 bytes on both 64 and 32 bit arches and luckily little
+   * endian. So we just read first 4 bytes.  */
+  if (target_read_memory (initial_stack + data_ofs, targ32, 4) != 0)
+    return 0;
+
+  byte_order = gdbarch_byte_order (target_gdbarch ());
+
+  anint = extract_unsigned_integer (targ32, sizeof (targ32), byte_order);
+
+  /* Size of pointer is assumed to be 4 bytes (32 bit arch.) */
+  data_ofs += (anint + 2) * ptr_size; /* + 2 comes from argc itself and
+                                                NULL terminating pointer in
+                                                argv.  */
+
+  /* Now loop over env table:  */
+  anint = 0;
+  while (target_read_memory (initial_stack + data_ofs, targ64, ptr_size)
+         == 0)
+    {
+      if (extract_unsigned_integer (targ64, ptr_size, byte_order) == 0)
+	anint = 1; /* Keep looping until non-null entry is found.  */
+      else if (anint)
+	break;
+      data_ofs += ptr_size;
+    }
+  initial_stack += data_ofs;
+
+  memset (readbuf, 0, len);
+  buff = readbuf;
+  while (len_read <= len-sizeof_auxv_t)
+    {
+      if (target_read_memory (initial_stack + len_read, buff, sizeof_auxv_t)
+	  == 0)
+        {
+	  /* Both 32 and 64 bit structures have int as the first field.  */
+          const ULONGEST a_type
+	    = extract_unsigned_integer (buff, sizeof (targ32), byte_order);
+
+          if (a_type == AT_NULL)
+	    break;
+	  buff += sizeof_auxv_t;
+	  len_read += sizeof_auxv_t;
+        }
+      else
+        break;
+    }
+  return len_read;
+}
diff --git a/gdb/nto-tdep.h b/gdb/nto-tdep.h
index bd85d2a..d029f07 100644
--- a/gdb/nto-tdep.h
+++ b/gdb/nto-tdep.h
@@ -168,4 +168,7 @@ int nto_in_dynsym_resolve_code (CORE_ADDR pc);
 
 char *nto_extra_thread_info (struct target_ops *self, struct thread_info *);
 
+LONGEST nto_read_auxv_from_initial_stack (CORE_ADDR inital_stack,
+					  gdb_byte *readbuf,
+					  LONGEST len, size_t sizeof_auxv_t);
 #endif
-- 
1.9.1