gdbserver: pass osabi to GDB in target description

On a Windows machine I built gdbserver, configured for the target
'x86_64-w64-mingw32', then on a GNU/Linux machine I built GDB with
support for all target (--enable-targets=all).

On the Windows machine I start gdbserver with a small test binary:

  $ gdbserver 192.168.129.25:54321 C:\some\directory\executable.exe

On the GNU/Linux machine I start GDB without the test binary, and
connect to gdbserver.

As I have not given GDB the test binary, my expectation is that GDB
would connect to gdbserver and then download the file over the remote
protocol, but instead I was presented with this message:

  (gdb) target remote 192.168.129.25:54321
  Remote debugging using 192.168.129.25:54321
  warning: C:\some\directory\executable.exe: No such file or directory.
  0x00007ffa3e1e1741 in ?? ()
  (gdb)

What I found is that if I told GDB where to find the binary, like
this:

  (gdb) file target:C:/some/directory/executable.exe
  A program is being debugged already.
  Are you sure you want to change the file? (y or n) y
  Reading C:/some/directory/executable.exe from remote target...
  warning: File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead.
  Reading C:/some/directory/executable.exe from remote target...
  Reading symbols from target:C:/some/directory/executable.exe...
  (gdb)

then GDB would download the executable.

I eventually tracked the problem down to exec_file_find (solib.c).
The remote target was passing an absolute Windows filename (beginning
with "C:/" in this case), but in exec_file_find GDB was failing the
IS_TARGET_ABSOLUTE_PATH call, and so was treating the filename as
relative.

The IS_TARGET_ABSOLUTE_PATH call was failing because GDB thought that
the file system kind was "unix", and as the filename didn't start with
a "/" it assumed the filename was not absolute.

But I'm connecting to a Windows target, my 'target-file-system-kind'
was set to "auto", so should be figuring out that my file-system is
"dos-based".

Looking in effective_target_file_system_kind (filesystem.c), we find
that the logic of "auto" is delegated to the current gdbarch.  However
in windows-tdep.c we see:

  set_gdbarch_has_dos_based_file_system (gdbarch, 1);

So if we are using a Windows gdbarch we should have "dos-based"
filesystems.  What this means is that after connecting to the remote
target GDB has selected the wrong gdbarch.

What's happening is that the target description sent back by the
remote target only includes the x86-64 registers.  There's no
information about which OS we're on.  As a consequence, GDB picks the
first x86-64 gdbarch which can handle the provided register set, which
happens to be a GNU/Linux gdbarch.

And indeed, there doesn't appear to be anywhere in gdbserver that sets
the osabi on the target descriptions, though some target descriptions
do have their osabi set when the description is created, e.g. in:

  gdb/arch/amd64.c	- Sets GNU/Linux osabi when appropriate.
  gdb/arch/i386.c	- Likewise.
  gdb/arch/tic6x.c	- Always set GNU/Linux osabi.

Most target descriptions are created without an osabi, gdbserver does
nothing to fix this, and the description is returned to GDB without an
osabi included.

I propose that we always set the osabi name on the target descriptions
returned from gdbserver.  We could try to do this when the description
is first created, but that would mean passing extra flags into the
tdesc creation code (or just passing the osabi string in), and I don't
think that's really necessary.  If we consider the tdesc creation as
being about figuring out which registers are on the target, then it
makes sense that the osabi information is injected later.

So what I've done is require the osabi name to be passed to the
init_target_desc function.  This is called, I believe, for all
targets, in the gdbserver code.

Now when I connect to the Windows remote the target description
returned includes the osabi name.  With this extra information GDB
selects the correct gdbarch object, which means that GDB understands
the target has a "dos-based" file-system.  With that correct GDB
understands that the filename it was given is absolute, and so fetches
the file from the remote as we'd like.

Approved-By: Luis Machado <luis.machado@arm.com>
Approved-By: Simon Marchi <simon.marchi@efficios.com>

diff --git a/gdbserver/linux-aarch32-tdesc.cc b/gdbserver/linux-aarch32-tdesc.cc
index b8987752b9f8bab5e9a514f78ffcd0e9e843a1d5..441fe668e6a4a236b09a4dd22f45b172eb5f492c 100644 (file)
--- a/gdbserver/linux-aarch32-tdesc.cc
+++ b/gdbserver/linux-aarch32-tdesc.cc
@@ -34,7 +34,7 @@ aarch32_linux_read_description ()
       tdesc_aarch32 = aarch32_create_target_description (false);
 
       static const char *expedite_regs[] = { "r11", "sp", "pc", 0 };
-      init_target_desc (tdesc_aarch32, expedite_regs);
+      init_target_desc (tdesc_aarch32, expedite_regs, GDB_OSABI_LINUX);
     }
   return tdesc_aarch32;
 }

diff --git a/gdbserver/linux-aarch64-tdesc.cc b/gdbserver/linux-aarch64-tdesc.cc
index 31ec7854cc0bd1124ddb1c7954ee6f6964b2a134..39d5bccdce18aba294440e5ed73fc73582c5db71 100644 (file)
--- a/gdbserver/linux-aarch64-tdesc.cc
+++ b/gdbserver/linux-aarch64-tdesc.cc
@@ -67,7 +67,8 @@ aarch64_linux_read_description (const aarch64_features &features)
 
       expedited_registers.push_back (nullptr);
 
-      init_target_desc (tdesc, (const char **) expedited_registers.data ());
+      init_target_desc (tdesc, (const char **) expedited_registers.data (),
+                       GDB_OSABI_LINUX);
 
       tdesc_aarch64_map[features] = tdesc;
     }

diff --git a/gdbserver/linux-arc-low.cc b/gdbserver/linux-arc-low.cc
index 1bcaf6c3f91118fbe8262173a33d26b28038900d..16d8d5824aa2f075f9d7920d48d121ddcbb84466 100644 (file)
--- a/gdbserver/linux-arc-low.cc
+++ b/gdbserver/linux-arc-low.cc
@@ -114,7 +114,7 @@ arc_linux_read_description (void)
   target_desc_up tdesc = arc_create_target_description (features);
 
   static const char *expedite_regs[] = { "sp", "status32", nullptr };
-  init_target_desc (tdesc.get (), expedite_regs);
+  init_target_desc (tdesc.get (), expedite_regs, GDB_OSABI_LINUX);
 
   return tdesc.release ();
 }

diff --git a/gdbserver/linux-arm-tdesc.cc b/gdbserver/linux-arm-tdesc.cc
index 559f9b0f3dc34fca09e64dede98d90784ac830a9..fff2e948f81f4b40e4cfec86e7ad07bf2a1d5199 100644 (file)
--- a/gdbserver/linux-arm-tdesc.cc
+++ b/gdbserver/linux-arm-tdesc.cc
@@ -37,7 +37,7 @@ arm_linux_read_description (arm_fp_type fp_type)
       tdesc = arm_create_target_description (fp_type, false);
 
       static const char *expedite_regs[] = { "r11", "sp", "pc", 0 };
-      init_target_desc (tdesc, expedite_regs);
+      init_target_desc (tdesc, expedite_regs, GDB_OSABI_LINUX);
 
       tdesc_arm_list[fp_type] = tdesc;
     }

diff --git a/gdbserver/linux-csky-low.cc b/gdbserver/linux-csky-low.cc
index 2eb5a2df17b9e6a5c58dcca714716b74cb5cd077..18a0d152b5ae9b27446675d37c2123b8e7169bc6 100644 (file)
--- a/gdbserver/linux-csky-low.cc
+++ b/gdbserver/linux-csky-low.cc
@@ -133,7 +133,7 @@ csky_target::low_arch_setup ()
 
   if (tdesc->expedite_regs.empty ())
     {
-      init_target_desc (tdesc.get (), expedite_regs);
+      init_target_desc (tdesc.get (), expedite_regs, GDB_OSABI_LINUX);
       gdb_assert (!tdesc->expedite_regs.empty ());
     }
 

diff --git a/gdbserver/linux-loongarch-low.cc b/gdbserver/linux-loongarch-low.cc
index 584ea64a7d95a4391758e850140274b05b0ef39c..cf7d6c0743cb16a2f032d418eb2600cb4cb48ed9 100644 (file)
--- a/gdbserver/linux-loongarch-low.cc
+++ b/gdbserver/linux-loongarch-low.cc
@@ -85,7 +85,7 @@ loongarch_target::low_arch_setup ()
 
   if (tdesc->expedite_regs.empty ())
     {
-      init_target_desc (tdesc.get (), expedite_regs);
+      init_target_desc (tdesc.get (), expedite_regs, GDB_OSABI_LINUX);
       gdb_assert (!tdesc->expedite_regs.empty ());
     }
   current_process ()->tdesc = tdesc.release ();

diff --git a/gdbserver/linux-riscv-low.cc b/gdbserver/linux-riscv-low.cc
index c4554c507a8c658612e295544465c076d33fa363..7170ad9922ef20d9fcbe0ab5e3c66b245d974a72 100644 (file)
--- a/gdbserver/linux-riscv-low.cc
+++ b/gdbserver/linux-riscv-low.cc
@@ -91,7 +91,7 @@ riscv_target::low_arch_setup ()
 
   if (tdesc->expedite_regs.empty ())
     {
-      init_target_desc (tdesc.get (), expedite_regs);
+      init_target_desc (tdesc.get (), expedite_regs, GDB_OSABI_LINUX);
       gdb_assert (!tdesc->expedite_regs.empty ());
     }
 

diff --git a/gdbserver/linux-tic6x-low.cc b/gdbserver/linux-tic6x-low.cc
index 707be2e7b0f9843ffafb4627f63d2de43f908bc8..754dd00590c747ad20f7cf5b13d7d07a6fad5675 100644 (file)
--- a/gdbserver/linux-tic6x-low.cc
+++ b/gdbserver/linux-tic6x-low.cc
@@ -228,7 +228,7 @@ tic6x_read_description (enum c6x_feature feature)
     {
       *tdesc = tic6x_create_target_description (feature);
       static const char *expedite_regs[] = { "A15", "PC", NULL };
-      init_target_desc (*tdesc, expedite_regs);
+      init_target_desc (*tdesc, expedite_regs, GDB_OSABI_LINUX);
     }
 
   return *tdesc;

diff --git a/gdbserver/linux-x86-tdesc.cc b/gdbserver/linux-x86-tdesc.cc
index 13c80762605c658a4a6d0c1105eadf270cd7fb83..6aa5c4ab9705a7e6e7b1ef0a06cc7894536f6e77 100644 (file)
--- a/gdbserver/linux-x86-tdesc.cc
+++ b/gdbserver/linux-x86-tdesc.cc
@@ -26,10 +26,21 @@
 void
 x86_linux_post_init_tdesc (target_desc *tdesc, bool is_64bit)
 {
+  enum gdb_osabi osabi = GDB_OSABI_LINUX;
+
+#ifndef IN_PROCESS_AGENT
+  /* x86 target descriptions are created with the osabi already set.
+     However, init_target_desc requires us to override the already set
+     value.  That's fine, out new string should match the old one.  */
+  gdb_assert (tdesc_osabi_name (tdesc) != nullptr);
+  gdb_assert (strcmp (tdesc_osabi_name (tdesc),
+                     gdbarch_osabi_name (osabi)) == 0);
+#endif /* ! IN_PROCESS_AGENT */
+
 #ifdef __x86_64__
   if (is_64bit)
-    init_target_desc (tdesc, amd64_expedite_regs);
+    init_target_desc (tdesc, amd64_expedite_regs, osabi);
   else
 #endif
-    init_target_desc (tdesc, i386_expedite_regs);
+    init_target_desc (tdesc, i386_expedite_regs, osabi);
 }

diff --git a/gdbserver/netbsd-aarch64-low.cc b/gdbserver/netbsd-aarch64-low.cc
index f20a1a717733831e5af654fff108c79a784d7865..8834e0ad89406ea905cc4cd3af86134ec62b30b6 100644 (file)
--- a/gdbserver/netbsd-aarch64-low.cc
+++ b/gdbserver/netbsd-aarch64-low.cc
@@ -98,7 +98,7 @@ netbsd_aarch64_target::low_arch_setup ()
     = aarch64_create_target_description ({});
 
   static const char *expedite_regs_aarch64[] = { "x29", "sp", "pc", NULL };
-  init_target_desc (tdesc, expedite_regs_aarch64);
+  init_target_desc (tdesc, expedite_regs_aarch64, GDB_OSABI_NETBSD);
 
   current_process ()->tdesc = tdesc;
 }

diff --git a/gdbserver/netbsd-amd64-low.cc b/gdbserver/netbsd-amd64-low.cc
index b3f3aab5ec357876e0ea6b83d68bdaf0ef51fd52..ad7cb430b9208b625fdc705bd5159879df874b7f 100644 (file)
--- a/gdbserver/netbsd-amd64-low.cc
+++ b/gdbserver/netbsd-amd64-low.cc
@@ -193,7 +193,7 @@ netbsd_amd64_target::low_arch_setup ()
   target_desc *tdesc
     = amd64_create_target_description (X86_XSTATE_SSE_MASK, false, false, false);
 
-  init_target_desc (tdesc, amd64_expedite_regs);
+  init_target_desc (tdesc, amd64_expedite_regs, GDB_OSABI_NETBSD);
 
   current_process ()->tdesc = tdesc;
 }

diff --git a/gdbserver/netbsd-i386-low.cc b/gdbserver/netbsd-i386-low.cc
index 247a39797c41b267088a1798fe552ac6d886cdbc..ea6fce4c6f96728756bd15c8571c49f153e97f77 100644 (file)
--- a/gdbserver/netbsd-i386-low.cc
+++ b/gdbserver/netbsd-i386-low.cc
@@ -142,7 +142,7 @@ netbsd_i386_target::low_arch_setup ()
   target_desc *tdesc
     = i386_create_target_description (X86_XSTATE_SSE_MASK, false, false);
 
-  init_target_desc (tdesc, i386_expedite_regs);
+  init_target_desc (tdesc, i386_expedite_regs, GDB_OSABI_NETBSD);
 
   current_process ()->tdesc = tdesc;
 }

diff --git a/gdbserver/tdesc.cc b/gdbserver/tdesc.cc
index d052f43c76e69c6f47f40e124b08866de3b2ba40..da1287abbbed5933bf8ceddd4aa5d7a70ad4d473 100644 (file)
--- a/gdbserver/tdesc.cc
+++ b/gdbserver/tdesc.cc
@@ -53,7 +53,8 @@ void target_desc::accept (tdesc_element_visitor &v) const
 
 void
 init_target_desc (struct target_desc *tdesc,
-                 const char **expedite_regs)
+                 const char **expedite_regs,
+                 enum gdb_osabi osabi)
 {
   int offset = 0;
 
@@ -88,6 +89,8 @@ init_target_desc (struct target_desc *tdesc,
   int expedite_count = 0;
   while (expedite_regs[expedite_count] != nullptr)
     tdesc->expedite_regs.push_back (expedite_regs[expedite_count++]);
+
+  set_tdesc_osabi (tdesc, osabi);
 #endif
 }
 

diff --git a/gdbserver/tdesc.h b/gdbserver/tdesc.h
index 4796b50b4d137758ee36def867ec6530e04e8f2b..e6cefe5af3ed53c427a6edb324cbd2a2b9b1db55 100644 (file)
--- a/gdbserver/tdesc.h
+++ b/gdbserver/tdesc.h
@@ -81,10 +81,11 @@ void copy_target_description (struct target_desc *dest,
                              const struct target_desc *src);
 
 /* Initialize TDESC, and then set its expedite_regs field to
-   EXPEDITE_REGS.  */
+   EXPEDITE_REGS and its osabi to OSABI.  */
 
 void init_target_desc (struct target_desc *tdesc,
-                      const char **expedite_regs);
+                      const char **expedite_regs,
+                      enum gdb_osabi osabi);
 
 /* Return the current inferior's target description.  Never returns
    NULL.  */

diff --git a/gdbserver/win32-i386-low.cc b/gdbserver/win32-i386-low.cc
index 0a761ca58ef38d89844c931175c0f468e560f2cd..13f9aca99b12147aa57d8700ee1acc209401e454 100644 (file)
--- a/gdbserver/win32-i386-low.cc
+++ b/gdbserver/win32-i386-low.cc
@@ -596,12 +596,12 @@ i386_arch_setup (void)
 #ifdef __x86_64__
   tdesc = amd64_create_target_description (X86_XSTATE_SSE_MASK, false,
                                           false, false);
-  init_target_desc (tdesc, amd64_expedite_regs);
+  init_target_desc (tdesc, amd64_expedite_regs, WINDOWS_OSABI);
   win32_tdesc = tdesc;
 #endif
 
   tdesc = i386_create_target_description (X86_XSTATE_SSE_MASK, false, false);
-  init_target_desc (tdesc, i386_expedite_regs);
+  init_target_desc (tdesc, i386_expedite_regs, WINDOWS_OSABI);
 #ifdef __x86_64__
   wow64_win32_tdesc = tdesc;
 #else

diff --git a/gdbserver/win32-low.h b/gdbserver/win32-low.h
index ff997df0a66b351b0fe9a8fce5fc51d627e71bb2..daed16a6ae6a097ad4383c7ebe8b3cd3752b5eae 100644 (file)
--- a/gdbserver/win32-low.h
+++ b/gdbserver/win32-low.h
@@ -21,6 +21,7 @@
 
 #include <windows.h>
 #include "nat/windows-nat.h"
+#include "gdbsupport/osabi.h"
 
 struct target_desc;
 
@@ -31,6 +32,12 @@ extern const struct target_desc *win32_tdesc;
 extern const struct target_desc *wow64_win32_tdesc;
 #endif
 
+#ifdef __CYGWIN__
+constexpr enum gdb_osabi WINDOWS_OSABI = GDB_OSABI_CYGWIN;
+#else
+constexpr enum gdb_osabi WINDOWS_OSABI = GDB_OSABI_WINDOWS;
+#endif
+
 struct win32_target_ops
 {
   /* Architecture-specific setup.  */