bfd/riscv: prepare to handle bare metal core dump creation

When creating a core file GDB will call the function
elfcore_write_prstatus to write out the general purpose registers
along with the pid/tid for the thread (into a prstatus structure) and
the executable name and arguments (into a prpsinfo_t structure).

However, for a bare metal RISC-V tool chain the prstatus_t and
prpsinfo_t types are not defined so the elfcore_write_prstatus
function will return NULL, preventing core file creation.

This commit provides the `elf_backend_write_core_note' hook and uses
the provided function to write out the required information.

In order to keep changes in the non bare metal tools to a minimum, the
provided backend function will itself return NULL when the prstatus_t
or pspsinfo_t types are available, the consequence of this is that the
generic code in elfcore_write_prstatus will be used just as before.
But, when prstatus_t or prpsinfo_t is not available, the new backend
function will write out the information using predefined offsets.

This new functionality will be used by a later GDB commit that will
add bare metal core dumps for RISC-V.

bfd/ChangeLog:

	* elfnn-riscv.c (PRPSINFO_PR_FNAME_LENGTH): Define.
	(PRPSINFO_PR_PSARGS_LENGTH): Define.
	(riscv_write_core_note): New function.
	(riscv_elf_grok_psinfo): Make use of two new length defines.
	(elf_backend_write_core_note): Define.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 31d0714da2700eddae0ee9019392b05ae6d4b147..9e7f90e16253def5b505603e9a3294480df59459 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,12 @@
+2021-03-05  Craig Blackmore  <craig.blackmore@embecosm.com>
+           Andrew Burgess  <andrew.burgess@embecosm.com>
+
+       * elfnn-riscv.c (PRPSINFO_PR_FNAME_LENGTH): Define.
+       (PRPSINFO_PR_PSARGS_LENGTH): Define.
+       (riscv_write_core_note): New function.
+       (riscv_elf_grok_psinfo): Make use of two new length defines.
+       (elf_backend_write_core_note): Define.
+
 2021-03-05  Craig Blackmore  <craig.blackmore@embecosm.com>
            Andrew Burgess  <andrew.burgess@embecosm.com>
 

diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index ec8a3e73c8fb60dfe0f0c017cfaa17da7245206e..76d29b733321e130fd85bcc3162ab9eabfc68309 100644 (file)
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -4877,6 +4877,8 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
 # define PRPSINFO_OFFSET_PR_PID                16
 # define PRPSINFO_OFFSET_PR_FNAME      32
 # define PRPSINFO_OFFSET_PR_PSARGS     48
+# define PRPSINFO_PR_FNAME_LENGTH      16
+# define PRPSINFO_PR_PSARGS_LENGTH     80
 #else
 # define PRSTATUS_SIZE                 376
 # define PRSTATUS_OFFSET_PR_CURSIG     12
@@ -4887,8 +4889,83 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
 # define PRPSINFO_OFFSET_PR_PID                24
 # define PRPSINFO_OFFSET_PR_FNAME      40
 # define PRPSINFO_OFFSET_PR_PSARGS     56
+# define PRPSINFO_PR_FNAME_LENGTH      16
+# define PRPSINFO_PR_PSARGS_LENGTH     80
 #endif
 
+/* Write PRSTATUS and PRPSINFO note into core file.  This will be called
+   before the generic code in elf.c.  By checking the compiler defines we
+   only perform any action here if the generic code would otherwise not be
+   able to help us.  The intention is that bare metal core dumps (where the
+   prstatus_t and/or prpsinfo_t might not be available) will use this code,
+   while non bare metal tools will use the generic elf code.  */
+
+static char *
+riscv_write_core_note (bfd *abfd ATTRIBUTE_UNUSED,
+                       char *buf ATTRIBUTE_UNUSED,
+                       int *bufsiz ATTRIBUTE_UNUSED,
+                       int note_type ATTRIBUTE_UNUSED, ...)
+{
+  switch (note_type)
+    {
+    default:
+      return NULL;
+
+#if !defined (HAVE_PRPSINFO_T)
+    case NT_PRPSINFO:
+      {
+       char data[PRPSINFO_SIZE] ATTRIBUTE_NONSTRING;
+       va_list ap;
+
+       va_start (ap, note_type);
+       memset (data, 0, sizeof (data));
+       strncpy (data + PRPSINFO_OFFSET_PR_FNAME, va_arg (ap, const char *),
+                 PRPSINFO_PR_FNAME_LENGTH);
+#if GCC_VERSION == 8000 || GCC_VERSION == 8001
+       DIAGNOSTIC_PUSH;
+       /* GCC 8.0 and 8.1 warn about 80 equals destination size with
+          -Wstringop-truncation:
+          https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85643
+        */
+       DIAGNOSTIC_IGNORE_STRINGOP_TRUNCATION;
+#endif
+       strncpy (data + PRPSINFO_OFFSET_PR_PSARGS, va_arg (ap, const char *),
+                 PRPSINFO_PR_PSARGS_LENGTH);
+#if GCC_VERSION == 8000 || GCC_VERSION == 8001
+       DIAGNOSTIC_POP;
+#endif
+       va_end (ap);
+       return elfcore_write_note (abfd, buf, bufsiz,
+                                  "CORE", note_type, data, sizeof (data));
+      }
+#endif /* !HAVE_PRPSINFO_T */
+
+#if !defined (HAVE_PRSTATUS_T)
+    case NT_PRSTATUS:
+      {
+        char data[PRSTATUS_SIZE];
+        va_list ap;
+        long pid;
+        int cursig;
+        const void *greg;
+
+        va_start (ap, note_type);
+        memset (data, 0, sizeof(data));
+        pid = va_arg (ap, long);
+        bfd_put_32 (abfd, pid, data + PRSTATUS_OFFSET_PR_PID);
+        cursig = va_arg (ap, int);
+        bfd_put_16 (abfd, cursig, data + PRSTATUS_OFFSET_PR_CURSIG);
+        greg = va_arg (ap, const void *);
+        memcpy (data + PRSTATUS_OFFSET_PR_REG, greg,
+                PRSTATUS_SIZE - PRSTATUS_OFFSET_PR_REG - ARCH_SIZE / 8);
+        va_end (ap);
+        return elfcore_write_note (abfd, buf, bufsiz,
+                                   "CORE", note_type, data, sizeof (data));
+      }
+#endif /* !HAVE_PRSTATUS_T */
+    }
+}
+
 /* Support for core dump NOTE sections.  */
 
 static bfd_boolean
@@ -4930,11 +5007,13 @@ riscv_elf_grok_psinfo (bfd *abfd, Elf_Internal_Note *note)
 
        /* pr_fname */
        elf_tdata (abfd)->core->program = _bfd_elfcore_strndup
-         (abfd, note->descdata + PRPSINFO_OFFSET_PR_FNAME, 16);
+         (abfd, note->descdata + PRPSINFO_OFFSET_PR_FNAME,
+           PRPSINFO_PR_FNAME_LENGTH);
 
        /* pr_psargs */
        elf_tdata (abfd)->core->command = _bfd_elfcore_strndup
-         (abfd, note->descdata + PRPSINFO_OFFSET_PR_PSARGS, 80);
+         (abfd, note->descdata + PRPSINFO_OFFSET_PR_PSARGS,
+           PRPSINFO_PR_PSARGS_LENGTH);
        break;
     }
 
@@ -5003,6 +5082,7 @@ riscv_elf_obj_attrs_arg_type (int tag)
 #define elf_backend_grok_prstatus              riscv_elf_grok_prstatus
 #define elf_backend_grok_psinfo                        riscv_elf_grok_psinfo
 #define elf_backend_object_p                   riscv_elf_object_p
+#define elf_backend_write_core_note            riscv_write_core_note
 #define elf_info_to_howto_rel                  NULL
 #define elf_info_to_howto                      riscv_info_to_howto_rela
 #define bfd_elfNN_bfd_relax_section            _bfd_riscv_relax_section