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				commit 4b654465bfc3034c969d2d942c14b2cedfd3e3b6
				Author: John Baldwin <jhb@FreeBSD.org>
				Date: Wed Jun 28 12:50:56 2017 -0700

				Read signal information from FreeBSD core dumps.

				FreeBSD recently added a new ELF core note which dumps the entire LWP
				info structure (the same structure returned by the ptrace PT_LWPINFO
				operation) for each thread. The plan is for this note to eventually
				supplant the older "thrmisc" ELF core note as it contains more
				information and it permits new information to be exported via both
				ptrace() and core dumps using the same structure.

				For signal information, the implementation is similar to the native
				implementation for FreeBSD processes. The PL_FLAG_SI flag must be
				checked to determine if the embedded siginfo_t structure is valid, and
				if so it is transferred into the caller's buffer.

				gdb/ChangeLog:

				* fbsd-tdep.c (LWPINFO_OFFSET, LWPINFO_PL_FLAGS)
				(LWPINFO64_PL_SIGINFO, LWPINFO32_PL_SIGINFO, PL_FLAG_SI)
				(SIZE64_SIGINFO_T, SIZE32_SIGINFO_T, fbsd_core_xfer_siginfo): New.
				(fbsd_init_abi): Install gdbarch "core_xfer_siginfo" method.

				diff --git gdb/fbsd-tdep.c gdb/fbsd-tdep.c
				index 32df104208..6f30197a83 100644
				--- gdb/fbsd-tdep.c
				+++ gdb/fbsd-tdep.c
				@@ -30,6 +30,28 @@
				#include "fbsd-tdep.h"


				+/* FreeBSD kernels 12.0 and later include a copy of the
				+ 'ptrace_lwpinfo' structure returned by the PT_LWPINFO ptrace
				+ operation in an ELF core note (NT_FREEBSD_PTLWPINFO) for each LWP.
				+ The constants below define the offset of field members and flags in
				+ this structure used by methods in this file. Note that the
				+ 'ptrace_lwpinfo' struct in the note is preceded by a 4 byte integer
				+ containing the size of the structure. */
				+
				+#define LWPINFO_OFFSET 0x4
				+
				+/* Offsets in ptrace_lwpinfo. */
				+#define LWPINFO_PL_FLAGS 0x8
				+#define LWPINFO64_PL_SIGINFO 0x30
				+#define LWPINFO32_PL_SIGINFO 0x2c
				+
				+/* Flags in pl_flags. */
				+#define PL_FLAG_SI 0x20 /* siginfo is valid */
				+
				+/* Sizes of siginfo_t. */
				+#define SIZE64_SIGINFO_T 80
				+#define SIZE32_SIGINFO_T 64
				+
				static struct gdbarch_data *fbsd_gdbarch_data_handle;

				struct fbsd_gdbarch_data
				@@ -113,6 +135,51 @@ fbsd_core_thread_name (struct gdbarch gdbarch, struct thread_info thr)
				return NULL;
				}

				+/* Implement the "core_xfer_siginfo" gdbarch method. */
				+
				+static LONGEST
				+fbsd_core_xfer_siginfo (struct gdbarch gdbarch, gdb_byte readbuf,
				+ ULONGEST offset, ULONGEST len)
				+{
				+ size_t siginfo_size;
				+
				+ if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
				+ siginfo_size = SIZE32_SIGINFO_T;
				+ else
				+ siginfo_size = SIZE64_SIGINFO_T;
				+ if (offset > siginfo_size)
				+ return -1;
				+
				+ thread_section_name section_name (".note.freebsdcore.lwpinfo", inferior_ptid);
				+ asection *section = bfd_get_section_by_name (core_bfd, section_name.c_str ());
				+ if (section == NULL)
				+ return -1;
				+
				+ gdb_byte buf[4];
				+ if (!bfd_get_section_contents (core_bfd, section, buf,
				+ LWPINFO_OFFSET + LWPINFO_PL_FLAGS, 4))
				+ return -1;
				+
				+ int pl_flags = extract_signed_integer (buf, 4, gdbarch_byte_order (gdbarch));
				+ if (!(pl_flags & PL_FLAG_SI))
				+ return -1;
				+
				+ if (offset + len > siginfo_size)
				+ len = siginfo_size - offset;
				+
				+ ULONGEST siginfo_offset;
				+ if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
				+ siginfo_offset = LWPINFO_OFFSET + LWPINFO32_PL_SIGINFO;
				+ else
				+ siginfo_offset = LWPINFO_OFFSET + LWPINFO64_PL_SIGINFO;
				+
				+ if (!bfd_get_section_contents (core_bfd, section, readbuf,
				+ siginfo_offset + offset, len))
				+ return -1;
				+
				+ return len;
				+}
				+
				static int
				find_signalled_thread (struct thread_info info, void data)
				{
				@@ -447,6 +514,7 @@ fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
				{
				set_gdbarch_core_pid_to_str (gdbarch, fbsd_core_pid_to_str);
				set_gdbarch_core_thread_name (gdbarch, fbsd_core_thread_name);
				+ set_gdbarch_core_xfer_siginfo (gdbarch, fbsd_core_xfer_siginfo);
				set_gdbarch_make_corefile_notes (gdbarch, fbsd_make_corefile_notes);
				set_gdbarch_print_auxv_entry (gdbarch, fbsd_print_auxv_entry);
				set_gdbarch_get_siginfo_type (gdbarch, fbsd_get_siginfo_type);