From 9871dc5976ded0788d8fb69acd78f14e64751d2e Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Wed, 17 Aug 2022 17:22:52 -0700
Subject: Use PIOD_READ_CHERI_CAP to read memory capabilities from running
 processes.

---
 gdb/fbsd-nat.c | 23 +++++++++++++++++++++++
 gdb/fbsd-nat.h |  4 ++++
 2 files changed, 27 insertions(+)

diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c
index 9b2a7eda647..992c138aaac 100644
--- a/gdb/fbsd-nat.c
+++ b/gdb/fbsd-nat.c
@@ -54,6 +54,10 @@
 #define	PT_SETREGSET	43	/* Set a target register set */
 #endif
 
+#ifndef PIOD_READ_CHERI_CAP
+#define	PIOD_READ_CHERI_CAP	7	/* Read CHERI capabilities */
+#endif
+
 /* Return the name of a file that can be opened to get the symbols for
    the child process identified by PID.  */
 
@@ -1953,6 +1957,25 @@ fbsd_nat_target::supports_disable_randomization ()
 #endif
 }
 
+#if __has_feature(capabilities)
+gdb::byte_vector
+fbsd_nat_target::read_capability (CORE_ADDR addr)
+{
+  struct ptrace_io_desc piod;
+  gdb::byte_vector cap_vec (sizeof (uintcap_t) + 1);
+
+  piod.piod_op = PIOD_READ_CHERI_CAP;
+  piod.piod_offs = (void *) (uintptr_t) addr;
+  piod.piod_addr = cap_vec.data ();
+  piod.piod_len = cap_vec.size ();
+  if (ptrace (PT_IO, get_ptrace_pid (inferior_ptid), (PTRACE_TYPE_ARG3) &piod,
+	      0) == -1)
+    return {};
+
+  return cap_vec;
+}
+#endif
+
 /* See fbsd-nat.h.  */
 bool
 fbsd_nat_target::have_register_set (ptid_t ptid, int fetch_op, void *regs,
diff --git a/gdb/fbsd-nat.h b/gdb/fbsd-nat.h
index b74be75d66c..1fc42528a23 100644
--- a/gdb/fbsd-nat.h
+++ b/gdb/fbsd-nat.h
@@ -109,6 +109,10 @@ public:
 
   bool supports_disable_randomization () override;
 
+#if __has_feature(capabilities)
+  gdb::byte_vector read_capability (CORE_ADDR addr) override;
+#endif
+
   /* Methods meant to be overridden by arch-specific target
      classes.  */
 
-- 
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