sandbox: Add a way to show the sandbox memory-mapping

This is mostly hidden in the background, but it is sometimes useful to
look at it. Add a function to allow this.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/cpu/cpu.c

@@ -253,6 +253,19 @@ phys_addr_t map_to_sysmem(const void *ptr)
 	return mentry->tag;
 }
 
+void sandbox_map_list(void)
+{
+	struct sandbox_mapmem_entry *mentry;
+	struct sandbox_state *state = state_get_current();
+
+	printf("Sandbox memory-mapping\n");
+	printf("%8s  %16s  %6s\n", "Addr", "Mapping", "Refcnt");
+	list_for_each_entry(mentry, &state->mapmem_head, sibling_node) {
+		printf("%8lx  %p  %6d\n", mentry->tag, mentry->ptr,
+		       mentry->refcnt);
+	}
+}
+
 unsigned long sandbox_read(const void *addr, enum sandboxio_size_t size)
 {
 	struct sandbox_state *state = state_get_current();

arch/sandbox/include/asm/cpu.h

@@ -8,4 +8,7 @@
 
 void cpu_sandbox_set_current(const char *name);
 
+/* show the mapping of sandbox addresses to pointers */
+void sandbox_map_list(void);
+
 #endif /* __SANDBOX_CPU_H */

cmd/sb.c

@@ -7,6 +7,7 @@
 #include <command.h>
 #include <dm.h>
 #include <spl.h>
+#include <asm/cpu.h>
 #include <asm/global_data.h>
 #include <asm/state.h>
 
@@ -29,6 +30,14 @@ static int do_sb_handoff(struct cmd_tbl *cmdtp, int flag, int argc,
 #endif
 }
 
+static int do_sb_map(struct cmd_tbl *cmdtp, int flag, int argc,
+		     char *const argv[])
+{
+	sandbox_map_list();
+
+	return 0;
+}
+
 static int do_sb_state(struct cmd_tbl *cmdtp, int flag, int argc,
 		       char *const argv[])
 {
@@ -42,8 +51,10 @@ static int do_sb_state(struct cmd_tbl *cmdtp, int flag, int argc,
 
 U_BOOT_LONGHELP(sb,
 	"handoff     - Show handoff data received from SPL\n"
+	"sb map         - Show mapped memory\n"
 	"sb state       - Show sandbox state");
 
 U_BOOT_CMD_WITH_SUBCMDS(sb, "Sandbox status commands", sb_help_text,
 	U_BOOT_SUBCMD_MKENT(handoff, 1, 1, do_sb_handoff),
+	U_BOOT_SUBCMD_MKENT(map, 1, 1, do_sb_map),
 	U_BOOT_SUBCMD_MKENT(state, 1, 1, do_sb_state));

doc/usage/cmd/sb.rst

@@ -12,6 +12,7 @@ Synopsis
 ::
 
     sb handoff
+    sb map
     sb state
 
 Description
@@ -26,6 +27,24 @@ sb handoff
 This shows information about any handoff information received from SPL. If
 U-Boot is started from an SPL build, it shows a valid magic number.
 
+sb map
+~~~~~~
+
+This shows any mappings between sandbox's emulated RAM and the underlying host
+address-space.
+
+Fields shown are:
+
+Addr
+    Address in emulated RAM
+
+Mapping
+    Equivalent address in the host address-space. While sandbox requests address
+    ``0x10000000`` from the OS, this is not always available.
+
+Refcnt
+    Shows the number of references to this mapping.
+
 sb state
 ~~~~~~~~
 
@@ -42,6 +61,12 @@ as ``sandbox_spl``::
     => sb handoff
     SPL handoff magic 14f93c7b
 
+This shows output from the *sb map* subcommand, with a single mapping::
+
+    Sandbox memory-mapping
+        Addr           Mapping  Refcnt
+    ff000000  000056185b46d6d0       2
+
 This shows output from the *sb state* subcommand::
 
     => sb state