[POWERPC] Editable kernel command-line in zImage binary.

zImage will set /chosen/bootargs (if it is otherwise empty) with the
contents of a buffer in the section "__builtin_cmdline".  This permits
tools to edit zImage binaries to set the command-line eventually
processed by vmlinux.

--
Signed-off-by: Michal Ostrowski <mostrows@watson.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 34 insertions, 0 deletions

diff --git a/arch/powerpc/boot/main.c b/arch/powerpc/boot/main.c
index 816446f0e497..b66634c9ea34 100644
--- a/arch/powerpc/boot/main.c
+++ b/arch/powerpc/boot/main.c
@@ -33,6 +33,14 @@ extern char _vmlinux_end[];
 extern char _initrd_start[];
 extern char _initrd_end[];
 
+/* A buffer that may be edited by tools operating on a zImage binary so as to
+ * edit the command line passed to vmlinux (by setting /chosen/bootargs).
+ * The buffer is put in it's own section so that tools may locate it easier.
+ */
+static char builtin_cmdline[512]
+        __attribute__((section("__builtin_cmdline")));
+
+
 struct addr_range {
         unsigned long addr;
         unsigned long size;
@@ -204,6 +212,23 @@ static int is_elf32(void *hdr)
         return 1;
 }
 
+void export_cmdline(void* chosen_handle)
+{
+        int len;
+        char cmdline[2] = { 0, 0 };
+
+        if (builtin_cmdline[0] == 0)
+                return;
+
+        len = getprop(chosen_handle, "bootargs", cmdline, sizeof(cmdline));
+        if (len > 0 && cmdline[0] != 0)
+                return;
+
+        setprop(chosen_handle, "bootargs", builtin_cmdline,
+                strlen(builtin_cmdline) + 1);
+}
+
+
 void start(unsigned long a1, unsigned long a2, void *promptr, void *sp)
 {
         int len;
@@ -289,6 +314,8 @@ void start(unsigned long a1, unsigned long a2, void *promptr, void *sp)
                 memmove((void *)vmlinux.addr,(void *)vmlinuz.addr,vmlinuz.size);
         }
 
+        export_cmdline(chosen_handle);
+
         /* Skip over the ELF header */
 #ifdef DEBUG
         printf("... skipping 0x%lx bytes of ELF header\n\r",
diff --git a/arch/powerpc/boot/prom.h b/arch/powerpc/boot/prom.h
index 3e2ddd4a5a81..a57b184c564f 100644
--- a/arch/powerpc/boot/prom.h
+++ b/arch/powerpc/boot/prom.h
@@ -31,4 +31,11 @@ static inline int getprop(void *phandle, const char *name,
         return call_prom("getprop", 4, 1, phandle, name, buf, buflen);
 }
 
+
+static inline int setprop(void *phandle, const char *name,
+                          void *buf, int buflen)
+{
+        return call_prom("setprop", 4, 1, phandle, name, buf, buflen);
+}
+
 #endif                          /* _PPC_BOOT_PROM_H_ */