Simplify the exported FindKernelConfig() function.

FindKernelConfig() is used to extract the kernel cmdline from a kernel
partition. It's only used in the chromeos-installer, but was a bit awkward.
This changes the calling parameters to make it simpler.

BUG=chromium:221544
BRANCH=none
TEST=manual
CQ-DEPEND=CL:46835

  FEATURES=test sudo emerge vboot_reference
  FEATURES=test emerge-$BOARD vboot_reference

Change-Id: Ib7192175d72ad51387d8d122ead4490a4aa62300
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/46834

3 files changed, 51 insertions, 27 deletions

diff --git a/utility/dump_kernel_config.c b/utility/dump_kernel_config.c
index 0a8e0279..e733a0d0 100644
--- a/utility/dump_kernel_config.c
+++ b/utility/dump_kernel_config.c
@@ -36,11 +36,9 @@ static int PrintHelp(void) {
 }
 
 int main(int argc, char* argv[]) {
-  uint8_t* blob;
-  size_t blob_size;
-  char* infile = NULL;
-  uint8_t *config = NULL;
-  uint64_t kernel_body_load_address = CROS_NO_ENTRY_ADDR;
+  char *infile = NULL;
+  char *config = NULL;
+  uint64_t kernel_body_load_address = USE_PREAMBLE_LOAD_ADDR;
   int parse_error = 0;
   char *e;
   int i;
@@ -82,22 +80,12 @@ int main(int argc, char* argv[]) {
     return 1;
   }
 
-  /* Map the kernel image blob. */
-  blob = MMapFile(infile, &blob_size);
-  if (!blob) {
-    VbExError("Error reading input file\n");
+  config = FindKernelConfig(infile, kernel_body_load_address);
+  if (!config)
     return 1;
-  }
 
-  config = FindKernelConfig(blob, (uint64_t)blob_size,
-                              kernel_body_load_address);
-  if (!config) {
-    VbExError("Error parsing input file\n");
-    munmap(blob, blob_size);
-    return 1;
-  }
+  printf("%s", config);
 
-  printf("%.*s", CROS_CONFIG_SIZE, config);
-  munmap(blob, blob_size);
+  free(config);
   return 0;
 }
diff --git a/utility/dump_kernel_config_lib.c b/utility/dump_kernel_config_lib.c
index 9559a739..464e349b 100644
--- a/utility/dump_kernel_config_lib.c
+++ b/utility/dump_kernel_config_lib.c
@@ -6,6 +6,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 #include <sys/mman.h>
 
 #include "dump_kernel_config.h"
@@ -13,8 +14,8 @@
 #include "kernel_blob.h"
 #include "vboot_api.h"
 
-uint8_t* FindKernelConfig(uint8_t* blob, uint64_t blob_size,
-                            uint64_t kernel_body_load_address) {
+static uint8_t* GetKernelConfig(uint8_t* blob, size_t blob_size,
+                                uint64_t kernel_body_load_address) {
 
   VbKeyBlockHeader* key_block;
   VbKernelPreambleHeader* preamble;
@@ -38,7 +39,7 @@ uint8_t* FindKernelConfig(uint8_t* blob, uint64_t blob_size,
   }
 
   /* Read body_load_address from preamble if no kernel_body_load_address */
-  if (kernel_body_load_address == CROS_NO_ENTRY_ADDR)
+  if (kernel_body_load_address == USE_PREAMBLE_LOAD_ADDR)
     kernel_body_load_address = preamble->body_load_address;
 
   /* The x86 kernels have a pointer to the kernel commandline in the zeropage
@@ -54,7 +55,7 @@ uint8_t* FindKernelConfig(uint8_t* blob, uint64_t blob_size,
   return blob + offset;
 }
 
-void* MMapFile(const char* filename, size_t *size) {
+static void* MMapFile(const char* filename, size_t *size) {
   FILE* f;
   uint8_t* buf;
   long file_size = 0;
@@ -86,3 +87,33 @@ void* MMapFile(const char* filename, size_t *size) {
   fclose(f);
   return buf;
 }
+
+
+char *FindKernelConfig(const char *infile, uint64_t kernel_body_load_address)
+{
+  uint8_t* blob;
+  size_t blob_size;
+  uint8_t *config = NULL;
+  char *newstr = NULL;
+
+  blob = MMapFile(infile, &blob_size);
+  if (!blob) {
+    VbExError("Error reading input file\n");
+    return 0;
+  }
+
+  config = GetKernelConfig(blob, blob_size, kernel_body_load_address);
+  if (!config) {
+    VbExError("Error parsing input file\n");
+    munmap(blob, blob_size);
+    return 0;
+  }
+
+  newstr = strndup((char *)config, CROS_CONFIG_SIZE);
+  if (!newstr)
+    VbExError("Can't allocate new string\n");
+
+  munmap(blob, blob_size);
+
+  return newstr;
+}
diff --git a/utility/include/dump_kernel_config.h b/utility/include/dump_kernel_config.h
index 2289da72..cacc5619 100644
--- a/utility/include/dump_kernel_config.h
+++ b/utility/include/dump_kernel_config.h
@@ -2,7 +2,7 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
- * Exports the kernel commandline from a given partition/image.
+ * Exports the kernel commandline from a given partition/image file.
  */
 
 #ifndef DUMP_KERNEL_CONFIG_UTILITY_H_
@@ -11,9 +11,14 @@
 #include <inttypes.h>
 #include <stdlib.h>
 
-uint8_t* FindKernelConfig(uint8_t* blob, uint64_t blob_size,
-                            uint64_t kernel_body_load_address);
+/* TODO(wfrichar): This needs a better location */
+#define MAX_KERNEL_CONFIG_SIZE     4096
 
-void* MMapFile(const char* filename, size_t *size);
+/* Use this to obtain the body load address from the kernel preamble */
+#define USE_PREAMBLE_LOAD_ADDR     (~0)
+
+/* Returns a new copy of the kernel cmdline. The caller must free it. */
+char *FindKernelConfig(const char *filename,
+                       uint64_t kernel_body_load_address);
 
 #endif  // DUMP_KERNEL_CONFIG_UTILITY_H_