[PATCH v2 1/2] nvram: Add dry_run argument to chrp_nvram_create_system_partition()

[Greg Kurz <groug@kaod.org>]

Since commit 55d9950aaa8e ("nvram: Introduce helper functions for CHRP
"system" and "free space" partitions") it is possible to pre-initialize
a "system" partition in the NVRAM with the data passed to all -prom-env
parameters on the QEMU command line.

Unfortunately, this doesn't take the total size of the data into account
and chrp_nvram_create_system_partition() may crash at some point if the
caller hasn't allocated enough space.

Add a dry_run argument that causes chrp_nvram_create_system_partition()
to only return the size of the partition without actually copying data
into it. This can be used by callers to allocate enough memory.

Signed-off-by: Greg Kurz <groug@kaod.org>
---
 hw/nvram/chrp_nvram.c         |   34 +++++++++++++++++++++++-----------
 hw/nvram/mac_nvram.c          |    2 +-
 hw/nvram/spapr_nvram.c        |    3 ++-
 hw/sparc/sun4m.c              |    2 +-
 hw/sparc64/sun4u.c            |    2 +-
 include/hw/nvram/chrp_nvram.h |    3 ++-
 6 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/hw/nvram/chrp_nvram.c b/hw/nvram/chrp_nvram.c
index d969f267048e..f5f7b2a97c18 100644
--- a/hw/nvram/chrp_nvram.c
+++ b/hw/nvram/chrp_nvram.c
@@ -24,37 +24,48 @@
 #include "hw/nvram/chrp_nvram.h"
 #include "sysemu/sysemu.h"
 
-static int chrp_nvram_set_var(uint8_t *nvram, int addr, const char *str)
+static int chrp_nvram_set_var(uint8_t *nvram, int addr, const char *str,
+                              bool dry_run)
 {
     int len;
 
     len = strlen(str) + 1;
-    memcpy(&nvram[addr], str, len);
-
+    if (!dry_run) {
+        memcpy(&nvram[addr], str, len);
+    }
     return addr + len;
 }
 
 /**
  * Create a "system partition", used for the Open Firmware
- * environment variables.
+ * environment variables. If @dry_run is false, only returns
+ * the size of the partition but don't write the data.
  */
-int chrp_nvram_create_system_partition(uint8_t *data, int min_len)
+int chrp_nvram_create_system_partition(uint8_t *data, int min_len, bool dry_run)
 {
     ChrpNvramPartHdr *part_header;
     unsigned int i;
     int end;
 
+    assert(data || dry_run);
+
     part_header = (ChrpNvramPartHdr *)data;
-    part_header->signature = CHRP_NVPART_SYSTEM;
-    pstrcpy(part_header->name, sizeof(part_header->name), "system");
+
+    if (!dry_run) {
+        part_header->signature = CHRP_NVPART_SYSTEM;
+        pstrcpy(part_header->name, sizeof(part_header->name), "system");
+    }
 
     end = sizeof(ChrpNvramPartHdr);
     for (i = 0; i < nb_prom_envs; i++) {
-        end = chrp_nvram_set_var(data, end, prom_envs[i]);
+        end = chrp_nvram_set_var(data, end, prom_envs[i], dry_run);
     }
 
     /* End marker */
-    data[end++] = '\0';
+    if (!dry_run) {
+        data[end] = '\0';
+    }
+    end++;
 
     end = (end + 15) & ~15;
     /* XXX: OpenBIOS is not able to grow up a partition. Leave some space for
@@ -62,8 +73,9 @@ int chrp_nvram_create_system_partition(uint8_t *data, int min_len)
     if (end < min_len) {
         end = min_len;
     }
-    chrp_nvram_finish_partition(part_header, end);
-
+    if (!dry_run) {
+        chrp_nvram_finish_partition(part_header, end);
+    }
     return end;
 }
 
diff --git a/hw/nvram/mac_nvram.c b/hw/nvram/mac_nvram.c
index beec1c4e4d11..4396f893f14a 100644
--- a/hw/nvram/mac_nvram.c
+++ b/hw/nvram/mac_nvram.c
@@ -141,7 +141,7 @@ static void pmac_format_nvram_partition_of(MacIONVRAMState *nvr, int off,
 
     /* OpenBIOS nvram variables partition */
     sysp_end = chrp_nvram_create_system_partition(&nvr->data[off],
-                                                  DEF_SYSTEM_SIZE) + off;
+                                                  DEF_SYSTEM_SIZE, false) + off;
 
     /* Free space partition */
     chrp_nvram_create_free_partition(&nvr->data[sysp_end], len - sysp_end);
diff --git a/hw/nvram/spapr_nvram.c b/hw/nvram/spapr_nvram.c
index 15d08281d411..992b818d34e7 100644
--- a/hw/nvram/spapr_nvram.c
+++ b/hw/nvram/spapr_nvram.c
@@ -188,7 +188,8 @@ static void spapr_nvram_realize(SpaprVioDevice *dev, Error **errp)
         }
     } else if (nb_prom_envs > 0) {
         /* Create a system partition to pass the -prom-env variables */
-        chrp_nvram_create_system_partition(nvram->buf, MIN_NVRAM_SIZE / 4);
+        chrp_nvram_create_system_partition(nvram->buf, MIN_NVRAM_SIZE / 4,
+                                           false);
         chrp_nvram_create_free_partition(&nvram->buf[MIN_NVRAM_SIZE / 4],
                                          nvram->size - MIN_NVRAM_SIZE / 4);
     }
diff --git a/hw/sparc/sun4m.c b/hw/sparc/sun4m.c
index 9be930415f8e..61804ccd4286 100644
--- a/hw/sparc/sun4m.c
+++ b/hw/sparc/sun4m.c
@@ -143,7 +143,7 @@ static void nvram_init(Nvram *nvram, uint8_t *macaddr,
     memset(image, '\0', sizeof(image));
 
     /* OpenBIOS nvram variables partition */
-    sysp_end = chrp_nvram_create_system_partition(image, 0);
+    sysp_end = chrp_nvram_create_system_partition(image, 0, false);
 
     /* Free space partition */
     chrp_nvram_create_free_partition(&image[sysp_end], 0x1fd0 - sysp_end);
diff --git a/hw/sparc64/sun4u.c b/hw/sparc64/sun4u.c
index 9e30203dcc44..2409e739e81b 100644
--- a/hw/sparc64/sun4u.c
+++ b/hw/sparc64/sun4u.c
@@ -136,7 +136,7 @@ static int sun4u_NVRAM_set_params(Nvram *nvram, uint16_t NVRAM_size,
     memset(image, '\0', sizeof(image));
 
     /* OpenBIOS nvram variables partition */
-    sysp_end = chrp_nvram_create_system_partition(image, 0);
+    sysp_end = chrp_nvram_create_system_partition(image, 0, false);
 
     /* Free space partition */
     chrp_nvram_create_free_partition(&image[sysp_end], 0x1fd0 - sysp_end);
diff --git a/include/hw/nvram/chrp_nvram.h b/include/hw/nvram/chrp_nvram.h
index 09941a9be454..1d32dbf61331 100644
--- a/include/hw/nvram/chrp_nvram.h
+++ b/include/hw/nvram/chrp_nvram.h
@@ -50,7 +50,8 @@ chrp_nvram_finish_partition(ChrpNvramPartHdr *header, uint32_t size)
     header->checksum = sum & 0xff;
 }
 
-int chrp_nvram_create_system_partition(uint8_t *data, int min_len);
+int chrp_nvram_create_system_partition(uint8_t *data, int min_len,
+                                       bool dry_run);
 int chrp_nvram_create_free_partition(uint8_t *data, int len);
 
 #endif