ifdtool: fix flumap handling in chipsets prior ibex peak/5 series

The Upper Map section in the descriptor contains a database of flash
chips (VSCC Table). Its offset is located at a fixed offset from
the beginning of the image. ifdtool falsely calculates the offset
from the descriptor signature which has moved by 16 bytes with
step b of the Ibex Peak (5 series) chipset. This produces bogus
output for all chipsets older than that.

This patch corrects the behavior by calculating the offset of
flumap by adding 4096 - 256 - 4 to the start of the image.

Change-Id: I14f029fe702c129dfd8069a58fbd41113700f7ef
Signed-off-by: Stefan Tauner <stefan.tauner@gmx.at>
Reviewed-on: https://review.coreboot.org/27858
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

util/ifdtool/ifdtool.c

@@ -77,6 +77,21 @@ static fdbar_t *find_fd(char *image, int size)
 	return PTR_IN_RANGE(fdb, image, size) ? fdb : NULL;
 }
 
+static char *find_flumap(char *image, int size)
+{
+	/* The upper map is located in the word before the 256B-long OEM section
+	 * at the end of the 4kB-long flash descriptor. In the official
+	 * documentation this is defined as FDBAR + 0xEFC. However, starting
+	 * with B-Step of Ibex Peak (5 series) the signature (and thus FDBAR)
+	 * has moved 16 bytes back to offset 0x10 of the image. Although
+	 * official documentation still maintains the offset relative to FDBAR
+	 * this is wrong and a simple fixed offset from the start of the image
+	 * works.
+	*/
+	char *flumap = image + 4096 - 256 - 4;
+	return PTR_IN_RANGE(flumap, image, size) ? flumap : NULL;
+}
+
 static fcba_t *find_fcba(char *image, int size)
 {
 	fdbar_t *fdb = find_fd(image, size);
@@ -586,7 +601,8 @@ static void dump_vscc(uint32_t vscc)
 static void dump_vtba(const vtba_t *vtba, int vtl)
 {
 	int i;
-	int num = (vtl >> 1) < 8 ? (vtl >> 1) : 8;
+	int max_len = sizeof(vtba_t)/sizeof(vscc_t);
+	int num = (vtl >> 1) < max_len ? (vtl >> 1) : max_len;
 
 	printf("ME VSCC table:\n");
 	for (i = 0; i < num; i++) {
@@ -633,14 +649,16 @@ static void dump_fd(char *image, int size)
 	printf("  PSL:     0x%04x\n", (fdb->flmap2 >> 8) & 0xffff);
 	printf("  FMSBA:   0x%x\n", ((fdb->flmap2) & 0xff) << 4);
 
-	printf("FLUMAP1:   0x%08x\n", fdb->flumap1);
+	char *flumap = find_flumap(image, size);
+	uint32_t flumap1 = *(uint32_t *)flumap;
+	printf("FLUMAP1:   0x%08x\n", flumap1);
 	printf("  Intel ME VSCC Table Length (VTL):        %d\n",
-		(fdb->flumap1 >> 8) & 0xff);
+		(flumap1 >> 8) & 0xff);
 	printf("  Intel ME VSCC Table Base Address (VTBA): 0x%06x\n\n",
-		(fdb->flumap1 & 0xff) << 4);
+		(flumap1 & 0xff) << 4);
 	dump_vtba((vtba_t *)
-			(image + ((fdb->flumap1 & 0xff) << 4)),
+			(image + ((flumap1 & 0xff) << 4)),
-			(fdb->flumap1 >> 8) & 0xff);
+			(flumap1 >> 8) & 0xff);
 	dump_oem((const uint8_t *)image + 0xf00);
 
 	const frba_t *frba = find_frba(image, size);

util/ifdtool/ifdtool.h

@@ -56,8 +56,6 @@ typedef struct {
 	uint32_t flmap0;
 	uint32_t flmap1;
 	uint32_t flmap2;
-	uint8_t  reserved[0xefc - 0x20];
-	uint32_t flumap1;
 } __attribute__((packed)) fdbar_t;
 
 // regions
@@ -113,6 +111,8 @@ typedef struct {
 
 typedef struct {
 	// Actual number of entries specified in vtl
+	/* FIXME: Rationale for the limit of 8.
+	 *        AFAICT it's 127, cf. flashrom's ich_descriptors_tool). */
 	vscc_t entry[8];
 } vtba_t;