lib/bootmem: Add bootmem_add_range_from function

This patch introduces a new function, bootmem_add_range_from, which
allows adding a memory range of a specific type only if it is carved
out from a range of another specific type. This is useful for cases
where memory needs to be allocated from a pre-defined region.

The function checks if the target range is fully contained within a
range of `from_tag` before marking it as `new_tag`. Error reporting
is included to log cases where the allocation is not possible.

BUG=b:438666196

Change-Id: Icfdb5ef9114572c075be6ef4e57d00151300a17a
Signed-off-by: Yidi Lin <yidilin@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/90469
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/bootmem.h

@@ -61,6 +61,22 @@ void bootmem_platform_add_ranges(void);
 void bootmem_add_range(uint64_t start, uint64_t size,
 		       const enum bootmem_type tag);
 
+/*
+ * bootmem_add_range_from - Add a memory range of a specific type from another range
+ * @start: Start address of the new memory range
+ * @size: Size of the new memory range
+ * @new_tag: The new bootmem_type for the range
+ * @from_tag: The bootmem_type from which the new range should be carved out
+ *
+ * This function adds a memory range with `new_tag` only if it is fully
+ * contained within an existing range of `from_tag`. This is useful for
+ * carving out specific memory regions from a larger, already defined area.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
+int bootmem_add_range_from(uint64_t start, uint64_t size, const enum bootmem_type new_tag,
+			   const enum bootmem_type from_tag);
+
 /* Print current range map of boot memory. */
 void bootmem_dump_ranges(void);
 

src/lib/bootmem.c

@@ -14,6 +14,8 @@ static int table_written;
 static struct memranges bootmem;
 static struct memranges bootmem_os;
 
+static const char *bootmem_range_string(const enum bootmem_type tag);
+
 static int bootmem_is_initialized(void)
 {
 	return initialized;
@@ -106,6 +108,24 @@ void bootmem_add_range(uint64_t start, uint64_t size,
 	};
 }
 
+int bootmem_add_range_from(uint64_t start, uint64_t size, const enum bootmem_type new_tag,
+			   const enum bootmem_type from_tag)
+{
+	if (new_tag == from_tag)
+		return -1;
+
+	if (!bootmem_region_targets_type(start, size, from_tag)) {
+		printk(BIOS_ERR, "%s: Failed to add the range [%#llx, %#llx)"
+		       " from tag %s to %s\n", __func__, start, start + size,
+		       bootmem_range_string(from_tag), bootmem_range_string(new_tag));
+		return -1;
+	}
+
+	bootmem_add_range(start, size, new_tag);
+
+	return 0;
+}
+
 void bootmem_write_memory_table(struct lb_memory *mem)
 {
 	const struct range_entry *r;