cbfs: Simplify cbfs_load_and_decompress() and stop exporting it

With the last external user to cbfs_load_and_decompress() gone, we can
stop exporting this function to the rest of coreboot and make it local
to cbfs.c. Also remove a couple of arguments that no longer really make
a difference and fold the stage-specific code for in-place LZ4
decompression into cbfs_prog_stage_load().

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I4b459650a28e020c4342a66090f55264fbd26363
Reviewed-on: https://review.coreboot.org/c/coreboot/+/52083
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/include/cbfs.h

@@ -165,13 +165,6 @@ void *cbfs_boot_map_optionrom(uint16_t vendor, uint16_t device);
 /* Return mapping of option ROM with revision number. Returns NULL on error. */
 void *cbfs_boot_map_optionrom_revision(uint16_t vendor, uint16_t device, uint8_t rev);
 
-/* Load |in_size| bytes from |rdev| at |offset| to the |buffer_size| bytes large |buffer|,
-   decompressing it according to |compression| in the process. Returns the decompressed file
-   size, or 0 on error. LZMA files will be mapped for decompression. LZ4 files will be
-   decompressed in-place with the buffer size requirements outlined in compression.h. */
-size_t cbfs_load_and_decompress(const struct region_device *rdev, size_t offset,
-	size_t in_size, void *buffer, size_t buffer_size, uint32_t compression);
-
 
 /**********************************************************************************************
  *                         INTERNAL HELPERS FOR INLINES, DO NOT USE.                          *

src/lib/cbfs.c

@@ -186,19 +186,20 @@ static inline bool cbfs_lzma_enabled(void)
 	return true;
 }
 
-size_t cbfs_load_and_decompress(const struct region_device *rdev, size_t offset, size_t in_size,
+static size_t cbfs_load_and_decompress(const struct region_device *rdev,
-				void *buffer, size_t buffer_size, uint32_t compression)
+				       void *buffer, size_t buffer_size, uint32_t compression)
 {
+	size_t in_size = region_device_sz(rdev);
 	size_t out_size;
 	void *map;
 
-	DEBUG("Decompressing %zu bytes to %p with algo %d\n", buffer_size, buffer, compression);
+	DEBUG("Decompressing %zu bytes to %p with algo %d\n", in_size, buffer, compression);
 
 	switch (compression) {
 	case CBFS_COMPRESS_NONE:
 		if (buffer_size < in_size)
 			return 0;
-		if (rdev_readat(rdev, buffer, offset, in_size) != in_size)
+		if (rdev_readat(rdev, buffer, 0, in_size) != in_size)
 			return 0;
 		return in_size;
 
@@ -206,9 +207,9 @@ size_t cbfs_load_and_decompress(const struct region_device *rdev, size_t offset,
 		if (!cbfs_lz4_enabled())
 			return 0;
 
-		/* cbfs_stage_load_and_decompress() takes care of in-place LZ4 decompression by
+		/* cbfs_prog_stage_load() takes care of in-place LZ4 decompression by
 		   setting up the rdev to be in memory. */
-		map = rdev_mmap(rdev, offset, in_size);
+		map = rdev_mmap_full(rdev);
 		if (map == NULL)
 			return 0;
 
@@ -223,7 +224,7 @@ size_t cbfs_load_and_decompress(const struct region_device *rdev, size_t offset,
 	case CBFS_COMPRESS_LZMA:
 		if (!cbfs_lzma_enabled())
 			return 0;
-		map = rdev_mmap(rdev, offset, in_size);
+		map = rdev_mmap_full(rdev);
 		if (map == NULL)
 			return 0;
 
@@ -241,33 +242,6 @@ size_t cbfs_load_and_decompress(const struct region_device *rdev, size_t offset,
 	}
 }
 
-static size_t cbfs_stage_load_and_decompress(const struct region_device *rdev, size_t offset,
-	size_t in_size, void *buffer, size_t buffer_size, uint32_t compression)
-{
-	struct region_device rdev_src;
-
-	if (compression == CBFS_COMPRESS_LZ4) {
-		if (!cbfs_lz4_enabled())
-			return 0;
-		/* Load the compressed image to the end of the available memory area for
-		   in-place decompression. It is the responsibility of the caller to ensure that
-		   buffer_size is large enough (see compression.h, guaranteed by cbfstool for
-		   stages). */
-		void *compr_start = buffer + buffer_size - in_size;
-		if (rdev_readat(rdev, compr_start, offset, in_size) != in_size)
-			return 0;
-		/* Create a region device backed by memory. */
-		rdev_chain(&rdev_src, &addrspace_32bit.rdev, (uintptr_t)compr_start, in_size);
-
-		return cbfs_load_and_decompress(&rdev_src, 0, in_size, buffer, buffer_size,
-						compression);
-	}
-
-	/* All other algorithms can use the generic implementation. */
-	return cbfs_load_and_decompress(rdev, offset, in_size, buffer, buffer_size,
-					compression);
-}
-
 static inline int tohex4(unsigned int c)
 {
 	return (c <= 9) ? (c + '0') : (c - 10 + 'a');
@@ -361,8 +335,7 @@ void *_cbfs_alloc(const char *name, cbfs_allocator_t allocator, void *arg,
 		return NULL;
 	}
 
-	size = cbfs_load_and_decompress(&rdev, 0, region_device_sz(&rdev),
+	size = cbfs_load_and_decompress(&rdev, loc, size, compression);
-					loc, size, compression);
 	if (!size)
 		return NULL;
 
@@ -421,8 +394,18 @@ cb_err_t cbfs_prog_stage_load(struct prog *pstage)
 			return CB_SUCCESS;
 	}
 
-	size_t fsize = cbfs_stage_load_and_decompress(&rdev, 0, region_device_sz(&rdev),
+	/* LZ4 stages can be decompressed in-place to save mapping scratch space. Load the
-				prog_start(pstage), prog_size(pstage), compression);
+	   compressed data to the end of the buffer and point &rdev to that memory location. */
+	if (cbfs_lz4_enabled() && compression == CBFS_COMPRESS_LZ4) {
+		size_t in_size = region_device_sz(&rdev);
+		void *compr_start = prog_start(pstage) + prog_size(pstage) - in_size;
+		if (rdev_readat(&rdev, compr_start, 0, in_size) != in_size)
+			return CB_ERR;
+		rdev_chain(&rdev, &addrspace_32bit.rdev, (uintptr_t)compr_start, in_size);
+	}
+
+	size_t fsize = cbfs_load_and_decompress(&rdev, prog_start(pstage), prog_size(pstage),
+						compression);
 	if (!fsize)
 		return CB_ERR;