host/lib: add lightweight flashrom wrapper library

Lightweight wrapper around flashrom, exposing two APIs:

    flashrom_read(programmer, region, data_out, size_out)
    flashrom_write(programmer, region, data, size)

|region| can be NULL, in which case operate on the whole flash chip.

The intended usage of this wrapper library is to read/write VBNV from
SPI flash directly, avoiding the call thru mosys (which has deprecated
the command).  Bringing this logic into crossystem directly will also
help with expanding VBNV to 64-bytes.

BUG=chromium:1032351,chromium:1030473,chromium:789276
BRANCH=none
TEST=provided unit tests

Change-Id: I3997bd03a2db7e58e4e76fc200c637dd3b5b20a4
Signed-off-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2218888

2 files changed, 208 insertions, 0 deletions

diff --git a/host/lib/flashrom.c b/host/lib/flashrom.c
new file mode 100644
index 00000000..061c5b84
--- /dev/null
+++ b/host/lib/flashrom.c
@@ -0,0 +1,158 @@
+/* Copyright 2020 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* For strdup */
+#define _POSIX_C_SOURCE 200809L
+
+#include <fcntl.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "2api.h"
+#include "2return_codes.h"
+#include "host_misc.h"
+#include "flashrom.h"
+#include "subprocess.h"
+
+#define FLASHROM_EXEC_NAME "flashrom"
+
+/**
+ * Helper to create a temporary file, and optionally write some data
+ * into it.
+ *
+ * @param data		If data needs to be written to the file, a
+ *			pointer to the buffer.  Pass NULL to just
+ *			create an empty temporary file.
+ * @param data_size	The size of the buffer to write, if applicable.
+ * @param path_out	An output pointer for the filename.  Caller
+ *			should free.
+ *
+ * @return VB2_SUCCESS on success, or a relevant error.
+ */
+static vb2_error_t write_temp_file(const uint8_t *data, uint32_t data_size,
+				   char **path_out)
+{
+	int fd;
+	ssize_t write_rv;
+	vb2_error_t rv;
+	char *path;
+
+	*path_out = NULL;
+	path = strdup(P_tmpdir "/vb2_flashrom.XXXXXX");
+
+	fd = mkstemp(path);
+	if (fd < 0) {
+		rv = VB2_ERROR_WRITE_FILE_OPEN;
+		goto fail;
+	}
+
+	while (data && data_size > 0) {
+		write_rv = write(fd, data, data_size);
+		if (write_rv < 0) {
+			close(fd);
+			unlink(path);
+			rv = VB2_ERROR_WRITE_FILE_DATA;
+			goto fail;
+		}
+
+		data_size -= write_rv;
+		data += write_rv;
+	}
+
+	close(fd);
+	*path_out = path;
+	return VB2_SUCCESS;
+
+ fail:
+	free(path);
+	return rv;
+}
+
+static vb2_error_t run_flashrom(const char *const argv[])
+{
+	int status = subprocess_run(argv, &subprocess_null, &subprocess_null,
+				    &subprocess_null);
+	if (status) {
+		fprintf(stderr, "Flashrom invocation failed (exit status %d):",
+			status);
+
+		for (const char *const *argp = argv; *argp; argp++)
+			fprintf(stderr, " %s", *argp);
+
+		fprintf(stderr, "\n");
+		return VB2_ERROR_FLASHROM;
+	}
+
+	return VB2_SUCCESS;
+}
+
+vb2_error_t flashrom_read(const char *programmer, const char *region,
+			  uint8_t **data_out, uint32_t *size_out)
+{
+	char *tmpfile;
+	char region_param[PATH_MAX];
+	vb2_error_t rv;
+
+	*data_out = NULL;
+	*size_out = 0;
+
+	VB2_TRY(write_temp_file(NULL, 0, &tmpfile));
+
+	if (region)
+		snprintf(region_param, sizeof(region_param), "%s:%s", region,
+			 tmpfile);
+
+	const char *const argv[] = {
+		FLASHROM_EXEC_NAME,
+		"-p",
+		programmer,
+		"-r",
+		region ? "-i" : tmpfile,
+		region ? region_param : NULL,
+		NULL,
+	};
+
+	rv = run_flashrom(argv);
+	if (rv == VB2_SUCCESS)
+		rv = vb2_read_file(tmpfile, data_out, size_out);
+
+	unlink(tmpfile);
+	free(tmpfile);
+	return rv;
+}
+
+vb2_error_t flashrom_write(const char *programmer, const char *region,
+			   uint8_t *data, uint32_t size)
+{
+	char *tmpfile;
+	char region_param[PATH_MAX];
+	vb2_error_t rv;
+
+	VB2_TRY(write_temp_file(data, size, &tmpfile));
+
+	if (region)
+		snprintf(region_param, sizeof(region_param), "%s:%s", region,
+			 tmpfile);
+
+	const char *const argv[] = {
+		FLASHROM_EXEC_NAME,
+		"-p",
+		programmer,
+		"-w",
+		region ? "-i" : tmpfile,
+		region ? region_param : NULL,
+		NULL,
+	};
+
+	rv = run_flashrom(argv);
+	unlink(tmpfile);
+	free(tmpfile);
+	return rv;
+}
diff --git a/host/lib/include/flashrom.h b/host/lib/include/flashrom.h
new file mode 100644
index 00000000..560fbb0e
--- /dev/null
+++ b/host/lib/include/flashrom.h
@@ -0,0 +1,50 @@
+/* Copyright 2020 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * Host utilites to execute flashrom command.
+ */
+
+#include <stdint.h>
+
+#include "2return_codes.h"
+
+#define FLASHROM_PROGRAMMER_INTERNAL_AP "host"
+#define FLASHROM_PROGRAMMER_INTERNAL_EC "ec"
+
+/**
+ * Read using flashrom into an allocated buffer.
+ *
+ * @param programmer	The name of the programmer to use.  There are
+ *			named constants FLASHROM_PROGRAMMER_INTERNAL_AP
+ *			and FLASHROM_PROGRAMMER_INTERNAL_EC available
+ *			for the AP and EC respectively, or a custom
+ *			programmer string can be provided.
+ * @param region	The name of the fmap region to read, or NULL to
+ *			read the entire flash chip.
+ * @param data_out	Output parameter of allocated buffer to read into.
+ *			The caller should free the buffer.
+ * @param size_out	Output parameter of buffer size.
+ *
+ * @return VB2_SUCCESS on success, or a relevant error.
+ */
+vb2_error_t flashrom_read(const char *programmer, const char *region,
+			  uint8_t **data_out, uint32_t *size_out);
+
+/**
+ * Write using flashrom from a buffer.
+ *
+ * @param programmer	The name of the programmer to use.  There are
+ *			named constants FLASHROM_PROGRAMMER_INTERNAL_AP
+ *			and FLASHROM_PROGRAMMER_INTERNAL_EC available
+ *			for the AP and EC respectively, or a custom
+ *			programmer string can be provided.
+ * @param region	The name of the fmap region to write, or NULL to
+ *			write the entire flash chip.
+ * @param data		The buffer to write.
+ * @param size		The size of the buffer to write.
+ *
+ * @return VB2_SUCCESS on success, or a relevant error.
+ */
+vb2_error_t flashrom_write(const char *programmer, const char *region,
+			   uint8_t *data, uint32_t size);