[sw/silicon_creator] Add structured kChipInfo to ROM

rules/autogen.bzl

@@ -65,35 +65,34 @@ autogen_hjson_header = rule(
     },
 )
 
-def _chip_info(ctx):
-    header = ctx.actions.declare_file("chip_info.h")
+def _chip_info_src(ctx):
+    out_source = ctx.actions.declare_file("chip_info.c")
     ctx.actions.run(
-        outputs = [header],
+        outputs = [
+            out_source,
+        ],
         inputs = [
             ctx.file.version,
             ctx.executable._tool,
         ],
         arguments = [
             "-o",
-            header.dirname,
+            out_source.dirname,
             "--ot_version_file",
             ctx.file.version.path,
         ],
         executable = ctx.executable._tool,
     )
+
     return [
-        CcInfo(compilation_context = cc_common.create_compilation_context(
-            includes = depset([header.dirname]),
-            headers = depset([header]),
-        )),
-        DefaultInfo(files = depset([header])),
+        DefaultInfo(files = depset([out_source])),
     ]
 
-autogen_chip_info = rule(
-    implementation = _chip_info,
+autogen_chip_info_src = rule(
+    implementation = _chip_info_src,
     attrs = {
         "version": attr.label(
-            default = "//util:ot_version_file",
+            default = "//util:scm_revision_file",
             allow_single_file = True,
         ),
         "_tool": attr.label(
@@ -104,6 +103,26 @@ autogen_chip_info = rule(
     },
 )
 
+def autogen_chip_info(name):
+    """Generates a cc_library named `name` that defines chip info."""
+
+    # Generate a C source file that defines the chip info struct. This is an
+    # implementation detail and should not be depended on externally.
+    chip_info_src_target = name + "_gen_src"
+    autogen_chip_info_src(name = chip_info_src_target)
+
+    # Package up the generated source file with its corresponding header file
+    # and dependencies. Any target that wants access to the chip info should
+    # depend on this.
+    native.cc_library(
+        name = name,
+        srcs = [chip_info_src_target],
+        hdrs = ["//sw/device/silicon_creator/lib:chip_info.h"],
+        deps = [
+            "//sw/device/lib/base:macros",
+        ],
+    )
+
 def _cryptotest_hjson_external(ctx):
     """
     Implementation of the Bazel rule for parsing externally-sourced test vectors.

sw/device/lib/arch/device.h

@@ -125,11 +125,11 @@ extern const uint32_t kUartNCOValue;
  * Helper macro to calculate the time it takes to transmit the entire UART TX
  * FIFO in CPU cycles.
  *
- * This macro assumes 10 bits per byte (no parity bits) and a 32 byte deep TX
+ * This macro assumes 10 bits per byte (no parity bits) and a 128 byte deep TX
  * FIFO.
  */
 #define CALCULATE_UART_TX_FIFO_CPU_CYCLES(baud_rate_, cpu_freq_) \
-  ((cpu_freq_)*10 * 32 / (baud_rate_))
+  ((cpu_freq_)*10 * 128 / (baud_rate_))
 
 /**
  * The time it takes to transmit the entire UART TX fifo in CPU cycles.

sw/device/lib/testing/test_rom/BUILD

@@ -5,16 +5,11 @@
 load("//rules:opentitan.bzl", "OPENTITAN_CPU", "opentitan_rom_binary")
 load("//rules:opentitan_test.bzl", "opentitan_functest")
 load("//rules:exclude_files.bzl", "exclude_files")
-load("//rules:autogen.bzl", "autogen_chip_info")
 load("//rules:linker.bzl", "ld_library")
 load("@rules_pkg//pkg:mappings.bzl", "pkg_files")
 
 package(default_visibility = ["//visibility:public"])
 
-autogen_chip_info(
-    name = "chip_info",
-)
-
 ld_library(
     name = "linker_script",
     script = "test_rom.ld",
@@ -120,7 +115,6 @@ cc_library(
     ],
     target_compatible_with = [OPENTITAN_CPU],
     deps = [
-        ":chip_info",
         ":target_test_rom_lib",
         ":test_rom_manifest",
         "//hw/ip/csrng/data:csrng_regs",
@@ -153,6 +147,7 @@ cc_library(
         "//sw/device/lib/testing:pinmux_testutils",
         "//sw/device/lib/testing/test_framework:check",
         "//sw/device/lib/testing/test_framework:status",
+        "//sw/device/silicon_creator/lib:chip_info",
         "//sw/device/silicon_creator/lib/base:sec_mmio",
         "//sw/device/silicon_creator/lib/base:static_critical_boot_measurements",
         "//sw/device/silicon_creator/lib/base:static_critical_epmp_state",

sw/device/lib/testing/test_rom/test_rom.c

@@ -22,8 +22,8 @@
 #include "sw/device/lib/testing/pinmux_testutils.h"
 #include "sw/device/lib/testing/test_framework/check.h"
 #include "sw/device/lib/testing/test_framework/status.h"
-#include "sw/device/lib/testing/test_rom/chip_info.h"  // Generated.
 #include "sw/device/silicon_creator/lib/base/sec_mmio.h"
+#include "sw/device/silicon_creator/lib/chip_info.h"
 #include "sw/device/silicon_creator/lib/drivers/flash_ctrl.h"
 #include "sw/device/silicon_creator/lib/drivers/retention_sram.h"
 #include "sw/device/silicon_creator/lib/manifest.h"
@@ -152,7 +152,7 @@ bool rom_test_main(void) {
   }
 
   // Print the chip version information
-  LOG_INFO("%s", chip_info);
+  LOG_INFO("kChipInfo: scm_revision=%x", kChipInfo.scm_revision);
 
   // Skip sram_init for test_rom
   dif_rstmgr_reset_info_bitfield_t reset_reasons;

sw/device/silicon_creator/lib/BUILD

@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 load("//rules:opentitan.bzl", "OPENTITAN_CPU")
+load("//rules:autogen.bzl", "autogen_chip_info")
 load("//rules:opentitan_test.bzl", "cw310_params", "opentitan_functest", "verilator_params")
 load("//rules:cross_platform.bzl", "dual_cc_device_library_of", "dual_cc_library", "dual_inputs")
 
@@ -272,6 +273,8 @@ filegroup(
     ],
 )
 
+autogen_chip_info(name = "chip_info")
+
 dual_cc_library(
     name = "shutdown",
     srcs = dual_inputs(
@@ -289,6 +292,7 @@ dual_cc_library(
             "@googletest//:gtest",
         ],
         shared = [
+            ":chip_info",
             ":error",
             ":epmp_defs",
             "//sw/device/lib/base:hardened",

sw/device/silicon_creator/lib/chip_info.h

@@ -0,0 +1,27 @@
+// Copyright lowRISC contributors.
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#ifndef OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_CHIP_INFO_H_
+#define OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_CHIP_INFO_H_
+
+#include <stdint.h>
+
+#include "sw/device/lib/base/macros.h"
+
+typedef struct chip_info {
+  // A truncated commit hash from the open-source OpenTitan repo that can be
+  // used to reproduce the ROM binary.
+  uint64_t scm_revision;
+} chip_info_t;
+
+// This struct contains information about the ROM's provenance, and critically,
+// it can be manually decoded from a hexdump. The linker script should place
+// this at the top of the ROM.
+extern const chip_info_t kChipInfo __attribute__((section(".chip_info")));
+
+// Track the size of `kChipInfo` so we can compute how much space is left in the
+// `.chip_info` section. If it becomes too large, linking will fail.
+OT_ASSERT_SIZE(chip_info_t, 8);
+
+#endif  // OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_CHIP_INFO_H_

sw/device/silicon_creator/lib/shutdown.c

@@ -15,6 +15,7 @@
 #include "sw/device/lib/base/memory.h"
 #include "sw/device/lib/base/multibits.h"
 #include "sw/device/lib/base/stdasm.h"
+#include "sw/device/silicon_creator/lib/chip_info.h"
 #include "sw/device/silicon_creator/lib/drivers/alert.h"
 #include "sw/device/silicon_creator/lib/drivers/lifecycle.h"
 #include "sw/device/silicon_creator/lib/drivers/otp.h"
@@ -325,7 +326,7 @@ enum {
   /**
    * UART TX FIFO size.
    */
-  kUartFifoSize = 32,
+  kUartFifoSize = 128,
 };
 
 /**
@@ -379,14 +380,19 @@ SHUTDOWN_FUNC(NO_MODIFIERS, shutdown_report_error(rom_error_t reason)) {
   uart_ctrl_reg = bitfield_bit32_write(uart_ctrl_reg, UART_CTRL_TX_BIT, true);
   abs_mmio_write32(kUartBase + UART_CTRL_REG_OFFSET, uart_ctrl_reg);
 
+  // Extract the commit hash from the `chip_info` at the top of ROM.
+  uint64_t chip_info_version = kChipInfo.scm_revision;
+  uint32_t chip_info_version_truncated = chip_info_version >> 32;
+
   // Print the error message and the raw life cycle state as reported by the
   // hardware.
   shutdown_print(kShutdownLogPrefixBootFault, redacted_error);
   shutdown_print(kShutdownLogPrefixLifecycle, raw_state);
+  shutdown_print(kShutdownLogPrefixVersion, chip_info_version_truncated);
 
 #ifdef OT_PLATFORM_RV32
   // Wait until UART TX is complete.
-  static_assert(2 * kErrorMsgLen <= kUartFifoSize,
+  static_assert(3 * kErrorMsgLen <= kUartFifoSize,
                 "Total message length must be less than TX FIFO size.");
   CSR_WRITE(CSR_REG_MCYCLE, 0);
   uint32_t mcycle;

sw/device/silicon_creator/lib/shutdown.h

@@ -87,6 +87,7 @@ typedef enum shutdown_error_redact {
 typedef enum shutdown_log_prefix {
   kShutdownLogPrefixBootFault = LOG_PREFIX_('B', 'F', 'V'),
   kShutdownLogPrefixLifecycle = LOG_PREFIX_('L', 'C', 'V'),
+  kShutdownLogPrefixVersion = LOG_PREFIX_('V', 'E', 'R'),
 } shutdown_log_prefix_t;
 
 /**

util/BUILD

@@ -23,6 +23,13 @@ genrule(
     stamp = 1,  # this provides volatile-status.txt
 )
 
+genrule(
+    name = "scm_revision_file",
+    outs = ["scm_revision.txt"],
+    cmd = """awk '/BUILD_SCM_REVISION/ { print $$2 }' bazel-out/volatile-status.txt > $@""",
+    stamp = 1,  # this provides volatile-status.txt
+)
+
 py_binary(
     name = "otbn_build",
     srcs = ["otbn_build.py"],

util/rom_chip_info.py

@@ -6,26 +6,39 @@
 """
 
 import argparse
+import hashlib
 import logging as log
 import sys
-from datetime import datetime
 from pathlib import Path
 
-header_template = r"""
+
+def generate_chip_info_c_source(scm_revision: int) -> str:
+    """Return the contents of a C source file that defines `kChipInfo`.
+
+    Args:
+        scm_revision: SHA1 sum identifying the current SCM revision.
+    """
+
+    SHA1_DIGEST_SIZE_BITS = hashlib.sha1().digest_size * 8
+    assert scm_revision.bit_length() <= SHA1_DIGEST_SIZE_BITS
+
+    # Truncate the SCM revision to the top N bits.
+    SCM_REVISION_SIZE_BITS = 64
+    shift_amount = SHA1_DIGEST_SIZE_BITS - SCM_REVISION_SIZE_BITS
+    scm_revision >>= shift_amount
+
+    return f"""
 // Copyright lowRISC contributors.
 // Licensed under the Apache License, Version 2.0, see LICENSE for details.
 // SPDX-License-Identifier: Apache-2.0
 //
 // --------- W A R N I N G: A U T O - G E N E R A T E D   C O D E !! ---------//
 
-#ifndef _F_CHIPINFO_H__
-#define _F_CHIPINFO_H__
-
-static const char chip_info[128] __attribute__((section(".chip_info"))) =
-  "Version: {%version%}, Build Date: {%build_date%}";
-
-#endif  // _F_CHIPINFO_H__
+#include "sw/device/silicon_creator/lib/chip_info.h"
 
+const chip_info_t kChipInfo __attribute__((section(".chip_info"))) = {{
+    .scm_revision = (uint64_t){scm_revision:#0x},
+}};
 """
 
 
@@ -57,24 +70,18 @@ def main():
         log.error(
             "Missing ot_version, provide --ot_version or --ot_version_file.")
         raise SystemExit(sys.exc_info()[1])
+    version = int(version, base=16)
+    log.info("Version: %x" % (version, ))
 
     outdir = Path(args.outdir)
 
     outdir.mkdir(parents=True, exist_ok=True)
-    out_path = outdir / "chip_info.h"
-
-    now = datetime.now()
-    wall_time = now.strftime("%Y-%m-%d %H:%M:%S")
-
-    log.info("Version: %s" % (version, ))
-    log.info("Build Date: %s" % (wall_time, ))
+    source_out_path = outdir / "chip_info.c"
 
-    output = header_template
-    output = output.replace('{%version%}', version, 1)
-    output = output.replace('{%build_date%}', wall_time, 1)
+    output = generate_chip_info_c_source(version)
 
-    with out_path.open(mode='w', encoding='UTF-8') as fout:
-        fout.write(output + "\n")
+    with source_out_path.open(mode='w', encoding='UTF-8') as fout:
+        fout.write(output)
 
 
 if __name__ == "__main__":