[rom_ext] Enable Oz to reduce firmware size

This change enables Oz for rom_ext to reduce code size (43084B -> 41868B). Since some targets can't be built with LLD, this commit introduces a new attribute, `with_features`, to the `opentitan_binary` rule to allow specifying additional features for the target. LTO is also ready to be enabled for those targets, but we found no size improvement (41868B v.s. 41896B), so we keep it off at the moment. Change-Id: I5a8e7e7fcbb7d1e435b987d955a3e5ff8e4b7383 Signed-off-by: Yi-Hsuan Deng <[email protected]>
lowRISC · Jan 10, 2025 · 8110d69 · 8110d69
1 parent f5e6ad8
commit 8110d69
Show file tree

Hide file tree

Showing 6 changed files with 59 additions and 5 deletions.
diff --git a/rules/rv.bzl b/rules/rv.bzl
@@ -19,10 +19,11 @@ PER_DEVICE_DEPS = {
 }
 
 def _opentitan_transition_impl(settings, attr):
+    features = settings["//command_line_option:features"] + attr.with_features
     return {
         "//command_line_option:platforms": attr.platform,
         "//command_line_option:copt": settings["//command_line_option:copt"],
-        "//command_line_option:features": settings["//command_line_option:features"],
+        "//command_line_option:features": features,
         "//hw/bitstream/universal:rom": "//hw/bitstream/universal:none",
         "//hw/bitstream/universal:otp": "//hw/bitstream/universal:none",
         "//hw/bitstream/universal:env": "//hw/bitstream/universal:none",
@@ -58,6 +59,8 @@ def rv_rule(**kwargs):
     attrs = kwargs.pop("attrs", {})
     if "platform" not in attrs:
         attrs["platform"] = attr.string(default = OPENTITAN_PLATFORM)
+    if "with_features" not in attrs:
+        attrs["with_features"] = attr.string_list(default = [])
     attrs["_allowlist_function_transition"] = attr.label(
         default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
     )

diff --git a/sw/device/silicon_creator/lib/sigverify/sphincsplus/utils.c b/sw/device/silicon_creator/lib/sigverify/sphincsplus/utils.c
@@ -17,7 +17,18 @@
 uint64_t spx_utils_bytes_to_u64(const uint8_t *in, size_t inlen) {
   uint64_t retval = 0;
   for (size_t i = 0; i < inlen; i++) {
-    retval |= ((uint64_t)in[i]) << (8 * (inlen - 1 - i));
+    // Perform native shift on u32 first to avoid __ashldi3 polyfill.
+    //
+    // The following code is equivalent to:
+    //     retval |= ((uint64_t)in[i]) << (8 * (inlen - 1 - i));
+    //
+    // See also pull #11451.
+    size_t offset = 8 * (inlen - 1 - i);
+    if (offset < 32) {
+      retval |= ((uint32_t)in[i]) << offset;
+    } else {
+      retval |= ((uint64_t)(((uint32_t)in[i]) << (offset - 32))) << 32;
+    }
   }
   return retval;
 }

diff --git a/sw/device/silicon_creator/rom_ext/BUILD b/sw/device/silicon_creator/rom_ext/BUILD
@@ -290,6 +290,10 @@ opentitan_binary(
     linker_script = ":ld_slot_a",
     manifest = ":manifest",
     spx_key = {"//sw/device/silicon_creator/rom/keys/fake/spx:prod_key_0_spx": "prod_key_0"},
+    with_features = [
+        "minsize",
+        "use_lld",
+    ],
     deps = [
         ":rom_ext",
         "//sw/device/lib/crt",
@@ -314,6 +318,10 @@ opentitan_binary(
     linker_script = ":ld_slot_b",
     manifest = ":manifest",
     spx_key = {"//sw/device/silicon_creator/rom/keys/fake/spx:prod_key_0_spx": "prod_key_0"},
+    with_features = [
+        "minsize",
+        "use_lld",
+    ],
     deps = [
         ":rom_ext",
         "//sw/device/lib/crt",
@@ -337,6 +345,10 @@ opentitan_binary(
     ],
     linker_script = ":ld_slot_virtual",
     manifest = ":manifest",
+    with_features = [
+        "minsize",
+        "use_lld",
+    ],
     deps = [
         ":rom_ext",
         "//sw/device/lib/crt",
@@ -360,6 +372,10 @@ opentitan_binary(
         ],
         linker_script = ":ld_slot_virtual",
         manifest = ":manifest",
+        with_features = [
+            "minsize",
+            "use_lld",
+        ],
         deps = [
             ":rom_ext",
             "//sw/device/lib/crt",
@@ -390,6 +406,10 @@ opentitan_binary(
     ],
     linker_script = ":ld_slot_a",
     manifest = ":manifest_bad_address_translation",
+    with_features = [
+        "minsize",
+        "use_lld",
+    ],
     deps = [
         ":rom_ext",
         "//sw/device/lib/crt",

diff --git a/sw/device/silicon_creator/rom_ext/rom_ext.c b/sw/device/silicon_creator/rom_ext/rom_ext.c
@@ -619,19 +619,23 @@ void rom_ext_main(void) {
   shutdown_finalize(error);
 }
 
+OT_USED
 void rom_ext_interrupt_handler(void) { shutdown_finalize(rom_ext_irq_error()); }
 
 // We only need a single handler for all ROM_EXT interrupts, but we want to
 // keep distinct symbols to make writing tests easier.  In the ROM_EXT,
 // alias all interrupt handler symbols to the single handler.
+OT_USED
 OT_ALIAS("rom_ext_interrupt_handler")
 void rom_ext_exception_handler(void);
 
+OT_USED
 OT_ALIAS("rom_ext_interrupt_handler")
 void rom_ext_nmi_handler(void);
 
 // A no-op immutable rom_ext fallback to avoid breaking tests before the
 // proper bazel target is ready.
 // TODO(opentitan#24368): Remove this nop fallback.
+OT_USED
 OT_SECTION(".rom_ext_immutable.fallback")
 void imm_rom_ext_placeholder(void) {}
diff --git a/sw/device/silicon_creator/rom_ext/sival/BUILD b/sw/device/silicon_creator/rom_ext/sival/BUILD
@@ -49,6 +49,10 @@ opentitan_binary(
     linkopts = LINK_ORDER,
     manifest = ":manifest_sival",
     spx_key = {"//sw/device/silicon_creator/rom/keys/fake/spx:prod_key_0_spx": "prod_key_0"},
+    with_features = [
+        "minsize",
+        "use_lld",
+    ],
     deps = [
         "//sw/device/lib/crt",
         "//sw/device/silicon_creator/lib:manifest_def",
@@ -71,6 +75,10 @@ opentitan_binary(
     linkopts = LINK_ORDER,
     manifest = ":manifest_sival",
     spx_key = {"//sw/device/silicon_creator/rom/keys/fake/spx:prod_key_0_spx": "prod_key_0"},
+    with_features = [
+        "minsize",
+        "use_lld",
+    ],
     deps = [
         "//sw/device/lib/crt",
         "//sw/device/silicon_creator/lib:manifest_def",
@@ -87,6 +95,10 @@ opentitan_binary(
     ],
     linker_script = "//sw/device/silicon_creator/rom_ext:ld_slot_a",
     linkopts = LINK_ORDER,
+    with_features = [
+        "minsize",
+        "use_lld",
+    ],
     deps = [
         "//sw/device/lib/crt",
         "//sw/device/silicon_creator/lib:manifest_def",
@@ -103,6 +115,10 @@ opentitan_binary(
     ],
     linker_script = "//sw/device/silicon_creator/rom_ext:ld_slot_b",
     linkopts = LINK_ORDER,
+    with_features = [
+        "minsize",
+        "use_lld",
+    ],
     deps = [
         "//sw/device/lib/crt",
         "//sw/device/silicon_creator/lib:manifest_def",

diff --git a/third_party/crt/repos.bzl b/third_party/crt/repos.bzl
@@ -15,7 +15,7 @@ def crt_repos(local = None):
         maybe(
             http_archive,
             name = "crt",
-            url = "https://github.com/lowRISC/crt/archive/refs/tags/v0.4.13.tar.gz",
-            strip_prefix = "crt-0.4.13",
-            sha256 = "9813c8a3aeb72c3951d305e19a69dbbd17a3a6313bef938c20b1e214eb51e6e6",
+            url = "https://github.com/lowRISC/crt/archive/refs/tags/v0.4.16.tar.gz",
+            strip_prefix = "crt-0.4.16",
+            integrity = "sha256-25pTbQERCq1+X5rEudAIIVvxlm3ylMP4svFhOKx4WS0=",
         )