[sw] Add DV_LOG_* macros for SW-to-DV logging

Each call site places a log_fields_t entry in a new .logs.fields ELF
section; extract_sw_logs.py produces the database consumed by
sw_logger_if to decode printf-style messages at simulation start, with
no UART overhead.

Add mocha_system_dv_log() to the HAL for CHERI-safe access to the log
write port (0x2002_0008). Add the .logs.fields section to the linker
script after .rodata so string constants are resolved before log entries
are laid out. Add dv_log.h/c implementing the DV_LOG_INFO/WARNING/ERROR/
FATAL macros and the runtime dv_log_write() function. Add
dv_log_smoketest to verify the end-to-end path.

Signed-off-by: martin-velay <mvelay@lowrisc.org>

Author: martin-velay

sw/device/lib/boot/mocha.ld

@@ -30,6 +30,17 @@ SECTIONS {
         . = ALIGN(8);
     } > ram
 
+    /* DV simulation log database. Each call site puts a log_fields_t entry here.
+     * extract_sw_logs.py reads the ELF section to produce a .logs.txt database
+     * consumed by sw_logger_if at simulation start. The first word is the section
+     * load address (header used by extract_sw_logs.py to map each entry to its
+     * runtime address). */
+    .logs.fields : {
+        QUAD(LOADADDR(.logs.fields));
+        KEEP(*(.logs.fields))
+        . = ALIGN(8);
+    } > ram
+
     /* capability relocation entries */
     /* __start___cap_relocs and __stop___cap_relocs are provided by the toolchain */
     __cap_relocs : {

sw/device/lib/hal/mocha.c

@@ -14,6 +14,7 @@
 static const uintptr_t rom_base = 0x80000ul;
 static const uintptr_t mailbox_base = 0x20010000ul;
 static const uintptr_t dv_test_status_base = 0x20020000ul;
+static const uintptr_t dv_log_base = 0x20020008ul;
 static const uintptr_t ethernet_base = 0x30000000ul;
 static const uintptr_t gpio_base = 0x40000000ul;
 static const uintptr_t clkmgr_base = 0x40020000ul;
@@ -201,3 +202,12 @@ void *mocha_system_dv_test_status(void)
     return (void *)dv_test_status_base;
 #endif /* defined(__riscv_zcherihybrid) */
 }
+
+void *mocha_system_dv_log(void)
+{
+#if defined(__riscv_zcherihybrid)
+    return create_mmio_capability(dv_log_base, 0x4u);
+#else /* !defined(__riscv_zcherihybrid) */
+    return (void *)dv_log_base;
+#endif /* defined(__riscv_zcherihybrid) */
+}

sw/device/lib/hal/mocha.h

@@ -52,3 +52,4 @@ plic_t mocha_system_plic(void);
 void *mocha_system_dram(void);
 
 void *mocha_system_dv_test_status(void);
+void *mocha_system_dv_log(void);

sw/device/lib/test_framework/CMakeLists.txt

@@ -2,7 +2,7 @@
 # Licensed under the Apache License, Version 2.0, see LICENSE for details.
 # SPDX-License-Identifier: Apache-2.0
 
-set(SRCS main.c)
+set(SRCS main.c dv_log.c)
 set(LIBS hal startup runtime)
 
 mocha_add_library(NAME test_framework SOURCES ${SRCS} LIBRARIES ${LIBS})

sw/device/lib/test_framework/dv_log.c

@@ -0,0 +1,23 @@
+// Copyright lowRISC contributors (COSMIC project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "test_framework/dv_log.h"
+
+#include <stdarg.h>
+
+#include "hal/mmio.h"
+#include "hal/mocha.h"
+
+void dv_log_write(const log_fields_t *log, ...)
+{
+    void *port = mocha_system_dv_log();
+    DEV_WRITE(port, (uint32_t)(uintptr_t)log);
+
+    va_list args;
+    va_start(args, log);
+    for (uint32_t i = 0; i < log->nargs; i++) {
+        DEV_WRITE(port, va_arg(args, uint32_t));
+    }
+    va_end(args);
+}

sw/device/lib/test_framework/dv_log.h

@@ -0,0 +1,54 @@
+// Copyright lowRISC contributors (COSMIC project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include <stdint.h>
+
+// SW-to-DV logging: writes a log_fields_t entry address + arguments to
+// SW_DV_LOG_ADDR; sw_logger_if reconstructs the formatted string in simulation.
+
+// const char * for string fields: required for a valid C99 static initialiser
+// (pointer-to-integer casts are not constant expressions).  extract_sw_logs.py
+// detects the rv64 ELF class and uses '<I4xQIIQ' (32 B) instead of '<IIIII'.
+typedef struct {
+    uint32_t    severity;
+    const char *file;
+    uint32_t    line;
+    uint32_t    nargs;
+    const char *format;
+} log_fields_t;
+
+// Writes the log entry address followed by each argument to SW_DV_LOG_ADDR.
+void dv_log_write(const log_fields_t *log, ...);
+
+// Count variadic arguments (0–8). DV_LOG_NARGS_SEQ_ is used directly by
+// DV_LOG_ rather than via a wrapper; see comment on DV_LOG_ for why.
+#define DV_LOG_NARGS_SEQ_(x1,x2,x3,x4,x5,x6,x7,x8,x9,N,...) N
+
+#define DV_LOG_CONCAT_(a, b) a##b
+#define DV_LOG_UNIQUE_(pfx)  DV_LOG_CONCAT_(pfx, __LINE__)
+
+// Internal macro shared by all severity levels.
+// DV_LOG_NARGS_SEQ_ is used inline (not via DV_LOG_NARGS wrapper) so that
+// ##__VA_ARGS__ operates directly on DV_LOG_'s own __VA_ARGS__.  Passing
+// __VA_ARGS__ through an extra macro call causes Clang to treat the empty
+// pack as one empty argument, returning N=1 instead of N=0 for 0-arg calls.
+#define DV_LOG_(sev, fmt, ...)                                               \
+    do {                                                                     \
+        static const log_fields_t DV_LOG_UNIQUE_(dv_log_entry_)             \
+            __attribute__((section(".logs.fields"), used)) = {               \
+                .severity = (sev),                                           \
+                .file     = __FILE__,                                        \
+                .line     = (uint32_t)__LINE__,                              \
+                .nargs    = DV_LOG_NARGS_SEQ_(x, ##__VA_ARGS__, 8,7,6,5,4,3,2,1,0), \
+                .format   = (fmt),                                           \
+            };                                                               \
+        dv_log_write(&DV_LOG_UNIQUE_(dv_log_entry_), ##__VA_ARGS__);         \
+    } while (0)
+
+#define DV_LOG_INFO(fmt, ...)    DV_LOG_(0, fmt, ##__VA_ARGS__)
+#define DV_LOG_WARNING(fmt, ...) DV_LOG_(1, fmt, ##__VA_ARGS__)
+#define DV_LOG_ERROR(fmt, ...)   DV_LOG_(2, fmt, ##__VA_ARGS__)
+#define DV_LOG_FATAL(fmt, ...)   DV_LOG_(3, fmt, ##__VA_ARGS__)

sw/device/tests/CMakeLists.txt

@@ -6,6 +6,7 @@ set(LIBS hal runtime startup test_framework)
 
 mocha_add_test(NAME test_framework_test SOURCES test_framework/smoketest.c LIBRARIES ${LIBS} VERILATOR_TIMEOUT 20 FPGA_TIMEOUT 10)
 mocha_add_test(NAME test_framework_exception_test SOURCES test_framework/exception.c LIBRARIES ${LIBS})
+mocha_add_test(NAME dv_log_smoketest SOURCES test_framework/dv_log_smoketest.c LIBRARIES ${LIBS} SKIP_VERILATOR SKIP_FPGA)
 mocha_add_test(NAME axi_sram_smoketest SOURCES axi_sram/smoketest.c LIBRARIES ${LIBS})
 mocha_add_test(NAME axi_sram_tag_test SOURCES axi_sram/tag_test.c LIBRARIES ${LIBS})
 mocha_add_test(NAME entropy_src_smoketest SOURCES entropy_src/smoketest.c LIBRARIES ${LIBS})

sw/device/tests/test_framework/dv_log_smoketest.c

@@ -0,0 +1,20 @@
+// Copyright lowRISC contributors (COSMIC project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+// Smoke test for the SW-DV log interface.
+
+#include "test_framework/dv_log.h"
+#include "hal/uart.h"
+
+bool test_main(uart_t console)
+{
+    (void)console;
+
+    DV_LOG_INFO("SW-DV log smoketest starting...");
+    DV_LOG_INFO("a = %d, b = %d, c = %d", 10, 20, 12);
+    DV_LOG_INFO("a + b + c = %d", 42);
+    DV_LOG_INFO("Smoke test for the SW-DV log interface, completed successfully!");
+
+    return true;
+}