Start adding abstract memory access for better tracing

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>

3 files changed, 133 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index e137324..0000e8f 100644
--- a/Makefile
+++ b/Makefile
@@ -5,6 +5,7 @@ SOURCE := \
 	exynos4412_gpios.c  \
 	exynos4412_gpios_data.c \
 	main.c \
+	memory.c \
 	modem_gpios_data.c \
 	tests.c \
 
diff --git a/memory.c b/memory.c
new file mode 100644
index 0000000..d05cee2
--- /dev/null
+++ b/memory.c
@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) 2021 Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+#include "memory.h"
+
+struct memory_mapping {
+	unsigned int *mmap_phys_base;
+	unsigned int *mmap_virt_base;
+	unsigned int mmap_length;
+};
+
+static bool addr_is_valid(struct memory_mapping *memory_mapping,
+			  unsigned int *addr)
+{
+	if (addr < memory_mapping->mmap_phys_base)
+		return false;
+
+	if (addr > (memory_mapping->mmap_phys_base + memory_mapping->mmap_length))
+		return false;
+
+	return true;
+}
+
+int init_memory_mapping(int debug, struct memory_mapping *memory_mapping,
+			off_t addr, size_t length)
+{
+	int fd;
+	int rc;
+	char *devmem = "/dev/mem";
+
+	fd =  open(devmem, O_RDWR | O_SYNC);
+	if (fd == -1) {
+		rc = errno;
+		printf("%s: opening %s failed with error %d: %s\n",
+		       __func__, devmem, rc, strerror(rc));
+		return -1;
+	}
+
+	memory_mapping->mmap_virt_base = mmap(0, length, PROT_READ|PROT_WRITE,
+					      MAP_SHARED, fd, addr);
+	if (memory_mapping->mmap_virt_base == MAP_FAILED) {
+		rc = errno;
+		printf("%s: mmap on %s failed with error %d: %s\n",
+		       __func__, devmem, rc, strerror(rc));
+		return -1;
+	}
+
+	rc = close(fd);
+	if (rc == -1) {
+		rc = errno;
+		printf("Closing %s failed with error %d: %s\n",
+		       devmem, rc, strerror(rc));
+		return -1;
+	}
+
+	if (debug)
+		printf("%s: mapped address 0 @ %p\n", __func__,
+		       memory_mapping->mmap_virt_base);
+
+	return 0;
+}
+
+int read_word(int debug, struct memory_mapping *memory_mapping,
+	      unsigned int addr, unsigned int *result)
+{
+	unsigned int *virt_addr;
+
+	if (!addr_is_valid(memory_mapping, (unsigned int *)addr))
+		return -EDOM;
+
+	virt_addr = memory_mapping->mmap_virt_base + addr;
+
+	*result = *virt_addr;
+
+	if (debug)
+		printf("%s: debug=%d, addr=0x%x, result=0x%x\n",
+		       __func__, debug, addr, *result);
+
+	return 0;
+}
diff --git a/memory.h b/memory.h
new file mode 100644
index 0000000..5a03e4d
--- /dev/null
+++ b/memory.h
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2021 Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef MEMORY_H
+#define MEMORY_H
+
+struct memory_mapping;
+
+int init_memory_mapping(int debug, struct memory_mapping *memory_mapping,
+			off_t addr, size_t length);
+int read_word(int debug, struct memory_mapping *memory_mapping,
+	      unsigned int addr, unsigned int *result);
+
+#endif /* MEMORY_H */