pagemap_dump!

kernel_module/user/README.md

@@ -12,6 +12,8 @@ These programs can also be compiled and used on host.
     1.  [myinsmod](myinsmod.c)
     1.  [myrmmod](myrmmod.c)
     1.  [init_hello](init_hello.c)
+    1.  [usermem](usermem.c)
+        1.  [pagemap_dump](pagemap_dump.c)
 1.  Module tests
     1.  [anonymous_inode](anonymous_inode.c)
     1.  [poll](poll.c)

kernel_module/user/pagemap_dump.c

@@ -0,0 +1,117 @@
+/*
+Only tested in x86_64.
+
+Adapted from: https://github.com/dwks/pagemap/blob/8a25747bc79d6080c8b94eac80807a4dceeda57a/pagemap2.c
+
+Dump the page map of a given process PID.
+
+Data sources: /proc/PIC/{map,pagemap}
+*/
+
+#define _POSIX_C_SOURCE 200809L
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/types.h>
+#define PAGE_SIZE 0x1000
+
+int main(int argc, char *argv[]) {
+	char buffer[BUFSIZ];
+	char maps_file[BUFSIZ];
+	char pagemap_file[BUFSIZ];
+	int maps;
+	int offset = 0;
+	int pagemap;
+
+	if (argc < 2) {
+		printf("Usage: %s pid1\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+	pid_t pid = (pid_t)strtoul(argv[1], NULL, 0);
+	snprintf(maps_file, sizeof(maps_file), "/proc/%lu/maps", (unsigned long)pid);
+	snprintf(pagemap_file, sizeof(pagemap_file), "/proc/%lu/pagemap", (unsigned long)pid);
+	maps = open(maps_file, O_RDONLY);
+	if (maps < 0) {
+		perror("open maps");
+		return EXIT_FAILURE;
+	}
+	pagemap = open(pagemap_file, O_RDONLY);
+	if (pagemap < 0) {
+		perror("open pagemap");
+		return EXIT_FAILURE;
+	}
+	printf("addr pfn soft-dirty file/shared swapped present library\n");
+	for (;;) {
+		ssize_t length = read(maps, buffer + offset, sizeof buffer - offset);
+		if (length <= 0) break;
+		length += offset;
+		for (size_t i = offset; i < (size_t)length; i++) {
+			unsigned long low = 0, high = 0;
+			if (buffer[i] == '\n' && i) {
+				size_t x = i - 1;
+				while(x && buffer[x] != '\n') x --;
+				if (buffer[x] == '\n') x++;
+				size_t beginning = x;
+				while(buffer[x] != '-' && x < sizeof buffer) {
+					char c = buffer[x++];
+					low *= 16;
+					if (c >= '0' && c <= '9') {
+						low += c - '0';
+					}
+					else if (c >= 'a' && c <= 'f') {
+						low += c - 'a' + 10;
+					}
+					else break;
+				}
+				while(buffer[x] != '-' && x < sizeof buffer) x++;
+				if (buffer[x] == '-') x++;
+				while(buffer[x] != ' ' && x < sizeof buffer) {
+					char c = buffer[x++];
+					high *= 16;
+					if (c >= '0' && c <= '9') {
+						high += c - '0';
+					}
+					else if (c >= 'a' && c <= 'f') {
+						high += c - 'a' + 10;
+					}
+					else break;
+				}
+
+				const char *lib_name = 0;
+				for (int field = 0; field < 4; field++) {
+					x++;
+					while(buffer[x] != ' ' && x < sizeof buffer) x++;
+				}
+				while (buffer[x] == ' ' && x < sizeof buffer) x++;
+				size_t y = x;
+				while (buffer[y] != '\n' && y < sizeof buffer) y++;
+				buffer[y] = 0;
+				lib_name = buffer + x;
+				{
+					unsigned long data;
+					for (unsigned long i = low; i < high; i += PAGE_SIZE) {
+						unsigned long index = (i / PAGE_SIZE) * sizeof(data);
+						if (pread(pagemap, &data, sizeof(data), index) != sizeof(data)) {
+							if (errno) perror("pread");
+							break;
+						}
+						printf("%lx %lx %d %d %d %d %s\n",
+							i,
+							data & 0x7fffffffffffff,
+							(data >> 55) & 1,
+							(data >> 61) & 1,
+							(data >> 62) & 1,
+							(data >> 63) & 1,
+							lib_name
+						);
+					}
+				}
+			}
+		}
+	}
+	close(maps);
+	close(pagemap);
+	return 0;
+}

kernel_module/user/usermem.c

@@ -0,0 +1,69 @@
+/*
+Only tested in x86_64.
+
+Provide an allocated userland memory address for us to test out kernel memory APIs, including:
+
+- /proc/pid/maps
+- /proc/pid/pagemap
+- /dev/mem
+
+Usage:
+
+	/usermem.out &
+
+Outputs address and pid, e.g.:
+
+	address 0x600800
+	pid 110
+
+Now translate the virtual address to physical for the given PID:
+
+	/pagemap2.out 110 | grep 0x600000
+
+where 0x600000 is the page that contains 0x600800.
+
+This produces a line of type:
+
+	0x600000 0x7c7b 0 0 0 1 /pagemap_test.out
+
+where 0x7c7b is the PFN. To get the physical address, just add three zeros back:
+
+	0x7c7b000
+
+Examine the physical memory from the QEMU monitor: on host:
+
+	./qemumonitor
+	xp 0x7c7b800
+
+Output:
+
+	0000000007c7b800: 0x12345678
+
+Yes!!! We read the correct value from the physical address.
+
+TODO: why does:
+
+	devmem2 0x7c7b800
+
+fail on the mmap? CONFIG_STRICT_DEVMEM is not set.
+*/
+
+#define _XOPEN_SOURCE 700
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+enum { I0 = 0x12345678 };
+
+static volatile uint32_t i = I0;
+
+int main(void) {
+	printf("address %p\n", (void *)&i);
+	printf("pid %ju\n", (uintmax_t)getpid());
+	while (i == I0) {
+		sleep(1);
+	}
+	printf("i %jx\n", (uintmax_t)i);
+	return EXIT_SUCCESS;
+}