Add more code on dynamic link testing

.gitignore

@@ -1,3 +1,4 @@
 kernel-hdr
 build
 progs/rsh
+etc/rc.d/99-imtesting

progs/dyn/Makefile

@@ -1,7 +1,13 @@
 CC?=$(CROSS_COMPILE)gcc
 O=build
 
-all: mkdirs $(O)/dyn $(O)/ld
+CFLAGS=-Wall \
+	   -Werror \
+	   -Wextra \
+	   -z max-page-size=0x1000 \
+	   -O0
+
+all: mkdirs $(O)/dyn $(O)/test $(O)/ld
 
 mkdirs:
 	mkdir -p $(O)
@@ -9,20 +15,24 @@ mkdirs:
 clean:
 	rm -rf $(O)
 
-install: mkdirs $(O)/dyn $(O)/ld
+install: mkdirs $(O)/dyn $(O)/test $(O)/ld
 	mkdir -p $(DESTDIR)/lib $(DESTDIR)/bin
 	install -D -m 0755 $(O)/dyn $(DESTDIR)/bin/
 	install -D -m 0755 $(O)/libfunc.so $(DESTDIR)/lib/
 	install -D -m 0755 $(O)/ld $(DESTDIR)/lib/
+	install -D -m 0755 $(O)/test $(DESTDIR)/bin/dyntest
 
-$(O)/ld: ld.c
-	$(CC) -static -o $@ $+
+$(O)/ld: ld.c ld-link.ld
+	$(CC) $(CFLAGS) -Tld-link.ld -static -o $@ ld.c
 
 $(O)/libfunc.o: lib.c
-	$(CC) -fPIC -c -o $@ $<
+	$(CC) $(CFLAGS) -fPIC -c -o $@ $<
 
 $(O)/libfunc.so: $(O)/libfunc.o
 	$(CROSS_COMPILE)ld -shared -o $@ $+
 
+$(O)/test: test.c
+	$(CC) $(CFLAGS) -nostdlib -o $@ test.c
+
 $(O)/dyn: dyn.c $(O)/libfunc.so
-	$(CC) -L$(O) -lfunc -o $@ dyn.c
+	$(CC) $(CFLAGS) -L$(O) -lfunc -o $@ dyn.c

progs/dyn/ld-link.ld

@@ -0,0 +1,23 @@
+ENTRY(_start);
+
+SECTIONS {
+    . = 0x200000;
+
+    _ld_start = .;
+    .text : ALIGN(4K) {
+        *(.init .fini)
+        *(.text .text.*)
+        *(.rodata .rodata.*)
+    }
+
+    .data : ALIGN(4K) {
+        *(.ctors .dtors)
+        *(.data .data.*)
+    }
+
+    .bss : ALIGN(4K) {
+        *(.bss)
+        *(COMMON)
+    }
+    _ld_end = .;
+}

progs/dyn/ld.c

@@ -1,9 +1,139 @@
+#include <sys/mman.h>
+#include <unistd.h>
 #include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
 #include <stdio.h>
+#include <errno.h>
 #include "elf.h"
 
-int main(int argc, char **argv) {
-    fprintf(stderr, "Dynamic linking not yet implemented\n");
-    exit(-1);
+extern char _ld_start, _ld_end;
+
+struct object {
+    //FILE *fp;
+    int fd;
+    Elf64_Ehdr ehdr;
+};
+
+static int elf_read(struct object *obj, void *dst, size_t count, off_t pos) {
+    ssize_t bread;
+    if (lseek(obj->fd, pos, SEEK_SET) != pos) {
+        return -1;
+    }
+    if ((bread = read(obj->fd, dst, count)) < 0) {
+        return -1;
+    }
+    if ((size_t) bread != count) {
+        errno = ENOEXEC;
+        return -1;
+    }
+    return 0;
+}
+
+static struct object *object_open(const char *pathname) {
+    struct object *obj = calloc(1, sizeof(struct object));
+
+    obj->fd = open(pathname, O_RDONLY, 0);
+    if (obj->fd < 0) {
+        return NULL;
+    }
+
+    if (elf_read(obj, &obj->ehdr, sizeof(Elf64_Ehdr), 0) != 0) {
+        close(obj->fd);
+        free(obj);
+        return NULL;
+    }
+
+    return obj;
+}
+
+static void object_close(struct object *obj) {
+    close(obj->fd);
+    free(obj);
+}
+
+static int object_load(struct object *obj) {
+    Elf64_Phdr phdr;
+
+    printf("%u program headers\n", obj->ehdr.e_phnum);
+    for (size_t i = 0; i < obj->ehdr.e_phnum; ++i) {
+        off_t phoff = obj->ehdr.e_phoff + i * obj->ehdr.e_phentsize;
+
+        if (elf_read(obj, &phdr, obj->ehdr.e_phentsize, phoff) != 0) {
+            return -1;
+        }
+
+        switch (phdr.p_type) {
+        case PT_LOAD:
+            {
+                uintptr_t base = phdr.p_vaddr & ~0xFFF;
+                size_t size = (((phdr.p_vaddr + phdr.p_memsz + 0xFFF) & ~0xFFF) - base) / 0x1000;
+
+                if (base < (uintptr_t) &_ld_end) {
+                    fprintf(stderr, "Segment will overwrite the loader code\n");
+                    errno = ENOEXEC;
+                    return -1;
+                }
+
+                void *addr = mmap((void *) base,
+                                  size * 0x1000,
+                                  PROT_READ | PROT_WRITE,
+                                  MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
+                                  -1, 0);
+                if (addr == MAP_FAILED) {
+                    perror("mmap()");
+                    return -1;
+                }
+
+                // Load filesz bytes
+                if (elf_read(obj, (void *) phdr.p_vaddr, phdr.p_filesz, phdr.p_offset) != 0) {
+                    return -1;
+                }
+
+                // Zero (memsz - filesz) bytes
+                if (phdr.p_memsz > phdr.p_filesz) {
+                    memset((void *) phdr.p_vaddr + phdr.p_filesz, 0, phdr.p_memsz - phdr.p_filesz);
+                }
+            }
+            break;
+        case PT_DYNAMIC:
+            fprintf(stderr, "TODO: handle dynamic binaries\n");
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+int main(int argc, char **argv) {
+    const char *prog;
+    struct object *program;
+
+    printf("_ld_start = %p, _ld_end = %p\n", &_ld_start, &_ld_end);
+
+    if (argc < 2) {
+        fprintf(stderr, "usage: %s PROGRAM [ARGS...]\n", argv[0]);
+        return -1;
+    }
+
+    prog = argv[1];
+    program = object_open(prog);
+
+    if (!program) {
+        fprintf(stderr, "Failed to load program: %s\n", prog);
+        return -1;
+    }
+
+    if (object_load(program) != 0) {
+        fprintf(stderr, "Failed to load object\n");
+    }
+
+    void (*entry) (void *p) = (void (*) (void *)) program->ehdr.e_entry;
+
+    object_close(program);
+
+    // TODO: form arg pointer like kernel does
+    entry(NULL);
+
     return 0;
 }

progs/dyn/test.c

@@ -0,0 +1,35 @@
+
+
+static inline long __syscall3(long n, long a1, long a2, long a3) {
+    unsigned long ret;
+    asm volatile ("syscall"
+                 :"=a"(ret)
+                 :"a"(n),"D"(a1),"S"(a2),"d"(a3)
+                 :"rcx","r11","memory");
+    return ret;
+}
+
+static inline long __syscall1(long n, long a1) {
+    unsigned long ret;
+    asm volatile ("syscall"
+                 :"=a"(ret)
+                 :"a"(n),"D"(a1)
+                 :"rcx","r11","memory");
+    return ret;
+}
+
+char data[128] = {0};
+
+void _start(void *arg) {
+    (void) arg;
+    const char *src = "abcde!\n";
+    for (long i = 0; i < 128; ++i) {
+        data[i] = src[i];
+        if (!src[i]) {
+            break;
+        }
+    }
+    __syscall3(1, 1, (long) data, 7);
+    __syscall1(60, 0);
+    while (1);
+}