* add macos support; no VMA filtering

* add macos REL sample

Author: blu

Makefile

@@ -5,30 +5,31 @@ CXXFLAGS += -std=c++11 -Ofast -fno-exceptions -fno-rtti -DNDEBUG -DPAGE_SIZE=$(s
 LDFLAGS += -lelf
 ASFLAGS += --strip-local-absolute
 # Optional test objects built by target ALL
-REL := test_rodata.o \
-	test_data.o \
-	test_bss.o \
-	test_cross_0.o \
-	test_cross_1.o \
-	test_bounce.o \
-	test_bounce_neon.o \
-	test_bounce_neon_aosoa.o \
-	test_bounce_neon_aosoa_bg.o \
-	test_bounce_data_aosoa_alt_0.o \
-	test_bounce_data_aosoa_alt_1.o \
-	test_bounce_data_aosoa_alt_2.o \
-	test_bounce_data_aosoa_alt_3.o
+REL := test_text.o \
+       test_rodata.o \
+       test_data.o \
+       test_bss.o \
+       test_cross_0.o \
+       test_cross_1.o \
+       test_bounce.o \
+       test_bounce_neon.o \
+       test_bounce_neon_aosoa.o \
+       test_bounce_neon_aosoa_bg.o \
+       test_bounce_data_aosoa_alt_0.o \
+       test_bounce_data_aosoa_alt_1.o \
+       test_bounce_data_aosoa_alt_2.o \
+       test_bounce_data_aosoa_alt_3.o
 
 OBJ := $(addsuffix .o, $(basename $(filter %.s %.c %.cpp, $(SRC))))
 
 $(TARGET): $(OBJ)
 	$(CC) $^ $(LDFLAGS) -o $(TARGET)
 
-reloc.o: reloc.c vma.h
+reloc.o: reloc.c vma.h char_ptr_arr.h
 
 reloc_add_aarch64.o: reloc_add_aarch64.c insn.h
 
-vma.o: vma.cpp vma.h
+vma.o: vma.cpp vma.h char_ptr_arr.h
 
 test_bounce.o: test_bounce.s
 	$(AS) $(ASFLAGS) --defsym FB_DIM_X=$(shell tput cols) --defsym FB_DIM_Y=$(shell tput lines) --defsym FRAMES=1024 -o $@ $^

Makefile.macos

@@ -0,0 +1,21 @@
+SRC := reloc.c reloc_add_aarch64.c insn.h
+TARGET := elvenrel
+CFLAGS += -std=gnu11 -Ofast -DNDEBUG -DPAGE_SIZE=$(shell getconf PAGE_SIZE) -fno-stack-protector -fPIC -I/opt/homebrew/include
+LDFLAGS += /opt/homebrew/lib/libelf.a
+ASFLAGS += --target=aarch64-none-linux-gnu
+# Optional test objects built by target ALL
+REL := test_text_macos.o
+
+OBJ := $(addsuffix .o, $(basename $(filter %.s %.c %.cpp, $(SRC))))
+
+$(TARGET): $(OBJ)
+	$(CC) $^ $(LDFLAGS) -o $(TARGET)
+
+reloc.o: reloc.c char_ptr_arr.h
+
+reloc_add_aarch64.o: reloc_add_aarch64.c insn.h
+
+all: $(TARGET) $(REL)
+
+clean:
+	rm -f $(TARGET) $(OBJ) $(REL)

README.md

@@ -1,15 +1,15 @@
 ## elvenrel
 
-Elven Relativism -- relocation and execution of aarch64 ELF relocatable objects (REL)
+Elven Relativism -- relocation and execution of aarch64 ELF relocatable objects (REL) on Linux and macOS.
 
 Program loads a multitude of ELF REL files, resolves all relocations (currently only SHT_RELA) and if symbol `_start` in some section `.text` is found, passes control to the former.
 
 ## Details
 
 * RELs loaded in the order specified on the command line; all relocations in a given REL performed at its loading time.
 * Missing-symbol (SHN_UNDEF) resolution via reverse-direction search among the preceding RELs; first-match deterministic.
-* Support for RO sections `.rodata` and `.text`; every other type of section is RW; `.bss` addressing may take HI21/LO12.
-* Address-space sanitation -- disposing of pre-existing VMAs (*VMA filtering*) via string matching to VMA backing path.
+* Support for RO sections `.rodata` and `.text`; every other type of section is RW.
+* Address-space sanitation (linux-only) -- disposing of pre-existing VMAs (*VMA filtering*) via string matching to VMA backing path.
 
 ## ToDo
 
@@ -24,10 +24,14 @@ Files used, with or without modifications, from external repositories:
 	linux.org/ arch/arm64/kernel/module.c    -> reloc_add_aarch64.c
 	linux.org/ arch/arm64/lib/strlen.S       -> strlen_linux.s
 
-## Building
+## Building: linux
 
 	$ make all
 
+## Building: macos
+
+	$ make -f Makefile.macos all
+
 ## Usage
 
 ```sh

char_ptr_arr.h

@@ -0,0 +1,10 @@
+#ifndef __char_ptr_arr_H__
+#include <stddef.h>
+
+struct char_ptr_arr_t {
+	size_t count;
+	char **arr;
+};
+
+#endif /* __char_ptr_arr_H__ */
+

reloc.c

@@ -7,7 +7,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#if __APPLE__ != 0
+#include <libelf/libelf.h>
+#else
 #include <libelf.h>
+#endif
 #include <fcntl.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -16,7 +20,23 @@
 #include <sys/stat.h>
 #include <sys/mman.h>
 
+#if __APPLE__ != 0
+#include "char_ptr_arr.h"
+#else
 #include "vma.h"
+#endif
+
+#if __APPLE__ != 0
+#ifndef EM_AARCH64
+#define EM_AARCH64 183
+#endif
+
+#ifndef MAP_POPULATE
+#define MAP_POPULATE 0
+#endif
+
+typedef Elf64_Half Elf64_Section;
+#endif
 
 int apply_relocate_add(Elf64_Shdr **sechdrs,
 					   unsigned int symsec,
@@ -63,12 +83,12 @@ const char *str_from_st_type(uint8_t x)
 		return "STT_TLS";
 	case STT_NUM:
 		return "STT_NUM";
-#if 0
 	case STT_LOOS:
 		return "STT_LOOS";
-#endif
+#if 0
 	case STT_GNU_IFUNC:
 		return "STT_GNU_IFUNC";
+#endif
 	case STT_HIOS:
 		return "STT_HIOS";
 	case STT_LOPROC:
@@ -90,12 +110,12 @@ const char *str_from_st_bind(uint8_t x)
 		return "STB_WEAK";
 	case STB_NUM:
 		return "STB_NUM";
-#if 0
 	case STB_LOOS:
 		return "STB_LOOS";
-#endif
+#if 0
 	case STB_GNU_UNIQUE:
 		return "STB_GNU_UNIQUE";
+#endif
 	case STB_HIOS:
 		return "STB_HIOS";
 	case STB_LOPROC:
@@ -253,14 +273,14 @@ static int
 	_load_elf_file_details(
 		Elf *elf,
 		ElfDetails *ret_details,
-		ptrdiff_t diff_exec)
+		void *rawdata_rw,
+		void *rawdata_ro)
 {
 	ElfDetails details;
 	char *ehdr_ident;
 	Elf64_Ehdr *ehdr64;
 	Elf64_Shdr *shdr64;
 	Elf_Scn *scn;
-	Elf_Data *data;
 	const char *scn_name;
 	Elf64_Shdr **section_list;
 	size_t scn_idx, n_elf_scns;
@@ -434,33 +454,26 @@ static int
 			}
 		}
 
-		/* Resolve the vaddr and size of ELF section data */
-		if ((data = elf_getdata(scn, 0)) != NULL) {
-			if (shdr64->sh_size != data->d_size) {
-				return -1;
-			}
-			/* Ignore empty sections */
-			if (data->d_size != 0) {
-				/* Section .bss does not have file backing */
-				if (scn_idx == bss_idx) {
-					const int prot_rw = PROT_READ | PROT_WRITE;
-					const int flag_priv_anon = MAP_PRIVATE | MAP_ANONYMOUS | MAP_POPULATE;
-
-					void *p = mmap(NULL, data->d_size, prot_rw, flag_priv_anon, -1, 0);
-
-					if (p == MAP_FAILED) {
-						fprintf(stderr, "error: cannot mmap bss\n");
-						return -1;
-					}
+		/* Resolve the vaddr of non-empty ELF section data */
+		if (shdr64->sh_size != 0) {
+			/* Section .bss does not have file backing */
+			if (scn_idx == bss_idx) {
+				const int prot_rw = PROT_READ | PROT_WRITE;
+				const int flag_priv_anon = MAP_PRIVATE | MAP_ANONYMOUS | MAP_POPULATE;
 
-					shdr64->sh_addr = (Elf64_Addr)p;
-				} else {
-					shdr64->sh_addr = (Elf64_Addr)data->d_buf;
+				void *p = mmap(NULL, shdr64->sh_size, prot_rw, flag_priv_anon, -1, 0);
 
-					if (scn_idx == text_idx ||
-					    scn_idx == rodata_idx) {
-						shdr64->sh_addr += diff_exec;
-					}
+				if (p == MAP_FAILED) {
+					fprintf(stderr, "error: cannot mmap bss\n");
+					return -1;
+				}
+
+				shdr64->sh_addr = (Elf64_Addr)p;
+			} else {
+				if (scn_idx == text_idx || scn_idx == rodata_idx) {
+					shdr64->sh_addr = (Elf64_Addr)(rawdata_ro + shdr64->sh_offset);
+				} else {
+					shdr64->sh_addr = (Elf64_Addr)(rawdata_rw + shdr64->sh_offset);
 				}
 			}
 		}
@@ -509,16 +522,21 @@ static int
 	relocate_elf_load_cu(
 		Elf *elf,
 		void **start,
-		ptrdiff_t diff_exec,
+		void *rawdata_rw,
+		void *rawdata_ro,
 		int flag_quiet)
 {
 	ElfDetails details = NULL;
 	Elf64_Sym *symtab;
 	uint64 n_symbols, i;
 	int rc;
 
+	if (!elf || !start || !rawdata_rw || !rawdata_ro) {
+		return -1;
+	}
+
 	/* Load ELF file section and symbol tables */
-	rc = _load_elf_file_details(elf, &details, diff_exec);
+	rc = _load_elf_file_details(elf, &details, rawdata_rw, rawdata_ro);
 	if (rc)
 		goto term;
 
@@ -554,7 +572,7 @@ static int
 		}
 
 		if (!flag_quiet) {
-			printf("%2ld: %016lx %-13s %-14s %-17s %s\n",
+			printf("%2lu: %016lx %-13s %-14s %-17s %s\n",
 				i,
 				symtab->st_value,
 				str_from_st_type(ELF64_ST_TYPE(symtab->st_info)),
@@ -591,15 +609,19 @@ static int
 static void print_usage(char **argv)
 {
 	printf("usage: %s <elf_rel_file> [<elf_rel_file>] ..\n"
+#if __APPLE__ == 0
 	       "\t--filter <string> : filter file mappings containing the specified string\n"
+#endif
 	       "\t--quiet           : suppress all reports\n"
 	       "\t--help            : this message\n", argv[0]);
 }
 
 int main(int argc, char **argv)
 {
 	size_t areas_capacity = 0, objs_capacity = 0;
+#if __APPLE__ == 0
 	struct char_ptr_arr_t areas = { .count = 0, .arr = NULL };
+#endif
 	struct char_ptr_arr_t objs = { .count = 0, .arr = NULL };
 	Elf *prev_elf = NULL;
 	void *start = NULL;
@@ -622,6 +644,7 @@ int main(int argc, char **argv)
 			continue;
 		}
 
+#if __APPLE__ == 0
 		if (!strcmp(argv[i], "--filter")) {
 			if (++i == argc) {
 				print_usage(argv);
@@ -634,6 +657,7 @@ int main(int argc, char **argv)
 			continue;
 		}
 
+#endif
 		/* Unprefixed arg must be a file */
 		if (objs.count == objs_capacity) {
 			objs.arr = (char **)realloc(objs.arr, objs_capacity = (objs_capacity + 1) * 2);
@@ -698,7 +722,7 @@ int main(int argc, char **argv)
 		ehdr64->e_entry = (Elf64_Addr)prev_elf;
 		prev_elf = elf;
 
-		if (relocate_elf_load_cu(elf, &start, q - p, flag_quiet)) {
+		if (relocate_elf_load_cu(elf, &start, p, q, flag_quiet)) {
 			fprintf(stderr, "error: cannot relocate_elf_load_cu\n");
 			return -1;
 		}
@@ -709,9 +733,11 @@ int main(int argc, char **argv)
 		}
 	}
 
+#if __linux__ != 0
 	if (areas.count && areas.arr != NULL)
 		vma_process(&areas, flag_quiet);
 
+#endif
 	if (start != NULL)
 		((void (*)(void))start)();