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-rw-r--r--lib/Makefile25
-rw-r--r--lib/include/auxv.h36
-rw-r--r--lib/include/elf.h75
-rw-r--r--lib/include/fmt.h8
-rw-r--r--lib/include/io.h5
-rw-r--r--lib/include/syscall.h63
-rw-r--r--lib/src/fmt.c117
-rw-r--r--lib/src/io.c37
8 files changed, 366 insertions, 0 deletions
diff --git a/lib/Makefile b/lib/Makefile
new file mode 100644
index 0000000..29c103a
--- /dev/null
+++ b/lib/Makefile
@@ -0,0 +1,25 @@
+# Copyright (c) 2020 Johannes Stoelp
+
+HDR+=include/auxv.h
+HDR+=include/elf.h
+HDR+=include/fmt.h
+HDR+=include/io.h
+HDR+=include/syscall.h
+
+DEP+=src/io.o
+DEP+=src/fmt.o
+
+libcommon.a: $(HDR) $(DEP)
+ ar -crs $@ $(filter %.o, $^)
+
+src/%.o: src/%.c
+ gcc -c -o $@ \
+ -g -O0 \
+ -Wall -Wextra \
+ -I$(CURDIR)/include \
+ -nostdlib \
+ $<
+
+clean:
+ rm -f $(DEP)
+ rm -f libcommon.a
diff --git a/lib/include/auxv.h b/lib/include/auxv.h
new file mode 100644
index 0000000..42dac38
--- /dev/null
+++ b/lib/include/auxv.h
@@ -0,0 +1,36 @@
+// Copyright (c) 2020 Johannes Stoelp
+
+#pragma once
+
+#include <stdint.h>
+
+/// ----------------
+/// Auxiliary Vector
+/// ----------------
+
+// NOTE: [x86-64] Either AT_EXECFD or AT_PHDR must be supplied by the Kernel.
+
+#define AT_NULL 0 /* [ignored] Mark end of auxiliary vetcor */
+#define AT_IGNORE 1 /* [ignored] */
+#define AT_EXECFD 2 /* [val] File descriptor of user program (in case Linux Kernel didn't mapped) */
+#define AT_PHDR 3 /* [ptr] Address of Phdr of use program (in case Kernel mapped user program) */
+#define AT_PHENT 4 /* [val] Size in bytes of one Phdr entry */
+#define AT_PHNUM 5 /* [val] Number of Phread entries */
+#define AT_PAGESZ 6 /* [val] System page size */
+#define AT_BASE 7 /* [ptr] `base address` interpreter was loaded to */
+#define AT_FLAGS 8 /* [val] */
+#define AT_ENTRY 9 /* [ptr] Entry point of user program */
+#define AT_NOTELF 10 /* [val] >0 if not an ELF file */
+#define AT_UID 11 /* [val] Real user id of process */
+#define AT_EUID 12 /* [val] Effective user id of process */
+#define AT_GID 13 /* [val] Real group id of process */
+#define AT_EGID 14 /* [val] Effective user id of process */
+#define AT_MAX_CNT 15
+
+typedef struct {
+ uint64_t tag;
+ union {
+ uint64_t val;
+ void* ptr;
+ };
+} Auxv64Entry;
diff --git a/lib/include/elf.h b/lib/include/elf.h
new file mode 100644
index 0000000..a0fe6f7
--- /dev/null
+++ b/lib/include/elf.h
@@ -0,0 +1,75 @@
+// Copyright (c) 2020 Johannes Stoelp
+
+#pragma once
+
+#include <stdint.h>
+
+/// --------------
+/// Program Header
+/// --------------
+
+#define PT_NULL 0 /* ignored */
+#define PT_LOAD 1 /* Mark loadable segment (allowed p_memsz > p_filesz). */
+#define PT_DYNAMIC 2 /* Location of .dynamic section */
+#define PT_INTERP 3 /* Location of .interp section */
+#define PT_NOTE 4 /* Location of auxiliary information */
+#define PT_SHLIB 5 /* Reserved, but unspecified semantic */
+#define PT_PHDR 6 /* Location & size of program headers itself */
+
+#define PT_GNU_EH_FRAME 0x6474e550 /* [x86-64] stack unwinding tables */
+#define PT_LOPROC 0x70000000
+#define PT_HIPROC 0x7fffffff
+
+#define PF_X 0x1 /* Phdr flag eXecute flag bitmask */
+#define PF_W 0x2 /* Phdr flag Write flag bitmask */
+#define PF_R 0x4 /* Phdr flag Read flag bitmask */
+
+typedef struct {
+ uint32_t type; // Segment kind.
+ uint32_t flags; // Flags describing Segment attributes like R, W, X.
+ uint64_t offset; // Offset into the file where the Segment starts.
+ uint64_t vaddr; // Virtual address of first byte of Segment in memory.
+ uint64_t paddr; // Physical address, ignored in our case.
+ uint64_t filesz; // Number of bytes of the Segment in the file image.
+ uint64_t memsz; // Number of bytes of the segement in memory.
+ uint64_t align;
+} Elf64Phdr;
+
+/// ---------------
+/// Dynamic Section
+/// ---------------
+
+#define DT_NULL 0 /* [ignored] Marks end of dynamic section */
+#define DT_NEEDED 1 /* [val] Name of needed library */
+#define DT_PLTRELSZ 2 /* [val] Size in bytes of PLT relocs */
+#define DT_PLTGOT 3 /* [ptr] Processor defined value */
+#define DT_HASH 4 /* [ptr] Address of symbol hash table */
+#define DT_STRTAB 5 /* [ptr] Address of string table */
+#define DT_SYMTAB 6 /* [ptr] Address of symbol table */
+#define DT_RELA 7 /* [ptr] Address of Rela relocs */
+#define DT_RELASZ 8 /* [val] Total size of Rela relocs */
+#define DT_RELAENT 9 /* [val] Size of one Rela reloc */
+#define DT_STRSZ 10 /* [val] Size of string table */
+#define DT_SYMENT 11 /* [val] Size of one symbol table entry */
+#define DT_INIT 12 /* [ptr] Address of init function */
+#define DT_FINI 13 /* [ptr] Address of termination function */
+#define DT_SONAME 14 /* [val] Name of shared object */
+#define DT_RPATH 15 /* [val] Library search path (deprecated) */
+#define DT_SYMBOLIC 16 /* [ignored] Start symbol search here */
+#define DT_REL 17 /* [ptr] Address of Rel relocs */
+#define DT_RELSZ 18 /* [val] Total size of Rel relocs */
+#define DT_RELENT 19 /* [val] Size of one Rel reloc */
+#define DT_PLTREL 20 /* [val] Type of reloc in PLT */
+#define DT_DEBUG 21 /* [ptr] For debugging; unspecified */
+#define DT_TEXTREL 22 /* [ignored] Reloc might modify .text */
+#define DT_JMPREL 23 /* [ptr] Address of PLT relocs */
+#define DT_BIND_NOW 24 /* [ignored] Process relocations of object */
+#define DT_MAX_CNT 25
+
+typedef struct {
+ uint64_t tag;
+ union {
+ uint64_t val;
+ void* ptr;
+ };
+} Elf64Dyn;
diff --git a/lib/include/fmt.h b/lib/include/fmt.h
new file mode 100644
index 0000000..61215bc
--- /dev/null
+++ b/lib/include/fmt.h
@@ -0,0 +1,8 @@
+// Copyright (c) 2020 Johannes Stoelp
+
+#pragma once
+
+#include <stdarg.h>
+
+int vfmt(char* buf, unsigned long len, const char* fmt, va_list ap);
+int fmt(char* buf, unsigned long len, const char* fmt, ...);
diff --git a/lib/include/io.h b/lib/include/io.h
new file mode 100644
index 0000000..5ca78a3
--- /dev/null
+++ b/lib/include/io.h
@@ -0,0 +1,5 @@
+// Copyright (c) 2020 Johannes Stoelp
+
+#pragma once
+
+int pfmt(const char* fmt, ...);
diff --git a/lib/include/syscall.h b/lib/include/syscall.h
new file mode 100644
index 0000000..4947155
--- /dev/null
+++ b/lib/include/syscall.h
@@ -0,0 +1,63 @@
+// Copyright (c) 2020 Johannes Stoelp
+
+#pragma once
+
+#if !defined(__linux__) || !defined(__x86_64__)
+# error "Only supported on linux(x86_64)!"
+#endif
+
+// Inline ASM
+// Syntax:
+// asm asm-qualifiers (AssemblerTemplate : OutputOperands : InputOperands : Clobbers)
+//
+// Output operand constraints:
+// = | operand (variable) is written to by this instruction
+// + | operand (variable) is written to / read from by this instruction
+//
+// Input/Output operand constraints:
+// r | allocate general purpose register
+//
+// Machine specific constraints (x86_64):
+// a | a register (eg rax)
+// d | d register (eg rdx)
+// D | di register (eg rdi)
+// S | si register (eg rsi)
+//
+// Local register variables:
+// In case a specific register is required which can not be specified via a
+// machine specific constraint.
+// ```c
+// register long r12 asm ("r12") = 42;
+// asm("nop" : : "r"(r12));
+// ```
+//
+// Reference:
+// https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
+// https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html#Machine-Constraints
+// https://gcc.gnu.org/onlinedocs/gcc/Local-Register-Variables.html
+
+// Linux syscall ABI
+// x86-64
+// #syscall: rax
+// ret : rax
+// instr : syscall
+// args : rdi rsi rdx r10 r8 r9
+//
+// Reference:
+// syscall(2)
+
+#define argcast(A) ((long)(A))
+#define syscall1(n, a1) _syscall1(n, argcast(a1))
+#define syscall3(n, a1, a2, a3) _syscall3(n, argcast(a1), argcast(a2), argcast(a3))
+
+static inline long _syscall1(long n, long a1) {
+ long ret;
+ asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1) : "memory");
+ return ret;
+}
+
+static inline long _syscall3(long n, long a1, long a2, long a3) {
+ long ret;
+ asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1), "S"(a2), "d"(a3) : "memory");
+ return ret;
+}
diff --git a/lib/src/fmt.c b/lib/src/fmt.c
new file mode 100644
index 0000000..be1ca3a
--- /dev/null
+++ b/lib/src/fmt.c
@@ -0,0 +1,117 @@
+// Copyright (c) 2020 Johannes Stoelp
+
+#include <fmt.h>
+
+static const char* num2dec(char* buf, unsigned long len, unsigned long long num) {
+ char* pbuf = buf + len - 1;
+ *pbuf = '\0';
+
+ if (num == 0) {
+ *(--pbuf) = '0';
+ }
+
+ while (num > 0 && pbuf != buf) {
+ char d = (num % 10) + '0';
+ *(--pbuf) = d;
+ num /= 10;
+ }
+ return pbuf;
+}
+
+static const char* num2hex(char* buf, unsigned long len, unsigned long long num) {
+ char* pbuf = buf + len - 1;
+ *pbuf = '\0';
+
+ if (num == 0) {
+ *(--pbuf) = '0';
+ }
+
+ while (num > 0 && pbuf != buf) {
+ char d = (num & 0xf);
+ *(--pbuf) = d + (d > 9 ? 'a' - 10 : '0');
+ num >>= 4;
+ }
+ return pbuf;
+}
+
+int vfmt(char* buf, unsigned long len, const char* fmt, va_list ap) {
+ unsigned i = 0;
+
+#define put(c) \
+ { \
+ char _c = (c); \
+ if (i < len) { \
+ buf[i] = _c; \
+ } \
+ ++i; \
+ }
+
+#define puts(s) \
+ while (*s) { \
+ put(*s++); \
+ }
+
+ char scratch[16];
+ int l_cnt = 0;
+
+ while (*fmt) {
+ if (*fmt != '%') {
+ put(*fmt++);
+ continue;
+ }
+
+ l_cnt = 0;
+
+ continue_fmt:
+ switch (*(++fmt /* constume '%' */)) {
+ case 'l':
+ ++l_cnt;
+ goto continue_fmt;
+ case 'd': {
+ long val = l_cnt > 0 ? va_arg(ap, long) : va_arg(ap, int);
+ if (val < 0) {
+ val *= -1;
+ put('-');
+ }
+ const char* ptr = num2dec(scratch, sizeof(scratch), val);
+ puts(ptr);
+ } break;
+ case 'x': {
+ unsigned long val = l_cnt > 0 ? va_arg(ap, unsigned long) : va_arg(ap, unsigned);
+ const char* ptr = num2hex(scratch, sizeof(scratch), val);
+ puts(ptr);
+ } break;
+ case 's': {
+ const char* ptr = va_arg(ap, const char*);
+ puts(ptr);
+ } break;
+ case 'p': {
+ const void* val = va_arg(ap, const void*);
+ const char* ptr = num2hex(scratch, sizeof(scratch), (unsigned long long)val);
+ put('0');
+ put('x');
+ puts(ptr);
+ } break;
+ default:
+ put(*fmt);
+ break;
+ }
+ ++fmt;
+ }
+
+#undef puts
+#undef put
+
+ if (buf) {
+ i < len ? (buf[i] = '\0') : (buf[len - 1] = '\0');
+ }
+ return i;
+}
+
+int fmt(char* buf, unsigned long len, const char* fmt, ...) {
+ va_list ap;
+ va_start(ap, fmt);
+ int ret = vfmt(buf, len, fmt, ap);
+ va_end(ap);
+ return ret;
+}
diff --git a/lib/src/io.c b/lib/src/io.c
new file mode 100644
index 0000000..efe938b
--- /dev/null
+++ b/lib/src/io.c
@@ -0,0 +1,37 @@
+// Copyright (c) 2020 Johannes Stoelp
+
+#include <io.h>
+#include <fmt.h>
+#include <syscall.h>
+
+#include <asm/unistd.h>
+
+// `pfmt` uses fixed-size buffer on the stack for formating the message
+// (for simplicity and since we don't impl buffered I/O).
+//
+// NOTE: This allows to specify a large buffer on the stack, but for
+// the purpose of this study that's fine, we are cautious.
+#define MAX_PRINTF_LEN 128
+
+#define FD_STDOUT 1
+#define FD_STDERR 2
+
+int pfmt(const char* fmt, ...) {
+ char buf[MAX_PRINTF_LEN];
+
+ va_list ap;
+ va_start(ap, fmt);
+ int ret = vfmt(buf, sizeof(buf), fmt, ap);
+ va_end(ap);
+
+ if (ret > MAX_PRINTF_LEN - 1) {
+ syscall3(__NR_write, FD_STDERR, buf, MAX_PRINTF_LEN - 1);
+
+ static const char warn[] = "\npfmt: Message truncated, max length can be configured by defining MAX_PRINTF_LEN\n";
+ syscall3(__NR_write, FD_STDOUT, warn, sizeof(warn));
+ return MAX_PRINTF_LEN - 1;
+ }
+
+ syscall3(__NR_write, FD_STDOUT, buf, ret);
+ return ret;
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-21 20:02:31 +0000