Split common headers in header/src files.

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;
+}