From 1d2a6f21294f8390b683e4e097cb49210ed832d1 Mon Sep 17 00:00:00 2001
From: johannst <johannes.stoelp@gmail.com>
Date: Fri, 26 Mar 2021 23:17:46 +0100
Subject: Added dyn allocator + syscall wrappers + minor fixes.
---
lib/include/alloc.h | 6 ++++++
lib/include/auxv.h | 2 +-
lib/include/common.h | 18 ++++++++----------
lib/include/syscall.h | 33 ++++++++++++++++++++++++---------
lib/include/syscalls.h | 23 +++++++++++++++++++++++
5 files changed, 62 insertions(+), 20 deletions(-)
create mode 100644 lib/include/alloc.h
create mode 100644 lib/include/syscalls.h
(limited to 'lib/include')
diff --git a/lib/include/alloc.h b/lib/include/alloc.h
new file mode 100644
index 0000000..baf8d3d
--- /dev/null
+++ b/lib/include/alloc.h
@@ -0,0 +1,6 @@
+// Copyright (c) 2021 Johannes Stoelp
+
+#pragma once
+
+void* alloc(unsigned size);
+void dealloc(void* ptr);
diff --git a/lib/include/auxv.h b/lib/include/auxv.h
index 42dac38..1ac953e 100644
--- a/lib/include/auxv.h
+++ b/lib/include/auxv.h
@@ -15,7 +15,7 @@
#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_PHNUM 5 /* [val] Number of Phdr 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] */
diff --git a/lib/include/common.h b/lib/include/common.h
index 5ea6050..631c25f 100644
--- a/lib/include/common.h
+++ b/lib/include/common.h
@@ -3,14 +3,12 @@
#pragma once
#include "io.h"
-#include "syscall.h"
-
-#include <asm/unistd.h>
-
-#define ERROR_ON(cond, ...) \
- do { \
- if ((cond)) { \
- efmt(__VA_ARGS__); \
- syscall1(__NR_exit, 1); \
- } \
+#include "syscalls.h"
+
+#define ERROR_ON(cond, fmt, ...) \
+ do { \
+ if ((cond)) { \
+ efmt("%s:%d " fmt, __FILE__, __LINE__ __VA_OPT__(, ) __VA_ARGS__); \
+ _exit(1); \
+ } \
} while (0)
diff --git a/lib/include/syscall.h b/lib/include/syscall.h
index 4947155..c9314d2 100644
--- a/lib/include/syscall.h
+++ b/lib/include/syscall.h
@@ -35,29 +35,44 @@
// 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
+//
+//
+// Linux syscall ABI - x86-64
+// #syscall: rax
+// ret : rax
+// instr : syscall
+// args : rdi rsi rdx r10 r8 r9
//
// Reference:
// syscall(2)
+//
+//
+// X86_64 `syscall` instruction additionally clobbers following registers:
+// rcx Store return address.
+// r11 Store RFLAGS.
+//
+// Reference:
+// https://www.felixcloutier.com/x86/syscall
#define argcast(A) ((long)(A))
#define syscall1(n, a1) _syscall1(n, argcast(a1))
+#define syscall2(n, a1, a2) _syscall2(n, argcast(a1), argcast(a2))
#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");
+ asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1) : "rcx", "r11", "memory");
+ return ret;
+}
+
+static inline long _syscall2(long n, long a1, long a2) {
+ long ret;
+ asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1), "S"(a2) : "rcx", "r11", "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");
+ asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1), "S"(a2), "d"(a3) : "rcx", "r11", "memory");
return ret;
}
diff --git a/lib/include/syscalls.h b/lib/include/syscalls.h
new file mode 100644
index 0000000..34b6b37
--- /dev/null
+++ b/lib/include/syscalls.h
@@ -0,0 +1,23 @@
+// Copyright (c) 2021 Johannes Stoelp
+
+#pragma once
+
+#include <stddef.h> // size_t
+#include <sys/types.h> // ssize_t, off_t, ...
+
+// Syscall definitions taken from corresponding man pages, eg
+// open(2)
+// read(2)
+// ...
+
+#define O_RDONLY 00
+int open(const char* path, int flags);
+
+ssize_t read(int fd, void* buf, size_t count);
+
+#define SEEK_SET 0
+#define SEEK_CUR 1
+#define SEEK_END 2
+off_t lseek(int fd, off_t offset, int whence);
+
+void _exit(int status);
--
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