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5 changed files with 211 additions and 46 deletions
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14
Makefile
View File

@ -1,4 +1,4 @@
all: buildtest
all: print print_x64 print_aarch64 print_mips32 buildtest
clean:
if test -f print; then rm print; fi
@ -15,6 +15,18 @@ buildtest: bldtst bldtst_llvm bldtst_x64 bldtst_aarch64 bldtst_mips32
.PHONY: all buildtest clean
print:
gcc -static -nostdlib -Wno-builtin-declaration-mismatch -fno-stack-protector -o print print.c
print_x64: print.c
clang --target=x86_64-linux-gnu -nostdlib -static -fuse-ld=lld -fno-stack-protector -o print_x64 print.c
print_aarch64: print.c
clang --target=aarch64-linux-gnu -nostdlib -static -fuse-ld=lld -fno-stack-protector -o print_aarch64 print.c
print_mips32: print.c
clang --target=mips-linux-gnu -nostdlib -static -fuse-ld=lld -fno-stack-protector -fno-pic -o print_mips32 print.c
bldtst: buildtest.c arch/*.c
gcc -static -nostdlib -Wno-builtin-declaration-mismatch -fno-stack-protector -o bldtst buildtest.c arch/*.c

22
arch/x86_64.c
View File

@ -1,50 +1,34 @@
#include <stdint.h>
#if defined(__x86_64__)
#define SYS_EXIT 60
void exit(int8_t status) {
asm volatile(
"syscall"
:
: "a"(SYS_EXIT), "D"(status)
: "a"(60), "D"(status)
:
);
}
#define SYS_WRITE 1
intptr_t write(int32_t fd, const void* buf, intptr_t size) {
intptr_t n_written = 0;
asm volatile (
"syscall\n"
"movq %0, %%rax\n"
: "=r"(n_written)
: "a"(SYS_WRITE), "D"(fd), "S"(buf), "d"(size) // RDI, RSI, RDX are used in x86-64 for write args
: "a"(1), "D"(fd), "S"(buf), "d"(size) // RDI, RSI, RDX are used in x86-64 for write args
: "rcx", "r11", "memory"
);
return n_written;
}
#define SYS_READ 0
intptr_t read(int32_t fd, const void* buf, intptr_t size) {
intptr_t n_read = 0;
asm volatile (
"syscall\n"
"movq %0, %%rax\n"
: "=r"(n_read)
: "a"(SYS_READ), "D"(fd), "S"(buf), "d"(size) // RDI, RSI, RDX are used in x86-64 for write args
: "rcx", "r11", "memory"
);
return n_read;
}
#define SYS_FORK 57
uint32_t fork() {
uint64_t rtn;
asm volatile(
"syscall\n" // syscall
"movq %0, %%rax\n" // save return value
: "=r"(rtn)
: "a"(SYS_FORK)
: "a"(57)
:
);
return (uint32_t)rtn;

38
buildtest.c
View File

@ -3,9 +3,8 @@
int main() {
#if defined(__x86_64__) || defined(__aarch64__) || defined(__mips__)
uint64_t pid = fork();
// Print the pid in hex
char msg[17] = {' '};
msg[16] = '\n';
for(int i = 0; i < 16; ++i) {
@ -16,23 +15,12 @@ int main() {
msg[i] = c;
}
write(STDIO, msg, 17);
// Child process exits
if(pid == 0) return 0;
//TODO: wait on child to remove zombie process
#if defined(__x86_64__)
// Test the read syscall
#define INPUT_BUFFER_LEN 4096
char input_buffer[INPUT_BUFFER_LEN] = {0};
write(STDIO, "Enter some text:", 16);
intptr_t n_read = read(STDIO, input_buffer, INPUT_BUFFER_LEN);
write(STDIO, input_buffer, n_read);
#endif
#else
char *msg = "Hello World!\n";
write(STDIO, msg, 13);
#endif
return 69;
}
void __libc_start_main() {exit(main());}
void _start() {
@ -42,3 +30,19 @@ void _start() {
void __start() {
_start();
}
/*
#if defined(__x86_64__)
printf("Compiled for x86_64 architecture\n");
#elif defined(__i386__)
printf("Compiled for x86 architecture\n");
#elif defined(__arm__)
printf("Compiled for ARM architecture\n");
#elif defined(__aarch64__)
printf("Compiled for ARM64 architecture\n");
#elif defined(__mips__)
printf("Compiled for ARM architecture\n");
#else
printf("Unknown architecture\n");
#endif
*/

173
print.c Normal file
View File

@ -0,0 +1,173 @@
long print(const void *buf, long count) {
#if defined(__x86_64__)
asm volatile (
"syscall"
:
: "a"(1), "D"(1), "S"(buf), "d"(count) // RDI, RSI, RDX are used in x86-64 for write args
: "rcx", "r11", "memory"
);
#elif defined(__aarch64__)
asm ( "mov x0, #1\n" // Move the exit status into register x0
"mov x1, %0\n" // Syscall number for 'exit' is 93 in AArch64
"mov x2, %1\n" // Syscall number for 'exit' is 93 in AArch64
"mov x8, #64\n" // Syscall number for 'exit' is 93 in AArch64
"svc #0\n" // Make the syscall
: // No output operands
: "r" (buf), "r"(count) // Input operand: status
: "x0", "x8" // Clobbered registers
);
#elif defined(__mips__)
asm ( "li $a0, 1\n"
"move $a1, %0\n"
"move $a2, %1\n"
"li $v0, 4004\n"
"syscall"
:
: "r"(buf), "r"(count)
: "a0", "a1", "a2", "v0" //TODO: temp registers clobbered by syscall should probably also be listed but this fn returns right away so it should be fine?
);
#endif
return 0;
}
#define CLONE_CHILD_SETTID 0x1000000
#define CLONE_CHILD_CLEARTID 0x200000
#if defined(__aarch64__)
long int fork() {
long int rtn;
long int flags = CLONE_CHILD_CLEARTID | CLONE_CHILD_SETTID;
asm volatile (
// Assembly Instructions
"mov x8, #220\n" // Syscall number for 'clone' is 220 in AArch64
"mov x0, %1\n" // clone flags
"mov x1, #0\n" // child stack pointer
"mov x2, #0\n" // parent_tidptr
"mov x3, #0\n" // tls
"mov x4, #0\n" // child_tidptr
"svc #0\n" // Make the syscall
"mov %0, x0\n" // save return value
// Output operands
: "=r" (rtn)
// Input operand
: "r" (flags)
// Clobbered registers
: "x0", "x1", "x2", "x3", "x4", "x8"
);
return rtn;
}
#elif defined(__x86_64__)
long int fork() {
long int rtn;
/*
long int flags = CLONE_CHILD_CLEARTID | CLONE_CHILD_SETTID;
asm volatile(
"movq %%rax, 56\n" // syscall number for 'clone' is 56 for x86-64
"movq %%rdi, %1\n" // clone flags
"movq %%rsi, 0\n" // child stack pointer
"movq %%rdx, 0\n" // parent tidptr
"movq %%r10, 0\n" // child tidptr
"movq %%r8, 0\n" // tls
"syscall\n" // syscall
"movq %0, %%rax\n" // save return value
: "=r"(rtn)
: "r"(flags)
: "rax", "rdi", "rsi", "rdx", "r10", "r8", "r9", "r10", "r11"
);
*/
asm volatile(
"syscall\n" // syscall
"movq %0, %%rax\n" // save return value
: "=r"(rtn)
: "a"(57)
:
);
return rtn;
}
#elif defined(__mips__)
long int fork() {
int rtn;
asm (
"li $v0, 4002\n"
"syscall\n"
"move %0, $v0"
:"=r" (rtn)
:
: "a0", "v0"
);
return (long int)rtn;
}
#endif
void exit(int status) {
#if defined(__x86_64__)
asm volatile(
"syscall"
:
: "a"(60), "D"(status)
:
);
#elif defined(__aarch64__)
asm ( "mov x0, %0\n" // Move the exit status into register x0
"mov x8, #93\n" // Syscall number for 'exit' is 93 in AArch64
"svc #0\n" // Make the syscall
: // No output operands
: "r" ((long)status) // Input operand: status
: "x0", "x8" // Clobbered registers
);
#elif defined(__mips__)
asm ( "move $a0, %0\n"
"li $v0, 4001\n"
"syscall"
:
: "r" (status)
: "a0", "v0"
);
#endif
for(;;);
}
int main() {
#if defined(__x86_64__) || defined(__aarch64__) || defined(__mips__)
long int pid = fork();
char msg[17] = {' '};
msg[16] = '\n';
for(int i = 0; i < 16; ++i) {
char nibble = (pid >> ((15 - i) * 4)) & 0xf;
char c;
if (nibble > 9) {c = nibble + '7';}
else {c = nibble + '0';}
msg[i] = c;
}
print(msg, 17);
#else
char *msg = "Hello World!\n";
print(msg, 13);
#endif
return 69;
}
void __libc_start_main() {exit(main());}
void _start() {
__libc_start_main();
}
void __start() {
_start();
}
/*
#if defined(__x86_64__)
printf("Compiled for x86_64 architecture\n");
#elif defined(__i386__)
printf("Compiled for x86 architecture\n");
#elif defined(__arm__)
printf("Compiled for ARM architecture\n");
#elif defined(__aarch64__)
printf("Compiled for ARM64 architecture\n");
#elif defined(__mips__)
printf("Compiled for ARM architecture\n");
#else
printf("Unknown architecture\n");
#endif
*/

10
sys.h
View File

@ -6,15 +6,7 @@ void exit(int8_t status);
#define STDIO 1
#define STDERR 2
intptr_t write(int32_t fd, const void* buf, intptr_t size);
#if defined(__x86_64__)
intptr_t read(int32_t fd, const void* buf, intptr_t size);
#endif
//intptr_t read(int32_t fd, const void* buf, intptr_t size);
uint32_t fork();
// Provide memset for clang
void *memset(void* s, int c, unsigned long n) {
int8_t* mem = s;
for(long int i = 0; i < n; ++i) mem[i] = c;
}
#endif // !MINIMALSYS_H