diff options
Diffstat (limited to 'tools/include/nolibc/nolibc.h')
| -rw-r--r-- | tools/include/nolibc/nolibc.h | 33 |
1 files changed, 22 insertions, 11 deletions
diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h index 2551e9b71167..b8cecb66d28b 100644 --- a/tools/include/nolibc/nolibc.h +++ b/tools/include/nolibc/nolibc.h @@ -422,16 +422,22 @@ struct stat { }) /* startup code */ +/* + * x86-64 System V ABI mandates: + * 1) %rsp must be 16-byte aligned right before the function call. + * 2) The deepest stack frame should be zero (the %rbp). + * + */ asm(".section .text\n" ".global _start\n" "_start:\n" "pop %rdi\n" // argc (first arg, %rdi) "mov %rsp, %rsi\n" // argv[] (second arg, %rsi) "lea 8(%rsi,%rdi,8),%rdx\n" // then a NULL then envp (third arg, %rdx) - "and $-16, %rsp\n" // x86 ABI : esp must be 16-byte aligned when - "sub $8, %rsp\n" // entering the callee + "xor %ebp, %ebp\n" // zero the stack frame + "and $-16, %rsp\n" // x86 ABI : esp must be 16-byte aligned before call "call main\n" // main() returns the status code, we'll exit with it. - "movzb %al, %rdi\n" // retrieve exit code from 8 lower bits + "mov %eax, %edi\n" // retrieve exit code (32 bit) "mov $60, %rax\n" // NR_exit == 60 "syscall\n" // really exit "hlt\n" // ensure it does not return @@ -600,20 +606,28 @@ struct sys_stat_struct { }) /* startup code */ +/* + * i386 System V ABI mandates: + * 1) last pushed argument must be 16-byte aligned. + * 2) The deepest stack frame should be set to zero + * + */ asm(".section .text\n" ".global _start\n" "_start:\n" "pop %eax\n" // argc (first arg, %eax) "mov %esp, %ebx\n" // argv[] (second arg, %ebx) "lea 4(%ebx,%eax,4),%ecx\n" // then a NULL then envp (third arg, %ecx) - "and $-16, %esp\n" // x86 ABI : esp must be 16-byte aligned when + "xor %ebp, %ebp\n" // zero the stack frame + "and $-16, %esp\n" // x86 ABI : esp must be 16-byte aligned before + "sub $4, %esp\n" // the call instruction (args are aligned) "push %ecx\n" // push all registers on the stack so that we "push %ebx\n" // support both regparm and plain stack modes "push %eax\n" "call main\n" // main() returns the status code in %eax - "movzbl %al, %ebx\n" // retrieve exit code from lower 8 bits - "movl $1, %eax\n" // NR_exit == 1 - "int $0x80\n" // exit now + "mov %eax, %ebx\n" // retrieve exit code (32-bit int) + "movl $1, %eax\n" // NR_exit == 1 + "int $0x80\n" // exit now "hlt\n" // ensure it does not ""); @@ -797,7 +811,6 @@ asm(".section .text\n" "and %r3, %r1, $-8\n" // AAPCS : sp must be 8-byte aligned in the "mov %sp, %r3\n" // callee, an bl doesn't push (lr=pc) "bl main\n" // main() returns the status code, we'll exit with it. - "and %r0, %r0, $0xff\n" // limit exit code to 8 bits "movs r7, $1\n" // NR_exit == 1 "svc $0x00\n" ""); @@ -994,7 +1007,6 @@ asm(".section .text\n" "add x2, x2, x1\n" // + argv "and sp, x1, -16\n" // sp must be 16-byte aligned in the callee "bl main\n" // main() returns the status code, we'll exit with it. - "and x0, x0, 0xff\n" // limit exit code to 8 bits "mov x8, 93\n" // NR_exit == 93 "svc #0\n" ""); @@ -1199,7 +1211,7 @@ asm(".section .text\n" "addiu $sp,$sp,-16\n" // the callee expects to save a0..a3 there! "jal main\n" // main() returns the status code, we'll exit with it. "nop\n" // delayed slot - "and $a0, $v0, 0xff\n" // limit exit code to 8 bits + "move $a0, $v0\n" // retrieve 32-bit exit code from v0 "li $v0, 4001\n" // NR_exit == 4001 "syscall\n" ".end __start\n" @@ -1397,7 +1409,6 @@ asm(".section .text\n" "add a2,a2,a1\n" // + argv "andi sp,a1,-16\n" // sp must be 16-byte aligned "call main\n" // main() returns the status code, we'll exit with it. - "andi a0, a0, 0xff\n" // limit exit code to 8 bits "li a7, 93\n" // NR_exit == 93 "ecall\n" ""); |