Initial import

libc/sysv/macros.h

@@ -0,0 +1,57 @@
+/*-*- mode:asm; indent-tabs-mode:t; tab-width:8; coding:utf-8               -*-│
+│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ This program is free software; you can redistribute it and/or modify         │
+│ it under the terms of the GNU General Public License as published by         │
+│ the Free Software Foundation; version 2 of the License.                      │
+│                                                                              │
+│ This program is distributed in the hope that it will be useful, but          │
+│ WITHOUT ANY WARRANTY; without even the implied warranty of                   │
+│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU             │
+│ General Public License for more details.                                     │
+│                                                                              │
+│ You should have received a copy of the GNU General Public License            │
+│ along with this program; if not, write to the Free Software                  │
+│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
+│ 02110-1301 USA                                                               │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#ifndef COSMOPOLITAN_LIBC_SYSV_MACROS_H_
+#define COSMOPOLITAN_LIBC_SYSV_MACROS_H_
+#ifdef __ASSEMBLER__
+#include "libc/macros.inc"
+/* clang-format off */
+
+/**
+ * @fileoverview System Five jump slot generator.
+ *
+ * We need to pass a magic number to the SYSCALL instruction in %rax.
+ * That's only possible to do in C using asm() macro wrappers, like in
+ * Chromium's "System Call Support" library. This technique is simpler
+ * to implement, gains us object-level ABI compatibility, hookability,
+ * and the ability to support significantly more functions, without the
+ * risk of slowing down builds too much with complicated headers.
+ */
+
+.macro	.scall	name:req num:req kw1 kw2
+  .ifnb	\kw2
+	.align	16
+\name:	movabs	$\num,%rax
+	jmp	*systemfive(%rip)
+  .else
+\name:	push	%rbp
+	mov	%rsp,%rbp
+	movabs	$\num,%rax
+	.hookable
+	call	*systemfive(%rip)
+	pop	%rbp
+	ret
+  .endif
+	.endfn	\name,\kw1,\kw2
+	.previous
+.endm
+
+/* clang-format on */
+#endif /* __ASSEMBLER__ */
+#endif /* COSMOPOLITAN_LIBC_SYSV_MACROS_H_ */