[PATCH v7 6/8] x86-64: Add rseq_load32_load32_relaxed

[Michael Jeanson <mjeanson@efficios.com>]

From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Implement rseq_load32_load32_relaxed() for the x86-64 architecture. This
static inline function implements a rseq critical section to load two
32-bit integer values atomically with respect to preemption and signal
delivery.

This implementation is imported from the librseq project.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
---
 .../unix/sysv/linux/x86_64/rseq-internal.h    | 109 ++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/x86_64/rseq-internal.h

diff --git a/sysdeps/unix/sysv/linux/x86_64/rseq-internal.h b/sysdeps/unix/sysv/linux/x86_64/rseq-internal.h
new file mode 100644
index 0000000000..fdca1b6439
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/rseq-internal.h
@@ -0,0 +1,109 @@
+/* Restartable Sequences internal API. x86_64 macros.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sysdeps/unix/sysv/linux/rseq-internal.h>
+
+#define __RSEQ_ASM_DEFINE_TABLE(label, version, flags,			\
+				start_ip, post_commit_offset, abort_ip)	\
+		".pushsection __rseq_cs, \"aw\"\n\t"			\
+		".balign 32\n\t"					\
+		__rseq_str(label) ":\n\t"				\
+		".long " __rseq_str(version) ", " __rseq_str(flags) "\n\t" \
+		".quad " __rseq_str(start_ip) ", " __rseq_str(post_commit_offset) ", " __rseq_str(abort_ip) "\n\t" \
+		".popsection\n\t"					\
+		".pushsection __rseq_cs_ptr_array, \"aw\"\n\t"		\
+		".quad " __rseq_str(label) "b\n\t"			\
+		".popsection\n\t"
+
+#define RSEQ_ASM_DEFINE_TABLE(label, start_ip, post_commit_ip, abort_ip) \
+	__RSEQ_ASM_DEFINE_TABLE(label, 0x0, 0x0, start_ip,		\
+				(post_commit_ip - start_ip), abort_ip)
+
+/*
+ * Exit points of a rseq critical section consist of all instructions outside
+ * of the critical section where a critical section can either branch to or
+ * reach through the normal course of its execution. The abort IP and the
+ * post-commit IP are already part of the __rseq_cs section and should not be
+ * explicitly defined as additional exit points. Knowing all exit points is
+ * useful to assist debuggers stepping over the critical section.
+ */
+#define RSEQ_ASM_DEFINE_EXIT_POINT(start_ip, exit_ip)			\
+		".pushsection __rseq_exit_point_array, \"aw\"\n\t"	\
+		".quad " __rseq_str(start_ip) ", " __rseq_str(exit_ip) "\n\t" \
+		".popsection\n\t"
+
+#define RSEQ_ASM_STORE_RSEQ_CS(label, cs_label, rseq_cs)		\
+		"leaq " __rseq_str(cs_label) "(%%rip), %%rax\n\t"	\
+		"movq %%rax, " __rseq_str(rseq_cs) "\n\t"		\
+		__rseq_str(label) ":\n\t"
+
+#define RSEQ_ASM_CMP_CPU_ID(cpu_id, current_cpu_id, label)		\
+		"cmpl %[" __rseq_str(cpu_id) "], " __rseq_str(current_cpu_id) "\n\t" \
+		"jnz " __rseq_str(label) "\n\t"
+
+#define RSEQ_ASM_DEFINE_ABORT(label, teardown, abort_label)		\
+		".pushsection __rseq_failure, \"ax\"\n\t"		\
+		/* Disassembler-friendly signature: ud1 <sig>(%rip),%edi. */ \
+		".byte 0x0f, 0xb9, 0x3d\n\t"				\
+		".long " __rseq_str(RSEQ_SIG) "\n\t"			\
+		__rseq_str(label) ":\n\t"				\
+		teardown						\
+		"jmp %l[" __rseq_str(abort_label) "]\n\t"		\
+		".popsection\n\t"
+
+#define RSEQ_ASM_DEFINE_CMPFAIL(label, teardown, cmpfail_label)		\
+		".pushsection __rseq_failure, \"ax\"\n\t"		\
+		__rseq_str(label) ":\n\t"				\
+		teardown						\
+		"jmp %l[" __rseq_str(cmpfail_label) "]\n\t"		\
+		".popsection\n\t"
+
+/*
+ * Load @src1 (32-bit) into @dst1 and load @src2 (32-bit) into @dst2.
+ */
+#define RSEQ_HAS_LOAD32_LOAD32_RELAXED 1
+static __always_inline int
+rseq_load32_load32_relaxed(uint32_t *dst1, uint32_t *src1,
+			       uint32_t *dst2, uint32_t *src2)
+{
+	__asm__ __volatile__ goto (
+		RSEQ_ASM_DEFINE_TABLE(3, 1f, 2f, 4f) /* start, commit, abort */
+		/* Start rseq by storing table entry pointer into rseq_cs. */
+		RSEQ_ASM_STORE_RSEQ_CS(1, 3b, %%fs:RSEQ_CS_OFFSET(%[rseq_offset]))
+		"movl %[src1], %%ebx\n\t"
+		"movl %[src2], %%ecx\n\t"
+		"movl %%ebx, %[dst1]\n\t"
+		/* final store */
+		"movl %%ecx, %[dst2]\n\t"
+		"2:\n\t"
+		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
+		: /* gcc asm goto does not allow outputs */
+		: [rseq_offset]		"r" (__rseq_offset),
+		  /* final store input */
+		  [dst1]		"m" (*dst1),
+		  [dst2]		"m" (*dst2),
+		  [src1]		"m" (*src1),
+		  [src2]		"m" (*src2)
+		: "memory", "cc", "ebx", "ecx", "rax"
+		: abort
+	);
+	rseq_after_asm_goto();
+	return 0;
+abort:
+	rseq_after_asm_goto();
+	return -1;
+}
-- 
2.34.1