From ae8ef112adf079ac4499a71080463ec0427713c3 Mon Sep 17 00:00:00 2001
From: Ed Schouten <ed@FreeBSD.org>
Date: Sat, 16 Dec 2017 19:40:28 +0000
Subject: [PATCH] Make truss(8) work for i686-unknown-cloudabi binaries on
 FreeBSD/amd64.

This change copies the existing amd64_cloudabi64.c to amd64_cloudabi32.c
and reimplements the functions for fetching system call arguments and
return values to use the same scheme as used by the vDSO that is used
when running cloudabi32 executables.

As arguments are automatically padded to 64-bit words by the vDSO in
userspace, we can copy the arguments directly into the array used by
truss(8) internally.

Reviewed by:	jhb
Differential Revision:	https://reviews.freebsd.org/D13516
---
 usr.bin/truss/Makefile           |   1 +
 usr.bin/truss/amd64-cloudabi32.c | 112 +++++++++++++++++++++++++++++++
 2 files changed, 113 insertions(+)
 create mode 100644 usr.bin/truss/amd64-cloudabi32.c

diff --git a/usr.bin/truss/Makefile b/usr.bin/truss/Makefile
index 27881fa0896..c657d837164 100644
--- a/usr.bin/truss/Makefile
+++ b/usr.bin/truss/Makefile
@@ -22,6 +22,7 @@ ABIS+=		i386-linux
 ABIS+=		amd64-linux
 ABIS+=		amd64-linux32
 ABIS+=		freebsd32
+ABIS+=		cloudabi32
 ABIS+=		cloudabi64
 .endif
 .if ${MACHINE_ARCH} == "powerpc64"
diff --git a/usr.bin/truss/amd64-cloudabi32.c b/usr.bin/truss/amd64-cloudabi32.c
new file mode 100644
index 00000000000..cc1b9313c93
--- /dev/null
+++ b/usr.bin/truss/amd64-cloudabi32.c
@@ -0,0 +1,112 @@
+/*-
+ * Copyright (c) 2015-2017 Nuxi, https://nuxi.nl/
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/ptrace.h>
+
+#include <machine/psl.h>
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <sysdecode.h>
+
+#include "truss.h"
+
+static int
+amd64_cloudabi32_fetch_args(struct trussinfo *trussinfo, unsigned int narg)
+{
+	struct current_syscall *cs;
+	struct ptrace_io_desc iorequest;
+	struct reg regs;
+	lwpid_t tid;
+
+	if (narg > 0) {
+		/* Fetch registers, containing the address of the arguments. */
+		tid = trussinfo->curthread->tid;
+		if (ptrace(PT_GETREGS, tid, (caddr_t)&regs, 0) == -1) {
+			fprintf(trussinfo->outfile,
+			    "-- CANNOT READ REGISTERS --\n");
+			return (-1);
+		}
+
+		/* Fetch arguments. They are already padded to 64 bits. */
+		cs = &trussinfo->curthread->cs;
+		iorequest.piod_op = PIOD_READ_D;
+		iorequest.piod_offs = (void *)regs.r_rcx;
+		iorequest.piod_addr = cs->args;
+		iorequest.piod_len = sizeof(cs->args[0]) * narg;
+		if (ptrace(PT_IO, tid, (caddr_t)&iorequest, 0) == -1 ||
+		    iorequest.piod_len == 0)
+			return (-1);
+	}
+	return (0);
+}
+
+static int
+amd64_cloudabi32_fetch_retval(struct trussinfo *trussinfo, long *retval,
+    int *errorp)
+{
+	struct ptrace_io_desc iorequest;
+	struct reg regs;
+	lwpid_t tid;
+
+	/* Fetch registers, containing the address of the return values. */
+	tid = trussinfo->curthread->tid;
+	if (ptrace(PT_GETREGS, tid, (caddr_t)&regs, 0) == -1) {
+		fprintf(trussinfo->outfile, "-- CANNOT READ REGISTERS --\n");
+		return (-1);
+	}
+
+	if (regs.r_rax == 0) {
+		/* System call succeeded. Fetch return values. */
+		iorequest.piod_op = PIOD_READ_D;
+		iorequest.piod_offs = (void *)regs.r_rcx;
+		iorequest.piod_addr = retval;
+		iorequest.piod_len = sizeof(retval[0]) * 2;
+		if (ptrace(PT_IO, tid, (caddr_t)&iorequest, 0) == -1 ||
+		    iorequest.piod_len == 0)
+			return (-1);
+		*errorp = 0;
+	} else {
+		/* System call failed. Set error. */
+		retval[0] = regs.r_rax;
+		*errorp = 1;
+	}
+	return (0);
+}
+
+static struct procabi amd64_cloudabi32 = {
+	"CloudABI ELF32",
+	SYSDECODE_ABI_CLOUDABI32,
+	amd64_cloudabi32_fetch_args,
+	amd64_cloudabi32_fetch_retval,
+	STAILQ_HEAD_INITIALIZER(amd64_cloudabi32.extra_syscalls),
+	{ NULL }
+};
+
+PROCABI(amd64_cloudabi32);