From 7b864e86e3e8e64fe69363137384ee9b858fe78d Mon Sep 17 00:00:00 2001
From: Bobby Bingham <koorogi@koorogi.info>
Date: Sat, 23 Feb 2019 17:12:37 -0600
Subject: [PATCH 2/3] ppc64: rewrite get/set/swapcontext in assembly
If getcontext makes any function call, which it does to call syscall, then
it must spill its return address to the stack. After it returns to its
caller, that return address can be clobbered. When setcontext is called
to resume this saved context, the correct return address is not available.
---
Makefile | 10 ++-------
arch/ppc64/getcontext.S | 25 +++++++++++++++++++++
arch/ppc64/getcontext.c | 45 -------------------------------------
arch/ppc64/retfromsyscall.c | 24 ++++++++++++++++++++
arch/ppc64/setcontext.S | 26 +++++++++++++++++++++
arch/ppc64/setcontext.c | 45 -------------------------------------
arch/ppc64/swapcontext.S | 28 +++++++++++++++++++++++
arch/ppc64/swapcontext.c | 45 -------------------------------------
8 files changed, 105 insertions(+), 143 deletions(-)
create mode 100644 arch/ppc64/getcontext.S
delete mode 100644 arch/ppc64/getcontext.c
create mode 100644 arch/ppc64/retfromsyscall.c
create mode 100644 arch/ppc64/setcontext.S
delete mode 100644 arch/ppc64/setcontext.c
create mode 100644 arch/ppc64/swapcontext.S
delete mode 100644 arch/ppc64/swapcontext.c
diff --git a/Makefile b/Makefile
index 51365a3..d6ff1b0 100644
--- a/Makefile
+++ b/Makefile
@@ -2,14 +2,8 @@ ARCH := $(shell uname -m)
CFLAGS = -ggdb3 -O2 -Wall -Iarch/${ARCH}
-LIBUCONTEXT_C_SRC = \
- arch/${ARCH}/makecontext.c
-
-LIBUCONTEXT_S_SRC = \
- arch/${ARCH}/getcontext.S \
- arch/${ARCH}/setcontext.S \
- arch/${ARCH}/swapcontext.S \
- arch/${ARCH}/startcontext.S
+LIBUCONTEXT_C_SRC = $(wildcard arch/${ARCH}/*.c)
+LIBUCONTEXT_S_SRC = $(wildcard arch/${ARCH}/*.S)
LIBUCONTEXT_OBJ = ${LIBUCONTEXT_C_SRC:.c=.o} ${LIBUCONTEXT_S_SRC:.S=.o}
LIBUCONTEXT_SOVERSION = 0
diff --git a/arch/ppc64/getcontext.S b/arch/ppc64/getcontext.S
new file mode 100644
index 0000000..935edd2
--- /dev/null
+++ b/arch/ppc64/getcontext.S
@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2019 Bobby Bingham <koorogi@koorogi.info>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied. In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+.global __getcontext
+.hidden __swapcontext
+__getcontext:
+ addis 2, 12, .TOC.-__getcontext@ha
+ addi 2, 12, .TOC.-__getcontext@l
+
+ .localentry __getcontext,.-__getcontext
+
+ li 4, 0
+ b __swapcontext
+
+.weak getcontext
+getcontext = __getcontext
diff --git a/arch/ppc64/getcontext.c b/arch/ppc64/getcontext.c
deleted file mode 100644
index 5da9dfb..0000000
--- a/arch/ppc64/getcontext.c
+++ /dev/null
@@ -1,45 +0,0 @@
-/*
- * Copyright (c) 2018 William Pitcock <nenolod@dereferenced.org>
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * This software is provided 'as is' and without any warranty, express or
- * implied. In no event shall the authors be liable for any damages arising
- * from the use of this software.
- */
-
-#define _GNU_SOURCE
-#include <stddef.h>
-#include <stdarg.h>
-#include <signal.h>
-#include <string.h>
-#include <stdint.h>
-#include <errno.h>
-#include <unistd.h>
-#include <sys/syscall.h>
-
-
-int
-__getcontext(ucontext_t *ucp)
-{
-#ifdef SYS_swapcontext
- int r;
-
- r = syscall(SYS_swapcontext, ucp, NULL, sizeof(ucontext_t));
- if (r < 0)
- {
- errno = -r;
- return -1;
- }
-
- return 0;
-#else
- errno = ENOSYS;
- return -1;
-#endif
-}
-
-
-extern __typeof(__getcontext) getcontext __attribute__((weak, __alias__("__getcontext")));
diff --git a/arch/ppc64/retfromsyscall.c b/arch/ppc64/retfromsyscall.c
new file mode 100644
index 0000000..22c5134
--- /dev/null
+++ b/arch/ppc64/retfromsyscall.c
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2019 Bobby Bingham <koorogi@koorogi.info>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied. In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#include <errno.h>
+
+__attribute__ ((visibility ("hidden")))
+int __retfromsyscall(long retval)
+{
+ if (retval < 0) {
+ errno = -retval;
+ return -1;
+ }
+ return 0;
+}
+
diff --git a/arch/ppc64/setcontext.S b/arch/ppc64/setcontext.S
new file mode 100644
index 0000000..5a0cde3
--- /dev/null
+++ b/arch/ppc64/setcontext.S
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2019 Bobby Bingham <koorogi@koorogi.info>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied. In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+.global __setcontext
+.hidden __swapcontext
+__setcontext:
+ addis 2, 12, .TOC.-__setcontext@ha
+ addi 2, 12, .TOC.-__setcontext@l
+
+ .localentry __setcontext,.-__setcontext
+
+ mr 4, 3
+ li 3, 0
+ b __swapcontext
+
+.weak setcontext
+setcontext = __setcontext
diff --git a/arch/ppc64/setcontext.c b/arch/ppc64/setcontext.c
deleted file mode 100644
index 59c65b4..0000000
--- a/arch/ppc64/setcontext.c
+++ /dev/null
@@ -1,45 +0,0 @@
-/*
- * Copyright (c) 2018 William Pitcock <nenolod@dereferenced.org>
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * This software is provided 'as is' and without any warranty, express or
- * implied. In no event shall the authors be liable for any damages arising
- * from the use of this software.
- */
-
-#define _GNU_SOURCE
-#include <stddef.h>
-#include <stdarg.h>
-#include <signal.h>
-#include <string.h>
-#include <stdint.h>
-#include <errno.h>
-#include <unistd.h>
-#include <sys/syscall.h>
-
-
-int
-__setcontext(const ucontext_t *ucp)
-{
-#ifdef SYS_swapcontext
- int r;
-
- r = syscall(SYS_swapcontext, NULL, (void *) ucp, sizeof(ucontext_t));
- if (r < 0)
- {
- errno = -r;
- return -1;
- }
-
- return r;
-#else
- errno = ENOSYS;
- return -1;
-#endif
-}
-
-
-extern __typeof(__setcontext) setcontext __attribute__((weak, __alias__("__setcontext")));
diff --git a/arch/ppc64/swapcontext.S b/arch/ppc64/swapcontext.S
new file mode 100644
index 0000000..982537a
--- /dev/null
+++ b/arch/ppc64/swapcontext.S
@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2019 Bobby Bingham <koorogi@koorogi.info>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied. In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+.global __swapcontext
+__swapcontext:
+ addis 2, 12, .TOC.-__swapcontext@ha
+ addi 2, 12, .TOC.-__swapcontext@l
+
+ .localentry __swapcontext,.-__swapcontext
+
+ li 0, 249 # SYS_swapcontext
+ li 5, 1696 # sizeof(ucontext_t)
+ sc
+
+.hidden __retfromsyscall
+ b __retfromsyscall
+
+.weak swapcontext
+swapcontext = __swapcontext
diff --git a/arch/ppc64/swapcontext.c b/arch/ppc64/swapcontext.c
deleted file mode 100644
index af14bc2..0000000
--- a/arch/ppc64/swapcontext.c
+++ /dev/null
@@ -1,45 +0,0 @@
-/*
- * Copyright (c) 2018 William Pitcock <nenolod@dereferenced.org>
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * This software is provided 'as is' and without any warranty, express or
- * implied. In no event shall the authors be liable for any damages arising
- * from the use of this software.
- */
-
-#define _GNU_SOURCE
-#include <stddef.h>
-#include <stdarg.h>
-#include <signal.h>
-#include <string.h>
-#include <stdint.h>
-#include <errno.h>
-#include <unistd.h>
-#include <sys/syscall.h>
-
-
-int
-__swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
-{
-#ifdef SYS_swapcontext
- int r;
-
- r = syscall(SYS_swapcontext, oucp, ucp, sizeof(ucontext_t));
- if (r < 0)
- {
- errno = -r;
- return -1;
- }
-
- return r;
-#else
- errno = ENOSYS;
- return -1;
-#endif
-}
-
-
-extern __typeof(__swapcontext) swapcontext __attribute__((weak, __alias__("__swapcontext")));
--
2.19.2
