From e7b9473e1591d4ab375a95ebbb9256adfe9d4670 Mon Sep 17 00:00:00 2001
From: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
Date: Fri, 16 Feb 2018 11:54:24 +0000
Subject: [PATCH] BL31: Introduce jump primitives
This patch introduces setjmp() and ongjmp() primitives to enable
standard setjmp/longjmp style execution. Both APIs parameters take a
pointer to struct jmpbuf type, which hosts CPU registers saved/restored
during jump.
As per the standard usage:
- setjmp() return 0 when a jump is setup; and a non-zero value when
returning from jump.
- The caller of setjmp() must not return, or otherwise update stack
pointer since.
Change-Id: I4af1d32e490cfa547979631b762b4cba188d0551
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
---
bl31/bl31.mk | 5 +--
include/lib/aarch64/setjmp.h | 59 ++++++++++++++++++++++++++++++++
lib/aarch64/setjmp.S | 65 ++++++++++++++++++++++++++++++++++++
3 files changed, 127 insertions(+), 2 deletions(-)
create mode 100644 include/lib/aarch64/setjmp.h
create mode 100644 lib/aarch64/setjmp.S
diff --git a/bl31/bl31.mk b/bl31/bl31.mk
index a6c0a9a07..51a831245 100644
--- a/bl31/bl31.mk
+++ b/bl31/bl31.mk
@@ -18,15 +18,16 @@ include lib/psci/psci_lib.mk
BL31_SOURCES += bl31/bl31_main.c \
bl31/interrupt_mgmt.c \
bl31/aarch64/bl31_entrypoint.S \
- bl31/aarch64/runtime_exceptions.S \
bl31/aarch64/crash_reporting.S \
+ bl31/aarch64/runtime_exceptions.S \
bl31/bl31_context_mgmt.c \
common/runtime_svc.c \
+ lib/aarch64/setjmp.S \
plat/common/aarch64/platform_mp_stack.S \
services/arm_arch_svc/arm_arch_svc_setup.c \
services/std_svc/std_svc_setup.c \
${PSCI_LIB_SOURCES} \
- ${SPM_SOURCES} \
+ ${SPM_SOURCES}
ifeq (${ENABLE_PMF}, 1)
diff --git a/include/lib/aarch64/setjmp.h b/include/lib/aarch64/setjmp.h
new file mode 100644
index 000000000..c65810d82
--- /dev/null
+++ b/include/lib/aarch64/setjmp.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef __JMP_H__
+#define __JMP_H__
+
+#define JMP_CTX_X19 0x0
+#define JMP_CTX_X21 0x10
+#define JMP_CTX_X23 0x20
+#define JMP_CTX_X25 0x30
+#define JMP_CTX_X27 0x40
+#define JMP_CTX_X29 0x50
+#define JMP_CTX_SP 0x60
+#define JMP_CTX_END 0x70
+
+#define JMP_SIZE (JMP_CTX_END >> 3)
+
+#ifndef __ASSEMBLY__
+
+#include <stdint.h>
+
+/* Jump buffer hosting x18 - x30 and sp_el0 registers */
+struct jmpbuf {
+ uint64_t buf[JMP_SIZE];
+} __aligned(16);
+
+
+/*
+ * Set a jump point, and populate the jump buffer with context information so
+ * that longjmp() can jump later. The caller must adhere to the following
+ * conditions:
+ *
+ * - After calling this function, the stack must not be shrunk. The contents of
+ * the stack must not be changed either.
+ *
+ * - If the caller were to 'return', the buffer must be considered invalid, and
+ * must not be used with longjmp().
+ *
+ * The caller will observe this function returning at two distinct
+ * circumstances, each with different return values:
+ *
+ * - Zero, when the buffer is setup;
+ *
+ * - Non-zero, when a call to longjmp() is made (presumably by one of the
+ * callee functions) with the same jump buffer.
+ */
+int setjmp(struct jmpbuf *buf);
+
+/*
+ * Reset execution to a jump point, and restore context information according to
+ * the jump buffer populated by setjmp().
+ */
+void longjmp(struct jmpbuf *buf);
+
+#endif /* __ASSEMBLY__ */
+#endif /* __JMP_H__ */
diff --git a/lib/aarch64/setjmp.S b/lib/aarch64/setjmp.S
new file mode 100644
index 000000000..9060cb756
--- /dev/null
+++ b/lib/aarch64/setjmp.S
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <asm_macros.S>
+#include <assert_macros.S>
+#include <setjmp.h>
+
+ .globl setjmp
+ .globl longjmp
+
+/*
+ * int setjmp(struct jmpbuf *buf);
+ *
+ * Sets a jump point in the buffer specified in x0. Returns 0 to the caller when
+ * when setting up the jump, and 1 when returning from the jump.
+ */
+func setjmp
+ mov x7, sp
+
+ stp x19, x20, [x0, #JMP_CTX_X19]
+ stp x21, x22, [x0, #JMP_CTX_X21]
+ stp x23, x24, [x0, #JMP_CTX_X23]
+ stp x25, x26, [x0, #JMP_CTX_X25]
+ stp x27, x28, [x0, #JMP_CTX_X27]
+ stp x29, x30, [x0, #JMP_CTX_X29]
+ stp x7, xzr, [x0, #JMP_CTX_SP]
+
+ mov x0, #0
+ ret
+endfunc setjmp
+
+
+/*
+ * void longjmp(struct jmpbuf *buf);
+ *
+ * Return to a jump point setup by setjmp()
+ */
+func longjmp
+ ldp x7, xzr, [x0, #JMP_CTX_SP]
+
+#if ENABLE_ASSERTIONS
+ /*
+ * Since we're unwinding the stack, assert that the stack being reset to
+ * is shallower.
+ */
+ mov x19, sp
+ cmp x7, x19
+ ASM_ASSERT(ge)
+#endif
+
+ ldp x19, x20, [x0, #JMP_CTX_X19]
+ ldp x21, x22, [x0, #JMP_CTX_X21]
+ ldp x23, x24, [x0, #JMP_CTX_X23]
+ ldp x25, x26, [x0, #JMP_CTX_X25]
+ ldp x27, x28, [x0, #JMP_CTX_X27]
+ ldp x29, x30, [x0, #JMP_CTX_X29]
+
+ mov sp, x7
+
+ mov x0, #1
+ ret
+endfunc longjmp
--
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