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 <[email protected]>

diff --git a/bl31/bl31.mk b/bl31/bl31.mk
index a6c0a9a07a641da007fce49a70a879632a7a948f..51a8312453be43021754ab92614429bfd4cdce83 100644 (file)
--- 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 (file)
index 0000000..c65810d
--- /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 (file)
index 0000000..9060cb7
--- /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