7751fbca44
QEMU requires that the semihosting trap instruction sequence, which consists of three uncompressed instructions, lie in the same page, and refuses to interpret the trap sequence if these instructions are placed across two different pages. This commit adds 16-byte alignment requirement to the `semihost_exec` function, which occupies 12 bytes, to ensure that the three trap sequence instructions in this function are never placed across two different pages. Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
38 lines
1.1 KiB
C
38 lines
1.1 KiB
C
/*
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* Copyright (c) 2022, Commonwealth Scientific and Industrial Research
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* Organisation (CSIRO) ABN 41 687 119 230.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/toolchain.h>
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#include <zephyr/arch/common/semihost.h>
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/*
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* QEMU requires that the semihosting trap instruction sequence, consisting of
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* three uncompressed instructions, lie in the same page, and refuses to
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* interpret the trap sequence if these instructions are placed across two
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* different pages.
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*
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* The `semihost_exec` function, which occupies 12 bytes, is aligned at a
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* 16-byte boundary to ensure that the three trap sequence instructions are
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* never placed across two different pages.
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*/
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long __aligned(16) semihost_exec(enum semihost_instr instr, void *args)
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{
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register unsigned long a0 __asm__ ("a0") = instr;
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register void *a1 __asm__ ("a1") = args;
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register long ret __asm__ ("a0");
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__asm__ volatile (
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".option push\n\t"
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".option norvc\n\t"
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"slli zero, zero, 0x1f\n\t"
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"ebreak\n\t"
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"srai zero, zero, 0x7\n\t"
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".option pop"
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: "=r" (ret) : "r" (a0), "r" (a1) : "memory");
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return ret;
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}
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