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https://github.com/smaeul/u-boot.git
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6ef83ab6be
U-Boot runs in supervisor mode. On ARMv6 and lower, software interrupts are taken in supervisor mode. When entering an interrupt, the link register is set to the address of the next instruction. However, if we are already in supervisor mode, this clobbers the link register. The debugger can't help us, since by the time it notices we've taken a software interrupt, the link register is already gone. Work around this by moving the return address to another register. Signed-off-by: Sean Anderson <sean.anderson@seco.com>
38 lines
633 B
ArmAsm
38 lines
633 B
ArmAsm
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* (C) 2022 Arm Ltd.
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*/
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#include <config.h>
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#include <asm/macro.h>
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#include <linux/linkage.h>
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.pushsection .text.smh_trap, "ax"
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/* long smh_trap(unsigned int sysnum, void *addr); */
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ENTRY(smh_trap)
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#if defined(CONFIG_ARM64)
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hlt #0xf000
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#elif defined(CONFIG_CPU_V7M)
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bkpt #0xab
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#elif defined(CONFIG_SYS_THUMB_BUILD)
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svc #0xab
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#else
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#if CONFIG_SYS_ARM_ARCH < 7
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/* Before the ARMv7 exception model, svc (swi) clobbers lr */
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mov r2, lr
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#endif
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svc #0x123456
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#endif
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#if defined(CONFIG_ARM64)
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ret
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#elif CONFIG_SYS_ARM_ARCH < 7
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bx r2
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#else
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bx lr
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#endif
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ENDPROC(smh_trap)
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.popsection
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