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bsps/arm: Avoid short range branch in start.S

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This commit is contained in:
Sebastian Huber
2018-11-20 13:09:53 +01:00
parent faafc22928
commit e0caabe08d
1 changed files with 13 additions and 14 deletions
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27
bsps/arm/shared/start/start.S
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@@ -276,34 +276,33 @@ _start:
#endif /* ARM_MULTILIB_VFP */
/*
* Branch to start hook 0.
* Invoke the start hook 0.
*
* The previous code and parts of the start hook 0 may run with an
* address offset. This implies that only branches relative to the
* program counter are allowed. After the start hook 0 it is assumed
* address offset. After the return from start hook 0 it is assumed
* that the code can run at its intended position. Thus the link
* register will be loaded with the absolute address. In THUMB mode
* the start hook 0 must be within a 2kByte range due to the branch
* instruction limitation.
* register will be loaded with the absolute address and the branch
* link instruction cannot be used. In THUMB mode the branch
* instruction as a very limited address range of 2KiB. Use a bx to
* the start hook 0 address instead corrected by the address offset.
*/
ldr lr, =.Lstart_hook_0_done
#ifdef __thumb__
orr lr, #1
#endif
SWITCH_FROM_ARM_TO_THUMB r0
mov r0, pc
ldr r1, =.Lget_absolute_pc
.Lget_absolute_pc:
sub r1, r0
ldr r7, =bsp_start_hook_0
add r7, r1
mov r0, r4 /* original CPSR value */
mov r1, r5 /* machine type number or ~0 for DT boot */
mov r2, r6 /* physical address of ATAGs or DTB */
b bsp_start_hook_0
bx r7
.Lstart_hook_0_done:
SWITCH_FROM_THUMB_TO_ARM
/*
* Initialize the exception vectors. This includes the exceptions
* vectors and the pointers to the default exception handlers.