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[arm] Fix usermode "movs pc" causing invalid CPU state 

A missing usermode check (present in MIPS and x86) causes user-mode
returns to attempt returning into another CPU mode, which causes a bunch
of issues, mainly going into an invalid CPU state and corrupting some
registers.

This fixes a couple of games only (Colin McRae Rally 2, TOCA World
Touring, Starsky & Hutch ...)
This commit is contained in:
David Guillen Fandos 2023-01-04 23:30:46 +01:00
parent 53ac0814de
commit 90170e3389
1 changed files with 6 additions and 3 deletions
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9
arm/arm_stub.S
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@ -337,8 +337,10 @@ defsymbl(execute_store_cpsr)
defsymbl(execute_spsr_restore)
save_flags()
add r1, reg_base, #SPSR_RAM_OFF @ r1 = spsr
ldr r2, [reg_base, #CPU_MODE] @ r2 = cpu_mode
cmp r2, #0 @ if usermode already, do not change
beq 2f @ just a regular indirect jump really
add r1, reg_base, #SPSR_RAM_OFF @ r1 = spsr
ldr r1, [r1, r2, lsl #2] @ r1 = spsr[cpu_mode] (new cpsr)
str r1, [reg_base, #REG_CPSR] @ update cpsr
mov reg_flags, r1 @ also, update shadow flags
@ -349,14 +351,15 @@ defsymbl(execute_spsr_restore)
ldr r1, [reg_base, #REG_CPSR] @ r1 = cpsr
tst r1, #0x20 @ see if Thumb mode is set
bne 2f @ if so handle it
bne 1f @ if so handle it
load_registers_arm() @ restore ARM registers
2:
call_c_function(block_lookup_address_arm)
restore_flags()
bx r0
2:
1:
load_registers_thumb() @ load Thumb registers
call_c_function(block_lookup_address_thumb)
restore_flags()