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py/asmthumb: Don't corrupt base register in large offset store.

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asm_thumb_store_reg_reg_offset() modifies the base register when storing
with a large offset which triggers the generic path. If a variable lives
in that register, this corrupts it. Fix this by saving the base register
on the stack before modifying it.

Signed-off-by: Chris Webb <chris@arachsys.com>
This commit is contained in:
Chris Webb 2025-07-27 22:16:24 +01:00 committed by Damien George
parent 69ead7d98e
commit f39434e9fb
1 changed files with 2 additions and 0 deletions
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py/asmthumb.c
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@ -492,8 +492,10 @@ void asm_thumb_store_reg_reg_offset(asm_thumb_t *as, uint reg_src, uint reg_base
asm_thumb_op32(as, (OP_LDR_STR_W_HI(operation_size, reg_base) | OP_STR_W), OP_LDR_STR_W_LO(reg_src, (offset << operation_size)));
} else {
// Must use the generic sequence
asm_thumb_op16(as, OP_PUSH_RLIST(1 << reg_base));
asm_thumb_add_reg_reg_offset(as, reg_base, reg_base, offset - 31, operation_size);
asm_thumb_op16(as, ((OP_LDR_STR_TABLE[operation_size] | OP_STR) << 11) | (31 << 6) | (reg_base << 3) | reg_src);
asm_thumb_op16(as, OP_POP_RLIST(1 << reg_base));
}
}