There is a subtle bug in arch/mips/lib/memset.S, used if option MIPS_OPTIMIZED_STRING_FUNCTIONS is enabled, which results in not writing the correct return value into v0 register if the value to fill memory with is 0. The bug stems from a missing '.set noreorder' directive before the first beqz instruction. This results in an assembler stuffing a 'nop' instruction in the beqz delay slot instead of an instruction writing the return value into v0 register that was supposed to go there. That leads to an error that appears when reading memory from SPI Flash and that was mentioned here: http://lists.infradead.org/pipermail/barebox/2021-June/036557.html There are a few ways of fixing this bug. The directive '.set noreorder' that shows up a bit later in code could be moved up and placed right before the memset label (as it was originally in Linux codebase - see a583158c9ce822c96a718fbf877cec1e5f9ad75d). Or, rather, the move and the branch instruction could be swapped, thus allowing the assembler to properly place move in delay slot (as it is done in Linux now - see 68dec269ee29c3abfd09596fbee7e40d875a6ab3) - that is what is done in this patch. Signed-off-by: Denis Orlov <denorl2009@xxxxxxxxx> --- arch/mips/lib/memset.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/mips/lib/memset.S b/arch/mips/lib/memset.S index 0b81bd7d8d..cd4e4ccfe8 100644 --- a/arch/mips/lib/memset.S +++ b/arch/mips/lib/memset.S @@ -34,8 +34,8 @@ */ LEAF(memset) - beqz a1, 1f move v0, a0 /* result */ + beqz a1, 1f andi a1, 0xff /* spread fillword */ LONG_SLL t1, a1, 8 -- 2.20.1 _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
