On Thu, Mar 10, 2022 at 11:42:06PM +0300, Denis Orlov wrote: > 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(-) Applied, thanks Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
