Hi Maciej, > > Anyway, as noted above that shouldn't cause a problem with user software > > and I think that any corruption you can see comes from elsewhere. You'll > > have to paper this $ra non-sign-extension issue over somehow to proceed > > though. > > I've extended do_IRQ with a register check under the condition that > user_mode(get_irq_regs()) is true, with the following sample results > where registers $2-$25 are printed if they are not sign-extended > properly (there is a certain amount of randomness to this): > > $10 : 00005f6362696c5f > epc = 0fb6db00 in ld.so.1[fb60000+19000] Debian-based Black Rhino libc.so.6 declares "ELF 32-bit LSB MIPS-III version 1" but functions such as strcmp contain both 64-bit and multimedia instructions (presumably hand coded in assembly for the R5900): 6005ea90 <strcmp>: ... 6005eb50: 78880000 lq t0,0(a0) 6005eb54: 710043a9 pcpyud t0,t0,zero 6005eb58: 1000000c b 6005eb8c <strcmp+0xfc> 6005eb5c: 71204ba9 pcpyud t1,t1,zero 6005eb60: dc880000 ld t0,0(a0) 6005eb64: 24840008 addiu a0,a0,8 6005eb68: dca90000 ld t1,0(a1) 6005eb6c: 710072a8 pceqb t6,t0,zero 6005eb70: 71207aa8 pceqb t7,t1,zero 6005eb74: 01cf7025 or t6,t6,t7 6005eb78: 71097aa8 pceqb t7,t0,t1 ... Hence corruption and register sign-extension failures. One can also note that according to the TX-79 manual, for a 32-bit kernel, several MIPS I instruction operations are undefined unless registers are sign-extended. It is unfortunate that these instructions seem untrappable by the R5900, instead silently causing strange behaviour and invalid results. Still left to explain is why the kernel stumbles on registers during initialisation, before user applications are invoked. Fredrik
