> The previous implementation did not cover all possible FPU combinations > and it silently allowed ABI incompatible objects to be loaded with the > wrong ABI. For example, the previous logic would set the FP_64 ABI as > the matching ABI for an FP_XX object combined with an FP_64A object. > This was wrong, and the matching ABI should have been FP_64A. > The previous logic is now replaced with a new one which determines the > appropriate FPU mode to be used rather than the FP ABI. This has the > advantage that the entire logic is much simpler since it is the FPU mode > we are interested in rather than the FP ABI resulting to code > simplifications. > For the record this code has been tested against the GLIBC implementation .MIPS.abiflags dynamic linker logic and a comprehensive ABI compatibility testsuite posted here: http://sourceware.org/ml/libc-alpha/2014-12/msg00852.html > + /* Lets see if this is an O32 ELF */ > + if (ehdr32->e_ident[EI_CLASS] == ELFCLASS32) { > + /* FR = 1 for N32 */ > + if (ehdr32->e_flags & EF_MIPS_ABI2) > + state->overall_fp_mode = FP_FR1; > + else > + /* Set a good default FPU mode for O32*/ Nit: spacing at the end of the comment. > /* If the EF_MIPS_FP64 flag was set, return MIPS_ABI_FP_64 */ Should say return MIPS_ABI_FP_OLD_64 in the comment. > if (ehdr->e_flags & EF_MIPS_FP64) > - return MIPS_ABI_FP_64; > + return MIPS_ABI_FP_OLD_64; > A couple of suggestions for rewording the mode selection comments: > + * - We want FR_FRE if FR=1 and FR=0 are both false. This means > + * that we don't have a single matching FR mode to satisfy > + * the requirements so our only solution is to use the emulated > + * mode We want FR_FRE if FRE=1 is true but both FR=1 and FR=0 are false. This means that we have a combination of program and interpreter that inherently require the hybrid FP mode. > + * - If FR1 and FRDEFAULT is true, that means we hit the any-abi or > + * fpxx case. This is because, in any-ABI (or no-ABI) we have no > FPU > + * instructions so we don't care about the mode. We will simply > use > + * the one preferred by the hardware. In fpxx case, that ABI can > + * handle both FR=1 and FR=0, so, again, we simply choose the one > + * preferred by the hardware. Next, if we only use single- > precision > + * FPU instructions, and the default ABI FPU mode is not good > + * (ie single + any ABI combination), we set again the FPU mode > to the > + * one is preferred by the hardware. Next, if we know that the code will only use single-precision instructions, shown by single being true but frdefault being false, then we again set the FPU mode to the one that is preferred by the hardware. > + * - We want FP_FR1 if that's the only matching mode and the > default one > + * is not good. > + * - Return with -ELIBADD if we can't find a matching FPU mode. > + */ > + if (prog_req.fre && !prog_req.frdefault && !prog_req.fr1) > + state->overall_fp_mode = FP_FRE; > + else if ((prog_req.fr1 && prog_req.frdefault) || > + (prog_req.single && !prog_req.frdefault)) > + /* Make sure 64-bit MIPS III/IV will not pick FR1 */ This is 64-bit MIPS III/IV and MIPS64(R1) > + state->overall_fp_mode = ((current_cpu_data.fpu_id & > MIPS_FPIR_F64) && > + (cpu_has_mips_r2 || cpu_has_mips_r6)) ? > + FP_FR1 : FP_FR0; > + else if (prog_req.fr1) > + state->overall_fp_mode = FP_FR1; > + else if (!prog_req.fre && !prog_req.frdefault && > + !prog_req.fr1 && !prog_req.single && !prog_req.soft) > return -ELIBBAD; > - } > > return 0; > } Thanks, Matthew
