Hello, I believe it's desireable to point to the faulting instruction upon an FPU trap and not the following one. Why? First, the FPU restores the state from before attempting to exectute the instruction. Second, with the current approach state is lost -- consider instructions in branch/jump delay slots. Third, erroneous execution is possible if SIG_FPE's handler is set to "ignore" by mistake. The following patch implements the described approach. It should not affect standard handlers which use setjmp()/longjmp(), but it should enable a smarter interpreting handler or just better diagnostics. Both the hardware and the emulator are handled. Tested successfully with gdb on an R3k, an R4k and the emulator. Maciej -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available + patch-mips-2.4.14-20011123-fpu-epc-0 diff -up --recursive --new-file linux-mips-2.4.14-20011123.macro/arch/mips/kernel/traps.c linux-mips-2.4.14-20011123/arch/mips/kernel/traps.c --- linux-mips-2.4.14-20011123.macro/arch/mips/kernel/traps.c Wed Nov 21 05:26:46 2001 +++ linux-mips-2.4.14-20011123/arch/mips/kernel/traps.c Sun Nov 25 13:25:06 2001 @@ -497,9 +497,6 @@ asmlinkage void do_fpe(struct pt_regs *r return; } - if (compute_return_epc(regs)) - return; - force_sig(SIGFPE, current); printk(KERN_DEBUG "Sent send SIGFPE to %s\n", current->comm); } diff -up --recursive --new-file linux-mips-2.4.14-20011123.macro/arch/mips/math-emu/cp1emu.c linux-mips-2.4.14-20011123/arch/mips/math-emu/cp1emu.c --- linux-mips-2.4.14-20011123.macro/arch/mips/math-emu/cp1emu.c Sun Oct 14 04:26:36 2001 +++ linux-mips-2.4.14-20011123/arch/mips/math-emu/cp1emu.c Sun Nov 25 13:29:30 2001 @@ -1721,6 +1721,9 @@ int fpu_emulator_cop1Handler(struct pt_r /* but if epc has advanced, then ignore it */ sig = 0; + if (sig) + xcp->cp0_epc = prevepc; + return sig; }
