On Wed, 12 Feb 2025, Thomas Weißschuh wrote: > diff --git a/tools/include/nolibc/arch-mips.h > b/tools/include/nolibc/arch-mips.h > index > 753a8ed2cf695f0b5eac4b5e4d317fdb383ebf93..638520a3427a985fdbd5f5a49b55853bbadeee75 > 100644 > --- a/tools/include/nolibc/arch-mips.h > +++ b/tools/include/nolibc/arch-mips.h > @@ -190,13 +257,33 @@ void __attribute__((weak, noreturn)) > __nolibc_entrypoint __no_stack_protector __ > "1:\n" > ".cpload $ra\n" > "move $a0, $sp\n" /* save stack pointer to $a0, as arg1 > of _start_c */ > + > +#if defined(_ABIO32) > "addiu $sp, $sp, -4\n" /* space for .cprestore to store $gp > */ > ".cprestore 0\n" > "li $t0, -8\n" > "and $sp, $sp, $t0\n" /* $sp must be 8-byte aligned > */ > "addiu $sp, $sp, -16\n" /* the callee expects to save a0..a3 > there */ > - "lui $t9, %hi(_start_c)\n" /* ABI requires current function > address in $t9 */ > +#else > + "daddiu $sp, $sp, -8\n" /* space for .cprestore to store $gp > */ > + ".cpsetup $ra, 0, 1b\n" > + "li $t0, -16\n" > + "and $sp, $sp, $t0\n" /* $sp must be 16-byte aligned > */ > +#endif
Why is this code breaking stack alignment just to have to fix it up two instructions down the line? Or is it that the incoming $sp is not aligned in the first place (in which case we're having a deeper problem). > + > + /* ABI requires current function address in $t9 */ > +#if defined(_ABIO32) || defined(_ABIN32) > + "lui $t9, %hi(_start_c)\n" > "ori $t9, %lo(_start_c)\n" > +#else > + "lui $t9, %highest(_start_c)\n" > + "ori $t9, %higher(_start_c)\n" > + "dsll $t9, 0x10\n" > + "ori $t9, %hi(_start_c)\n" > + "dsll $t9, 0x10\n" > + "ori $t9, %lo(_start_c)\n" This could be optimised using a temporary (e.g. $at, but I guess any will do as I gather we don't have any ABI abnormalities here). > +#endif > + > "jalr $t9\n" /* transfer to c runtime > */ > " nop\n" /* delayed slot On an unrelated matter JALR above ought to be JAL (or otherwise there's no point in using the .cprestore pseudo-op). And I fail to see why this code has to be "noreorder" (except for the .cpload piece, of course), it's just asking for troubles. Maciej
