From: Eldar Abusalimov <eldar.abusalimov@xxxxxxxxx> Date: Mon, 3 Aug 2009 21:36:31 +0400 > Hi, David! > > I've been looking into traps-related routines for some time, and was > confused with srmmu user stack checking code. > > Here is the corresponding part of etrap.S file: > > 278 .globl tsetup_srmmu_stackchk > 279 tsetup_srmmu_stackchk: > 280 /* Check results of callers andcc %sp, 0x7, %g0 */ > 281 bne trap_setup_user_stack_is_bolixed > 282 sethi %hi(PAGE_OFFSET), %glob_tmp > 283 > 284 cmp %glob_tmp, %sp > 285 bleu,a 1f > 286 lda [%g0] ASI_M_MMUREGS, %glob_tmp ! read MMU control > 287 > 288 trap_setup_user_stack_is_bolixed: > 289 /* From user/kernel into invalid window w/bad user > 290 * stack. Save bad user stack, and return to caller. > 291 */ > 292 SAVE_BOLIXED_USER_STACK(curptr, g3) > 293 restore %g0, %g0, %g0 > 294 > 295 jmpl %t_retpc + 0x8, %g0 > 296 mov %t_kstack, %sp > 297 > 298 1: > 299 /* Clear the fault status and turn on the no_fault bit. */ > 300 or %glob_tmp, 0x2, %glob_tmp ! or in > no_fault bit > 301 sta %glob_tmp, [%g0] ASI_M_MMUREGS ! set it > 302 > 303 /* Dump the registers and cross fingers. */ > 304 STORE_WINDOW(sp) > > On the line 284 we compare user stack pointer with PAGE_OFFSET, and if > it is greater than PAGE_OFFSET, then we consider user stack is still > ok and continue checking. On the contrary, if %sp is small enough, > bollixed stack handler is entered at once. Is it right? We want to fall through to line 288 if PAGE_OFFSET > %sp and that's what we do. Your reading of the logic seems to be reversed, either that or you're missing the fallthrough there for when the branch isn't taken. :-) -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
