/* * This file contains the code that gets mapped at the upper end of each task's text * region. For now, it contains the signal trampoline code only. * * Copyright (C) 1999-2003 Hewlett-Packard Co * David Mosberger-Tang */ #include #include #include #include #include #include #include /* * We can't easily refer to symbols inside the kernel. To avoid full runtime relocation, * complications with the linker (which likes to create PLT stubs for branches * to targets outside the shared object) and to avoid multi-phase kernel builds, we * simply create minimalistic "patch lists" in special ELF sections. */ .section ".data.patch.fsyscall_table", "a" .previous #define LOAD_FSYSCALL_TABLE(reg) \ [1:] movl reg=0; \ .xdata4 ".data.patch.fsyscall_table", 1b-. .section ".data.patch.brl_fsys_bubble_down", "a" .previous #define BRL_COND_FSYS_BUBBLE_DOWN(pr) \ [1:](pr)brl.cond.sptk 0; \ .xdata4 ".data.patch.brl_fsys_bubble_down", 1b-. GLOBAL_ENTRY(__kernel_syscall_via_break) .prologue .altrp b6 .body /* * Note: for (fast) syscall restart to work, the break instruction must be * the first one in the bundle addressed by syscall_via_break. */ { .mib break 0x100000 nop.i 0 br.ret.sptk.many b6 } END(__kernel_syscall_via_break) /* * On entry: * r11 = saved ar.pfs * r15 = system call # * b0 = saved return address * b6 = return address * On exit: * r11 = saved ar.pfs * r15 = system call # * b0 = saved return address * all other "scratch" registers: undefined * all "preserved" registers: same as on entry */ GLOBAL_ENTRY(__kernel_syscall_via_epc) .prologue .altrp b6 .body { /* * Note: the kernel cannot assume that the first two instructions in this * bundle get executed. The remaining code must be safe even if * they do not get executed. */ adds r17=-1024,r15 // A mov r10=0 // A default to successful syscall execution epc // B causes split-issue } ;; rsm psr.be // M2 (5 cyc to srlz.d) LOAD_FSYSCALL_TABLE(r14) // X ;; mov r16=IA64_KR(CURRENT) // M2 (12 cyc) shladd r18=r17,3,r14 // A mov r19=NR_syscalls-1 // A ;; lfetch [r18] // M0|1 mov r29=psr // M2 (12 cyc) // If r17 is a NaT, p6 will be zero cmp.geu p6,p7=r19,r17 // A (sysnr > 0 && sysnr < 1024+NR_syscalls)? ;; mov r21=ar.fpsr // M2 (12 cyc) tnat.nz p10,p9=r15 // I0 mov.i r26=ar.pfs // I0 (would stall anyhow due to srlz.d...) ;; srlz.d // M0 (forces split-issue) ensure PSR.BE==0 (p6) ld8 r18=[r18] // M0|1 nop.i 0 ;; nop.m 0 (p6) mov b7=r18 // I0 (p6) tbit.z.unc p8,p0=r18,0 // I0 (dual-issues with "mov b7=r18"!) nop.m 0 nop.i 0 (p8) br.dptk.many b7 // B mov r27=ar.rsc // M2 (12 cyc) (p6) rsm psr.i // M2 /* * brl.cond doesn't work as intended because the linker would convert this branch * into a branch to a PLT. Perhaps there will be a way to avoid this with some * future version of the linker. In the meantime, we just use an indirect branch * instead. */ #ifdef CONFIG_ITANIUM (p6) add r14=-8,r14 // r14 <- addr of fsys_bubble_down entry ;; (p6) ld8 r14=[r14] // r14 <- fsys_bubble_down ;; (p6) mov b7=r14 (p6) br.sptk.many b7 #else BRL_COND_FSYS_BUBBLE_DOWN(p6) #endif mov r10=-1 (p10) mov r8=EINVAL (p9) mov r8=ENOSYS FSYS_RETURN END(__kernel_syscall_via_epc) # define ARG0_OFF (16 + IA64_SIGFRAME_ARG0_OFFSET) # define ARG1_OFF (16 + IA64_SIGFRAME_ARG1_OFFSET) # define ARG2_OFF (16 + IA64_SIGFRAME_ARG2_OFFSET) # define SIGHANDLER_OFF (16 + IA64_SIGFRAME_HANDLER_OFFSET) # define SIGCONTEXT_OFF (16 + IA64_SIGFRAME_SIGCONTEXT_OFFSET) # define FLAGS_OFF IA64_SIGCONTEXT_FLAGS_OFFSET # define CFM_OFF IA64_SIGCONTEXT_CFM_OFFSET # define FR6_OFF IA64_SIGCONTEXT_FR6_OFFSET # define BSP_OFF IA64_SIGCONTEXT_AR_BSP_OFFSET # define RNAT_OFF IA64_SIGCONTEXT_AR_RNAT_OFFSET # define UNAT_OFF IA64_SIGCONTEXT_AR_UNAT_OFFSET # define FPSR_OFF IA64_SIGCONTEXT_AR_FPSR_OFFSET # define PR_OFF IA64_SIGCONTEXT_PR_OFFSET # define RP_OFF IA64_SIGCONTEXT_IP_OFFSET # define SP_OFF IA64_SIGCONTEXT_R12_OFFSET # define RBS_BASE_OFF IA64_SIGCONTEXT_RBS_BASE_OFFSET # define LOADRS_OFF IA64_SIGCONTEXT_LOADRS_OFFSET # define base0 r2 # define base1 r3 /* * When we get here, the memory stack looks like this: * * +===============================+ * | | * // struct sigframe // * | | * +-------------------------------+ <-- sp+16 * | 16 byte of scratch | * | space | * +-------------------------------+ <-- sp * * The register stack looks _exactly_ the way it looked at the time the signal * occurred. In other words, we're treading on a potential mine-field: each * incoming general register may be a NaT value (including sp, in which case the * process ends up dying with a SIGSEGV). * * The first thing need to do is a cover to get the registers onto the backing * store. Once that is done, we invoke the signal handler which may modify some * of the machine state. After returning from the signal handler, we return * control to the previous context by executing a sigreturn system call. A signal * handler may call the rt_sigreturn() function to directly return to a given * sigcontext. However, the user-level sigreturn() needs to do much more than * calling the rt_sigreturn() system call as it needs to unwind the stack to * restore preserved registers that may have been saved on the signal handler's * call stack. */ #define SIGTRAMP_SAVES \ .unwabi 3, 's'; /* mark this as a sigtramp handler (saves scratch regs) */ \ .unwabi @svr4, 's'; /* backwards compatibility with old unwinders (remove in v2.7) */ \ .savesp ar.unat, UNAT_OFF+SIGCONTEXT_OFF; \ .savesp ar.fpsr, FPSR_OFF+SIGCONTEXT_OFF; \ .savesp pr, PR_OFF+SIGCONTEXT_OFF; \ .savesp rp, RP_OFF+SIGCONTEXT_OFF; \ .savesp ar.pfs, CFM_OFF+SIGCONTEXT_OFF; \ .vframesp SP_OFF+SIGCONTEXT_OFF GLOBAL_ENTRY(__kernel_sigtramp) // describe the state that is active when we get here: .prologue SIGTRAMP_SAVES .body .label_state 1 adds base0=SIGHANDLER_OFF,sp adds base1=RBS_BASE_OFF+SIGCONTEXT_OFF,sp br.call.sptk.many rp=1f 1: ld8 r17=[base0],(ARG0_OFF-SIGHANDLER_OFF) // get pointer to signal handler's plabel ld8 r15=[base1] // get address of new RBS base (or NULL) cover // push args in interrupted frame onto backing store ;; cmp.ne p1,p0=r15,r0 // do we need to switch rbs? (note: pr is saved by kernel) mov.m r9=ar.bsp // fetch ar.bsp .spillsp.p p1, ar.rnat, RNAT_OFF+SIGCONTEXT_OFF (p1) br.cond.spnt setup_rbs // yup -> (clobbers p8, r14-r16, and r18-r20) back_from_setup_rbs: alloc r8=ar.pfs,0,0,3,0 ld8 out0=[base0],16 // load arg0 (signum) adds base1=(ARG1_OFF-(RBS_BASE_OFF+SIGCONTEXT_OFF)),base1 ;; ld8 out1=[base1] // load arg1 (siginfop) ld8 r10=[r17],8 // get signal handler entry point ;; ld8 out2=[base0] // load arg2 (sigcontextp) ld8 gp=[r17] // get signal handler's global pointer adds base0=(BSP_OFF+SIGCONTEXT_OFF),sp ;; .spillsp ar.bsp, BSP_OFF+SIGCONTEXT_OFF st8 [base0]=r9 // save sc_ar_bsp adds base0=(FR6_OFF+SIGCONTEXT_OFF),sp adds base1=(FR6_OFF+16+SIGCONTEXT_OFF),sp ;; stf.spill [base0]=f6,32 stf.spill [base1]=f7,32 ;; stf.spill [base0]=f8,32 stf.spill [base1]=f9,32 mov b6=r10 ;; stf.spill [base0]=f10,32 stf.spill [base1]=f11,32 ;; stf.spill [base0]=f12,32 stf.spill [base1]=f13,32 ;; stf.spill [base0]=f14,32 stf.spill [base1]=f15,32 br.call.sptk.many rp=b6 // call the signal handler .ret0: adds base0=(BSP_OFF+SIGCONTEXT_OFF),sp ;; ld8 r15=[base0] // fetch sc_ar_bsp mov r14=ar.bsp ;; cmp.ne p1,p0=r14,r15 // do we need to restore the rbs? (p1) br.cond.spnt restore_rbs // yup -> (clobbers r14-r18, f6 & f7) ;; back_from_restore_rbs: adds base0=(FR6_OFF+SIGCONTEXT_OFF),sp adds base1=(FR6_OFF+16+SIGCONTEXT_OFF),sp ;; ldf.fill f6=[base0],32 ldf.fill f7=[base1],32 ;; ldf.fill f8=[base0],32 ldf.fill f9=[base1],32 ;; ldf.fill f10=[base0],32 ldf.fill f11=[base1],32 ;; ldf.fill f12=[base0],32 ldf.fill f13=[base1],32 ;; ldf.fill f14=[base0],32 ldf.fill f15=[base1],32 mov r15=__NR_rt_sigreturn .restore sp // pop .prologue break __BREAK_SYSCALL .prologue SIGTRAMP_SAVES setup_rbs: mov ar.rsc=0 // put RSE into enforced lazy mode ;; .save ar.rnat, r19 mov r19=ar.rnat // save RNaT before switching backing store area adds r14=(RNAT_OFF+SIGCONTEXT_OFF),sp mov r18=ar.bspstore mov ar.bspstore=r15 // switch over to new register backing store area ;; .spillsp ar.rnat, RNAT_OFF+SIGCONTEXT_OFF st8 [r14]=r19 // save sc_ar_rnat .body mov.m r16=ar.bsp // sc_loadrs <- (new bsp - new bspstore) << 16 adds r14=(LOADRS_OFF+SIGCONTEXT_OFF),sp ;; invala sub r15=r16,r15 extr.u r20=r18,3,6 ;; mov ar.rsc=0xf // set RSE into eager mode, pl 3 cmp.eq p8,p0=63,r20 shl r15=r15,16 ;; st8 [r14]=r15 // save sc_loadrs (p8) st8 [r18]=r19 // if bspstore points at RNaT slot, store RNaT there now .restore sp // pop .prologue br.cond.sptk back_from_setup_rbs .prologue SIGTRAMP_SAVES .spillsp ar.rnat, RNAT_OFF+SIGCONTEXT_OFF .body restore_rbs: // On input: // r14 = bsp1 (bsp at the time of return from signal handler) // r15 = bsp0 (bsp at the time the signal occurred) // // Here, we need to calculate bspstore0, the value that ar.bspstore needs // to be set to, based on bsp0 and the size of the dirty partition on // the alternate stack (sc_loadrs >> 16). This can be done with the // following algorithm: // // bspstore0 = rse_skip_regs(bsp0, -rse_num_regs(bsp1 - (loadrs >> 19), bsp1)); // // This is what the code below does. // alloc r2=ar.pfs,0,0,0,0 // alloc null frame adds r16=(LOADRS_OFF+SIGCONTEXT_OFF),sp adds r18=(RNAT_OFF+SIGCONTEXT_OFF),sp ;; ld8 r17=[r16] ld8 r16=[r18] // get new rnat extr.u r18=r15,3,6 // r18 <- rse_slot_num(bsp0) ;; mov ar.rsc=r17 // put RSE into enforced lazy mode shr.u r17=r17,16 ;; sub r14=r14,r17 // r14 (bspstore1) <- bsp1 - (sc_loadrs >> 16) shr.u r17=r17,3 // r17 <- (sc_loadrs >> 19) ;; loadrs // restore dirty partition extr.u r14=r14,3,6 // r14 <- rse_slot_num(bspstore1) ;; add r14=r14,r17 // r14 <- rse_slot_num(bspstore1) + (sc_loadrs >> 19) ;; shr.u r14=r14,6 // r14 <- (rse_slot_num(bspstore1) + (sc_loadrs >> 19))/0x40 ;; sub r14=r14,r17 // r14 <- -rse_num_regs(bspstore1, bsp1) movl r17=0x8208208208208209 ;; add r18=r18,r14 // r18 (delta) <- rse_slot_num(bsp0) - rse_num_regs(bspstore1,bsp1) setf.sig f7=r17 cmp.lt p7,p0=r14,r0 // p7 <- (r14 < 0)? ;; (p7) adds r18=-62,r18 // delta -= 62 ;; setf.sig f6=r18 ;; xmpy.h f6=f6,f7 ;; getf.sig r17=f6 ;; add r17=r17,r18 shr r18=r18,63 ;; shr r17=r17,5 ;; sub r17=r17,r18 // r17 = delta/63 ;; add r17=r14,r17 // r17 <- delta/63 - rse_num_regs(bspstore1, bsp1) ;; shladd r15=r17,3,r15 // r15 <- bsp0 + 8*(delta/63 - rse_num_regs(bspstore1, bsp1)) ;; mov ar.bspstore=r15 // switch back to old register backing store area ;; mov ar.rnat=r16 // restore RNaT mov ar.rsc=0xf // (will be restored later on from sc_ar_rsc) // invala not necessary as that will happen when returning to user-mode br.cond.sptk back_from_restore_rbs END(__kernel_sigtramp)