/*
* 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 <davidm@hpl.hp.com>
*/
#include <asm/asmmacro.h>
#include <asm/errno.h>
#include <asm/asm-offsets.h>
#include <asm/sigcontext.h>
#include <asm/system.h>
#include <asm/unistd.h>
#include "paravirt_inst.h"
/*
* 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)
# 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)
/*
* 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_I(r20, r22) // 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_FROM_PSR(p0, r29, r8) // 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) tbit.z.unc p8,p0=r18,0 // I0 (dual-issues with "mov b7=r18"!)
nop.i 0
;;
SSM_PSR_I(p8, p14, r25)
(p6) mov b7=r18 // I0
(p8) br.dptk.many b7 // B
mov r27=ar.rsc // M2 (12 cyc)
/*
* 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
SSM_PSR_I(p0, p14, r10)
mov r10=-1
(p10) mov r8=EINVAL
(p9) mov r8=ENOSYS
FSYS_RETURN
#ifdef CONFIG_PARAVIRT
/*
* padd to make the size of this symbol constant
* independent of paravirtualization.
*/
.align PAGE_SIZE / 8
#endif
END(__kernel_syscall_via_epc)
