;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ;;
;; Copyright (C) KolibriOS team 2004-2007. All rights reserved. ;;
;; Distributed under terms of the GNU General Public License ;;
;; ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
$Revision: 889 $
align 4
proc map_page stdcall,lin_addr:dword,phis_addr:dword,flags:dword
push ebx
mov eax, [phis_addr]
and eax, not 0xFFF
or eax, [flags]
mov ebx, [lin_addr]
shr ebx, 12
mov [page_tabs+ebx*4], eax
mov eax, [lin_addr]
invlpg [eax]
pop ebx
ret
endp
align 4
map_space: ;not implemented
ret
proc map_io_mem stdcall, base:dword, size:dword, flags:dword
push edi
mov ecx, [size]
add ecx, 4095
and ecx, -4096
mov [size], ecx
xor edx, edx
call @mem_alloc@8
test eax, eax
jz .fail
mov edx, eax
mov edi, eax
shr edi, 10
add edi, page_tabs
mov ecx, [size]
shr ecx, 12
mov eax, [base]
and eax, -4096
or eax, [flags]
@@:
stosd
add eax, 0x1000
loop @B
mov eax, [base]
and eax, 4095
add eax, edx
.fail:
pop edi
ret
endp
; param
; eax= page base + page flags
; ebx= linear address
; ecx= count
align 4
commit_pages:
push edi
test ecx, ecx
jz .fail
mov edi, ebx
mov ebx, pg_data.pg_mutex
call wait_mutex ;ebx
mov edx, 0x1000
mov ebx, edi
shr ebx, 12
@@:
mov [page_tabs+ebx*4], eax
; push eax
; invlpg [edi]
; pop eax
add edi, edx
add eax, edx
inc ebx
dec ecx
jnz @B
mov [pg_data.pg_mutex],ecx
.fail:
pop edi
ret
; param
; eax= base
; ecx= count
align 4
release_pages:
pushad
mov ebx, pg_data.pg_mutex
call wait_mutex ;ebx
mov esi, eax
mov edi, eax
shr esi, 10
add esi, page_tabs
@@:
xor eax, eax
xchg eax, [esi]
push eax
invlpg [edi]
pop eax
.next:
add edi, 0x1000
add esi, 4
dec ecx
jnz @B
and [pg_data.pg_mutex],0
popad
ret
; param
; eax= base
; ecx= count
align 4
unmap_pages:
push edi
mov edi, eax
mov edx, eax
shr edi, 10
add edi, page_tabs
xor eax, eax
@@:
stosd
invlpg [edx]
add edx, 0x1000
loop @b
pop edi
ret
align 4
proc map_page_table stdcall, lin_addr:dword, phis_addr:dword
push ebx
mov ebx, [lin_addr]
shr ebx, 22
mov eax, [phis_addr]
and eax, not 0xFFF
or eax, PG_UW ;+PG_NOCACHE
mov dword [master_tab+ebx*4], eax
mov eax, [lin_addr]
shr eax, 10
add eax, page_tabs
invlpg [eax]
pop ebx
ret
endp
align 4
proc init_LFB
locals
pg_count dd ?
endl
cmp dword [LFBAddress], -1
jne @f
mov [BOOT_VAR+0x901c],byte 2
mov ecx, 0x280000
mov edx, PG_SW
call @mem_alloc@8
mov [LFBAddress], eax
ret
@@:
test [SCR_MODE],word 0100000000000000b
jnz @f
mov [BOOT_VAR+0x901c],byte 2
ret
@@:
call init_mtrr
mov eax, [LFBAddress]
or eax, PG_LARGE+PG_UW
mov [_sys_pdbr+(LFB_BASE shr 20)], eax
add eax, 0x00400000
mov [_sys_pdbr+4+(LFB_BASE shr 20)], eax
mov dword [exp_lfb+4], LFB_BASE
bt [cpu_caps], CAPS_PGE
jnc @F
or dword [_sys_pdbr+(LFB_BASE shr 20)], PG_GLOBAL
@@:
mov dword [LFBAddress], LFB_BASE
mov eax, cr3 ;flush TLB
mov cr3, eax
ret
endp
align 4
proc new_mem_resize stdcall, new_size:dword
mov ebx, pg_data.pg_mutex
call wait_mutex ;ebx
mov edi, [new_size]
add edi,4095
and edi,not 4095
mov [new_size], edi
mov edx,[current_slot]
cmp [edx+APPDATA.heap_base],0
jne .exit
mov esi, [edx+APPDATA.mem_size]
add esi, 4095
and esi, not 4095
cmp edi, esi
jae .expand
shr edi, 12
shr esi, 12
@@:
mov ecx, [app_page_tabs+edi*4]
test ecx, 1
jz .next
mov dword [app_page_tabs+edi*4], 2
mov ebx, edi
shl ebx, 12
invlpg [ebx]
call @core_free@4
.next:
add edi, 1
cmp edi, esi
jb @B
.update_size:
mov ebx, [new_size]
call update_mem_size
xor eax, eax
dec [pg_data.pg_mutex]
ret
.expand:
push esi
push edi
add edi, 0x3FFFFF
and edi, not(0x3FFFFF)
add esi, 0x3FFFFF
and esi, not(0x3FFFFF)
cmp esi, edi
jae .grow
xchg esi, edi
@@:
call _alloc_page
test eax, eax
jz .exit
stdcall map_page_table, edi, eax
push edi
shr edi, 10
add edi, page_tabs
mov ecx, 1024
xor eax, eax
cld
rep stosd
pop edi
add edi, 0x00400000
cmp edi, esi
jb @B
.grow:
pop edi
pop esi
@@:
call _alloc_page
test eax, eax
jz .exit
stdcall map_page,esi,eax,dword PG_UW
push edi
mov edi, esi
xor eax, eax
mov ecx, 1024
cld
rep stosd
pop edi
add esi, 0x1000
cmp esi, edi
jb @B
jmp .update_size
.exit:
xor eax, eax
inc eax
dec [pg_data.pg_mutex]
ret
endp
update_mem_size:
; in: edx = slot base
; ebx = new memory size
; destroys eax,ecx,edx
mov [APPDATA.mem_size+edx],ebx
;search threads and update
;application memory size infomation
mov ecx,[APPDATA.dir_table+edx]
mov eax,2
.search_threads:
;eax = current slot
;ebx = new memory size
;ecx = page directory
cmp eax,[TASK_COUNT]
jg .search_threads_end
mov edx,eax
shl edx,5
cmp word [CURRENT_TASK+edx+TASKDATA.state],9 ;if slot empty?
jz .search_threads_next
shl edx,3
cmp [SLOT_BASE+edx+APPDATA.dir_table],ecx ;if it is our thread?
jnz .search_threads_next
mov [SLOT_BASE+edx+APPDATA.mem_size],ebx ;update memory size
.search_threads_next:
inc eax
jmp .search_threads
.search_threads_end:
ret
; param
; eax= linear address
;
; retval
; eax= phisical page address
align 4
get_pg_addr:
shr eax, 12
mov eax, [page_tabs+eax*4]
and eax, 0xFFFFF000
ret
align 4
proc page_fault_handler
test byte [esp+12+2], 2
jnz v86_page_fault
.err_code equ ebp+32
.err_addr equ ebp-4
pushad
mov ebp, esp
mov eax, cr2
push eax
mov ax, app_data
mov ds, ax
mov es, ax
inc [pg_data.pages_faults]
mov ebx, [.err_addr]
mov eax, [.err_code]
cmp ebx, HEAP_BASE
jb .user_space ;ñòðà Ãèöà â ïà ìÿòè ïðèëîæåÃèÿ ;
cmp ebx, LFB_BASE
jb .kernel_heap
cmp ebx, page_tabs
jb .lfb
cmp ebx, heap_tabs
jb .user_tabs
cmp ebx, OS_BASE
jb .heap_tab
; cmp ebx, kernel_tabs
; jb .alloc;.app_tabs ;òà áëèöû ñòðà Ãèö ïðèëîæåÃèÿ ;
;ïðîñòî ñîçäà äèì îäÃó
.lfb:
shr ebx, 22
mov edx, [_sys_pdbr + ebx*4]
mov [master_tab + ebx*4], edx
jmp .exit
.user_tabs:
shr ebx, 12
and ebx, 0x3FF
mov edx, [master_tab + ebx*4]
test edx, PG_MAP
jnz .fail
call _alloc_page
test eax, eax
jz .fail
lea edx, [eax + PG_UW]
lea edi, [eax + OS_BASE]
mov ecx, 1024
xor eax, eax
cld
rep stosd
mov [master_tab + ebx*4], edx
jmp .exit
.heap_tab:
shr ebx, 12
and ebx, 0x3FF
mov edx, [master_tab + ebx*4]
test edx, PG_MAP
jz .check_ptab ;òà áëèöà ñòðà Ãèö ÃÃ¥ ñîçäà ÃÃ
jmp .fail
align 4
.kernel_heap:
shr ebx, 22
mov edx, [master_tab + ebx*4]
test edx, PG_MAP
jz .check_ptab ;òà áëèöà ñòðà Ãèö ÃÃ¥ ñîçäà ÃÃ
jmp .exit
.check_ptab:
mov edx, [_sys_pdbr + ebx*4]
test edx, PG_MAP
jnz @F
xor ecx, ecx
call @core_alloc@4
test eax, eax
jz .fail
lea edx, [eax + PG_UW]
lea edi, [eax + OS_BASE]
mov ecx, 1024
xor eax, eax
cld
rep stosd
mov [_sys_pdbr + ebx*4], edx
@@:
mov [master_tab + ebx*4], edx
jmp .exit
align 4
.user_space:
test eax, PG_MAP
jnz .err_access ;Ñòðà Ãèöà ïðèñóòñòâóåò
;Îøèáêà äîñòóïà ?
shr ebx, 12
mov ecx, ebx
shr ecx, 10
mov edx, [master_tab + ecx*4]
test edx, PG_MAP
jz .fail ;òà áëèöà ñòðà Ãèö ÃÃ¥ ñîçäà ÃÃ
;ÃåâåðÃûé à äðåñ â ïðîãðà ììå
mov eax, [page_tabs+ebx*4]
test eax, 2
jz .fail ;à äðåñ ÃÃ¥ çà ðåçåðâèðîâà à äëÿ ;
;èñïîëüçîâà Ãèÿ. ÎøèáêÃ
.alloc:
call _alloc_page
test eax, eax
jz .fail
stdcall map_page,[ebp-4],eax,dword PG_UW
mov edi, [ebp-4]
and edi, 0xFFFFF000
mov ecx, 1024
xor eax, eax
cld
rep stosd
.exit:
mov esp, ebp
popad
add esp, 4
iretd
.err_access:
;Ãèêîãäà ÃÃ¥ ïðîèñõîäèò
jmp .fail
.kernel_space:
test eax, PG_MAP
jz .fail ;ñòðà Ãèöà ÃÃ¥ ïðèñóòñòâóåò
test eax, 4 ;U/S
jnz .fail ;ïðèëîæåÃèå îáðà òèëîñü ê ïà ìÿòè
;ÿäðÃ
test eax, 8
jnz .fail ;óñòà Ãîâëåà çà ðåçåðâèðîâà ÃÃûé áèò
;â òà áëèöà õ ñòðà Ãèö. äîáà âëåÃî â P4/Xeon
;ïîïûòêà çà ïèñè â çà ùèù¸ÃÃóþ ñòðà Ãèöó ÿäðÃ
cmp ebx, tss._io_map_0
jb .fail
cmp ebx, tss._io_map_0+8192
jae .fail
; io permission map
; copy-on-write protection
call _alloc_page
test eax, eax
jz .fail
push eax
stdcall map_page,[ebp-4],eax,dword PG_SW
pop eax
mov edi, [.err_addr]
and edi, -4096
lea esi, [edi+(not tss._io_map_0)+1]; -tss._io_map_0
mov ebx, esi
shr ebx, 12
mov edx, [current_slot]
or eax, PG_SW
mov [edx+APPDATA.io_map+ebx*4], eax
add esi, [default_io_map]
mov ecx, 4096/4
cld
rep movsd
jmp .exit
;ÃÃ¥ îáðà áà òûâà åì. ÎøèáêÃ
.fail:
mov esp, ebp
popad
add esp, 4
; iretd
save_ring3_context ;debugger support
mov bl, 14
jmp exc_c
iretd
endp
align 4
proc map_mem stdcall, lin_addr:dword,pdir:dword,\
ofs:dword,buf_size:dword
mov eax, [buf_size]
test eax, eax
jz .exit
mov eax, [pdir]
and eax, 0xFFFFF000
stdcall map_page,[ipc_pdir],eax,PG_UW
mov ebx, [ofs]
shr ebx, 22
mov esi, [ipc_pdir]
mov edi, [ipc_ptab]
mov eax, [esi+ebx*4]
and eax, 0xFFFFF000
jz .exit
stdcall map_page,edi,eax,PG_UW
; inc ebx
; add edi, 0x1000
; mov eax, [esi+ebx*4]
; test eax, eax
; jz @f
; and eax, 0xFFFFF000
; stdcall map_page, edi, eax
@@: mov edi, [lin_addr]
and edi, 0xFFFFF000
mov ecx, [buf_size]
add ecx, 4095
shr ecx, 12
inc ecx
mov edx, [ofs]
shr edx, 12
and edx, 0x3FF
mov esi, [ipc_ptab]
.map: mov eax, [esi+edx*4]
and eax, 0xFFFFF000
jz .exit
stdcall map_page,edi,eax,PG_UW
dec ecx
jz .exit
add edi, 0x1000
inc edx
cmp edx, 0x400
jnz .map
inc ebx
mov eax, [ipc_pdir]
mov eax, [eax+ebx*4]
and eax, 0xFFFFF000
jz .exit
stdcall map_page,esi,eax,PG_UW
xor edx, edx
jmp .map
.exit:
ret
endp
align 4
proc map_memEx stdcall, lin_addr:dword,pdir:dword,\
ofs:dword,buf_size:dword
mov eax, [buf_size]
test eax, eax
jz .exit
mov eax, [pdir]
and eax, 0xFFFFF000
stdcall map_page,[proc_mem_pdir],eax,dword PG_UW
mov ebx, [ofs]
shr ebx, 22
mov esi, [proc_mem_pdir]
mov edi, [proc_mem_tab]
mov eax, [esi+ebx*4]
and eax, 0xFFFFF000
test eax, eax
jz .exit
stdcall map_page,edi,eax,dword PG_UW
@@: mov edi, [lin_addr]
and edi, 0xFFFFF000
mov ecx, [buf_size]
add ecx, 4095
shr ecx, 12
inc ecx
mov edx, [ofs]
shr edx, 12
and edx, 0x3FF
mov esi, [proc_mem_tab]
.map: mov eax, [esi+edx*4]
; and eax, 0xFFFFF000
; test eax, eax
; jz .exit
stdcall map_page,edi,eax,dword PG_UW
add edi, 0x1000
inc edx
dec ecx
jnz .map
.exit:
ret
endp
sys_IPC:
;input:
; eax=1 - set ipc buffer area
; ebx=address of buffer
; ecx=size of buffer
; eax=2 - send message
; ebx=PID
; ecx=address of message
; edx=size of message
cmp eax,1
jne @f
call set_ipc_buff
mov [esp+36], eax
ret
@@:
cmp eax, 2
jne @f
stdcall sys_ipc_send, ebx, ecx, edx
mov [esp+36], eax
ret
@@:
xor eax, eax
not eax
mov [esp+36], eax
ret
align 4
proc set_ipc_buff
mov eax,[current_slot]
pushf
cli
mov [eax+APPDATA.ipc_start],ebx ;set fields in extended information area
mov [eax+APPDATA.ipc_size],ecx
add ecx, ebx
add ecx, 4095
and ecx, not 4095
.touch: mov eax, [ebx]
add ebx, 0x1000
cmp ebx, ecx
jb .touch
popf
xor eax, eax
ret
endp
proc sys_ipc_send stdcall, PID:dword, msg_addr:dword, msg_size:dword
locals
dst_slot dd ?
dst_offset dd ?
buf_size dd ?
used_buf dd ?
endl
pushf
cli
mov eax, [PID]
call pid_to_slot
test eax,eax
jz .no_pid
mov [dst_slot], eax
shl eax,8
mov edi,[eax+SLOT_BASE+0xa0] ;is ipc area defined?
test edi,edi
jz .no_ipc_area
mov ebx, edi
and ebx, 0xFFF
mov [dst_offset], ebx
mov esi, [eax+SLOT_BASE+0xa4]
mov [buf_size], esi
mov ecx, [ipc_tmp]
cmp esi, 0x40000-0x1000 ; size of [ipc_tmp] minus one page
jbe @f
push eax
lea ecx, [esi+0x1000]
xor edx, edx
call @mem_alloc@8
mov ecx, eax
pop eax
@@:
mov [used_buf], ecx
stdcall map_mem, ecx, [SLOT_BASE+eax+0xB8],\
edi, esi
mov edi, [dst_offset]
add edi, [used_buf]
cmp dword [edi], 0
jnz .ipc_blocked ;if dword [buffer]<>0 - ipc blocked now
mov edx, dword [edi+4]
lea ebx, [edx+8]
add ebx, [msg_size]
cmp ebx, [buf_size]
ja .buffer_overflow ;esi<0 - not enough memory in buffer
mov dword [edi+4], ebx
mov eax,[TASK_BASE]
mov eax, [eax+0x04] ;eax - our PID
add edi, edx
mov [edi], eax
mov ecx, [msg_size]
mov [edi+4], ecx
add edi, 8
mov esi, [msg_addr]
cld
rep movsb
mov ebx, [ipc_tmp]
mov edx, ebx
shr ebx, 12
xor eax, eax
mov [page_tabs+ebx*4], eax
invlpg [edx]
mov ebx, [ipc_pdir]
mov edx, ebx
shr ebx, 12
xor eax, eax
mov [page_tabs+ebx*4], eax
invlpg [edx]
mov ebx, [ipc_ptab]
mov edx, ebx
shr ebx, 12
xor eax, eax
mov [page_tabs+ebx*4], eax
invlpg [edx]
mov eax, [dst_slot]
shl eax, 8
or [eax+SLOT_BASE+0xA8],dword 0x40
cmp dword [check_idle_semaphore],20
jge .ipc_no_cis
mov dword [check_idle_semaphore],5
.ipc_no_cis:
push 0
jmp .ret
.no_pid:
popf
mov eax, 4
ret
.no_ipc_area:
popf
xor eax, eax
inc eax
ret
.ipc_blocked:
push 2
jmp .ret
.buffer_overflow:
push 3
.ret:
mov eax, [used_buf]
cmp eax, [ipc_tmp]
jz @f
stdcall free_kernel_space,eax
@@:
pop eax
popf
ret
endp
align 4
sysfn_meminfo:
; add ebx, new_app_base
cmp ebx, OS_BASE
jae .fail
mov eax, [_mem_amount]
shr eax, 12
mov [ebx], eax
shl eax, 12
mov [esp+36], eax
call _get_free_mem
mov [ebx+4], eax
mov edx, [pg_data.pages_faults]
mov [ebx+8], edx
mov esi, [heap_size]
mov [ebx+12], esi
mov edi, [heap_free]
mov [ebx+16], edi
mov eax, [heap_blocks]
mov [ebx+20], eax
mov ecx, [free_blocks]
mov [ebx+24], ecx
ret
.fail:
mov dword [esp+36], -1
ret
align 4
new_services:
cmp eax,4
jle sys_sheduler
cmp eax, 11
jb .fail
ja @f
call init_heap
mov [esp+36], eax
ret
@@:
cmp eax, 12
ja @f
stdcall user_alloc, ebx
mov [esp+36], eax
ret
@@:
cmp eax, 13
ja @f
stdcall user_free, ebx
mov [esp+36], eax
ret
@@:
cmp eax, 14
ja @f
cmp ebx, OS_BASE
jae .fail
stdcall get_event_ex, ebx, ecx
mov [esp+36], eax
ret
@@:
cmp eax, 15
ja @f
mov ecx, [current_slot]
mov eax, [ecx+APPDATA.fpu_handler]
mov [ecx+APPDATA.fpu_handler], ebx
mov [esp+36], eax
ret
@@:
cmp eax, 16
ja @f
test ebx, ebx
jz .fail
cmp ebx, OS_BASE
jae .fail
stdcall get_service, ebx
mov [esp+36], eax
ret
@@:
cmp eax, 17
ja @f
call srv_handlerEx ;ebx
mov [esp+36], eax
ret
@@:
cmp eax, 18
ja @f
mov ecx, [current_slot]
mov eax, [ecx+APPDATA.sse_handler]
mov [ecx+APPDATA.sse_handler], ebx
mov [esp+36], eax
ret
@@:
cmp eax, 19
ja @f
cmp ebx, OS_BASE
jae .fail
stdcall load_library, ebx
mov [esp+36], eax
ret
@@:
cmp eax, 20
ja @F
mov eax, ecx
call user_realloc
mov [esp+36], eax
ret
@@:
cmp eax, 21 ;for test purposes only
ja @f ;will be removed soon
cmp ebx, OS_BASE
jae .fail
mov ecx, ebx
call @load_pe_driver@4
mov [esp+36], eax
ret
.fail:
xor eax, eax
mov [esp+36], eax
ret
align 4
proc init_mtrr
cmp [BOOT_VAR+0x901c],byte 2
je .exit
bt [cpu_caps], CAPS_MTRR
jnc .exit
mov eax, cr0
or eax, 0x60000000 ;disable caching
mov cr0, eax
wbinvd ;invalidate cache
mov ecx, 0x2FF
rdmsr ;
push eax
xor edx, edx
xor eax, eax
mov ecx, 0x2FF
wrmsr ;disable all MTRR
mov eax, [_mem_amount]
; round eax up to next power of 2
dec eax
bsr ecx, eax
mov eax, 2
shl eax, cl
stdcall set_mtrr, edx,edx,eax,MEM_WB
stdcall set_mtrr, 1,[LFBAddress],[LFBSize],MEM_WC
xor edx, edx
xor eax, eax
mov ecx, 0x204
mov ebx, 6
@@:
wrmsr ;disable unused MTRR
inc ecx
wrmsr
inc ecx
dec ebx
jnz @b
wbinvd ;again invalidate
pop eax
or eax, 0x800 ;set default memtype to UC
and al, 0xF0
mov ecx, 0x2FF
wrmsr ;and enable MTRR
mov eax, cr0
and eax, not 0x60000000
mov cr0, eax ; enable caching
.exit:
ret
endp
align 4
proc set_mtrr stdcall, reg:dword,base:dword,size:dword,mem_type:dword
xor edx, edx
mov eax, [base]
or eax, [mem_type]
mov ecx, [reg]
lea ecx, [0x200+ecx*2]
wrmsr
mov ebx, [size]
dec ebx
mov eax, 0xFFFFFFFF
mov edx, 0x0000000F
sub eax, ebx
sbb edx, 0
or eax, 0x800
inc ecx
wrmsr
ret
endp
align 4
proc stall stdcall, delay:dword
push ecx
push edx
push ebx
push eax
mov eax, [delay]
mul [stall_mcs]
mov ebx, eax ;low
mov ecx, edx ;high
rdtsc
add ebx, eax
adc ecx,edx
@@:
rdtsc
sub eax, ebx
sbb edx, ecx
jb @B
pop eax
pop ebx
pop edx
pop ecx
ret
endp
align 4
proc create_ring_buffer stdcall, size:dword, flags:dword
locals
buf_ptr dd ?
endl
mov ecx, [size]
test ecx, 4095
jnz .fail
add ecx, ecx
xor edx, edx
call @mem_alloc@8
test eax, eax
mov [buf_ptr], eax
jz .fail
push ebx
xor ecx, ecx
mov edx, [size]
shr edx, 12
mov ebx, edx
dec edx
bsr ecx, edx
inc ecx
call @core_alloc@4
test eax, eax
jz .mm_fail
or eax, [flags]
mov edx, [buf_ptr]
lea ecx, [ebx*4]
shr edx, 10
@@:
mov [page_tabs+edx], eax
mov [page_tabs+edx+ecx], eax
add eax, 0x1000
add edx, 4
dec ebx
jnz @B
mov eax, [buf_ptr]
pop ebx
ret
.mm_fail:
;stdcall free_kernel_space, [buf_ptr]
pop ebx
xor eax, eax
.fail:
ret
endp
align 4
_balloc: ; gcc fastcall
@balloc@4:
mov eax, [_pg_balloc]
add ecx, 4095
and ecx, -4096
add ecx, eax
mov [_pg_balloc], ecx
add eax, OS_BASE
ret