Adjust b_net_rx for zerocopy

Author: Ian Seyler

api/libBareMetal.asm

@@ -7,13 +7,13 @@
 
 ; Kernel functions
 b_input			equ 0x0000000000100010	; Scans keyboard for input. OUT: AL = 0 if no key pressed, otherwise ASCII code
-b_output		equ 0x0000000000100018	; Displays a number of characters. IN: RSI = message location, RCX = number of characters
+b_output		equ 0x0000000000100018	; Displays a number of characters. IN: RSI = Memory address of message, RCX = number of characters
 
-b_net_tx		equ 0x0000000000100020	; Transmit a packet via a network interface. IN: RSI = Memory location where packet is stored, RCX = Length of packet, RDX = Device
-b_net_rx		equ 0x0000000000100028	; Polls the network interface for received packet. IN: RDI = Memory location where packet will be stored, RDX = Device. OUT: RCX = Length of packet
+b_net_tx		equ 0x0000000000100020	; Transmit a packet via a network interface. IN: RSI = Memory address of where packet is stored, RCX = Length of packet, RDX = Device
+b_net_rx		equ 0x0000000000100028	; Polls the network interface for received packet. IN: RDX = Device. OUT: RDI = Memory address of where packet was stored, RCX = Length of packet
 
-b_nvs_read		equ 0x0000000000100030	; Read data from a non-volatile storage device. IN: RAX = Starting sector, RCX = Number of sectors to read, RDX = Device, RDI = Memory location to store data
-b_nvs_write		equ 0x0000000000100038	; Write data to a non-volatile storage device. IN: RAX = Starting sector, RCX = Number of sectors to write, RDX = Device, RSI = Memory location of data to store
+b_nvs_read		equ 0x0000000000100030	; Read data from a non-volatile storage device. IN: RAX = Starting sector, RCX = Number of sectors to read, RDX = Device, RDI = Memory address to store data
+b_nvs_write		equ 0x0000000000100038	; Write data to a non-volatile storage device. IN: RAX = Starting sector, RCX = Number of sectors to write, RDX = Device, RSI = Memory address of data to store
 
 b_system		equ 0x0000000000100040	; Configure system. IN: RCX = Function, RAX = Variable 1, RDX = Variable 2. OUT: RAX = Result
 

api/libBareMetal.c

@@ -30,7 +30,7 @@ void b_net_tx(void *mem, u64 len, u64 iid) {
 
 u64 b_net_rx(void *mem, u64 iid) {
 	u64 tlong;
-	asm volatile ("call *0x00100028" : "=c"(tlong) : "D"(mem), "d"(iid));
+	asm volatile ("call *0x00100028" : "=D"(mem), "=c"(tlong) : "d"(iid));
 	return tlong;
 }
 

src/drivers/net/i8254x.asm

@@ -270,9 +270,9 @@ net_i8254x_transmit:
 
 ; -----------------------------------------------------------------------------
 ; net_i8254x_poll - Polls the Intel 8254x NIC for a received packet
-;  IN:	RDI = Location to store packet
-;	RDX = Interface ID
-; OUT:	RCX = Length of packet
+;  IN:	RDX = Interface ID
+; OUT:	RDI = Location of stored packet
+;	RCX = Length of packet
 ; Note:	RDESC Descriptor Format:
 ;	First Qword:
 ;	Bits 63:0 - Buffer Address
@@ -283,8 +283,8 @@ net_i8254x_transmit:
 ;	Bits 47:40 - Errors
 ;	Bits 63:48 - Special
 net_i8254x_poll:
-	push rdi
 	push rsi			; Used for the base MMIO of the NIC
+	push rbx
 	push rax
 
 	mov rdi, [rdx+nt_rx_desc]
@@ -293,8 +293,9 @@ net_i8254x_poll:
 	; Calculate the descriptor to read from
 	mov eax, [rdx+nt_rx_head]	; Get rx_lasthead
 	shl eax, 4			; Quick multiply by 16
-	add eax, 8			; Offset to bytes received
 	add rdi, rax			; Add offset to RDI
+	mov rbx, [rdi]
+	add rdi, 8			; Offset to bytes received
 	; Todo: read all 64 bits. check status bit for DD
 	xor ecx, ecx			; Clear RCX
 	mov cx, [rdi]			; Get the packet length
@@ -303,6 +304,7 @@ net_i8254x_poll:
 
 	xor eax, eax
 	stosq				; Clear the descriptor length and status
+	mov rdi, rbx
 
 	; Increment i8254x_rx_lasthead and the Receive Descriptor Tail
 	mov eax, [rdx+nt_rx_head]	; Get rx_lasthead
@@ -315,16 +317,10 @@ net_i8254x_poll:
 	and eax, i8254x_MAX_DESC - 1
 	mov [rsi+i8254x_RDT], eax	; Write the updated Receive Descriptor Tail
 
-	pop rax
-	pop rsi
-	pop rdi
-	ret
-
 net_i8254x_poll_end:
-	xor ecx, ecx
 	pop rax
+	pop rbx
 	pop rsi
-	pop rdi
 	ret
 ; -----------------------------------------------------------------------------
 

src/syscalls/io.asm

@@ -29,7 +29,7 @@ b_input_no_serial:
 
 ; -----------------------------------------------------------------------------
 ; b_output -- Outputs characters
-;  IN:	RSI = message location (non zero-terminated)
+;  IN:	RSI = Memory address of message (non zero-terminated)
 ;	RCX = number of chars to output
 ; OUT:	All registers preserved
 b_output:

src/syscalls/net.asm

@@ -42,7 +42,7 @@ b_net_status_end:
 
 ; -----------------------------------------------------------------------------
 ; b_net_tx -- Transmit a packet via the network
-;  IN:	RSI = Memory location where packet is stored
+;  IN:	RSI = Memory address of where packet is stored
 ;	RCX = Length of packet
 ;	RDX = Interface ID
 ; OUT:	Nothing. All registers preserved
@@ -75,8 +75,8 @@ b_net_tx_maxcheck:
 	call [rdx+nt_transmit]		; Call driver transmit function passing RDX as interface
 
 	; Increment interface counters
-	inc qword [rdx+nt_tx_packets]		; Increment TXPackets
-	add qword [rdx+nt_tx_bytes], rcx	; Increment TXBytes
+	inc qword [rdx+nt_tx_packets]
+	add qword [rdx+nt_tx_bytes], rcx
 
 	; Unlock the network interface
 	mov rax, rdx
@@ -93,53 +93,33 @@ b_net_tx_fail:
 
 ; -----------------------------------------------------------------------------
 ; b_net_rx -- Polls the network for received data
-;  IN:	RDI = Memory location where packet will be stored
-;	RDX = Interface ID
-; OUT:	RCX = Length of packet, 0 if no data
+;  IN:	RDX = Interface ID
+; OUT:	RDI = Memory address of where packet was stored
+;	RCX = Length of packet, 0 if no data
 ;	All other registers preserved
 b_net_rx:
-	push rdi
-	push rsi
 	push rdx
-	push rax
 
 	xor ecx, ecx
 
-	cmp byte [os_NetEnabled], 1	; Check if networking is enabled
-	jne b_net_rx_nodata
+	cmp byte [os_net_icount], dl	; Check if interface is valid
+	ja b_net_rx_end
 
 	shl edx, 7			; Quick multiply by 128
 	add edx, net_table		; Add offset to net_table
 
 	; Call the driver poll function
-	call [rdx+nt_poll]			; Call driver poll function passing RDX as interface
+	call [rdx+nt_poll]		; Call driver poll function passing RDX as interface
 
 	cmp cx, 0
-	je b_net_rx_nodata
+	je b_net_rx_end
 
 	; Increment interface counters
-	inc qword [rdx+nt_rx_packets]		; Increment RXPackets
-	add qword [rdx+nt_rx_bytes], rcx	; Increment RXBytes
-
-	mov rsi, os_PacketBuffers	; Packet exists here
-	push rcx
-	rep movsb			; Copy packet to requested address
-	pop rcx
+	inc qword [rdx+nt_rx_packets]
+	add qword [rdx+nt_rx_bytes], rcx
 
-; TODO is b_net_rx_nodata needed if CX is already set
 b_net_rx_end:
-	pop rax
-	pop rdx
-	pop rsi
-	pop rdi
-	ret
-
-b_net_rx_nodata:
-	xor ecx, ecx
-	pop rax
 	pop rdx
-	pop rsi
-	pop rdi
 	ret
 ; -----------------------------------------------------------------------------