From d54596514c30343305b7cc4b8be36c712d536e7a Mon Sep 17 00:00:00 2001
From: root <>
Date: Sun, 11 May 2025 08:22:07 +0000
Subject: [PATCH 01/10] echo then close connection
---
main.s | 54 +++++++++++++++++++++++++++++++++++++++++++++++-------
readline.s | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 83 insertions(+), 7 deletions(-)
create mode 100644 readline.s
diff --git a/main.s b/main.s
index 881a3d5..8905309 100644
--- a/main.s
+++ b/main.s
@@ -24,8 +24,10 @@ POLLIN equ 1
POLLOUT equ 4
SHUT_RDWR equ 2
-pollfd_size equ 4 + 2 + 2 ; $ man 2 poll
-pollfds_capacity equ 100
+pollfd_size equ 4 + 2 + 2 ; $ man 2 poll
+pollfds_capacity equ 100
+client_size equ 1 + 256 + 256 ; state, line buffer, uri
+clients_capacity equ pollfds_capacity - 1
SECTION .data
server_path db "server.sock", 0x00
@@ -33,15 +35,18 @@ server_path_len equ $ - server_path
sockaddr_size equ 2 + 108 ; $ man 7 unix
goodbye db "goodbye", 0x0a
goodbye_len equ $ - goodbye
+pollfds_len dq 0
+clients_len dq 0
SECTION .bss
sockaddr resb sockaddr_size
pollfds resb pollfd_size * pollfds_capacity
-pollfds_len resb 8
+clients resb (4 + client_size) * clients_capacity
SECTION .text
%include "server.s"
+%include "readline.s"
_start:
call make_server
@@ -84,11 +89,27 @@ pollfds__scan__found__client:
; TODO check r10w, incl for POLLNVAL & POLLERR
push rdi
+ mov rdi, r14
+ call clients__append
+
+ mov r12, [clients_len]
+ add r12, -1
+ imul r12, client_size
+ add r12, clients
+ add r12, 4
+
+ mov rdi, r14
+ mov rsi, r12
+ mov rdx, 256
+ call readline
+ cmp rax, 0 ; TODO
+ jl exit
+ ;push rax ; TODO
+
+ mov rdx, rax
mov rax, SYS_WRITE
- mov rdi, 0
- mov edi, r14d
- mov rsi, goodbye
- mov rdx, goodbye_len
+ mov rdi, r14
+ mov rsi, r12
syscall
cmp rax, 0
jl exit ; TODO handle this gracefully
@@ -132,6 +153,7 @@ pollfds__scan__found__server:
; edi - fd
; si - events
pollfds__append:
+ ; TODO check against pollfds_capacity
mov r10, [pollfds_len]
mov [pollfds + r10 * pollfd_size], edi
mov [pollfds + r10 * pollfd_size + 4], si
@@ -157,6 +179,24 @@ pollfds__clear:
mov [pollfds_len], r10
ret
+; esi - fd
+clients__append:
+ ; TODO check against client_capacity
+ mov r10, [clients_len]
+ imul r10, client_size
+ add r10, clients
+ mov [r10], esi
+ add r10, 4
+ mov r8b, 0
+ mov r11, 0
+
+clients__append__init:
+ cmp r11, client_size
+ jge return
+ mov [r10 + r11], r8b
+ add r11, 1
+ jmp clients__append__init
+
return:
ret
diff --git a/readline.s b/readline.s
new file mode 100644
index 0000000..aba4769
--- /dev/null
+++ b/readline.s
@@ -0,0 +1,36 @@
+; Returns length in rax
+; Errors (in rax):
+; -1024 - line too long
+; other negative - error from read(2)
+; Arguments:
+; rdi - fd
+; rsi - buffer
+; rdx - max length
+readline:
+ push rdi
+ push rsi
+ push rdx
+ mov rax, SYS_READ
+ syscall
+ pop rdx
+ pop rsi
+ pop rdi
+ cmp rax, 0
+ jl return
+ mov r10, 0
+
+readline__scan:
+ cmp r10, rax
+ jge readline__overflow
+ mov r11b, [rsi + r10]
+ add r10, 1
+ cmp r11b, 0x0a ; '\n'
+ jne readline__scan
+
+readline__return:
+ mov rax, r10
+ ret
+
+readline__overflow:
+ mov rax, -1024
+ ret
From 29f54ba779b0ac2c89f88a3d5c5825b0b8ec197d Mon Sep 17 00:00:00 2001
From: root <>
Date: Tue, 13 May 2025 12:07:03 +0000
Subject: [PATCH 02/10] echo server, multiple clients, lines <256 bytes
---
client.s | 104 ++++++++++++++++++++++++++++
clients.s | 69 +++++++++++++++++++
constants.c | 2 +
main.s | 192 +++++++++++++++++++++++-----------------------------
pollfds.s | 30 ++++++++
readline.s | 19 ++++--
6 files changed, 304 insertions(+), 112 deletions(-)
create mode 100644 client.s
create mode 100644 clients.s
create mode 100644 pollfds.s
diff --git a/client.s b/client.s
new file mode 100644
index 0000000..073f42c
--- /dev/null
+++ b/client.s
@@ -0,0 +1,104 @@
+; Errors (in rax):
+; 0 - EOF
+; -1024 - line too long
+; other negative - from read(2)
+; Arguments:
+; rdi - fd
+; rsi - address of client within clients array
+; rdx - pollfds index
+client__pollin:
+ push rdi
+ push rsi
+ push rdx
+
+ mov r10, 0
+ mov r10b, [rsi + 4 + 2] ; buffer_len
+
+ mov rdx, 0
+ mov dl, 255
+ sub dl, r10b ; rdx = 255 - buffer_len
+ add rsi, 8
+ add rsi, r10
+ call readline
+
+ mov r10, rdi
+
+ pop rdx
+ pop rsi
+ pop rdi
+
+ cmp rax, 0
+ jle return
+
+ add [rsi + 4 + 2], al ; buffer_len += rax
+
+ cmp r10, 0
+ jg client__pollin__complete_line
+
+ add [rsi + 4 + 1], al ; line_len += rax
+ ret
+
+client__pollin__complete_line:
+ add [rsi + 4 + 1], r10b ; line_len += r10
+ mov word [pollfds + rdx * pollfd_size + 4], POLLOUT
+ ret
+
+; rdi - fd
+; rsi - address of client within clients array
+; rdx - pollfds index
+client__pollout:
+ push rdi
+ push rsi
+ push rdx
+
+ mov rax, SYS_WRITE
+ mov rdx, 0
+ mov dl, [rsi + 4 + 1]
+ add rsi, 8
+ syscall
+
+ pop rdx
+ pop rsi
+ pop rdi
+
+ cmp rax, 0
+ jl return
+
+ mov r10, rsi
+ add r10, 8
+ mov r11, 0
+ mov r11b, [rsi + 4 + 2]
+ sub r11, rax
+ add r11, r10
+
+client__pollout__shunt:
+ cmp r10, r11
+ jge client__pollout__shunt__finished
+ mov r8b, [r10 + rax]
+ mov [r10], r8b
+ add r10, 1
+ jmp client__pollout__shunt
+
+client__pollout__shunt__finished:
+ sub [rsi + 4 + 2], al ; buffer_len -= rax
+ sub [rsi + 4 + 1], al ; line_len -= rax
+ cmp byte [rsi + 4 + 1], 0
+ je client__pollout__wrote_line
+ ret
+
+client__pollout__wrote_line:
+ mov word [pollfds + rdx * pollfd_size + 4], POLLIN
+ ret
+
+; rdi - fd
+client__shutdown_close:
+ mov rax, SYS_SHUTDOWN
+ push rdi
+ mov rsi, SHUT_RDWR
+ syscall
+
+ mov rax, SYS_CLOSE
+ pop rdi
+ syscall
+
+ ret
diff --git a/clients.s b/clients.s
new file mode 100644
index 0000000..1af458b
--- /dev/null
+++ b/clients.s
@@ -0,0 +1,69 @@
+; edi - fd
+clients__append:
+ ; TODO check against client_capacity
+ mov r10, [clients_len]
+ imul r10, client_size
+ add r10, clients
+ mov [r10], edi
+
+ add qword [clients_len], 1
+
+ mov r11, 4
+
+clients__append__write_zeros:
+ cmp r11, 8
+ jge return
+ mov byte [r10 + r11], 0
+ add r11, 1
+ jmp clients__append__write_zeros
+
+; edi - fd
+clients__search:
+ mov r11, [clients_len]
+ imul r11, client_size
+ add r11, clients
+ mov r10, clients
+
+clients__search__loop:
+ cmp r10, r11
+ jge clients__search__fail
+ mov r8d, [r10]
+ cmp r8d, edi
+ je clients__search__succ
+ add r10, client_size
+ jmp clients__search__loop
+
+clients__search__fail:
+ mov r10, -1
+
+clients__search__succ:
+ mov rax, r10
+ ret
+
+; rdi - address of client within clients array
+clients__remove:
+ mov r10, [clients_len]
+ cmp r10, 1
+ jle clients__clear
+
+ add r10, -1
+ mov [clients_len], r10
+
+ mov r10, 0
+ mov r11, r10
+ imul r11, client_size
+ add r11, clients
+
+clients__remove__loop:
+ cmp r10, client_size
+ jge return
+ mov r8b, [r11 + r10]
+ mov [rdi + r10], r8b
+ add r10, 1
+ jmp clients__remove__loop
+
+; rdi - address of client within clients array
+clients__clear:
+ mov r10, 0
+ mov [clients_len], r10
+ ret
diff --git a/constants.c b/constants.c
index 2e7aab3..8239355 100644
--- a/constants.c
+++ b/constants.c
@@ -14,5 +14,7 @@ void main() {
printf("sizeof(short) %d\n", sizeof(short));
printf("POLLIN %d\n", POLLIN);
printf("POLLOUT %d\n", POLLOUT);
+ printf("POLLERR %d\n", POLLERR);
+ printf("POLLNVAL %d\n", POLLNVAL);
printf("SHUT_RDWR %d\n", SHUT_RDWR);
}
diff --git a/main.s b/main.s
index 8905309..190f240 100644
--- a/main.s
+++ b/main.s
@@ -22,11 +22,19 @@ F_SETFL equ 4
O_NONBLOCK equ 2048
POLLIN equ 1
POLLOUT equ 4
+POLLERR equ 8
+POLLNVAL equ 32
+; TODO(?) POLLPRI: see poll(2), tcp(7)
SHUT_RDWR equ 2
+;STATE_READING equ 0
+;STATE_WRITING equ 1
+
pollfd_size equ 4 + 2 + 2 ; $ man 2 poll
pollfds_capacity equ 100
-client_size equ 1 + 256 + 256 ; state, line buffer, uri
+
+; fd, state, line_len, buffer_len, uri_len, buffer, uri
+client_size equ 4 + 4 + 255 + 255
clients_capacity equ pollfds_capacity - 1
SECTION .data
@@ -47,11 +55,14 @@ SECTION .text
%include "server.s"
%include "readline.s"
+%include "clients.s"
+%include "pollfds.s"
+%include "client.s"
_start:
call make_server
mov rbx, rax ; server fd
- mov rdi, rax
+ mov rdi, rbx
mov rsi, POLLIN
call pollfds__append
@@ -63,144 +74,113 @@ poll:
syscall
cmp rax, 0
je poll
- jl exit ; TODO handle this gracefully
- mov rdi, rbx
+ jl exit ; poll(2) returned error TODO
-; rdi - server fd
-pollfds__scan:
+scan:
mov r15, 0
-pollfds__scan__loop:
+; Variables:
+; r15 - pollfds index
+; r14w - poll(2) revents
+; r13d - fd
+; r12 - client memory address
+scan__loop:
cmp r15, [pollfds_len]
jge poll
- mov r10w, [pollfds + r15 * pollfd_size + 6]
- cmp r10w, 0
- jne pollfds__scan__found
+ mov r14w, [pollfds + r15 * pollfd_size + 6]
+ cmp r14w, 0
+ jne scan__found
add r15, 1
- jmp pollfds__scan__loop
+ jmp scan__loop
-pollfds__scan__found:
- mov r14, 0
- mov r14d, [pollfds + r15 * pollfd_size]
- cmp r14d, edi
- je pollfds__scan__found__server
+scan__found:
+ mov r13, 0
+ mov r13d, [pollfds + r15 * pollfd_size]
+ cmp r13d, ebx
+ je scan__found__server
-pollfds__scan__found__client:
- ; TODO check r10w, incl for POLLNVAL & POLLERR
- push rdi
+scan__found__client:
+ mov rdi, r13
+ call clients__search
+ mov r12, rax
+ cmp r12, 0
+ jl _client__not_stored
- mov rdi, r14
- call clients__append
+ mov r10w, r14w
+ and r10w, POLLERR | POLLNVAL
+ cmp r10w, 0
+ jne _client__error
- mov r12, [clients_len]
- add r12, -1
- imul r12, client_size
- add r12, clients
- add r12, 4
+ mov r10w, r14w
+ and r10w, POLLIN
+ cmp r10w, 0
+ jne _client__pollin
- mov rdi, r14
- mov rsi, r12
- mov rdx, 256
- call readline
- cmp rax, 0 ; TODO
- jl exit
- ;push rax ; TODO
+ mov r10w, r14w
+ and r10w, POLLOUT
+ cmp r10w, 0
+ jne _client__pollout
- mov rdx, rax
- mov rax, SYS_WRITE
- mov rdi, r14
- mov rsi, r12
- syscall
- cmp rax, 0
- jl exit ; TODO handle this gracefully
+ ; TODO what did poll(2) detect in this case?
+ add r15, 1
+ jmp scan__loop
- mov rax, SYS_SHUTDOWN
- mov rdi, 0
- mov edi, r14d
- mov rsi, SHUT_RDWR
- syscall
-
- mov rax, SYS_CLOSE
- mov rdi, 0
- mov edi, r14d
- syscall
+_client__error:
+ mov rdi, r12
+ call clients__remove
+_client__not_stored:
+ mov rdi, r13
+ call client__shutdown_close
mov rdi, r15
call pollfds__remove
+ jmp scan__loop
- pop rdi
- jmp pollfds__scan__loop
+_client__pollin:
+ mov rdi, r13
+ mov rsi, r12
+ mov rdx, r15
+ call client__pollin
+ cmp rax, 0
+ jle _client__error
+ add r15, rax
+ jmp scan__loop
-pollfds__scan__found__server:
- ; TODO check r10w, incl for POLLNVAL & POLLERR
- push rdi
+_client__pollout:
+ mov rdi, r13
+ mov rsi, r12
+ mov rdx, r15
+ call client__pollout
+ add r15, 1
+ jmp scan__loop
+
+scan__found__server:
+ cmp r14w, POLLIN
+ jne exit
mov rax, SYS_ACCEPT
+ mov rdi, r13
mov rsi, 0
mov rdx, 0
syscall
cmp rax, 0
- jl exit ; TODO handle this gracefully
+ jl exit ; accept(2) returned error TODO
mov rdi, rax
- mov si, POLLIN | POLLOUT
+ push rdi
+ mov si, POLLIN
call pollfds__append
pop rdi
+ call clients__append
+
add r15, 1
- jmp pollfds__scan__loop
-
-; edi - fd
-; si - events
-pollfds__append:
- ; TODO check against pollfds_capacity
- mov r10, [pollfds_len]
- mov [pollfds + r10 * pollfd_size], edi
- mov [pollfds + r10 * pollfd_size + 4], si
- add r10, 1
- mov [pollfds_len], r10
- ret
-
-; rdi - pollfds array index to remove
-pollfds__remove:
- mov r11, [pollfds_len]
- cmp rdi, r10
- jge return ; XXX index out of bounds, do some other error?
- cmp r11, 1
- jle pollfds__clear
- mov r10, [pollfds + (r11 - 1) * pollfd_size]
- mov [pollfds + rdi * pollfd_size], r10
- sub r11, 1
- mov [pollfds_len], r11
- ret
-
-pollfds__clear:
- mov r10, 0
- mov [pollfds_len], r10
- ret
-
-; esi - fd
-clients__append:
- ; TODO check against client_capacity
- mov r10, [clients_len]
- imul r10, client_size
- add r10, clients
- mov [r10], esi
- add r10, 4
- mov r8b, 0
- mov r11, 0
-
-clients__append__init:
- cmp r11, client_size
- jge return
- mov [r10 + r11], r8b
- add r11, 1
- jmp clients__append__init
+ jmp scan__loop
return:
ret
exit:
mov rax, SYS_EXIT
- mov rdi, 0
+ mov rdi, 255
syscall
diff --git a/pollfds.s b/pollfds.s
new file mode 100644
index 0000000..4eed357
--- /dev/null
+++ b/pollfds.s
@@ -0,0 +1,30 @@
+; edi - fd
+; si - events
+pollfds__append:
+ ; TODO check against pollfds_capacity
+ mov r10, [pollfds_len]
+ mov [pollfds + r10 * pollfd_size], edi
+ mov [pollfds + r10 * pollfd_size + 4], si
+ mov r11w, 0
+ mov [pollfds + r10 * pollfd_size + 6], r11w
+ add r10, 1
+ mov [pollfds_len], r10
+ ret
+
+; rdi - pollfds array index to remove
+pollfds__remove:
+ mov r11, [pollfds_len]
+ cmp rdi, r11
+ jge return ; XXX index out of bounds, do some other error?
+ cmp r11, 1
+ jle pollfds__clear
+ mov r10, [pollfds + (r11 - 1) * pollfd_size]
+ mov [pollfds + rdi * pollfd_size], r10
+ sub r11, 1
+ mov [pollfds_len], r11
+ ret
+
+pollfds__clear:
+ mov r10, 0
+ mov [pollfds_len], r10
+ ret
diff --git a/readline.s b/readline.s
index aba4769..35e30dd 100644
--- a/readline.s
+++ b/readline.s
@@ -1,34 +1,41 @@
-; Returns length in rax
+; Returns:
+; rax - read(2) length
+; rdi - if line is complete, line length;
+; if line was incomplete, 0;
+; if EOF or read(2) returned an error, undefined
; Errors (in rax):
; -1024 - line too long
; other negative - error from read(2)
+; 0 - EOF from read(2)
; Arguments:
; rdi - fd
; rsi - buffer
; rdx - max length
readline:
- push rdi
push rsi
push rdx
mov rax, SYS_READ
syscall
pop rdx
pop rsi
- pop rdi
cmp rax, 0
jl return
mov r10, 0
readline__scan:
- cmp r10, rax
+ cmp r10, rdx
jge readline__overflow
+ cmp r10, rax
+ jge readline__incomplete_line
mov r11b, [rsi + r10]
add r10, 1
cmp r11b, 0x0a ; '\n'
jne readline__scan
+ mov rdi, r10
+ ret
-readline__return:
- mov rax, r10
+readline__incomplete_line:
+ mov rdi, 0
ret
readline__overflow:
From 8ab750ba97160be5199589d3e82f6a8a35a65a10 Mon Sep 17 00:00:00 2001
From: root <>
Date: Tue, 13 May 2025 12:22:34 +0000
Subject: [PATCH 03/10] bugfix: removing pollfds[0] actually removed
pollfds[-1]
this bug created this weird behaviour:
1. client 1 connects
2. client 2 connents
3. client 1 disconnects
4. client 2 sends a line
5. client 2 is disconnected by the server
---
clients.s | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/clients.s b/clients.s
index 1af458b..e87dde4 100644
--- a/clients.s
+++ b/clients.s
@@ -49,11 +49,12 @@ clients__remove:
add r10, -1
mov [clients_len], r10
- mov r10, 0
mov r11, r10
imul r11, client_size
add r11, clients
+ mov r10, 0
+
clients__remove__loop:
cmp r10, client_size
jge return
From 484d81baa86e5151d15462a1153e65854f1abcfc Mon Sep 17 00:00:00 2001
From: root <>
Date: Sat, 17 May 2025 08:10:55 +0000
Subject: [PATCH 04/10] client__pollin: read as much as possible;
client__pollout: do processing
---
client.s | 173 +++++++++++++++++++++++++++++++++++++----------------
main.s | 17 ++++--
readline.s | 51 +++++-----------
3 files changed, 149 insertions(+), 92 deletions(-)
diff --git a/client.s b/client.s
index 073f42c..557898f 100644
--- a/client.s
+++ b/client.s
@@ -1,75 +1,146 @@
+; Returns:
+; rax - 0
; Errors (in rax):
-; 0 - EOF
-; -1024 - line too long
-; other negative - from read(2)
+; rax - 0 - EOF
+; rax - -1024 - line too long
+; rax - other negative - from read(2)
; Arguments:
; rdi - fd
; rsi - address of client within clients array
; rdx - pollfds index
+; Variables:
+; rbx - pollfds index
+; r12 - client buffer
+; r13 - start of line scanning
+; r14 - client buffer end
client__pollin:
- push rdi
- push rsi
- push rdx
+ push rbx
+ push r12
+ push r13
+ push r14
- mov r10, 0
- mov r10b, [rsi + 4 + 2] ; buffer_len
+ mov rbx, rdx
+ mov r12, rsi
+ add r12, OFFSET_CLIENT_BUFFER
+ mov r13, 0
+ mov r13b, [rsi + OFFSET_CLIENT_BUFFER_LEN]
+ add r13, r12
+ mov r14, r12
+ add r14, 255
- mov rdx, 0
- mov dl, 255
- sub dl, r10b ; rdx = 255 - buffer_len
- add rsi, 8
- add rsi, r10
- call readline
-
- mov r10, rdi
-
- pop rdx
- pop rsi
- pop rdi
+ mov rax, SYS_READ
+ mov rsi, r13
+ mov rdx, 255
+ sub rdx, [rsi + OFFSET_CLIENT_BUFFER_LEN]
+ syscall
cmp rax, 0
- jle return
+ jle client__pollin__return ; TODO verify this shit
- add [rsi + 4 + 2], al ; buffer_len += rax
+ ; buffer_len += read(2) length
+ add [rsi + OFFSET_CLIENT_BUFFER_LEN], al
- cmp r10, 0
- jg client__pollin__complete_line
+ mov rdi, r13
+ mov rsi, rax
+ call scanline
- add [rsi + 4 + 1], al ; line_len += rax
- ret
+ cmp rax, 0
+ je client__pollin__no_line
-client__pollin__complete_line:
- add [rsi + 4 + 1], r10b ; line_len += r10
+ mov rax, 1
mov word [pollfds + rdx * pollfd_size + 4], POLLOUT
+
+client__pollin__return:
+ pop r14
+ pop r13
+ pop r12
+ pop rbx
ret
+client__pollin__no_line:
+ mov r10, r13
+ add r10, rax
+ cmp r10, r14
+ jge client__pollin__line_too_long
+ mov rax, 1
+ jmp client__pollin__return
+
+client__pollin__line_too_long:
+ mov rax, -1024
+ jmp client__pollin__return
+
+client__pollin__line:
+ pop rdx
+ mov word [pollfds + rdx * pollfd_size + 4], POLLOUT
+ push rdx
+ ; TODO do something to the line
+ ; problem: we can't write here because the socket may
+ ; block;
+ ; how do we deal with multiple lines?
+ ; XXX call read(2) trying to fill the whole buffer
+ ; - if we have at least 1 line,
+ ; update the state and go back to main loop;
+ ; do whatever logic is necessary until we need to
+ ; call read(2) or write(2) next, ie nothing;
+ ; set POLLOUT and process line(s) in write(2) block
+ ; - if we have no line and we filled the buffer,
+ ; return -1024
+ ; - if we have no line, go back to main loop
+ ; we could have multiple lines, and that's okay
+ ; XXX so this plan will work actually
+ ; XXX should we do logic here or in the write(2) block?
+ ; probably there, so here we just accumulate lines
+ ret
+
+; Returns:
+; rax - non-negative from write(2)
+; Errors:
+; rax - -1024 - no line was buffered
+; rax - other negative - from write(2)
+; Arguments:
; rdi - fd
; rsi - address of client within clients array
; rdx - pollfds index
+; Variables:
+; rbx - pollfds index
+; r12 - address of client within clients array
+; r13 - line length
+; r11 - client buffer end of text after call to write(2)
client__pollout:
- push rdi
- push rsi
- push rdx
+ push rbx
+ push r12
+ push r13
+
+ mov rbx, rdx
+ mov r12, rsi
+
+ mov rdi, r12
+ mov rsi, 255
+ call scanline
+
+ ; poll(2)'d for POLLOUT but we had no line buffered;
+ ; should be impossible
+ cmp rax, 0
+ mov rax, -1024
+ je client__pollout__return
+
+ mov r13, rax
mov rax, SYS_WRITE
- mov rdx, 0
- mov dl, [rsi + 4 + 1]
- add rsi, 8
+ mov rsi, r12
+ add rsi, OFFSET_CLIENT_BUFFER
+ mov rdx, r13
syscall
- pop rdx
- pop rsi
- pop rdi
-
+ ; error from write(2)
cmp rax, 0
- jl return
+ jl client__pollout__return
- mov r10, rsi
- add r10, 8
+ mov r10, r12
mov r11, 0
- mov r11b, [rsi + 4 + 2]
+ mov r11b, [r12 + OFFSET_CLIENT_BUFFER_LEN]
+ add r11, r12
sub r11, rax
- add r11, r10
client__pollout__shunt:
cmp r10, r11
@@ -80,14 +151,16 @@ client__pollout__shunt:
jmp client__pollout__shunt
client__pollout__shunt__finished:
- sub [rsi + 4 + 2], al ; buffer_len -= rax
- sub [rsi + 4 + 1], al ; line_len -= rax
- cmp byte [rsi + 4 + 1], 0
- je client__pollout__wrote_line
- ret
+ ; buffer_len -= rax
+ sub [r12 + OFFSET_CLIENT_BUFFER_LEN], al
+ cmp rax, r13
+ jl client__pollout__return
+ mov word [pollfds + rbx * pollfd_size + 4], POLLIN
-client__pollout__wrote_line:
- mov word [pollfds + rdx * pollfd_size + 4], POLLIN
+client__pollout__return:
+ pop r13
+ pop r12
+ pop rbx
ret
; rdi - fd
diff --git a/main.s b/main.s
index 190f240..3331bd8 100644
--- a/main.s
+++ b/main.s
@@ -30,11 +30,18 @@ SHUT_RDWR equ 2
;STATE_READING equ 0
;STATE_WRITING equ 1
+; offsets into client struct
+OFFSET_CLIENT_FD equ 0
+OFFSET_CLIENT_STATE equ 4
+OFFSET_CLIENT_BUFFER_LEN equ 5
+OFFSET_CLIENT_BUFFER equ 6
+
pollfd_size equ 4 + 2 + 2 ; $ man 2 poll
pollfds_capacity equ 100
-; fd, state, line_len, buffer_len, uri_len, buffer, uri
-client_size equ 4 + 4 + 255 + 255
+client_buffer_size equ 255
+; fd, state, buffer_len, buffer
+client_size equ 4 + 2 + client_buffer_size
clients_capacity equ pollfds_capacity - 1
SECTION .data
@@ -109,7 +116,7 @@ scan__found__client:
mov r10w, r14w
and r10w, POLLERR | POLLNVAL
cmp r10w, 0
- jne _client__error
+ jne _client__error_or_eof
mov r10w, r14w
and r10w, POLLIN
@@ -125,7 +132,7 @@ scan__found__client:
add r15, 1
jmp scan__loop
-_client__error:
+_client__error_or_eof:
mov rdi, r12
call clients__remove
@@ -142,7 +149,7 @@ _client__pollin:
mov rdx, r15
call client__pollin
cmp rax, 0
- jle _client__error
+ jle _client__error_or_eof
add r15, rax
jmp scan__loop
diff --git a/readline.s b/readline.s
index 35e30dd..b1698a0 100644
--- a/readline.s
+++ b/readline.s
@@ -1,43 +1,20 @@
; Returns:
-; rax - read(2) length
-; rdi - if line is complete, line length;
-; if line was incomplete, 0;
-; if EOF or read(2) returned an error, undefined
-; Errors (in rax):
-; -1024 - line too long
-; other negative - error from read(2)
-; 0 - EOF from read(2)
+; rax - if line: line length; otherwise: 0
; Arguments:
-; rdi - fd
-; rsi - buffer
-; rdx - max length
-readline:
- push rsi
- push rdx
- mov rax, SYS_READ
- syscall
- pop rdx
- pop rsi
- cmp rax, 0
- jl return
- mov r10, 0
+; rdi - buffer
+; rsi - max length
+scanline:
+ mov rax, 0
-readline__scan:
- cmp r10, rdx
- jge readline__overflow
- cmp r10, rax
- jge readline__incomplete_line
- mov r11b, [rsi + r10]
- add r10, 1
- cmp r11b, 0x0a ; '\n'
- jne readline__scan
- mov rdi, r10
+scanline__loop:
+ cmp rax, rsi
+ jge scanline__incomplete_line
+ mov r10b, [rdi + rax]
+ add rax, 1
+ cmp r10b, 0x0a ; '\n'
+ jne scanline__loop
ret
-readline__incomplete_line:
- mov rdi, 0
- ret
-
-readline__overflow:
- mov rax, -1024
+scanline__incomplete_line:
+ mov rax, 0
ret
From cbde04fc7c1d0237af2faad74db7bbb1fd97c89d Mon Sep 17 00:00:00 2001
From: root <>
Date: Sat, 17 May 2025 08:15:07 +0000
Subject: [PATCH 05/10] client__pollin diagram
---
client-pollin.txt | 50 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 50 insertions(+)
create mode 100644 client-pollin.txt
diff --git a/client-pollin.txt b/client-pollin.txt
new file mode 100644
index 0000000..2e0f6b1
--- /dev/null
+++ b/client-pollin.txt
@@ -0,0 +1,50 @@
+client buffer
+
+##########++++++++A++++++A+++A++..........
+^ ^ ^ ^ ^ ^ ^
+| | | | | | |
+| | | | | | +-- end of buffer
+| | | | | |
+| | | | | +-- end of read(2) bytes
+| | | | |
+| | +-- newlines
+| |
+| +-- start of line scanning
+|
++-- start of line
+
+
+# original idea
+
+- consume many lines in client__pollin
+- problem: in the echo server case, we want to write each line but a call to
+ write(2) may block, so we can't do line processing in client__pollin
+- solution: process lines in client__pollout
+
+i = scan_start
+while i < buffer_end:
+ byte = mem[i]
+ i += 1
+ if byte == '\n':
+ handle(line_start, i - line_start)
+ line_start = i
+ scan_start = i
+
+if line_start + read(2)_length >= buffer_end:
+ out_of_memory()
+ return
+
+i = line_start
+while i < line_start + read(2)_length:
+ mem[i - line_start + buffer_start] = mem[i]
+ i += 1
+
+
+# better idea
+
+in pollin handler, just read once
+indicate to the caller:
+- we read a complete line (ie 0x0a is present)
+- we read an incomplete non-empty line
+- we read nothing (EOF)
+- error from read(2)
From 05f614b224dd13623e240a9075b0ade2b312b982 Mon Sep 17 00:00:00 2001
From: root <>
Date: Sat, 17 May 2025 08:20:30 +0000
Subject: [PATCH 06/10] typo: writing POLLOUT beyond pollfds array bounds
---
client.s | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/client.s b/client.s
index 557898f..a8d670f 100644
--- a/client.s
+++ b/client.s
@@ -48,7 +48,7 @@ client__pollin:
je client__pollin__no_line
mov rax, 1
- mov word [pollfds + rdx * pollfd_size + 4], POLLOUT
+ mov word [pollfds + rbx * pollfd_size + 4], POLLOUT
client__pollin__return:
pop r14
From 65dc844f54aaa51aebd4db2078e138ac7aca6020 Mon Sep 17 00:00:00 2001
From: root <>
Date: Sat, 17 May 2025 08:27:15 +0000
Subject: [PATCH 07/10] typo: writing buffer_len to somewhere undefined
---
client.s | 24 +-----------------------
1 file changed, 1 insertion(+), 23 deletions(-)
diff --git a/client.s b/client.s
index a8d670f..85fed8d 100644
--- a/client.s
+++ b/client.s
@@ -38,7 +38,7 @@ client__pollin:
jle client__pollin__return ; TODO verify this shit
; buffer_len += read(2) length
- add [rsi + OFFSET_CLIENT_BUFFER_LEN], al
+ add [r12 - OFFSET_CLIENT_BUFFER + OFFSET_CLIENT_BUFFER_LEN], al
mov rdi, r13
mov rsi, rax
@@ -69,28 +69,6 @@ client__pollin__line_too_long:
mov rax, -1024
jmp client__pollin__return
-client__pollin__line:
- pop rdx
- mov word [pollfds + rdx * pollfd_size + 4], POLLOUT
- push rdx
- ; TODO do something to the line
- ; problem: we can't write here because the socket may
- ; block;
- ; how do we deal with multiple lines?
- ; XXX call read(2) trying to fill the whole buffer
- ; - if we have at least 1 line,
- ; update the state and go back to main loop;
- ; do whatever logic is necessary until we need to
- ; call read(2) or write(2) next, ie nothing;
- ; set POLLOUT and process line(s) in write(2) block
- ; - if we have no line and we filled the buffer,
- ; return -1024
- ; - if we have no line, go back to main loop
- ; we could have multiple lines, and that's okay
- ; XXX so this plan will work actually
- ; XXX should we do logic here or in the write(2) block?
- ; probably there, so here we just accumulate lines
- ret
; Returns:
; rax - non-negative from write(2)
From 76b53ad30c5b9d1defa63bc3ef91b378e5e27c92 Mon Sep 17 00:00:00 2001
From: root <>
Date: Sat, 17 May 2025 08:37:23 +0000
Subject: [PATCH 08/10] fix: negative line length, write(2) to bad fd
---
client.s | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/client.s b/client.s
index 85fed8d..fa59078 100644
--- a/client.s
+++ b/client.s
@@ -92,15 +92,17 @@ client__pollout:
mov rbx, rdx
mov r12, rsi
+ push rdi
mov rdi, r12
+ add rdi, OFFSET_CLIENT_BUFFER
mov rsi, 255
call scanline
+ pop rdi
; poll(2)'d for POLLOUT but we had no line buffered;
; should be impossible
cmp rax, 0
- mov rax, -1024
- je client__pollout__return
+ je client__pollout__no_line
mov r13, rax
@@ -135,6 +137,9 @@ client__pollout__shunt__finished:
jl client__pollout__return
mov word [pollfds + rbx * pollfd_size + 4], POLLIN
+client__pollout__no_line:
+ mov rax, -1024
+
client__pollout__return:
pop r13
pop r12
From c90622c5647bd45a1ee21b5453cbdf2192873f46 Mon Sep 17 00:00:00 2001
From: root <>
Date: Sat, 17 May 2025 08:46:26 +0000
Subject: [PATCH 09/10] fix: client__pollout always returning error, not
handling error
---
client.s | 7 ++++---
main.s | 2 ++
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/client.s b/client.s
index fa59078..38e08cb 100644
--- a/client.s
+++ b/client.s
@@ -137,15 +137,16 @@ client__pollout__shunt__finished:
jl client__pollout__return
mov word [pollfds + rbx * pollfd_size + 4], POLLIN
-client__pollout__no_line:
- mov rax, -1024
-
client__pollout__return:
pop r13
pop r12
pop rbx
ret
+client__pollout__no_line:
+ mov rax, -1024
+ jmp client__pollout__return
+
; rdi - fd
client__shutdown_close:
mov rax, SYS_SHUTDOWN
diff --git a/main.s b/main.s
index 3331bd8..ffa5496 100644
--- a/main.s
+++ b/main.s
@@ -158,6 +158,8 @@ _client__pollout:
mov rsi, r12
mov rdx, r15
call client__pollout
+ cmp rax, 0
+ jle _client__error_or_eof
add r15, 1
jmp scan__loop
From 44cf92c998c46811753c790c40157e490a5e0388 Mon Sep 17 00:00:00 2001
From: root <>
Date: Sat, 17 May 2025 09:07:03 +0000
Subject: [PATCH 10/10] fix: read(2)ing too many bytes
---
client.s | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/client.s b/client.s
index 38e08cb..d3a1e7a 100644
--- a/client.s
+++ b/client.s
@@ -31,7 +31,7 @@ client__pollin:
mov rax, SYS_READ
mov rsi, r13
mov rdx, 255
- sub rdx, [rsi + OFFSET_CLIENT_BUFFER_LEN]
+ sub dl, [rsi + OFFSET_CLIENT_BUFFER_LEN]
syscall
cmp rax, 0