mu/linux/ex4.subx

# Read a character from stdin, save it to a global, write it to stdout.
#
# To run:
#   $ bootstrap/bootstrap translate ex4.subx -o ex4
#   $ bootstrap/bootstrap run ex4

== data

# the global variable we save to
X:
    0/imm32  # space for read() to write to

== code

Entry:
# read(stdin, X, 1)
# . fd = 0 (stdin)
bb/copy-to-ebx  0/imm32
# . data = X (location to write result to)
b9/copy-to-ecx  X/imm32
# . size = 1 character
ba/copy-to-edx  1/imm32
# . syscall
e8/call  syscall_read/disp32

# write(stdout, X, 1)
# . fd = 1 (stdout)
bb/copy-to-ebx  1/imm32
# . initialize X (location to read from)
b9/copy-to-ecx  X/imm32
# . size = 1 character
ba/copy-to-edx  1/imm32
# . syscall
e8/call  syscall_write/disp32

# exit(ebx)
e8/call  syscall_exit/disp32

# . . vim:nowrap:textwidth=0
4808 - clean up comments in all subx files 2018-12-01 00:45:15 +00:00			`# Read a character from stdin, save it to a global, write it to stdout.`
4392 2018-07-24 18:53:45 +00:00			`#`
5521 2019-08-20 06:45:04 +00:00			`# To run:`
. 2021-03-30 01:47:52 +00:00			`# $ bootstrap/bootstrap translate ex4.subx -o ex4`
7847 2021-03-04 08:24:24 +00:00			`# $ bootstrap/bootstrap run ex4`
4326 - new example: read() from stdin Currently only runs in emulated mode. Likely a paging issue, writing data to code page. I'm not checking the return value. 2018-07-08 06:38:59 +00:00
5647 - experimental support for swapping OS 2019-09-12 02:04:49 +00:00			`== data`
switch to new syntax for segment headers in C++ 2019-05-18 07:00:18 +00:00
			`# the global variable we save to`
			`X:`
			`0/imm32 # space for read() to write to`

5647 - experimental support for swapping OS 2019-09-12 02:04:49 +00:00			`== code`
4780 2018-11-26 08:26:20 +00:00
5410 - 4 examples passing Clean up other examples as well to satisfy the requirements in commit 5404. 2019-07-17 07:47:11 +00:00			`Entry:`
5647 - experimental support for swapping OS 2019-09-12 02:04:49 +00:00			`# read(stdin, X, 1)`
4808 - clean up comments in all subx files 2018-12-01 00:45:15 +00:00			`# . fd = 0 (stdin)`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`bb/copy-to-ebx 0/imm32`
4808 - clean up comments in all subx files 2018-12-01 00:45:15 +00:00			`# . data = X (location to write result to)`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`b9/copy-to-ecx X/imm32`
4808 - clean up comments in all subx files 2018-12-01 00:45:15 +00:00			`# . size = 1 character`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`ba/copy-to-edx 1/imm32`
4808 - clean up comments in all subx files 2018-12-01 00:45:15 +00:00			`# . syscall`
5647 - experimental support for swapping OS 2019-09-12 02:04:49 +00:00			`e8/call syscall_read/disp32`
4356 - subx: first program with a data segment We read() a character from stdin and write() it out to stdout, saving it to a global variable in between. ELF binaries are inefficient; you can ask for a low alignment, but the kernel may not be able to handle it. If you set up a high alignment then you end up wasting an increasing amount of space in each segment because of the constraint that the offset bear some relationship with the loaded address. 2018-07-16 18:03:08 +00:00
5647 - experimental support for swapping OS 2019-09-12 02:04:49 +00:00			`# write(stdout, X, 1)`
4808 - clean up comments in all subx files 2018-12-01 00:45:15 +00:00			`# . fd = 1 (stdout)`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`bb/copy-to-ebx 1/imm32`
4808 - clean up comments in all subx files 2018-12-01 00:45:15 +00:00			`# . initialize X (location to read from)`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`b9/copy-to-ecx X/imm32`
4808 - clean up comments in all subx files 2018-12-01 00:45:15 +00:00			`# . size = 1 character`
5592 - switch register names to lowercase 2019-08-26 18:55:26 +00:00			`ba/copy-to-edx 1/imm32`
4808 - clean up comments in all subx files 2018-12-01 00:45:15 +00:00			`# . syscall`
5647 - experimental support for swapping OS 2019-09-12 02:04:49 +00:00			`e8/call syscall_write/disp32`
4326 - new example: read() from stdin Currently only runs in emulated mode. Likely a paging issue, writing data to code page. I'm not checking the return value. 2018-07-08 06:38:59 +00:00
5647 - experimental support for swapping OS 2019-09-12 02:04:49 +00:00			`# exit(ebx)`
			`e8/call syscall_exit/disp32`
4326 - new example: read() from stdin Currently only runs in emulated mode. Likely a paging issue, writing data to code page. I'm not checking the return value. 2018-07-08 06:38:59 +00:00
4802 Some automated commenting cleanup. Still needs more careful manual scanning. sed -i 's/^# 1-3/# . 1-3/' .subx /.subx sed -i 's/^# op/# . op/' .subx /.subx sed -i 's/# vim/# . . vim/' .subx /.subx sed -i 's/^ # push args/ # . . push args/' .subx /.subx sed -i 's/^ # discard args/ # . . discard args/' .subx /.subx sed -i 's/^ # call/ # . . call/' .subx /.subx sed -i 's/^ # prolog/ # . prolog/' .subx /.subx sed -i 's/^ # epilog/ # . epilog/' .subx /.subx sed -i 's/^ # save registers/ # . save registers/' .subx /.subx sed -i 's/^ # restore registers/ # . restore registers/' .subx /.subx sed -i 's/ operand / register /' .subx /*.subx 2018-11-30 19:10:44 +00:00			`# . . vim:nowrap:textwidth=0`