Turning HUNK_SYMBOL offsets into pointers

BSzili · 19 March 2022, 07:28

I'd like to create a simple DLL/SO-like dynamic linking system to aid some future ports. There are existing implementations (Quake2 DLLs from Hyperion, FPSE plugins, etc.), but they are inconvenient as you have to manually create a symbol table with every exported symbol. I decided to use the HUNK_SYMBOL in unstripped executables to avoid doing double work. The "DLL" files will be regular executables started from shell, so in case of HUNK_CODE I was able to add the offsets to BADDR(cli_Module)+4 of the CommandLineInterface struct to get the address of functions. Is there a way to do the same for HUNK_DATA and HUNK_BSS the get the addresses of global variables?

hooverphonique · 19 March 2022, 11:36

Did you try traversing the hunk list? Each hunk (when loaded through LoadSeg, et.al.) has a size and pointer to next hunk placed just before the actual hunk data.

BSzili · 19 March 2022, 12:04

I see, so the first longword I skipped was the size of the hunk. I forgot to mention, but the global variables seem to have a lower memory address than BADDR(cli_Module), so going forward in the list wouldn't help in this case.
edit: I missed the part about the pointer, I'll check this out.

a/b · 19 March 2022, 12:11

Quote:

Originally Posted by hooverphonique

Did you try traversing the hunk list? Each hunk (when loaded through LoadSeg, et.al.) has a size and pointer to next hunk placed just before the actual hunk data.

Pedantic correction: bcpl pointer. So, for each hunk:
address-8 = hunk size in bytes
address-4 = bcpl pointer to next hunk (0 if none)

BSzili · 19 March 2022, 12:15

Thanks for the help! It seems like the first longword stored at BADDR(cli_Module) is indeed a BPTR to the next hunk which is lower than the address of the global variables. Now I just have to figure out which ones comes after which and I'm set.

BSzili · 30 July 2022, 19:00

I ended up finishing the dynamic linking library, now it's up on GitHub:
https://github.com/BSzili/libdl-hunk/

bebbo · 31 July 2022, 11:33

There are libraries and there is https://aminet.net/dev/gg/a2ixlibrary-2.1.lha

/shrug

BSzili · 31 July 2022, 14:25

I saw this, but it's for ixemul.library only. My solution is independent from the C library and only uses exec and dos functions. The program and libraries can be linked different C-libraries as long as they don't pass incompatible stdio handles, or try to free memory allocated by the other.

19 March 2022, 07:28	#1
BSzili old chunk of coal Join Date: Nov 2011 Location: Hungary Posts: 1,289	Turning HUNK_SYMBOL offsets into pointers I'd like to create a simple DLL/SO-like dynamic linking system to aid some future ports. There are existing implementations (Quake2 DLLs from Hyperion, FPSE plugins, etc.), but they are inconvenient as you have to manually create a symbol table with every exported symbol. I decided to use the HUNK_SYMBOL in unstripped executables to avoid doing double work. The "DLL" files will be regular executables started from shell, so in case of HUNK_CODE I was able to add the offsets to BADDR(cli_Module)+4 of the CommandLineInterface struct to get the address of functions. Is there a way to do the same for HUNK_DATA and HUNK_BSS the get the addresses of global variables?

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19 March 2022, 11:36	#2
hooverphonique ex. demoscener "Bigmama" Join Date: Jun 2012 Location: Fyn / Denmark Posts: 1,624	Did you try traversing the hunk list? Each hunk (when loaded through LoadSeg, et.al.) has a size and pointer to next hunk placed just before the actual hunk data.

19 March 2022, 12:04	#3
BSzili old chunk of coal Join Date: Nov 2011 Location: Hungary Posts: 1,289	I see, so the first longword I skipped was the size of the hunk. I forgot to mention, but the global variables seem to have a lower memory address than BADDR(cli_Module), so going forward in the list wouldn't help in this case. edit: I missed the part about the pointer, I'll check this out.

19 March 2022, 12:15	#5
BSzili old chunk of coal Join Date: Nov 2011 Location: Hungary Posts: 1,289	Thanks for the help! It seems like the first longword stored at BADDR(cli_Module) is indeed a BPTR to the next hunk which is lower than the address of the global variables. Now I just have to figure out which ones comes after which and I'm set.

30 July 2022, 19:00	#6
BSzili old chunk of coal Join Date: Nov 2011 Location: Hungary Posts: 1,289	I ended up finishing the dynamic linking library, now it's up on GitHub: https://github.com/BSzili/libdl-hunk/

31 July 2022, 11:33	#7
bebbo bye Join Date: Jun 2016 Location: Some / Where Posts: 680	There are libraries and there is https://aminet.net/dev/gg/a2ixlibrary-2.1.lha /shrug

31 July 2022, 14:25	#8
BSzili old chunk of coal Join Date: Nov 2011 Location: Hungary Posts: 1,289	I saw this, but it's for ixemul.library only. My solution is independent from the C library and only uses exec and dos functions. The program and libraries can be linked different C-libraries as long as they don't pass incompatible stdio handles, or try to free memory allocated by the other.

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