Linking addresses and -mcog

Circuitsoft

I'm trying to convert Lonesock's FastFullDuplexSerial object to C, and running into issues.

All my experience with linking and symbols has been on processors with only one address space, so I'm not sure how to do this on PropGCC.

alex@alex-thinks ~/Projects/Parallax Library/serial $ cat Makefile 
CC=/opt/parallax/bin/propeller-elf-gcc
CFLAGS=-g3 -DTEST
all: ffds1
ffds1m.o: ffds1m.S
        $(CC) -c -o $@ -mcog $^ -g3
ffds1: ffds1.o ffds1m.o
        $(CC) -o $@ $^
alex@alex-thinks ~/Projects/Parallax Library/serial $ make -j2
/opt/parallax/bin/propeller-elf-gcc -g3 -DTEST   -c -o ffds1.o ffds1.c
/opt/parallax/bin/propeller-elf-gcc -c -o ffds1m.o -mcog ffds1m.S -g3
/opt/parallax/bin/propeller-elf-gcc -o ffds1 ffds1.o ffds1m.o
ffds1m.o: In function `ffds1.entry':
(.ffds1.text+0x4): relocation truncated to fit: R_PROPELLER_SRC against symbol `ffds1.ctra_val' defined in .ffds1.text section in ffds1m.o
ffds1m.o: In function `ffds1.entry':
(.ffds1.text+0x8): relocation truncated to fit: R_PROPELLER_SRC against symbol `ffds1.maskTX' defined in .ffds1.text section in ffds1m.o
ffds1m.o: In function `ffds1.entry':
(.ffds1.text+0xc): relocation truncated to fit: R_PROPELLER_SRC against symbol `ffds1.ctrb_val' defined in .ffds1.text section in ffds1m.o
ffds1m.o: In function `ffds1.entry':
(.ffds1.text+0x14): relocation truncated to fit: R_PROPELLER_DST against `step_clocks'
ffds1m.o: In function `ffds1.entry':
(.ffds1.text+0x14): relocation truncated to fit: R_PROPELLER_SRC against symbol `ffds1.period_ptr' defined in .ffds1.text section in ffds1m.o
ffds1m.o: In function `ffds1.entry':
(.ffds1.text+0x1c): relocation truncated to fit: R_PROPELLER_DST against `timestamp'
ffds1m.o: In function `ffds1.entry':
(.ffds1.text+0x1c): relocation truncated to fit: R_PROPELLER_SRC against `step_clocks'
ffds1m.o: In function `ffds1.entry':
(.ffds1.text+0x20): relocation truncated to fit: R_PROPELLER_DST against `timestamp'
ffds1m.o: In function `rx_main':
(.ffds1.text+0x28): relocation truncated to fit: R_PROPELLER_DST against `lockstep_ret'
ffds1m.o: In function `rx_main':
(.ffds1.text+0x28): relocation truncated to fit: R_PROPELLER_SRC against `tx_jump'
ffds1m.o: In function `rx_main':
(.ffds1.text+0x2c): additional relocation overflows omitted from the output
collect2: ld returned 1 exit status
make: *** [ffds1] Error 1

I'm sure that all these problems need the same fix, but I just don't know what it is.

jazzed

Try following this example: https://code.google.com/p/propgcc/source/browse/demos/toggle/gas_toggle/

Circuitsoft

Ok.The ".cog_ram" directive after the section name isn't explained. Can you expand on that?

jazzed

Circuitsoft wrote: »

Ok.The ".cog_ram" directive after the section name isn't explained. Can you expand on that?

.cog_ram Marks symbols to indicate that their values should be treated as long word
addresses, not byte addresses, by the linker. This is intended to duplicate the
standard behavior of the PASM assembler.

https://propgcc.googlecode.com/files/as.pdf page 211

Circuitsoft

Ah, so .cog_ram means I can use the symbols locally within the assembler, but I need to multiply their addresses by 4, and add the __start offset to access them from outside before calling coginit.

jazzed

Circuitsoft wrote: »

Ah, so .cog_ram means I can use the symbols locally within the assembler, but I need to multiply their addresses by 4, and add the __start offset to access them from outside before calling coginit.

Actually, I think it means you don't need to multiply their addresses. Eric or David may have better explanations - i'm not much of a gas user.

ersmith

Circuitsoft wrote: »

Ah, so .cog_ram means I can use the symbols locally within the assembler, but I need to multiply their addresses by 4, and add the __start offset to access them from outside before calling coginit.

That's pretty much correct: .cog_ram makes the symbols long addresses rather than byte addresses, so if you want to refer to them in C functions (which typically expect byte addresses) you will have to multiply by 4. You could equally well modify the original assembly to use byte addresses instead; that's what spin2cpp --gas will do.

Eric