RAM restricted to offset 0.

[tobygomersall]

I have been learning how to compile rust for a PicoRV32 running on an FPGA with a simple hello world project.

The build system depends on this crate (picorv32-rt) and works correctly if I specify the RAM offset in memory.x to be 0x00000000. However, If I try to build with the RAM offset set to anything other than 0x00000000 then I get the following error:

error: linking with `rust-lld` failed: exit status: 1
  |
  = note: "rust-lld" "-flavor" "gnu" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/hello_world-d4686bcf81ebe3fc.hello_world.4b9de73c-cgu.0.rcgu.o" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/hello_world-d4686bcf81ebe3fc.hello_world.4b9de73c-cgu.1.rcgu.o" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/hello_world-d4686bcf81ebe3fc.hello_world.4b9de73c-cgu.2.rcgu.o" "--as-needed" "-L" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps" "-L" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/release/deps" "-L" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/build/hello-world-afce2ada90003271/out" "-L" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/build/picorv32-rt-09e83ab27c5016e1/out" "-L" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/build/picorv32-rt-09e83ab27c5016e1/out" "-L" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/build/picorv32-b61a8cc3c2e7815b/out" "-L" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/build/riscv-3a3b4c9fe2d93f17/out" "-L" "/home/toby/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/riscv32imc-unknown-none-elf/lib" "--start-group" "-Bstatic" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/libpanic_halt-aea83376b0334f55.rlib" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/libpicorv32_rt-5008630363f2bd7b.rlib" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/libpicorv32-1b73dced3ca29185.rlib" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/libriscv-3402687458f5892a.rlib" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/libbit_field-e25dfa1160590cf0.rlib" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/libbare_metal-ff4fa36d97cf66d9.rlib" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/libr0-d835aacd4e55ffe9.rlib" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/libfixedvec-0ead9ae3dec59c6d.rlib" "/home/toby/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/riscv32imc-unknown-none-elf/lib/librustc_std_workspace_core-1ca50dceae486887.rlib" "/home/toby/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/riscv32imc-unknown-none-elf/lib/libcore-452968c43ebb50a5.rlib" "--end-group" "/home/toby/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/riscv32imc-unknown-none-elf/lib/libcompiler_builtins-997a38c6b1cb6cd6.rlib" "-Bdynamic" "-znoexecstack" "-L" "/home/toby/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/riscv32imc-unknown-none-elf/lib" "-o" "/home/toby/SmartAcoustics/development/Coucal/coucal-examples/hello_world/target/riscv32imc-unknown-none-elf/release/deps/hello_world-d4686bcf81ebe3fc" "--gc-sections" "-O1" "-Tlink.x"
  = note: rust-lld: error: section '.stack' will not fit in region 'RAM': overflowed by 4096 bytes
          rust-lld: error: section '.stack' will not fit in region 'RAM': overflowed by 4096 bytes
          

error: could not compile `hello-world` due to previous error

I have fixed this by copying picorv32-rt/link.x into my project and modifying it in the following way (which I copied from the riscv-rt/link.x):

diff --git a/link.x b/link.x
index c2ffb9b..322d145 100644
--- a/link.x
+++ b/link.x
@@ -55,7 +55,7 @@ SECTIONS
   PROVIDE(_heap_size = 0);
 
   /* fictitious region that represents the memory available for the heap */
-  .heap (INFO) :
+  .heap (NOLOAD) :
   {
     _sheap = .;
     . += _heap_size;
@@ -64,7 +64,7 @@ SECTIONS
   } > RAM
 
   /* fictitious region that represents the memory available for the stack */
-  .stack (INFO) :
+  .stack (NOLOAD) :
   {
     _estack = .;
     . = _stack_start;

Can we fix this in the crate? I'm complete linker script beginner so I apologize if I'm doing something stupid or have set my build system up incorrectly.