Implementing stack unwinding

[tsatke]

I'm trying to get stack unwinding implemented using https://github.com/nbdd0121/unwinding .
That requires a linker symbol __etext and __eh_frame, which are not provided by the rust linker. (flavour GNU LLD and __GNU_EH_FRAME_HDR doesn't work, since the linker still doesn't emit the symbol for some reason)
I'm having a hard time creating a link script that lets me still boot the kernel, since the boot loader fails to map pages (depends on the build script what mapping exactly fails), and I don't have any experience with writing link scripts.

The question is: How do I implement stack unwinding? Or at least what would a link script have to provide at which locations, to still work with the https://github.com/rust-osdev/bootloader , which I'm using?

If I'm running into the wrong direction, please let me know!

[bjorn3]

Just to confirm you have set panic-strategy to unwind in the target spec, right? Also try passing --eh-frame-hdr as linker argument. That should cause __GNU_EH_FRAME_HDR to be provided.

[tsatke]

Now I got the old error again.

Full error

cargo b Compiling martim v0.1.0 (/Users/tsatke/Development/github.com/martimos/kernel) error: linking with `rust-lld` failed: exit status: 1 | = note: "rust-lld" "-flavor" "gnu" "--eh-frame-hdr" "/var/folders/8q/k0fjrmzd3pq24266vh_lpgrc0000gn/T/rustcdTo1c2/symbols.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.18f83gufxpnuhzwv.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.1m5fyokp83xbhd65.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.1s14ocg5eh88r6hl.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.1sw36b7oyoet1n9l.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.23jhhpsd6i2ykqip.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.243dcfnucz9eyscx.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.2gz03mrlircz77ub.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.2qmwowszfpozoiwd.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.2tp5p4vpp6hbpuus.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.2wuamfb6twymhnhi.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.2zi984d8lqkun8j0.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.3mkq4hf69cw338ir.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.3rwsry8nn07gf66i.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.3xgsjdlvwx1nblvu.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.415c4w1fgnyvnkgl.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.4iye53pc3ivg4xll.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.4nw7b46fyl7dmngf.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.4z0cpf7ow7oikx30.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.4zru2bd45xw0n5xl.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.53agq0sek6o78iv7.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.53n9hzk3q8iw40q0.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.540x858gs1narabz.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.5ai58t5alqjbcc6x.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.5ehb5fwioyk2aco8.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.5fyb9o56rs7mfnik.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.7ul1oosnmcu0we1.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.82553vfs9apmin.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.9oxhliym0abrq7s.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.oal8nt40qn6pqgl.rcgu.o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911.4boytl9dsmp4i97s.rcgu.o" "--as-needed" "-L" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps" "-L" "/Users/tsatke/Development/github.com/martimos/kernel/target/debug/deps" "-L" "/Users/tsatke/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/x86_64-martim/lib" "-Bstatic" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libmartim-ee61516665077449.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/liblinked_list_allocator-f20f0f81768eaece.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libspinning_top-f5b08bf39ede435a.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libnoto_sans_mono_bitmap-e7a25d9e72cda330.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libpc_keyboard-540f0e6b9fc6a5e5.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libfutures_util-f308cbeae853f055.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libpin_project_lite-91ba5756210f9591.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libfutures_task-37446cd9071990ce.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libpin_utils-e6786f5fa2647b63.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libfutures_core-e309bf4dc56200cf.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libconquer_once-a0c830253f705237.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libcrossbeam_queue-616a2361f3c33e91.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libcrossbeam_utils-d432a3d1d24bd3cd.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libcfg_if-dc08127856ffaa4b.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libkernel_constants-56fc7b3b9951b7ce.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libuart_16550-762edde3044468aa.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libpic8259-39f4e3fcdf3fa4e7.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/liblazy_static-6183329ed1ae5709.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libspin-63f49f2ac6171b14.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libx86_64-3f1dc1f3221e201c.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libvolatile-fb45d84958a12832.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libbitflags-188c7fa18b85e6af.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libbit_field-1bcc97373793b5ff.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libkstd-6af96e4d0cdfd78a.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libspin-313c65d9ea76e027.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/liblock_api-326233d38bc6166e.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libscopeguard-af1bce1d6b066adc.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libunwinding-3fe4452918606348.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libgimli-7bea3e8cbb895daa.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libbootloader-ff8684e16fff74dc.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/liballoc-63e543bab37a4a12.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/librustc_std_workspace_core-98476eeb5bec2c9e.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libcore-391cc2d89b35edca.rlib" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libcompiler_builtins-018094c474eb0434.rlib" "-Bdynamic" "--eh-frame-hdr" "-znoexecstack" "-L" "/Users/tsatke/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/x86_64-martim/lib" "-o" "/Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/martim-74deb89d94380911" "--gc-sections" = note: rust-lld: error: undefined symbol: __etext >>> referenced by unwinding.4edbead8-cgu.13 >>> unwinding-3fe4452918606348.unwinding.4edbead8-cgu.13.rcgu.o:(_$LT$unwinding..unwinder..find_fde..gnu_eh_frame_hdr..StaticFinder$u20$as$u20$unwinding..unwinder..find_fde..FDEFinder$GT$::find_fde::h31f8791ff0ece925) in archive /Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libunwinding-3fe4452918606348.rlib

      rust-lld: error: undefined symbol: __GNU_EH_FRAME_HDR
      >>> referenced by unwinding.4edbead8-cgu.13
      >>>               unwinding-3fe4452918606348.unwinding.4edbead8-cgu.13.rcgu.o:(_$LT$unwinding..unwinder..find_fde..gnu_eh_frame_hdr..StaticFinder$u20$as$u20$unwinding..unwinder..find_fde..FDEFinder$GT$::find_fde::h31f8791ff0ece925) in archive /Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libunwinding-3fe4452918606348.rlib
      >>> referenced by unwinding.4edbead8-cgu.13
      >>>               unwinding-3fe4452918606348.unwinding.4edbead8-cgu.13.rcgu.o:(_$LT$unwinding..unwinder..find_fde..gnu_eh_frame_hdr..StaticFinder$u20$as$u20$unwinding..unwinder..find_fde..FDEFinder$GT$::find_fde::h31f8791ff0ece925) in archive /Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libunwinding-3fe4452918606348.rlib

error: could not compile martim due to previous error

  = note: rust-lld: error: undefined symbol: __etext
          >>> referenced by unwinding.4edbead8-cgu.13
          >>>               unwinding-3fe4452918606348.unwinding.4edbead8-cgu.13.rcgu.o:(_$LT$unwinding..unwinder..find_fde..gnu_eh_frame_hdr..StaticFinder$u20$as$u20$unwinding..unwinder..find_fde..FDEFinder$GT$::find_fde::h31f8791ff0ece925) in archive /Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libunwinding-3fe4452918606348.rlib

          rust-lld: error: undefined symbol: __GNU_EH_FRAME_HDR
          >>> referenced by unwinding.4edbead8-cgu.13
          >>>               unwinding-3fe4452918606348.unwinding.4edbead8-cgu.13.rcgu.o:(_$LT$unwinding..unwinder..find_fde..gnu_eh_frame_hdr..StaticFinder$u20$as$u20$unwinding..unwinder..find_fde..FDEFinder$GT$::find_fde::h31f8791ff0ece925) in archive /Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libunwinding-3fe4452918606348.rlib
          >>> referenced by unwinding.4edbead8-cgu.13
          >>>               unwinding-3fe4452918606348.unwinding.4edbead8-cgu.13.rcgu.o:(_$LT$unwinding..unwinder..find_fde..gnu_eh_frame_hdr..StaticFinder$u20$as$u20$unwinding..unwinder..find_fde..FDEFinder$GT$::find_fde::h31f8791ff0ece925) in archive /Users/tsatke/Development/github.com/martimos/kernel/target/x86_64-martim/debug/deps/libunwinding-3fe4452918606348.rlib

In the full error you can see that --eh-frame-hdr is being passed in.

I think the problem is, that rust-lld uses another linker implementation.

rust-lld
lld is a generic driver.
Invoke ld.lld (Unix), ld64.lld (macOS), lld-link (Windows), wasm-ld (WebAssembly) instead

And ld64 doesn't care about --eh-frame-hdr.

[bjorn3]

I think the problem is, that rust-lld uses another linker implementation.

The linker flavor is set to ld.lld, so it should act like an ELF linker. If you set the linker flavor to ld64.lld it would act like the ld64 Mach-O linker.

Now I got the old error again.

Maybe you need to declare those symbols in a linker script? See https://github.com/nbdd0121/unwinding#baremetal

[tsatke]

Which brings us back to the original question, how such a linker script would look like. But I don't understand how that has to look like. I can create a simple one, and it lets me compile and even boot, but the bootloader immediately fails to map some pages and the kernel halts.

[bjorn3]

Unfortunately I don't know enough about linker scripts to help you.

[tsatke]

Thank you so much anyways, especially for the quick replies. Really awesome that we could clear this up within a few hours!