#11058: selected processor does not support ARM mode ----------------------------------------+------------------------------ Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: arm Type of failure: Building GHC failed | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ----------------------------------------+------------------------------ Comment (by bgamari): Here is a summary of the issue sent to ghc-devs,

Indeed this appears to be regression compared to 7.10.2 for some. However for most users it will be a significant improvement in stability.

ARM processors can run code encoded in one of several instruction sets of which ARM and Thumb are two. The issue here is that we have never been able to handle Thumb instructions correctly; we fare even worse in cases where we have Thumb and ARM instructions in the same executable due to various linker issues:

* the runtime's linker doesn't support loading heterogeneous code at all

* the system's dynamic linker will almost certainly screw up our info tables due to the need for a trampoline (for this reason , I'm not even sure whether it's possible to handle Thumb-ARM interworking in Haskell code)

There are several places where Thumb instructions could come from,

1. GHCi produced them in mkJumpToAddr

2. native code compiled with GCC, which defaults to Thumb on many systems

3. system libraries, which are Thumb on many distributions

The solution which Erik implemented was to switch entirely to ARM. (1) was addressed by changing the GHC, (2) was fixed by explicitly passing -marm to GCC. I'm actually not sure the state of (3).

Regardless, the solution to (2) is clearly upsetting your system. This is odd as I was under the impression that all non-microcontroller ARM devices support the full ARM instruction set (the Cortex devices, on the other hand, only support Thumb but are totally incapable of running GHC at all). What hardware and distribution is this?

Cheers,

~ Ben

-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11058#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11058: selected processor does not support ARM mode ----------------------------------------+------------------------------ Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: arm Type of failure: Building GHC failed | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ----------------------------------------+------------------------------ Comment (by erikd): I *think* this is fixable, but it requires a bit of fiddling about. As noted by @joeyhess in #10469 the Clang/LLVM target triple for `armel` is `armv4t-unknown-linux-gnueabi`. What we need to fix this is: * `configure.ac` needs to distinguish between Debian's `armhf` and `armel`. * `compiler/llvmGen/LlvmCodeGen/Ppr.hs` needs to set a different target triple depending on whether its build `armel` vs `armhf`. This also assumes that GCC build for `armel` understands the `-marm` flag that was a significant part of the fix for #10375. I'll see if I can get an `armel` chroot set up on one of my `armhf` boards to allow me to debug this. Assuming that works, I should have fix in a couple of days. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11058#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11058: selected processor does not support ARM mode ----------------------------------------+------------------------------ Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: arm Type of failure: Building GHC failed | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ----------------------------------------+------------------------------ Comment (by nomeata): Thanks for the progress so far. Do you already have an idea what might be causing the segfaults? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11058#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11058: selected processor does not support ARM mode ----------------------------------------+------------------------------ Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: arm Type of failure: Building GHC failed | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ----------------------------------------+------------------------------ Comment (by erikd): This gets stranger still. If I simply revert commit `933adc0f31164cb651d` (on master) it still doesn't build on `armel`. Going to try build the debian ghc-7.10.2 package just to make sure I know what I'm doing. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11058#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11058: selected processor does not support ARM mode ----------------------------------------+------------------------------ Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: arm Type of failure: Building GHC failed | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ----------------------------------------+------------------------------ Changes (by bgamari): * cc: bgamari (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11058#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11058: selected processor does not support ARM mode ----------------------------------------+------------------------------ Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: arm Type of failure: Building GHC failed | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ----------------------------------------+------------------------------ Comment (by glaubitz): Replying to [comment:9 erikd]:

This gets stranger still. If I simply revert commit `933adc0f31164cb651d` (on master) it still doesn't build on `armel`.

Works here. I took 7.10.3-4 from Debian, reverted the change and was immediately able to build ghc again. My suggested workaround in Debian is therefore to revert the change when compiling on armel while keeping the change on all other architectures. This will allow us to continue using ghc on armel again and in the future, this issue will hopefully be fixed properly. Adrian -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11058#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11058: selected processor does not support ARM mode ----------------------------------------+------------------------------ Reporter: nomeata | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: arm Type of failure: Building GHC failed | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ----------------------------------------+------------------------------ Comment (by nomeata): I just tried with 8.0.1-rc1, it is not fixed: https://buildd.debian.org/status/fetch.php?pkg=ghc&arch=armel&ver=8.0.0.20160111-3&stamp=1453130686 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11058#comment:15 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler