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7a4ab56ecb
Patched `rts` heap reservation logic on Android:
* Need for patch
- There seems to be a bug on Android. Sometimes simple commands like `ghc --help` usage 90% - 100% cpu and hangs.
- It doesn't happen every time, but ~25% of the times (at least in my
testing).
* Cause of the bug
- The function `osReserveHeapMemory` tries to allocate virtual space starting
from `0x4200000000`. The allocated space has to start at an address >= this address.
- If the kernel doesn't allocate inside this space, it keeps on repeating the
`mmap` call with increasing starting point.
- Now, on Android the kernel sometimes return an address above (as in counting)
this `hint` address. It repeatedly returns the same address for subsequent calls.
- Thus, an infinite loop occurs.
References:
- 383be28ffd/rts/posix/OSMem.c (L461)
- https://github.com/termux/termux-packages/pull/22991#issuecomment-2759137291
* Solution (proposed by Robert Kirkman):
- It introduces a new helper function `osTryReserveHeapMemoryRecursive`.
This transforms the heap reservation logic into a recursive one.
- `osTryReserveHeapMemory()` is run multiple times without unmapping the
undesired addresses. Thus, forcing the kernel to map subsequent calls of
`mmap` to a new, unique address until an address above the `0x4200000000`
mark is obtained.
- After which each recursive call unmaps its undesired address before returning
the desired address (in order from last mapped to first mapped).
References:
- https://gitlab.haskell.org/ghc/ghc/-/merge_requests/14164
- https://github.com/termux/termux-packages/pull/22991#issuecomment-2761325484
Co-authored-by: Robert Kirkman <rkirkman@termux.dev>
Signed-off-by: Aditya Alok <alok@termux.dev>
19 lines
784 B
Diff
19 lines
784 B
Diff
--- ghc-9.12.1/m4/fp_gcc_supports_no_pie.m4 2025-02-24 22:46:43.263794157 +0530
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+++ ghc-9.12.1.mod/m4/fp_gcc_supports_no_pie.m4 2025-03-25 14:39:14.331731419 +0530
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@@ -6,15 +6,6 @@
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[
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AC_REQUIRE([AC_PROG_CC])
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AC_MSG_CHECKING([whether CC supports -no-pie])
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- echo 'int main() { return 0; }' > conftest.c
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- "$CC" $CONF_GCC_CC_OPTS_STAGE2 -c conftest.c
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- # Some GCC versions only warn when passed an unrecognized flag.
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- if "$CC" $CONF_GCC_LINKER_OPTS_STAGE2 -no-pie -Werror conftest.o -o conftest > conftest.txt 2>&1 && ! grep -i unrecognized conftest.txt > /dev/null 2>&1; then
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- CONF_GCC_SUPPORTS_NO_PIE=YES
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- AC_MSG_RESULT([yes])
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- else
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CONF_GCC_SUPPORTS_NO_PIE=NO
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AC_MSG_RESULT([no])
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- fi
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- rm -f conftest.c conftest.o conftest
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])
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