Kernel设置为64K PageSize后 无法启动

[Xinmudotmoe]

同时 大多数elf的配置中对齐为0x4000(16k) 这可能与ld.bfd的代码有关

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000027a6c 0x0000000000027a6c  R E    `0x4000`
  LOAD           0x000000000002af30 0x000000000002af30 0x000000000002af30
                 0x00000000000021f0 0x0000000000002390  RW     `0x4000`
  DYNAMIC        0x000000000002bec0 0x000000000002bec0 0x000000000002bec0
                 0x0000000000000140 0x0000000000000140  RW     0x8
  GNU_EH_FRAME   0x00000000000242b0 0x00000000000242b0 0x00000000000242b0
                 0x000000000000088c 0x000000000000088c  R      0x4
  GNU_STACK      0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000000  RW     0x10
  GNU_RELRO      0x000000000002af30 0x000000000002af30 0x000000000002af30
                 0x00000000000010d0 0x00000000000010d0  R      0x1

[Xinmudotmoe]

内核无法构建

复显步骤

1. 使用 https://github.com/chenhuacai/linux/tree/loongarch-next
2. 龙架构下执行 make defconfig
3. 修改Kernel type and options - Page Table Layout - 64KB with 2 levels 注:64KB 3 Levels也会触发
4. make vmlinux 注:此处跳过ko相关构建,仅以构建内核为目标

报错信息

mm/huge_memory.c: 在函数‘hugepage_init’中:
././include/linux/compiler_types.h:442:45: 错误：call to ‘__compiletime_assert_381’ declared with attribute error: BUILD_BUG_ON failed: ((16 + (16 - 3))-16) > 11
  442 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
      |                                             ^
././include/linux/compiler_types.h:423:25: 附注：in definition of macro ‘__compiletime_assert’
  423 |                         prefix ## suffix();                             \
      |                         ^~~~~~
././include/linux/compiler_types.h:442:9: 附注：in expansion of macro ‘_compiletime_assert’
  442 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
      |         ^~~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:39:37: 附注：in expansion of macro ‘compiletime_assert’
   39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
      |                                     ^~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:50:9: 附注：in expansion of macro ‘BUILD_BUG_ON_MSG’
   50 |         BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
      |         ^~~~~~~~~~~~~~~~
./include/linux/bug.h:24:25: 附注：in expansion of macro ‘BUILD_BUG_ON’
   24 |                         BUILD_BUG_ON(cond);             \
      |                         ^~~~~~~~~~~~
mm/huge_memory.c:686:9: 附注：in expansion of macro ‘MAYBE_BUILD_BUG_ON’
  686 |         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER > MAX_PAGE_ORDER);
      |         ^~~~~~~~~~~~~~~~~~

目前可能的缓解

避免在以64K页表为目标时编译 mm/huge_memory.c 关闭透明大页特性. 龙架构下 CONFIG_PAGE_SIZE_64KB 与 CONFIG_TRANSPARENT_HUGEPAGE 配置可能冲突.

[chenhuacai]

不能构建那前面的panic从何而来？

[Xinmudotmoe]

不能构建那前面的panic从何而来？

关掉透明大页配置后构建出来的

[chenhuacai]

ARCH_FORCE_MAX_ORDER设置的是多少？

[Xinmudotmoe]

ARCH_FORCE_MAX_ORDER设置的是多少？

CONFIG_ARCH_FORCE_MAX_ORDER=11
CONFIG_PAGE_SIZE_64KB=y

不过看arch/loongarch/Kconfig 的话, ARCH_FORCE_MAX_ORDER有default "13" if PAGE_SIZE_64KB 问题是否出在make defconfig?

[chenhuacai]

make defconfig应该做不到非常智能地解决这个问题。

[xry111]

Just put a static_assert to reject invalid ARCH_FORCE_MAX_ORDER + PAGE_SIZE combinations and tell the user to adjust ARCH_FORCE_MAX_ORDER?

[xry111]

IIUC the static assert (actually a BUILD_BUG_ON) is in-place now. I hit it several days ago building a MIPS kernel.

[xry111]

Ref https://sourceware.org/pipermail/libc-alpha/2024-September/160253.html