From f45711b39e03ff5e80b60dcc1fd34b3fc7d3d36c Mon Sep 17 00:00:00 2001 From: Waldemar Brodkorb Date: Wed, 21 Oct 2026 02:02:50 +0200 Subject: [PATCH] sh: Select BINFMT_FLAT_NO_DATA_START_OFFSET for !MMU binfmt_flat offsets the in-memory start of the data segment by MAX_SHARED_LIBS words and then aligns it to FLAT_DATA_ALIGN, so FLAT_FLAG_RAM binaries end up with a gap between text and data (commit 2217b9826246 ("binfmt_flat: revert "binfmt_flat: don't offset the data start"")). SH position-independent code finds the GOT with a PC-relative mova of _GLOBAL_OFFSET_TABLE_, which assumes data follows text directly, as elf2flt lays out the image. With the gap, the GOT register points below the real GOT, so every GOT load reads the neighbouring slot and gets a wrong pointer. On a J2 (sh2eb, no MMU) this made userland crash or hang right after start-up. In my case the data was moved up by 0x20 bytes. Commit 04d82a6d0881 ("binfmt_flat: allow not offsetting data start") added CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET for architectures that cannot tolerate such a gap; currently only riscv !MMU selects it. Select it on SH as well when building without an MMU. Tested on a J2 board (Numato Mimas V2, sh2eb, no MMU) with Linux 7.3 and FLAT binaries built with elf2flt: with this change the data segment starts exactly at the end of text and init runs. Without the patch bootup fails with: [ 12.080472] Fixing up unaligned userspace access in "init" pid=1 pc=0x(ptrval) ins=0x6583 [ 12.123609] Fixing up unaligned userspace access in "init" pid=1 pc=0x(ptrval) ins=0x6583 [ 12.175153] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00 Fixes: 2217b9826246 ("binfmt_flat: revert "binfmt_flat: don't offset the data start"") Signed-off-by: Waldemar Brodkorb Assisted-by: LLM Reviewed-by: John Paul Adrian Glaubitz Signed-off-by: John Paul Adrian Glaubitz --- arch/sh/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index d60f1d5a94c0..b501153551c0 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -15,6 +15,7 @@ config SUPERH select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_WANT_IPC_PARSE_VERSION select ARCH_NEED_CMPXCHG_1_EMU + select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU select CPU_NO_EFFICIENT_FFS select DMA_DECLARE_COHERENT select GENERIC_ATOMIC64