From: Will Deacon <will@xxxxxxxxxx> commit 13b0566962914e167cb3238fbe29ced618f07a27 upstream. Due to undocumented, hysterical raisins on x86, the CFI jump-table sections in .text are needlessly aligned to PMD_SIZE in the vmlinux linker script. When compiling a CFI-enabled arm64 kernel with a 64KiB page-size, a PMD maps 512MiB of virtual memory and so the .text section increases to a whopping 940MiB and blows the final Image up to 960MiB. Others report a link failure. Since the CFI jump-table requires only instruction alignment, reduce the alignment directives to function alignment for parity with other parts of the .text section. This reduces the size of the .text section for the aforementioned 64KiB page size arm64 kernel to 19MiB for a much more reasonable total Image size of 39MiB. Cc: Sami Tolvanen <samitolvanen@xxxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: "Mohan Rao .vanimina" <mailtoc.mohanrao@xxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Nathan Chancellor <nathan@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/all/CAL_GTzigiNOMYkOPX1KDnagPhJtFNqSK=1USNbS0wUL4PW6-Uw@xxxxxxxxxxxxxx/ Fixes: cf68fffb66d6 ("add support for Clang CFI") Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx> Tested-by: Mark Rutland <mark.rutland@xxxxxxx> Reviewed-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220922215715.13345-1-will@xxxxxxxxxx Signed-off-by: Will Deacon <will@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/asm-generic/vmlinux.lds.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -543,10 +543,9 @@ */ #ifdef CONFIG_CFI_CLANG #define TEXT_CFI_JT \ - . = ALIGN(PMD_SIZE); \ + ALIGN_FUNCTION(); \ __cfi_jt_start = .; \ *(.text..L.cfi.jumptable .text..L.cfi.jumptable.*) \ - . = ALIGN(PMD_SIZE); \ __cfi_jt_end = .; #else #define TEXT_CFI_JT
