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The ABI mandates that the %esp register must be a multiple of 16 when executing a 'call' instruction. Commit2ab446336b("tools/nolibc: i386: shrink _start with _start_c") simplified the _start function, but it didn't take care of the %esp alignment, causing SIGSEGV on SSE and AVX programs that use aligned move instruction (e.g., movdqa, movaps, and vmovdqa). The 'and $-16, %esp' aligns the %esp at a multiple of 16. Then 'push %eax' will subtract the %esp by 4; thus, it breaks the 16-byte alignment. Make sure the %esp is correctly aligned after the push by subtracting 12 before the push. Extra: Add 'add $12, %esp' before the 'and $-16, %esp' to avoid over-estimating for particular cases as suggested by Willy. A test program to validate the %esp alignment on _start can be found at: https://lore.kernel.org/lkml/ZOoindMFj1UKqo+s@biznet-home.integral.gnuweeb.org [ Thomas: trim Fixes tag commit id ] Cc: Zhangjin Wu <falcon@tinylab.org> Fixes:2ab446336b("tools/nolibc: i386: shrink _start with _start_c") Reported-by: Nicholas Rosenberg <inori@vnlx.org> Acked-by: Thomas Weißschuh <linux@weissschuh.net> Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org> Reviewed-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org> Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.