| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 05/97] fs/select: avoid clang stack usage warning | Date | Wed, 22 Jan 2020 10:28:09 +0100 |
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From: Arnd Bergmann <arnd@arndb.de>
commit ad312f95d41c9de19313c51e388c4984451c010f upstream.
The select() implementation is carefully tuned to put a sensible amount of data on the stack for holding a copy of the user space fd_set, but not too large to risk overflowing the kernel stack.
When building a 32-bit kernel with clang, we need a little more space than with gcc, which often triggers a warning:
fs/select.c:619:5: error: stack frame size of 1048 bytes in function 'core_sys_select' [-Werror,-Wframe-larger-than=] int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
I experimentally found that for 32-bit ARM, reducing the maximum stack usage by 64 bytes keeps us reliably under the warning limit again.
Link: http://lkml.kernel.org/r/20190307090146.1874906-1-arnd@arndb.de Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Andi Kleen <ak@linux.intel.com> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Eric Dumazet <edumazet@google.com> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Miles Chen <miles.chen@mediatek.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- include/linux/poll.h | 4 ++++ 1 file changed, 4 insertions(+)
--- a/include/linux/poll.h +++ b/include/linux/poll.h @@ -14,7 +14,11 @@ extern struct ctl_table epoll_table[]; /* for sysctl */ /* ~832 bytes of stack space used max in sys_select/sys_poll before allocating additional memory. */ +#ifdef __clang__ +#define MAX_STACK_ALLOC 768 +#else #define MAX_STACK_ALLOC 832 +#endif #define FRONTEND_STACK_ALLOC 256 #define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC #define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC
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