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Date: Mon, 25 Apr 2022 20:13:05 -0300 From: Jason Gunthorpe <jgg@...pe.ca> To: Mateusz Jończyk <mat.jonczyk@...pl> Cc: netdev@...r.kernel.org, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, David Laight <David.Laight@...LAB.COM>, Andrew Morton <akpm@...ux-foundation.org>, Christophe Leroy <christophe.leroy@...roup.eu>, Anshuman Khandual <anshuman.khandual@....com>, linux-rdma@...r.kernel.org Subject: Re: "mm: uninline copy_overflow()" breaks i386 build in Mellanox MLX4 On Thu, Apr 21, 2022 at 10:47:01PM +0200, Mateusz Jończyk wrote: > Hello, > > commit ad7489d5262d ("mm: uninline copy_overflow()") > > breaks for me a build for i386 in the Mellanox MLX4 driver: > > In file included from ./arch/x86/include/asm/preempt.h:7, > from ./include/linux/preempt.h:78, > from ./include/linux/percpu.h:6, > from ./include/linux/context_tracking_state.h:5, > from ./include/linux/hardirq.h:5, > from drivers/net/ethernet/mellanox/mlx4/cq.c:37: > In function ‘check_copy_size’, > inlined from ‘copy_to_user’ at ./include/linux/uaccess.h:159:6, > inlined from ‘mlx4_init_user_cqes’ at drivers/net/ethernet/mellanox/mlx4/cq.c:317:9, > inlined from ‘mlx4_cq_alloc’ at drivers/net/ethernet/mellanox/mlx4/cq.c:394:10: > ./include/linux/thread_info.h:228:4: error: call to ‘__bad_copy_from’ declared with attribute error: copy source size is too small > 228 | __bad_copy_from(); > | ^~~~~~~~~~~~~~~~~ > make[5]: *** [scripts/Makefile.build:288: drivers/net/ethernet/mellanox/mlx4/cq.o] Błąd 1 > make[4]: *** [scripts/Makefile.build:550: drivers/net/ethernet/mellanox/mlx4] Błąd 2 > make[3]: *** [scripts/Makefile.build:550: drivers/net/ethernet/mellanox] Błąd 2 > make[2]: *** [scripts/Makefile.build:550: drivers/net/ethernet] Błąd 2 > make[1]: *** [scripts/Makefile.build:550: drivers/net] Błąd 2 > > Reverting this commit fixes the build. Disabling Mellanox Ethernet drivers > in Kconfig (tested only with also disabling of all Infiniband support) also fixes the build. > > It appears that uninlining of copy_overflow() causes GCC to analyze the code deeper. This looks like a compiler bug to me, array_size(entries, cqe_size) cannot be known at compile time, so the __builtin_constant_p(bytes) should be compile time false meaning the other two bad branches should have been eliminated. Jason
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