kernel/arch/mips/include/asm/checksum.h, branch linux-rolling-stable

MIPS: Add 'memory' clobber to csum_ipv6_magic() inline assembler

2024-02-23T08:51:27Z

[ Upstream commit d55347bfe4e66dce2e1e7501e5492f4af3e315f8 ] After 'lib: checksum: Use aligned accesses for ip_fast_csum and csum_ipv6_magic tests' was applied, the test_csum_ipv6_magic unit test started failing for all mips platforms, both little and bit endian. Oddly enough, adding debug code into test_csum_ipv6_magic() made the problem disappear. The gcc manual says: "The "memory" clobber tells the compiler that the assembly code performs memory reads or writes to items other than those listed in the input and output operands (for example, accessing the memory pointed to by one of the input parameters) " This is definitely the case for csum_ipv6_magic(). Indeed, adding the 'memory' clobber fixes the problem. Cc: Charlie Jenkins Cc: Palmer Dabbelt Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Guenter Roeck Reviewed-by: Charlie Jenkins Signed-off-by: Thomas Bogendoerfer Signed-off-by: Sasha Levin

MIPS: Rewrite `csum_tcpudp_nofold' in plain C

2022-05-23T09:29:59Z

Recent commit 198688edbf77 ("MIPS: Fix inline asm input/output type mismatch in checksum.h used with Clang") introduced a code size and performance regression with 64-bit code emitted for `csum_tcpudp_nofold' by GCC, caused by a redundant truncation operation produced due to a data type change made to the variable associated with the inline assembly's output operand. The intent previously expressed here with operands and constraints for optimal code was to have the output operand share a register with one inputs, both of a different integer type each. This is perfectly valid with the MIPS psABI where a register can hold integer data of different types and the assembly code used here makes data stored in the output register match the data type used with the output operand, however it has turned out impossible to express this arrangement in source code such as to satisfy LLVM, apparently due to the compiler's internal limitations. There is nothing peculiar about the inline assembly `csum_tcpudp_nofold' includes however, though it does choose assembly instructions carefully. Rewrite this piece of assembly in plain C then, using corresponding C language operations, making GCC produce the same assembly instructions, possibly shuffled, in the general case and sometimes actually fewer of them where an input is constant, because the compiler does not have to reload it to a register (operand constraints could be adjusted for that, but the plain C approach is cleaner anyway). Example code size changes are as follows, for a 32-bit configuration: text data bss total filename 5920480 1347236 126592 7394308 vmlinux-old 5920480 1347236 126592 7394308 vmlinux-now 5919728 1347236 126592 7393556 vmlinux-c and for a 64-bit configuration: text data bss total filename 6024112 1790828 225728 8040668 vmlinux-old 6024128 1790828 225728 8040684 vmlinux-now 6023760 1790828 225728 8040316 vmlinux-c respectively, where "old" is with the commit referred reverted, "now" is with no change, and "c" is with this change applied. Signed-off-by: Maciej W. Rozycki Signed-off-by: Thomas Bogendoerfer

MIPS: Fix inline asm input/output type mismatch in checksum.h used with Clang

2021-01-27T20:59:28Z

Fix the following build error when make M=samples/bpf used with Clang: CLANG-bpf samples/bpf/sockex2_kern.o In file included from samples/bpf/sockex2_kern.c:7: In file included from ./include/uapi/linux/if_tunnel.h:7: In file included from ./include/linux/ip.h:16: In file included from ./include/linux/skbuff.h:28: In file included from ./include/net/checksum.h:22: ./arch/mips/include/asm/checksum.h:161:9: error: unsupported inline asm: input with type 'unsigned long' matching output with type '__wsum' (aka 'unsigned int') : "0" ((__force unsigned long)daddr), ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1 error generated. This is a known issue on MIPS [1], the changed code can be compiled successfully by both GCC and Clang. [1] https://lore.kernel.org/linux-mips/CAG_fn=W0JHf8QyUX==+rQMp8PoULHrsQCa9Htffws31ga8k-iw@mail.gmail.com/ Signed-off-by: Tiezhu Yang Signed-off-by: Thomas Bogendoerfer

mips: propagate the calling convention change down into __csum_partial_copy_..._user()

2020-08-20T19:45:20Z

and turn the exception handlers into simply returning 0, which simplifies the hell out of things in csum_partial.S Signed-off-by: Al Viro

mips: __csum_partial_copy_kernel() has no users left

2020-08-20T19:45:20Z

Signed-off-by: Al Viro

mips: csum_and_copy_{to,from}_user() are never called under KERNEL_DS

2020-08-20T19:45:19Z

they are only called for iovec-backed iov_iter and under KERNEL_DS an attempt to create such a beast will yield a kvec-backed one. Signed-off-by: Al Viro

saner calling conventions for csum_and_copy_..._user()

2020-08-20T19:45:15Z

All callers of these primitives will * discard anything we might've copied in case of error * ignore the csum value in case of error * always pass 0xffffffff as the initial sum, so the resulting csum value (in case of success, that is) will never be 0. That suggest the following calling conventions: * don't pass err_ptr - just return 0 on error. * don't bother with zeroing destination, etc. in case of error * don't pass the initial sum - just use 0xffffffff. This commit does the minimal conversion in the instances of csum_and_copy_...(); the changes of actual asm code behind them are done later in the series. Note that this asm code is often shared with csum_partial_copy_nocheck(); the difference is that csum_partial_copy_nocheck() passes 0 for initial sum while csum_and_copy_..._user() pass 0xffffffff. Fortunately, we are free to pass 0xffffffff in all cases and subsequent patches will use that freedom without any special comments. A part that could be split off: parisc and uml/i386 claimed to have csum_and_copy_to_user() instances of their own, but those were identical to the generic one, so we simply drop them. Not sure if it's worth a separate commit... Signed-off-by: Al Viro

csum_partial_copy_nocheck(): drop the last argument

2020-08-20T19:45:14Z

It's always 0. Note that we theoretically could use ~0U as well - result will be the same modulo 0xffff, _if_ the damn thing did the right thing for any value of initial sum; later we'll make use of that when convenient. However, unlike csum_and_copy_..._user(), there are instances that did not work for arbitrary initial sums; c6x is one such. Signed-off-by: Al Viro

unify generic instances of csum_partial_copy_nocheck()

2020-08-20T19:45:14Z

quite a few architectures have the same csum_partial_copy_nocheck() - simply memcpy() the data and then return the csum of the copy. hexagon, parisc, ia64, s390, um: explicitly spelled out that way. arc, arm64, csky, h8300, m68k/nommu, microblaze, mips/GENERIC_CSUM, nds32, nios2, openrisc, riscv, unicore32: end up picking the same thing spelled out in lib/checksum.h (with varying amounts of perversions along the way). everybody else (alpha, arm, c6x, m68k/mmu, mips/!GENERIC_CSUM, powerpc, sh, sparc, x86, xtensa) have non-generic variants. For all except c6x the declaration is in their asm/checksum.h. c6x uses the wrapper from asm-generic/checksum.h that would normally lead to the lib/checksum.h instance, but in case of c6x we end up using an asm function from arch/c6x instead. Screw that mess - have architectures with private instances define _HAVE_ARCH_CSUM_AND_COPY in their asm/checksum.h and have the default one right in net/checksum.h conditional on _HAVE_ARCH_CSUM_AND_COPY *not* defined. Signed-off-by: Al Viro

MIPS: checksum: fix sparse flooding on asm/checksum.h

2020-06-25T08:37:23Z

csum_fold() in MIPS' asm/checksum.h is another source of sparse flooding when building different networking source code. The thing is that only half of __wsum <--> u32 casts inside the function is forced, which is insufficient. Add all necessary forced typecasting to stop floods and simplify actual bug hunting. Signed-off-by: Alexander Lobakin Signed-off-by: Thomas Bogendoerfer