| Message ID | 20220203151344.437113-1-drjones@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [kvm-unit-tests,v2] arm64: Fix compiling with ancient compiler | expand |
On 03/02/2022 16.13, Andrew Jones wrote: > When compiling with an ancient compiler (gcc-4.8.5-36.el7_6.2.aarch64) > the build fails with > > lib/libcflat.a(alloc.o): In function `mult_overflow': > /home/drjones/kvm-unit-tests/lib/alloc.c:19: undefined reference to `__multi3' > > According to kernel commit fb8722735f50 ("arm64: support __int128 on > gcc 5+") gcc older than 5 will emit __multi3 for __int128 multiplication. > To fix this, let's just use check_mul_overflow(), which does overflow > checking with GCC7.1+ and nothing for older gcc. We lose the fallback > for older gcc, but oh, well, the heavily negative diffstat is just too > tempting to go for another solution. Sounds ok to me, too. Reviewed-by: Thomas Huth <thuth@redhat.com>
On Thu, Feb 03, 2022 at 04:13:44PM +0100, Andrew Jones wrote: > When compiling with an ancient compiler (gcc-4.8.5-36.el7_6.2.aarch64) > the build fails with > > lib/libcflat.a(alloc.o): In function `mult_overflow': > /home/drjones/kvm-unit-tests/lib/alloc.c:19: undefined reference to `__multi3' > > According to kernel commit fb8722735f50 ("arm64: support __int128 on > gcc 5+") gcc older than 5 will emit __multi3 for __int128 multiplication. > To fix this, let's just use check_mul_overflow(), which does overflow > checking with GCC7.1+ and nothing for older gcc. We lose the fallback > for older gcc, but oh, well, the heavily negative diffstat is just too > tempting to go for another solution. > > While we're cleaning up lib/alloc.c with the function deletion also take > the opportunity to clean up the include style and add an SPDX header. > > Signed-off-by: Andrew Jones <drjones@redhat.com> > --- > lib/alloc.c | 41 ++++++----------------------------------- > 1 file changed, 6 insertions(+), 35 deletions(-) > Applied to misc/queue https://gitlab.com/rhdrjones/kvm-unit-tests/-/commits/misc/queue Thanks, drew
diff --git a/lib/alloc.c b/lib/alloc.c index f4266f5d064e..51d774ddf5df 100644 --- a/lib/alloc.c +++ b/lib/alloc.c @@ -1,48 +1,19 @@ -#include "alloc.h" -#include "asm/page.h" -#include "bitops.h" +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#include <alloc.h> +#include <bitops.h> +#include <asm/page.h> +#include <linux/compiler.h> void *malloc(size_t size) { return memalign(sizeof(long), size); } -static bool mult_overflow(size_t a, size_t b) -{ -#if BITS_PER_LONG == 32 - /* 32 bit system, easy case: just use u64 */ - return (u64)a * (u64)b >= (1ULL << 32); -#else -#ifdef __SIZEOF_INT128__ - /* if __int128 is available use it (like the u64 case above) */ - unsigned __int128 res = a; - res *= b; - res >>= 64; - return res != 0; -#else - u64 tmp; - - if ((a >> 32) && (b >> 32)) - return true; - if (!(a >> 32) && !(b >> 32)) - return false; - tmp = (u32)a; - tmp *= (u32)b; - tmp >>= 32; - if (a < b) - tmp += a * (b >> 32); - else - tmp += b * (a >> 32); - return tmp >> 32; -#endif /* __SIZEOF_INT128__ */ -#endif /* BITS_PER_LONG == 32 */ -} - void *calloc(size_t nmemb, size_t size) { void *ptr; - assert(!mult_overflow(nmemb, size)); + assert(!check_mul_overflow(nmemb, size)); ptr = malloc(nmemb * size); if (ptr) memset(ptr, 0, nmemb * size);
When compiling with an ancient compiler (gcc-4.8.5-36.el7_6.2.aarch64) the build fails with lib/libcflat.a(alloc.o): In function `mult_overflow': /home/drjones/kvm-unit-tests/lib/alloc.c:19: undefined reference to `__multi3' According to kernel commit fb8722735f50 ("arm64: support __int128 on gcc 5+") gcc older than 5 will emit __multi3 for __int128 multiplication. To fix this, let's just use check_mul_overflow(), which does overflow checking with GCC7.1+ and nothing for older gcc. We lose the fallback for older gcc, but oh, well, the heavily negative diffstat is just too tempting to go for another solution. While we're cleaning up lib/alloc.c with the function deletion also take the opportunity to clean up the include style and add an SPDX header. Signed-off-by: Andrew Jones <drjones@redhat.com> --- lib/alloc.c | 41 ++++++----------------------------------- 1 file changed, 6 insertions(+), 35 deletions(-)