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[13.113.80.70]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-71afc9c5ad4sm1115566b3a.188.2024.09.24.05.32.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Sep 2024 05:32:35 -0700 (PDT) From: Zhang Boyang To: Linus Torvalds , linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Ferdinand Blomqvist , Kees Cook , Randy Dunlap , Zhang Boyang Subject: [PATCH 3/5] rslib: Fix wrong result if gffunc(0) != 1 Date: Tue, 24 Sep 2024 20:31:39 +0800 Message-Id: <20240924123141.16962-4-zhangboyang.id@gmail.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20240924123141.16962-1-zhangboyang.id@gmail.com> References: <20240924123141.16962-1-zhangboyang.id@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The rslib allows customizing the finite field by the `gffunc' parameter of init_rs_non_canonical(). However, there are several places in rslib use hard-coded 1, leading to errors if gffunc(0) !=3D 1. This patch replaces hard-coded 1 with alpha_to[0] to fix this problem. One of such `gffunc' might be gffunc'(x) =3D swab16(gffunc(swab16(x))), as gffunc'(0) =3D swab16(1). This special gffunc'(x) is useful when implementing RS coder for 16 bit foreign-endian symbols. Fixes: d7e5a5462f68 ("[RSLIB] Support non-canonical GF representations") Signed-off-by: Zhang Boyang --- lib/reed_solomon/decode_rs.c | 4 ++-- lib/reed_solomon/reed_solomon.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/lib/reed_solomon/decode_rs.c b/lib/reed_solomon/decode_rs.c index 805de84ae83d..6c1d53d1b702 100644 --- a/lib/reed_solomon/decode_rs.c +++ b/lib/reed_solomon/decode_rs.c @@ -104,7 +104,7 @@ =20 decode: memset(&lambda[1], 0, nroots * sizeof(lambda[0])); - lambda[0] =3D 1; + lambda[0] =3D alpha_to[0]; =20 if (no_eras > 0) { /* Init lambda to be the erasure locator polynomial */ @@ -198,7 +198,7 @@ memcpy(®[1], &lambda[1], nroots * sizeof(reg[0])); count =3D 0; /* Number of roots of lambda(x) */ for (i =3D 1, k =3D iprim - 1; i <=3D nn; i++, k =3D rs_modnn(rs, k + ipr= im)) { - q =3D 1; /* lambda[0] is always 0 */ + q =3D alpha_to[0]; /* lambda[0] is always 0 */ for (j =3D deg_lambda; j > 0; j--) { if (reg[j] !=3D nn) { reg[j] =3D rs_modnn(rs, reg[j] + j); diff --git a/lib/reed_solomon/reed_solomon.c b/lib/reed_solomon/reed_solomo= n.c index bbc01bad3053..bb4f44c8edba 100644 --- a/lib/reed_solomon/reed_solomon.c +++ b/lib/reed_solomon/reed_solomon.c @@ -131,9 +131,9 @@ static struct rs_codec *codec_init(int symsize, int gfp= oly, int (*gffunc)(int), rs->iprim =3D iprim / prim; =20 /* Form RS code generator polynomial from its roots */ - rs->genpoly[0] =3D 1; + rs->genpoly[0] =3D rs->alpha_to[0]; for (i =3D 0, root =3D fcr * prim; i < nroots; i++, root +=3D prim) { - rs->genpoly[i + 1] =3D 1; + rs->genpoly[i + 1] =3D rs->alpha_to[0]; /* Multiply rs->genpoly[] by @**(root + x) */ for (j =3D i; j > 0; j--) { if (rs->genpoly[j] !=3D 0) { --=20 2.30.2