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rslib: Fix decoding of shortened codes
[ Upstream commit 2034a42d17
]
The decoding of shortenend codes is broken. It only works as expected if
there are no erasures.
When decoding with erasures, Lambda (the error and erasure locator
polynomial) is initialized from the given erasure positions. The pad
parameter is not accounted for by the initialisation code, and hence
Lambda is initialized from incorrect erasure positions.
The fix is to adjust the erasure positions by the supplied pad.
Signed-off-by: Ferdinand Blomqvist <ferdinand.blomqvist@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190620141039.9874-3-ferdinand.blomqvist@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 2 additions and 2 deletions
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@ -99,9 +99,9 @@
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if (no_eras > 0) {
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if (no_eras > 0) {
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/* Init lambda to be the erasure locator polynomial */
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/* Init lambda to be the erasure locator polynomial */
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lambda[1] = alpha_to[rs_modnn(rs,
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lambda[1] = alpha_to[rs_modnn(rs,
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prim * (nn - 1 - eras_pos[0]))];
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prim * (nn - 1 - (eras_pos[0] + pad)))];
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for (i = 1; i < no_eras; i++) {
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for (i = 1; i < no_eras; i++) {
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u = rs_modnn(rs, prim * (nn - 1 - eras_pos[i]));
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u = rs_modnn(rs, prim * (nn - 1 - (eras_pos[i] + pad)));
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for (j = i + 1; j > 0; j--) {
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for (j = i + 1; j > 0; j--) {
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tmp = index_of[lambda[j - 1]];
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tmp = index_of[lambda[j - 1]];
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if (tmp != nn) {
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if (tmp != nn) {
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