Skip to content

Fix signed overflow in modem training phase arithmetic #128

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
coral wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Fix signed overflow in modem training phase arithmetic #128

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 5 additions & 5 deletions src/v17rx.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -679,7 +679,7 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
out is the phase. */
/* Check if we just saw A or B */
/* atan(1/3) = 18.433 degrees */
if ((uint32_t) (angle - s->last_angles[0]) < (uint32_t) DDS_PHASE(180.0f))
if (((uint32_t) angle - (uint32_t) s->last_angles[0]) < (uint32_t) DDS_PHASE(180.0f))
{
angle = s->last_angles[0];
s->last_angles[0] = DDS_PHASE(270.0f + 18.433f);
Expand All @@ -694,7 +694,7 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
/* Make a step shift in the phase, to pull it into line. We need to rotate the equalizer
buffer, as well as the carrier phase, for this to play out nicely. */
/* angle is now the difference between where A is, and where it should be */
phase_step = angle - DDS_PHASE(180.0f + 18.433f);
phase_step = (uint32_t) angle - (uint32_t) DDS_PHASE(180.0f + 18.433f);
#if defined(SPANDSP_USE_FIXED_POINTx)
ip = phase_step >> 16;
span_log(&s->logging, SPAN_LOG_FLOW, "Spin (short) by %d\n", ip);
Expand Down Expand Up @@ -728,7 +728,7 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
/* Look for the initial ABAB sequence to display a phase reversal, which will
signal the start of the scrambled CDBA segment */
i = s->training_count + 1;
ang = angle - s->last_angles[i & 1];
ang = (int32_t) ((uint32_t) angle - (uint32_t) s->last_angles[i & 1]);
s->last_angles[i & 1] = angle;
s->diff_angles[i & 0xF] = s->diff_angles[(i - 2) & 0xF] + (ang >> 4);
if ((ang > DDS_PHASE(90.0f) || ang < DDS_PHASE(-90.0f)) && s->training_count >= 13)
Expand Down Expand Up @@ -767,7 +767,7 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
/* Make a step shift in the phase, to pull it into line. We need to rotate the equalizer buffer,
as well as the carrier phase, for this to play out nicely. */
/* angle is now the difference between where C is, and where it should be */
phase_step = angle - DDS_PHASE(18.433f);
phase_step = (uint32_t) angle - (uint32_t) DDS_PHASE(18.433f);
#if defined(SPANDSP_USE_FIXED_POINTx)
ip = phase_step >> 16;
span_log(&s->logging, SPAN_LOG_FLOW, "Spin (long) by %d\n", ip);
Expand Down Expand Up @@ -936,7 +936,7 @@ static void process_half_baud(v17_rx_state_t *s, const complexf_t *sample)
/* Look for the initial ABAB sequence to display a phase reversal, which will
signal the start of the scrambled CDBA segment */
angle = arctan2(z.im, z.re);
ang = angle - s->last_angles[s->training_count & 1];
ang = (int32_t) ((uint32_t) angle - (uint32_t) s->last_angles[s->training_count & 1]);
if (ang > DDS_PHASE(90.0f) || ang < DDS_PHASE(-90.0f))
{
/* We seem to have a phase reversal */
Expand Down
4 changes: 2 additions & 2 deletions src/v27ter_rx.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -601,7 +601,7 @@ static __inline__ void process_half_baud(v27ter_rx_state_t *s, const complexf_t
/* Look for the initial ABAB sequence to display a phase reversal, which will
signal the start of the scrambled ABAB segment */
i = s->training_count + 1;
ang = angle - s->last_angles[i & 1];
ang = (int32_t) ((uint32_t) angle - (uint32_t) s->last_angles[i & 1]);
s->last_angles[i & 1] = angle;
s->diff_angles[i & 0xF] = s->diff_angles[(i - 2) & 0xF] + (ang >> 4);
if ((ang > DDS_PHASE(45.0f) || ang < DDS_PHASE(-45.0f)) && s->training_count >= 13)
Expand Down Expand Up @@ -641,7 +641,7 @@ static __inline__ void process_half_baud(v27ter_rx_state_t *s, const complexf_t

/* Make a step shift in the phase, to pull it into line. We need to rotate the equalizer
buffer, as well as the carrier phase, for this to play out nicely. */
angle += DDS_PHASE(180.0f);
angle = (int32_t) ((uint32_t) angle + (uint32_t) DDS_PHASE(180.0f));
#if defined(SPANDSP_USE_FIXED_POINT)
z16 = complex_seti16(fixed_cos(angle >> 16), -fixed_sin(angle >> 16));
for (i = 0; i < V27TER_EQUALIZER_LEN; i++)
Expand Down
2 changes: 1 addition & 1 deletion src/v29rx.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -571,7 +571,7 @@ static void process_half_baud(v29_rx_state_t *s, complexf_t *sample)
/* Look for the initial ABAB sequence to display a phase reversal, which will
signal the start of the scrambled CDCD segment */
i = s->training_count + 1;
ang = angle - s->last_angles[i & 1];
ang = (int32_t) ((uint32_t) angle - (uint32_t) s->last_angles[i & 1]);
s->last_angles[i & 1] = angle;
s->diff_angles[i & 0xF] = s->diff_angles[(i - 2) & 0xF] + (ang >> 4);
if ((ang > DDS_PHASE(45.0f) || ang < DDS_PHASE(-45.0f)) && s->training_count >= 13)
Expand Down