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FreeRTOS+TCP Fix usGenerateChecksum on 8-bit platforms with odd-aligned buffers (#286)

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* Change type of usGenerateChecksum's ulAlignBits to intptr_t

Not all platforms have 32-bit pointers. 8-bit machines such as avr8 have
16-bit pointers.

This patch changes the type of ulAlignBits and renames it to uxAlignBits to
reflect the type change.

This fixes a compiler warning on machines with pointers that aren't
32-bits.

Signed-off-by: Andy Bennett <andyjpb@ashurst.eu.org>

* Fix usGenerateChecksum on odd-aligned buffers with non zero usSum

usGenerateChecksum would generate an incorrect checksum when pucNextData
was odd-aligned and usSum was non-zero.

This was caused by the byte order of usSum not matching the byte order of
the subsequent summing operation.

Odd-aligned buffers are common on 8-bit platforms such as avr8 when using
one of the FreeRTOS dynamic heap allocators.

Signed-off-by: Andy Bennett <andyjpb@ashurst.eu.org>

* Feedback from PR#122

https://github.com/FreeRTOS/FreeRTOS/pull/122

 + Use a uintptr_t rather than an intptr_t.

Changes supplied by Hein Tibosch.

Signed-off-by: Andy Bennett <andyjpb@ashurst.eu.org>

Co-authored-by: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
This commit is contained in:
Andy Bennett 2020-09-25 05:53:43 +01:00 • committed by GitHub
parent 7bcc5b48b1
commit 5d0908b23f
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1 changed files with 15 additions and 7 deletions
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22
FreeRTOS-Plus/Source/FreeRTOS-Plus-TCP/FreeRTOS_IP.c
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@ -2430,7 +2430,8 @@ aid though to optimise the calculations. */
xUnion32 xSum2, xSum, xTerm;
xUnionPtr xSource;
xUnionPtr xLastSource;
uint32_t ulAlignBits, ulCarry = 0UL;
uintptr_t uxAlignBits;
uint32_t ulCarry = 0UL;
uint16_t usTemp;
size_t uxDataLengthBytes = uxByteCount;
@ -2444,12 +2445,19 @@ size_t uxDataLengthBytes = uxByteCount;
xTerm.u32 = 0UL;
xSource.u8ptr = ipPOINTER_CAST( uint8_t *, pucNextData );
/* coverity[misra_c_2012_rule_11_4_violation] */
/* The object pointer expression "pucNextData" of type "uint8_t const *" is cast to an integer type "unsigned int". */
ulAlignBits = ( ( ( uint32_t ) pucNextData ) & 0x03U ); /*lint !e9078 !e923*/ /* gives 0, 1, 2, or 3 */
uxAlignBits = ( ( ( uintptr_t ) pucNextData ) & 0x03U );
/*
* If pucNextData is non-aligned then the checksum is starting at an
* odd position and we need to make sure the usSum value now in xSum is
* as if it had been "aligned" in the same way.
*/
if( ( uxAlignBits & 1UL) != 0U )
{
xSum.u32 = ( ( xSum.u32 & 0xffU ) << 8 ) | ( ( xSum.u32 & 0xff00U ) >> 8 );
}
/* If byte (8-bit) aligned... */
if( ( ( ulAlignBits & 1UL ) != 0UL ) && ( uxDataLengthBytes >= ( size_t ) 1 ) )
if( ( ( uxAlignBits & 1UL ) != 0UL ) && ( uxDataLengthBytes >= ( size_t ) 1 ) )
{
xTerm.u8[ 1 ] = *( xSource.u8ptr );
xSource.u8ptr++;
@ -2458,7 +2466,7 @@ size_t uxDataLengthBytes = uxByteCount;
}
/* If half-word (16-bit) aligned... */
if( ( ( ulAlignBits == 1U ) || ( ulAlignBits == 2U ) ) && ( uxDataLengthBytes >= 2U ) )
if( ( ( uxAlignBits == 1U ) || ( uxAlignBits == 2U ) ) && ( uxDataLengthBytes >= 2U ) )
{
xSum.u32 += *(xSource.u16ptr);
xSource.u16ptr++;
@ -2539,7 +2547,7 @@ size_t uxDataLengthBytes = uxByteCount;
/* coverity[value_overwrite] */
xSum.u32 = ( uint32_t ) xSum.u16[ 0 ] + xSum.u16[ 1 ];
if( ( ulAlignBits & 1U ) != 0U )
if( ( uxAlignBits & 1U ) != 0U )
{
/* Quite unlikely, but pucNextData might be non-aligned, which would
mean that a checksum is calculated starting at an odd position. */