On Fri, 14 Feb 2020 at 00:48, Philippe Mathieu-Daudé <[email protected]> wrote:
>
> The command is 32-bit, but we are loading the 16 upper bits with
> the 'get_uint16(s->scb + 2)' call.
>
> Once shifted by 16, the command bits match the status bits:
>
> - Command
> Bit 31 ACK-CX Acknowledges that the CU completed an Action Command.
> Bit 30 ACK-FR Acknowledges that the RU received a frame.
> Bit 29 ACK-CNA Acknowledges that the Command Unit became not active.
> Bit 28 ACK-RNR Acknowledges that the Receive Unit became not ready.
>
> - Status
> Bit 15 CX The CU finished executing a command with its I(interrupt)
> bit set.
> Bit 14 FR The RU finished receiving a frame.
> Bit 13 CNA The Command Unit left the Active state.
> Bit 12 RNR The Receive Unit left the Ready state.
>
> Add the SCB_COMMAND_ACK_MASK definition to simplify the code.
>
> This fixes Coverity 1419392 (CONSTANT_EXPRESSION_RESULT):
>
> /hw/net/i82596.c: 352 in examine_scb()
> 346 cuc = (command >> 8) & 0x7;
> 347 ruc = (command >> 4) & 0x7;
> 348 DBG(printf("MAIN COMMAND %04x cuc %02x ruc %02x\n", command,
> cuc, ruc));
> 349 /* and clear the scb command word */
> 350 set_uint16(s->scb + 2, 0);
> 351
> >>> CID 1419392: (CONSTANT_EXPRESSION_RESULT)
> >>> "command & (2147483648UL /* 1UL << 31 */)" is always 0 regardless
> of the values of its operands. This occurs as the logical operand of "if".
> 352 if (command & BIT(31)) /* ACK-CX */
> 353 s->scb_status &= ~SCB_STATUS_CX;
> >>> CID 1419392: (CONSTANT_EXPRESSION_RESULT)
> >>> "command & (1073741824UL /* 1UL << 30 */)" is always 0 regardless
> of the values of its operands. This occurs as the logical operand of "if".
> 354 if (command & BIT(30)) /*ACK-FR */
> 355 s->scb_status &= ~SCB_STATUS_FR;
> >>> CID 1419392: (CONSTANT_EXPRESSION_RESULT)
> >>> "command & (536870912UL /* 1UL << 29 */)" is always 0 regardless of
> the values of its operands. This occurs as the logical operand of "if".
> 356 if (command & BIT(29)) /*ACK-CNA */
> 357 s->scb_status &= ~SCB_STATUS_CNA;
> >>> CID 1419392: (CONSTANT_EXPRESSION_RESULT)
> >>> "command & (268435456UL /* 1UL << 28 */)" is always 0 regardless of
> the values of its operands. This occurs as the logical operand of "if".
> 358 if (command & BIT(28)) /*ACK-RNR */
> 359 s->scb_status &= ~SCB_STATUS_RNR;
>
> Fixes: Covertiy CID 1419392 (commit 376b851909)
("Coverity")
> Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Jason, are you planning to pick this one up?
thanks
-- PMM
