Hi all,
We are trying to get Clang's -Wsometimes-uninitialized turned on for the
kernel as it can catch some bugs that GCC can't. This warning came up:
drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:6: warning: variable 'len' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/broadcom/bnxt/bnxt.c:1703:19: note: uninitialized use occurs here
cpr->rx_bytes += len;
^~~
drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:2: note: remove the 'if' if its condition is always false
if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/broadcom/bnxt/bnxt.c:1540:18: note: initialize the variable 'len' to silence this warning
unsigned int len;
^
= 0
1 warning generated.
It seems like the logical change to make is this; however, I am not sure
if this has any other unintended consequences since this is a rather
dense function. I would much appreciate your input, especially if there
is a better way to fix it.
Cheers,
Nathan
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 0bb9d7b3a2b6..7d3d206c2e86 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -1615,7 +1615,7 @@ static int bnxt_rx_pkt(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
bnxt_reuse_rx_agg_bufs(cpr, cp_cons, agg_bufs);
rc = -EIO;
- goto next_rx;
+ goto next_rx_no_prod_no_len;
}
len = le32_to_cpu(rxcmp->rx_cmp_len_flags_type) >> RX_CMP_LEN_SHIFT;
On Thu, Mar 07, 2019 at 05:57:35PM -0700, Nathan Chancellor wrote:
> Hi all,
>
> We are trying to get Clang's -Wsometimes-uninitialized turned on for the
> kernel as it can catch some bugs that GCC can't. This warning came up:
>
> drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:6: warning: variable 'len' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
> if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/broadcom/bnxt/bnxt.c:1703:19: note: uninitialized use occurs here
> cpr->rx_bytes += len;
> ^~~
> drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:2: note: remove the 'if' if its condition is always false
> if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/broadcom/bnxt/bnxt.c:1540:18: note: initialize the variable 'len' to silence this warning
> unsigned int len;
> ^
> = 0
> 1 warning generated.
>
> It seems like the logical change to make is this; however, I am not sure
> if this has any other unintended consequences since this is a rather
> dense function. I would much appreciate your input, especially if there
> is a better way to fix it.
>
> Cheers,
> Nathan
>
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 0bb9d7b3a2b6..7d3d206c2e86 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -1615,7 +1615,7 @@ static int bnxt_rx_pkt(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
> bnxt_reuse_rx_agg_bufs(cpr, cp_cons, agg_bufs);
>
> rc = -EIO;
> - goto next_rx;
> + goto next_rx_no_prod_no_len;
> }
>
> len = le32_to_cpu(rxcmp->rx_cmp_len_flags_type) >> RX_CMP_LEN_SHIFT;
Gentle ping (if there was a response to this, I didn't receive it). I
know I sent it in the middle of a merge window so I get if it slipped
through the cracks.
Thanks,
Nathan
+ Broadcom folks from commit c0c050c58d84 ("bnxt_en: New Broadcom
ethernet driver."). Looks like Michael wrote and is still maintaining
the driver.
On Wed, Mar 20, 2019 at 12:08 PM Nathan Chancellor
<[email protected]> wrote:
>
> On Thu, Mar 07, 2019 at 05:57:35PM -0700, Nathan Chancellor wrote:
> > Hi all,
> >
> > We are trying to get Clang's -Wsometimes-uninitialized turned on for the
> > kernel as it can catch some bugs that GCC can't. This warning came up:
> >
> > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:6: warning: variable 'len' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
> > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1703:19: note: uninitialized use occurs here
> > cpr->rx_bytes += len;
> > ^~~
> > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:2: note: remove the 'if' if its condition is always false
> > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1540:18: note: initialize the variable 'len' to silence this warning
> > unsigned int len;
> > ^
> > = 0
> > 1 warning generated.
> >
> > It seems like the logical change to make is this; however, I am not sure
> > if this has any other unintended consequences since this is a rather
> > dense function. I would much appreciate your input, especially if there
> > is a better way to fix it.
I agree that `goto next_rx_no_prod_no_len` appears to be most correct;
though I don't understand why this function is a mix of early return
codes, vs setting rc then updating *raw_cons. The alternative is
probably zero initializing len, but I'm not sure whether *raw_cons
should be updated in that case or not. Thanks for bringing this up
and the patch. Sorry for the delay in review. Can folks at Broadcom
please clarify?
--
Thanks,
~Nick Desaulniers
On Wed, Mar 20, 2019 at 9:41 PM 'Nick Desaulniers' via Clang Built
Linux <[email protected]> wrote:
>
> + Broadcom folks from commit c0c050c58d84 ("bnxt_en: New Broadcom
> ethernet driver."). Looks like Michael wrote and is still maintaining
> the driver.
>
> On Wed, Mar 20, 2019 at 12:08 PM Nathan Chancellor
> <[email protected]> wrote:
> >
> > On Thu, Mar 07, 2019 at 05:57:35PM -0700, Nathan Chancellor wrote:
> > > Hi all,
> > >
> > > We are trying to get Clang's -Wsometimes-uninitialized turned on for the
> > > kernel as it can catch some bugs that GCC can't. This warning came up:
> > >
> > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:6: warning: variable 'len' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
> > > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1703:19: note: uninitialized use occurs here
> > > cpr->rx_bytes += len;
> > > ^~~
> > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:2: note: remove the 'if' if its condition is always false
> > > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1540:18: note: initialize the variable 'len' to silence this warning
> > > unsigned int len;
> > > ^
> > > = 0
> > > 1 warning generated.
> > >
> > > It seems like the logical change to make is this; however, I am not sure
> > > if this has any other unintended consequences since this is a rather
> > > dense function. I would much appreciate your input, especially if there
> > > is a better way to fix it.
>
> I agree that `goto next_rx_no_prod_no_len` appears to be most correct;
> though I don't understand why this function is a mix of early return
> codes, vs setting rc then updating *raw_cons. The alternative is
> probably zero initializing len, but I'm not sure whether *raw_cons
> should be updated in that case or not. Thanks for bringing this up
> and the patch. Sorry for the delay in review. Can folks at Broadcom
> please clarify?
I also came up with a workaround for this, but did it the other way round:
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 0bb9d7b3a2b6..48bdb87574c3 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -1608,6 +1608,7 @@ static int bnxt_rx_pkt(struct bnxt *bp, struct
bnxt_cp_ring_info *cpr,
}
*event |= BNXT_RX_EVENT;
+ len = le32_to_cpu(rxcmp->rx_cmp_len_flags_type) >> RX_CMP_LEN_SHIFT;
rx_buf->data = NULL;
if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
bnxt_reuse_rx_data(rxr, cons, data);
@@ -1618,7 +1619,6 @@ static int bnxt_rx_pkt(struct bnxt *bp, struct
bnxt_cp_ring_info *cpr,
goto next_rx;
}
- len = le32_to_cpu(rxcmp->rx_cmp_len_flags_type) >> RX_CMP_LEN_SHIFT;
dma_addr = rx_buf->mapping;
if (bnxt_rx_xdp(bp, rxr, cons, data, &data_ptr, &len, event)) {
Presumably one of the two is correct here, but I don't know which one ;-)
Arnd
Hi Arnd,
On Fri, Mar 22, 2019 at 03:32:50PM +0100, Arnd Bergmann wrote:
> On Wed, Mar 20, 2019 at 9:41 PM 'Nick Desaulniers' via Clang Built
> Linux <[email protected]> wrote:
> >
> > + Broadcom folks from commit c0c050c58d84 ("bnxt_en: New Broadcom
> > ethernet driver."). Looks like Michael wrote and is still maintaining
> > the driver.
> >
> > On Wed, Mar 20, 2019 at 12:08 PM Nathan Chancellor
> > <[email protected]> wrote:
> > >
> > > On Thu, Mar 07, 2019 at 05:57:35PM -0700, Nathan Chancellor wrote:
> > > > Hi all,
> > > >
> > > > We are trying to get Clang's -Wsometimes-uninitialized turned on for the
> > > > kernel as it can catch some bugs that GCC can't. This warning came up:
> > > >
> > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:6: warning: variable 'len' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
> > > > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1703:19: note: uninitialized use occurs here
> > > > cpr->rx_bytes += len;
> > > > ^~~
> > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:2: note: remove the 'if' if its condition is always false
> > > > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1540:18: note: initialize the variable 'len' to silence this warning
> > > > unsigned int len;
> > > > ^
> > > > = 0
> > > > 1 warning generated.
> > > >
> > > > It seems like the logical change to make is this; however, I am not sure
> > > > if this has any other unintended consequences since this is a rather
> > > > dense function. I would much appreciate your input, especially if there
> > > > is a better way to fix it.
> >
> > I agree that `goto next_rx_no_prod_no_len` appears to be most correct;
> > though I don't understand why this function is a mix of early return
> > codes, vs setting rc then updating *raw_cons. The alternative is
> > probably zero initializing len, but I'm not sure whether *raw_cons
> > should be updated in that case or not. Thanks for bringing this up
> > and the patch. Sorry for the delay in review. Can folks at Broadcom
> > please clarify?
>
> I also came up with a workaround for this, but did it the other way round:
>
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 0bb9d7b3a2b6..48bdb87574c3 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -1608,6 +1608,7 @@ static int bnxt_rx_pkt(struct bnxt *bp, struct
> bnxt_cp_ring_info *cpr,
> }
> *event |= BNXT_RX_EVENT;
>
> + len = le32_to_cpu(rxcmp->rx_cmp_len_flags_type) >> RX_CMP_LEN_SHIFT;
> rx_buf->data = NULL;
> if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> bnxt_reuse_rx_data(rxr, cons, data);
> @@ -1618,7 +1619,6 @@ static int bnxt_rx_pkt(struct bnxt *bp, struct
> bnxt_cp_ring_info *cpr,
> goto next_rx;
> }
>
> - len = le32_to_cpu(rxcmp->rx_cmp_len_flags_type) >> RX_CMP_LEN_SHIFT;
> dma_addr = rx_buf->mapping;
>
> if (bnxt_rx_xdp(bp, rxr, cons, data, &data_ptr, &len, event)) {
>
> Presumably one of the two is correct here, but I don't know which one ;-)
>
> Arnd
Did you want to submit this a formal patch? Since no one from Broadcom
has chipped in yet, it'd probably be better to submit this for review
and get comments that way. I cannot imagine that this is any worse than
what is currently happening (adding uninitialized stack memory to
rx_bytes when jumping to next_rx) and I like it better than modifying
the goto statement.
This is the only other warning I run into in arm, arm64 and x86_64
all{yes,mod}config so I'd like to get it resolved soon so we can turn on
this warning for the whole kernel.
Cheers,
Nathan
On Thu, Apr 25, 2019 at 11:33:04AM -0700, Michael Chan wrote:
> On Thu, Apr 25, 2019 at 11:14 AM Nathan Chancellor
> <[email protected]> wrote:
> >
> > Hi Arnd,
> >
> > On Fri, Mar 22, 2019 at 03:32:50PM +0100, Arnd Bergmann wrote:
> > > On Wed, Mar 20, 2019 at 9:41 PM 'Nick Desaulniers' via Clang Built
> > > Linux <[email protected]> wrote:
> > > >
> > > > + Broadcom folks from commit c0c050c58d84 ("bnxt_en: New Broadcom
> > > > ethernet driver."). Looks like Michael wrote and is still maintaining
> > > > the driver.
> > > >
> > > > On Wed, Mar 20, 2019 at 12:08 PM Nathan Chancellor
> > > > <[email protected]> wrote:
> > > > >
> > > > > On Thu, Mar 07, 2019 at 05:57:35PM -0700, Nathan Chancellor wrote:
> > > > > > Hi all,
> > > > > >
> > > > > > We are trying to get Clang's -Wsometimes-uninitialized turned on for the
> > > > > > kernel as it can catch some bugs that GCC can't. This warning came up:
> > > > > >
> > > > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:6: warning: variable 'len' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
> > > > > > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > > > > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1703:19: note: uninitialized use occurs here
> > > > > > cpr->rx_bytes += len;
> > > > > > ^~~
> > > > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:2: note: remove the 'if' if its condition is always false
> > > > > > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > > > > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1540:18: note: initialize the variable 'len' to silence this warning
> > > > > > unsigned int len;
> > > > > > ^
> > > > > > = 0
> > > > > > 1 warning generated.
> > > > > >
> > > > > > It seems like the logical change to make is this; however, I am not sure
> > > > > > if this has any other unintended consequences since this is a rather
> > > > > > dense function. I would much appreciate your input, especially if there
> > > > > > is a better way to fix it.
> > > >
> > > > I agree that `goto next_rx_no_prod_no_len` appears to be most correct;
> > > > though I don't understand why this function is a mix of early return
> > > > codes, vs setting rc then updating *raw_cons. The alternative is
> > > > probably zero initializing len, but I'm not sure whether *raw_cons
> > > > should be updated in that case or not. Thanks for bringing this up
> > > > and the patch. Sorry for the delay in review. Can folks at Broadcom
> > > > please clarify?
>
> Sorry, I somehow missed this email earlier. "goto
> next_rx_no_prod_no_len" is the most correct fix. The "cpr->rx_bytes
> += len" logic was added about a year ago when we added the DIM
> (Dynamic Interrupt Moderation) support and we missed fixing this goto.
>
> I can prepare and send the patch later today. Thanks.
Thank you for the reply, I appreciate it! I'll be on the lookout for the
patch.
Cheers,
Nathan
On Thu, Apr 25, 2019 at 11:14 AM Nathan Chancellor
<[email protected]> wrote:
>
> Hi Arnd,
>
> On Fri, Mar 22, 2019 at 03:32:50PM +0100, Arnd Bergmann wrote:
> > On Wed, Mar 20, 2019 at 9:41 PM 'Nick Desaulniers' via Clang Built
> > Linux <[email protected]> wrote:
> > >
> > > + Broadcom folks from commit c0c050c58d84 ("bnxt_en: New Broadcom
> > > ethernet driver."). Looks like Michael wrote and is still maintaining
> > > the driver.
> > >
> > > On Wed, Mar 20, 2019 at 12:08 PM Nathan Chancellor
> > > <[email protected]> wrote:
> > > >
> > > > On Thu, Mar 07, 2019 at 05:57:35PM -0700, Nathan Chancellor wrote:
> > > > > Hi all,
> > > > >
> > > > > We are trying to get Clang's -Wsometimes-uninitialized turned on for the
> > > > > kernel as it can catch some bugs that GCC can't. This warning came up:
> > > > >
> > > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:6: warning: variable 'len' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
> > > > > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > > > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1703:19: note: uninitialized use occurs here
> > > > > cpr->rx_bytes += len;
> > > > > ^~~
> > > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:2: note: remove the 'if' if its condition is always false
> > > > > if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
> > > > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > > drivers/net/ethernet/broadcom/bnxt/bnxt.c:1540:18: note: initialize the variable 'len' to silence this warning
> > > > > unsigned int len;
> > > > > ^
> > > > > = 0
> > > > > 1 warning generated.
> > > > >
> > > > > It seems like the logical change to make is this; however, I am not sure
> > > > > if this has any other unintended consequences since this is a rather
> > > > > dense function. I would much appreciate your input, especially if there
> > > > > is a better way to fix it.
> > >
> > > I agree that `goto next_rx_no_prod_no_len` appears to be most correct;
> > > though I don't understand why this function is a mix of early return
> > > codes, vs setting rc then updating *raw_cons. The alternative is
> > > probably zero initializing len, but I'm not sure whether *raw_cons
> > > should be updated in that case or not. Thanks for bringing this up
> > > and the patch. Sorry for the delay in review. Can folks at Broadcom
> > > please clarify?
Sorry, I somehow missed this email earlier. "goto
next_rx_no_prod_no_len" is the most correct fix. The "cpr->rx_bytes
+= len" logic was added about a year ago when we added the DIM
(Dynamic Interrupt Moderation) support and we missed fixing this goto.
I can prepare and send the patch later today. Thanks.