| Message ID | faa40e6b31ecc9387ad1644bb1957aa53d7c682f.1668814746.git.gustavoars@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | scsi: qla2xxx: Replace one-element array with flexible-array member | expand |
On Fri, Nov 18, 2022 at 05:47:13PM -0600, Gustavo A. R. Silva wrote: > One-element arrays as fake flex arrays are deprecated and we are moving > towards adopting C99 flexible-array members, instead. So, replace > one-element array declaration in struct ct_sns_gpnft_rsp, which is > ultimately being used inside a union: > > drivers/scsi/qla2xxx/qla_def.h: > 3240 struct ct_sns_gpnft_pkt { > 3241 union { > 3242 struct ct_sns_req req; > 3243 struct ct_sns_gpnft_rsp rsp; > 3244 } p; > 3245 }; > > Important to mention is that doing a build before/after this patch results > in no binary differences. > > This help us make progress towards globally enabling > -fstrict-flex-arrays=3 [1]. > > Link: https://github.com/KSPP/linux/issues/245 > Link: https://github.com/KSPP/linux/issues/193 > Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1] > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org>
Le 19/11/2022 à 00:47, Gustavo A. R. Silva a écrit : > One-element arrays as fake flex arrays are deprecated and we are moving > towards adopting C99 flexible-array members, instead. So, replace > one-element array declaration in struct ct_sns_gpnft_rsp, which is > ultimately being used inside a union: > > drivers/scsi/qla2xxx/qla_def.h: > 3240 struct ct_sns_gpnft_pkt { > 3241 union { > 3242 struct ct_sns_req req; > 3243 struct ct_sns_gpnft_rsp rsp; > 3244 } p; > 3245 }; > > Important to mention is that doing a build before/after this patch results > in no binary differences. Hi, even with the: > rspsz = sizeof(struct ct_sns_gpnft_rsp) + > - ((vha->hw->max_fibre_devices - 1) * > + (vha->hw->max_fibre_devices * > sizeof(struct ct_sns_gpn_ft_data)); change ? CJ > > This help us make progress towards globally enabling > -fstrict-flex-arrays=3 [1]. > > Link: https://github.com/KSPP/linux/issues/245 > Link: https://github.com/KSPP/linux/issues/193 > Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1] > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > --- > drivers/scsi/qla2xxx/qla_def.h | 4 ++-- > drivers/scsi/qla2xxx/qla_gs.c | 2 +- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/scsi/qla2xxx/qla_def.h b/drivers/scsi/qla2xxx/qla_def.h > index a26a373be9da..1eea977ef426 100644 > --- a/drivers/scsi/qla2xxx/qla_def.h > +++ b/drivers/scsi/qla2xxx/qla_def.h > @@ -3151,12 +3151,12 @@ struct ct_sns_gpnft_rsp { > uint8_t vendor_unique; > }; > /* Assume the largest number of targets for the union */ > - struct ct_sns_gpn_ft_data { > + DECLARE_FLEX_ARRAY(struct ct_sns_gpn_ft_data { > u8 control_byte; > u8 port_id[3]; > u32 reserved; > u8 port_name[8]; > - } entries[1]; > + }, entries); > }; > > /* CT command response */ > diff --git a/drivers/scsi/qla2xxx/qla_gs.c b/drivers/scsi/qla2xxx/qla_gs.c > index 64ab070b8716..69d3bc795f90 100644 > --- a/drivers/scsi/qla2xxx/qla_gs.c > +++ b/drivers/scsi/qla2xxx/qla_gs.c > @@ -4073,7 +4073,7 @@ int qla24xx_async_gpnft(scsi_qla_host_t *vha, u8 fc4_type, srb_t *sp) > sp->u.iocb_cmd.u.ctarg.req_size = GPN_FT_REQ_SIZE; > > rspsz = sizeof(struct ct_sns_gpnft_rsp) + > - ((vha->hw->max_fibre_devices - 1) * > + (vha->hw->max_fibre_devices * > sizeof(struct ct_sns_gpn_ft_data)); > > sp->u.iocb_cmd.u.ctarg.rsp = dma_alloc_coherent(&vha->hw->pdev->dev,
On Sat, Nov 19, 2022 at 09:44:02AM +0100, Christophe JAILLET wrote: > Le 19/11/2022 à 00:47, Gustavo A. R. Silva a écrit : > > One-element arrays as fake flex arrays are deprecated and we are moving > > towards adopting C99 flexible-array members, instead. So, replace > > one-element array declaration in struct ct_sns_gpnft_rsp, which is > > ultimately being used inside a union: > > > > drivers/scsi/qla2xxx/qla_def.h: > > 3240 struct ct_sns_gpnft_pkt { > > 3241 union { > > 3242 struct ct_sns_req req; > > 3243 struct ct_sns_gpnft_rsp rsp; > > 3244 } p; > > 3245 }; > > > > Important to mention is that doing a build before/after this patch results > > in no binary differences. > > Hi, > > even with the: > > > rspsz = sizeof(struct ct_sns_gpnft_rsp) + > > - ((vha->hw->max_fibre_devices - 1) * > > + (vha->hw->max_fibre_devices * > > sizeof(struct ct_sns_gpn_ft_data)); > > change ? Yep; that change compensates for the removal of the 1 in the declaration of entries[]. The above piece of code is a common idiom to calculate the size for an allocation when a one-element array is involved. In the original code (vha->hw->max_fibre_devices - 1) compensates for the _extra_ size of one element of type struct ct_sns_gpn_ft_data in sizeof(struct ct_sns_gpnft_rsp). -- Gustavo > > CJ > > > > > This help us make progress towards globally enabling > > -fstrict-flex-arrays=3 [1]. > > > > Link: https://github.com/KSPP/linux/issues/245 > > Link: https://github.com/KSPP/linux/issues/193 > > Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1] > > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > > --- > > drivers/scsi/qla2xxx/qla_def.h | 4 ++-- > > drivers/scsi/qla2xxx/qla_gs.c | 2 +- > > 2 files changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/scsi/qla2xxx/qla_def.h b/drivers/scsi/qla2xxx/qla_def.h > > index a26a373be9da..1eea977ef426 100644 > > --- a/drivers/scsi/qla2xxx/qla_def.h > > +++ b/drivers/scsi/qla2xxx/qla_def.h > > @@ -3151,12 +3151,12 @@ struct ct_sns_gpnft_rsp { > > uint8_t vendor_unique; > > }; > > /* Assume the largest number of targets for the union */ > > - struct ct_sns_gpn_ft_data { > > + DECLARE_FLEX_ARRAY(struct ct_sns_gpn_ft_data { > > u8 control_byte; > > u8 port_id[3]; > > u32 reserved; > > u8 port_name[8]; > > - } entries[1]; > > + }, entries); > > }; > > /* CT command response */ > > diff --git a/drivers/scsi/qla2xxx/qla_gs.c b/drivers/scsi/qla2xxx/qla_gs.c > > index 64ab070b8716..69d3bc795f90 100644 > > --- a/drivers/scsi/qla2xxx/qla_gs.c > > +++ b/drivers/scsi/qla2xxx/qla_gs.c > > @@ -4073,7 +4073,7 @@ int qla24xx_async_gpnft(scsi_qla_host_t *vha, u8 fc4_type, srb_t *sp) > > sp->u.iocb_cmd.u.ctarg.req_size = GPN_FT_REQ_SIZE; > > rspsz = sizeof(struct ct_sns_gpnft_rsp) + > > - ((vha->hw->max_fibre_devices - 1) * > > + (vha->hw->max_fibre_devices * > > sizeof(struct ct_sns_gpn_ft_data)); > > sp->u.iocb_cmd.u.ctarg.rsp = dma_alloc_coherent(&vha->hw->pdev->dev, >
Le 19/11/2022 à 09:56, Gustavo A. R. Silva a écrit : > On Sat, Nov 19, 2022 at 09:44:02AM +0100, Christophe JAILLET wrote: >> Le 19/11/2022 à 00:47, Gustavo A. R. Silva a écrit : >>> One-element arrays as fake flex arrays are deprecated and we are moving >>> towards adopting C99 flexible-array members, instead. So, replace >>> one-element array declaration in struct ct_sns_gpnft_rsp, which is >>> ultimately being used inside a union: >>> >>> drivers/scsi/qla2xxx/qla_def.h: >>> 3240 struct ct_sns_gpnft_pkt { >>> 3241 union { >>> 3242 struct ct_sns_req req; >>> 3243 struct ct_sns_gpnft_rsp rsp; >>> 3244 } p; >>> 3245 }; >>> >>> Important to mention is that doing a build before/after this patch results >>> in no binary differences. >> >> Hi, >> >> even with the: >> >>> rspsz = sizeof(struct ct_sns_gpnft_rsp) + >>> - ((vha->hw->max_fibre_devices - 1) * >>> + (vha->hw->max_fibre_devices * >>> sizeof(struct ct_sns_gpn_ft_data)); >> >> change ? > > Yep; that change compensates for the removal of the 1 in the declaration > of entries[]. > > The above piece of code is a common idiom to calculate the size for an > allocation when a one-element array is involved. In the original code > (vha->hw->max_fibre_devices - 1) compensates for the _extra_ size of one > element of type struct ct_sns_gpn_ft_data in sizeof(struct ct_sns_gpnft_rsp). > Yes, I do agree, that the code is equivalent. I was surprised that a compiler was smart enough to generate the same binary code. With gcc 11.3.0 (x86_64), I do get some differences when I do: make drivers/scsi/qla2xxx/qla_gs.o objdump -D drivers/scsi/qla2xxx/qla_gs.o > before.asm patch -p1 < patch.diff make drivers/scsi/qla2xxx/qla_gs.o objdump -D drivers/scsi/qla2xxx/qla_gs.o > after.asm diff -u before.asm after.asm Mostly some slight ordering of instruction changes, but the binary are not the same. CJ > -- > Gustavo > >> >> CJ >> >>> >>> This help us make progress towards globally enabling >>> -fstrict-flex-arrays=3 [1]. >>> >>> Link: https://github.com/KSPP/linux/issues/245 >>> Link: https://github.com/KSPP/linux/issues/193 >>> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1] >>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> >>> --- >>> drivers/scsi/qla2xxx/qla_def.h | 4 ++-- >>> drivers/scsi/qla2xxx/qla_gs.c | 2 +- >>> 2 files changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/scsi/qla2xxx/qla_def.h b/drivers/scsi/qla2xxx/qla_def.h >>> index a26a373be9da..1eea977ef426 100644 >>> --- a/drivers/scsi/qla2xxx/qla_def.h >>> +++ b/drivers/scsi/qla2xxx/qla_def.h >>> @@ -3151,12 +3151,12 @@ struct ct_sns_gpnft_rsp { >>> uint8_t vendor_unique; >>> }; >>> /* Assume the largest number of targets for the union */ >>> - struct ct_sns_gpn_ft_data { >>> + DECLARE_FLEX_ARRAY(struct ct_sns_gpn_ft_data { >>> u8 control_byte; >>> u8 port_id[3]; >>> u32 reserved; >>> u8 port_name[8]; >>> - } entries[1]; >>> + }, entries); >>> }; >>> /* CT command response */ >>> diff --git a/drivers/scsi/qla2xxx/qla_gs.c b/drivers/scsi/qla2xxx/qla_gs.c >>> index 64ab070b8716..69d3bc795f90 100644 >>> --- a/drivers/scsi/qla2xxx/qla_gs.c >>> +++ b/drivers/scsi/qla2xxx/qla_gs.c >>> @@ -4073,7 +4073,7 @@ int qla24xx_async_gpnft(scsi_qla_host_t *vha, u8 fc4_type, srb_t *sp) >>> sp->u.iocb_cmd.u.ctarg.req_size = GPN_FT_REQ_SIZE; >>> rspsz = sizeof(struct ct_sns_gpnft_rsp) + >>> - ((vha->hw->max_fibre_devices - 1) * >>> + (vha->hw->max_fibre_devices * >>> sizeof(struct ct_sns_gpn_ft_data)); >>> sp->u.iocb_cmd.u.ctarg.rsp = dma_alloc_coherent(&vha->hw->pdev->dev, >> >
> Yes, I do agree, that the code is equivalent. I was surprised that a > compiler was smart enough to generate the same binary code. We discard the tiny changes that don't affect the logic or the control flow of the program. -- Gustavo
diff --git a/drivers/scsi/qla2xxx/qla_def.h b/drivers/scsi/qla2xxx/qla_def.h index a26a373be9da..1eea977ef426 100644 --- a/drivers/scsi/qla2xxx/qla_def.h +++ b/drivers/scsi/qla2xxx/qla_def.h @@ -3151,12 +3151,12 @@ struct ct_sns_gpnft_rsp { uint8_t vendor_unique; }; /* Assume the largest number of targets for the union */ - struct ct_sns_gpn_ft_data { + DECLARE_FLEX_ARRAY(struct ct_sns_gpn_ft_data { u8 control_byte; u8 port_id[3]; u32 reserved; u8 port_name[8]; - } entries[1]; + }, entries); }; /* CT command response */ diff --git a/drivers/scsi/qla2xxx/qla_gs.c b/drivers/scsi/qla2xxx/qla_gs.c index 64ab070b8716..69d3bc795f90 100644 --- a/drivers/scsi/qla2xxx/qla_gs.c +++ b/drivers/scsi/qla2xxx/qla_gs.c @@ -4073,7 +4073,7 @@ int qla24xx_async_gpnft(scsi_qla_host_t *vha, u8 fc4_type, srb_t *sp) sp->u.iocb_cmd.u.ctarg.req_size = GPN_FT_REQ_SIZE; rspsz = sizeof(struct ct_sns_gpnft_rsp) + - ((vha->hw->max_fibre_devices - 1) * + (vha->hw->max_fibre_devices * sizeof(struct ct_sns_gpn_ft_data)); sp->u.iocb_cmd.u.ctarg.rsp = dma_alloc_coherent(&vha->hw->pdev->dev,
One-element arrays as fake flex arrays are deprecated and we are moving towards adopting C99 flexible-array members, instead. So, replace one-element array declaration in struct ct_sns_gpnft_rsp, which is ultimately being used inside a union: drivers/scsi/qla2xxx/qla_def.h: 3240 struct ct_sns_gpnft_pkt { 3241 union { 3242 struct ct_sns_req req; 3243 struct ct_sns_gpnft_rsp rsp; 3244 } p; 3245 }; Important to mention is that doing a build before/after this patch results in no binary differences. This help us make progress towards globally enabling -fstrict-flex-arrays=3 [1]. Link: https://github.com/KSPP/linux/issues/245 Link: https://github.com/KSPP/linux/issues/193 Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1] Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- drivers/scsi/qla2xxx/qla_def.h | 4 ++-- drivers/scsi/qla2xxx/qla_gs.c | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-)