On 1/23/2025 4:43 PM, Dmitry Baryshkov wrote: > On Thu, Jan 23, 2025 at 03:19:21PM +0530, Ekansh Gupta wrote: >> >> >> On 1/23/2025 1:18 PM, Dmitry Baryshkov wrote: >>> On Thu, Jan 23, 2025 at 11:16:41AM +0530, Ekansh Gupta wrote: >>>> >>>> On 10/7/2024 7:27 PM, Dmitry Baryshkov wrote: >>>>> On Mon, Oct 07, 2024 at 02:15:15PM GMT, Ekansh Gupta wrote: >>>>>> InvokeV2 request is intended to support multiple enhanced invoke >>>>>> requests like CRC check, performance counter enablement and polling >>>>>> mode for RPC invocations. CRC check is getting enabled as part of >>>>>> this patch. CRC check for input and output argument helps in ensuring >>>>>> data consistency over a remote call. If user intends to enable CRC >>>>>> check, first local user CRC is calculated at user end and a CRC buffer >>>>>> is passed to DSP to capture remote CRC values. DSP is expected to >>>>>> write to the remote CRC buffer which is then compared at user level >>>>>> with the local CRC values. >>>>> This doesn't explain why this is necessary. Why do you need to checksum >>>>> arguments? >>>> This helps if the user suspects any data inconsistencies in the buffers passed to DSP over >>>> remote call. This is not enabled by default and user can enable it as per their reqirement. >>>> I'll add this information. >>> An inconsistency where? Between the kernel and the DSP? Between the user >>> and the DSP? Does it cover buffer contents or just the addresses? >> Inconsistency between user and DSP. crc_user is calculated at user library before >> making ioctl call and it is compared against the crc data which is filled by DSP and >> copied to user. >> This covers inconsistency in buffer contents. > What is the reason for possible inconsistencies? Is it a debugging > feature? This is a debugging feature. Buffer data corruption might result in inconsistency. > >>>>> Also, what if the DSP firmware doesn't support CRC? How should userspace >>>>> know that? >>>> CRC support on DSP is there since long time(>6years). >>> This doesn't give us a lot. Upstream kernel supports fastrpc since >>> MSM8916 and MSM8996. Do those platforms support CRC? >> The metadata buffer as of today also carries space for CRC information: >> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/misc/fastrpc.c#n877 >> >> So this is common across all platforms. >> >> In case CRC is not supported on any older platform, it would result in crc mismatch at user library. >> As of now a warning is getting logged there, I can add the information suggesting the failure might >> also occur if CRC is not supported. > Logs go to /dev/null, they are ignored by users, etc. So either there > should be an actual error being returned by the kernel / library, or it > can be completely ignored and skipped. > > So, do MSM8916 / MSM8996 / SDM845 support CRC? If not, that must be > handled somehow. I see it's supported on SDM845 but not on MSM89##. I'll just send the new patch version for now as CRC mismatch failures are getting ignored. > >>> And if they do, why do we need the invoke_v2? Can we modify existing >>> code instead? >> invoke_v2 is needed because there is a need to pass user crc pointer over ioctl call which >> cannot be achieved using existing code. Also there are plans to add more features to this >> invoke_v2 request which will carry some information from user. > Is it really extensible without breaking the ABI? I'm planning to keep reserved bits in uapi struct for the same. Do you see any problem with this? >>>> From user space CRC check failure is >>>> not fatal and is printed as a warning. But if copy of CRC to user fails, it will result in remote >>>> call failure. Should I keep it as fatal considering that ever very old DSP support this or should >>>> I consider the copy failure as non-fatal as userspace is treating this as a warning? >>> warnings can remain unseen for a long time. Consider a GUI app. Nobody >>> is there to view kernel warnings or library output. >> Let me see if this can be done. Are you suggesting that the app will be somewhat tracking >> if there is any crc check mismatch failures? > I suggest returning -EIO to the app. I'll check this. > >>>>>> Signed-off-by: Ekansh Gupta <quic_ekangupt@xxxxxxxxxxx> >>>>>> --- >>>>>> drivers/misc/fastrpc.c | 161 ++++++++++++++++++++++++------------ >>>>>> include/uapi/misc/fastrpc.h | 7 ++ >>>>>> 2 files changed, 116 insertions(+), 52 deletions(-) >>>>>> >>>>>> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c >>>>>> index 74181b8c386b..8e817a763d1d 100644 >>>>>> --- a/drivers/misc/fastrpc.c >>>>>> +++ b/drivers/misc/fastrpc.c >>>>>> @@ -573,13 +573,15 @@ static void fastrpc_get_buff_overlaps(struct fastrpc_invoke_ctx *ctx) >>>>>> >>>>>> static struct fastrpc_invoke_ctx *fastrpc_context_alloc( >>>>>> struct fastrpc_user *user, u32 kernel, u32 sc, >>>>>> - struct fastrpc_invoke_args *args) >>>>>> + struct fastrpc_invoke_v2 *inv2) >>>>>> { >>>>>> struct fastrpc_channel_ctx *cctx = user->cctx; >>>>>> struct fastrpc_invoke_ctx *ctx = NULL; >>>>>> + struct fastrpc_invoke_args *args = NULL; >>>>> Why do you need to init to NULL if you are going to set it two lines >>>>> below? >>>>> >>>>>> unsigned long flags; >>>>>> int ret; >>>>>> >>>>>> + args = (struct fastrpc_invoke_args *)inv2->inv.args; >>>>> Why does it need a typecast? >>>>> >>>>>> ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); >>>>>> if (!ctx) >>>>>> return ERR_PTR(-ENOMEM); >>>>>> @@ -611,6 +613,7 @@ static struct fastrpc_invoke_ctx *fastrpc_context_alloc( >>>>>> /* Released in fastrpc_context_put() */ >>>>>> fastrpc_channel_ctx_get(cctx); >>>>>> >>>>>> + ctx->crc = (u32 *)(uintptr_t)inv2->crc; >>>>> Oh, but why? Also is it a user pointer or in-kernel data? If it's a >>>>> user-based pointer, where is the accessiblity check? Why isn't it >>>>> annotated properly? >>>> This is a user pointer where the crc data is expected to be copied. There is no >>>> other access to this pointer from kernel. I'm planning to change the data type >>>> for crc as (void __user*) inside fastrpc_invoke_ctx structure. >>> Yes, please. Also make sure that sparse doesn't add any warnings >>> regarding pointer conversions. >> Ack. >>>>>> ctx->sc = sc; >>>>>> ctx->retval = -1; >>>>>> ctx->pid = current->pid; >>>>>> @@ -1070,6 +1073,7 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx, >>>>>> struct fastrpc_invoke_buf *list; >>>>>> struct fastrpc_phy_page *pages; >>>>>> u64 *fdlist; >>>>>> + u32 *crclist; >>>>>> int i, inbufs, outbufs, handles; >>>>>> >>>>>> inbufs = REMOTE_SCALARS_INBUFS(ctx->sc); >>>>>> @@ -1078,6 +1082,7 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx, >>>>>> list = fastrpc_invoke_buf_start(rpra, ctx->nscalars); >>>>>> pages = fastrpc_phy_page_start(list, ctx->nscalars); >>>>>> fdlist = (uint64_t *)(pages + inbufs + outbufs + handles); >>>>>> + crclist = (u32 *)(fdlist + FASTRPC_MAX_FDLIST); >>>>> I think we should rewrite this parsing somehow. Is the format of data >>>>> documented somewhere? >>>> fdlist, crclist and poll(planned) are the only pointers that is being used. I'm planning >>>> to store these pointers to ctx structure and directly use it wherever needed. This will >>>> clean-up this unnecessary calculations at multiple places. >>> Please do. Nevertheless, the format also must be documented. >> Ack. >>>>>> >>>>>> for (i = inbufs; i < ctx->nbufs; ++i) { >>>>>> if (!ctx->maps[i]) { >>>>>> @@ -1102,6 +1107,12 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx, >>>>>> fastrpc_map_put(mmap); >>>>>> } >>>>>> >>>>>> + if (ctx->crc && crclist && rpra) { >>>>>> + if (copy_to_user((void __user *)ctx->crc, crclist, >>>>>> + FASTRPC_MAX_CRCLIST * sizeof(u32))) >>>>> Oh, so it's a user pointer. Then u32* was completely incorrect. >>>>> Also you are copying FASTRPC_MAX_CRCLIST elements. Are all of them >>>>> filled? Or are we leaking some data to userspace? >>>> Yes, right. Planning clean-up in next patch. >>>> >>>> All of FASTRPC_MAX_CRCLIST is filled with crc data by DSP so copying should be fine. >>> Huh? I definitely want to see documentation for function arguments. >> Sure. I'll also modify the metadata layout doc here to add fdlist, CRC and other planned contents. >> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/misc/fastrpc.c#n842 > This is not a documentation. E.g. I can not write code using that > description. For example, it mentions neither FDLIST nor CRC. I'm planning to add complete documentation for CRC and polling mode in user library project. If I need to add documentation in driver, can you pls suggest what is the right place to add the information? Thanks for your comments. --ekansh > >>>>>> + return -EFAULT; >>>>>> + } >>>>>> + >>>>>> return 0; >>>>>> } >>>>>>
