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? > > > >>> 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. > > 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? > > > >> 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. > > > >>>> 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. > > > >>>> + return -EFAULT; > >>>> + } > >>>> + > >>>> return 0; > >>>> } > >>>> -- With best wishes Dmitry
