linux-hardening - Re: [PATCH v5 08/12] firmware: qcom: tzmem: export shm

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Message-ID: <2455f20c-130c-4f27-9cf4-6411e485b845@quicinc.com>
Date: Tue, 1 Jul 2025 17:17:44 +0530
From: Kuldeep Singh <quic_kuldsing@...cinc.com>
To: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>,
        Jens Wiklander
	<jens.wiklander@...aro.org>,
        Sumit Garg <sumit.garg@...nel.org>,
        "Bjorn
 Andersson" <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Apurupa Pattapu
	<quic_apurupa@...cinc.com>,
        Kees Cook <kees@...nel.org>,
        "Gustavo A. R.
 Silva" <gustavoars@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>
CC: Harshal Dev <quic_hdev@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <op-tee@...ts.trustedfirmware.org>, <linux-kernel@...r.kernel.org>,
        <linux-hardening@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linaro-mm-sig@...ts.linaro.org>, <linux-doc@...r.kernel.org>,
        Neil Armstrong
	<neil.armstrong@...aro.org>
Subject: Re: [PATCH v5 08/12] firmware: qcom: tzmem: export shm_bridge
 create/delete


On 5/27/2025 12:26 PM, Amirreza Zarrabi wrote:
> Anyone with access to contiguous physical memory should be able to
> share memory with QTEE using shm_bridge.
> 
> Tested-by: Neil Armstrong <neil.armstrong@...aro.org>
> Signed-off-by: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>
> ---
>  drivers/firmware/qcom/qcom_tzmem.c       | 57 +++++++++++++++++++++++++-------
>  include/linux/firmware/qcom/qcom_tzmem.h | 15 +++++++++
>  2 files changed, 60 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/firmware/qcom/qcom_tzmem.c b/drivers/firmware/qcom/qcom_tzmem.c
> index 4fe333fd2f07..e9e4f06924ae 100644
> --- a/drivers/firmware/qcom/qcom_tzmem.c
> +++ b/drivers/firmware/qcom/qcom_tzmem.c
> @@ -108,25 +108,61 @@ static int qcom_tzmem_init(void)
>  	return 0;
>  }
>  
> -static int qcom_tzmem_init_area(struct qcom_tzmem_area *area)
> +/**
> + * qcom_tzmem_shm_bridge_create() - Create a SHM bridge.
> + * @paddr: Physical address of the memory to share.
> + * @size: Size of the memory to share.
> + * @handle: Handle to the SHM bridge.
> + *
> + * On platforms that support SHM bridge, this function creates a SHM bridge
> + * for the given memory region with QTEE. The handle returned by this function
> + * must be passed to qcom_tzmem_shm_bridge_delete() to free the SHM bridge.
> + *
> + * Return: On success, returns 0; on failure, returns < 0.
> + */
> +int qcom_tzmem_shm_bridge_create(phys_addr_t paddr, size_t size, u64 *handle)
>  {
>  	u64 pfn_and_ns_perm, ipfn_and_s_perm, size_and_flags;
> -	int ret;
>  
>  	if (!qcom_tzmem_using_shm_bridge)
>  		return 0;
>  
> -	pfn_and_ns_perm = (u64)area->paddr | QCOM_SCM_PERM_RW;
> -	ipfn_and_s_perm = (u64)area->paddr | QCOM_SCM_PERM_RW;
> -	size_and_flags = area->size | (1 << QCOM_SHM_BRIDGE_NUM_VM_SHIFT);
> +	pfn_and_ns_perm = paddr | QCOM_SCM_PERM_RW;
> +	ipfn_and_s_perm = paddr | QCOM_SCM_PERM_RW;
> +	size_and_flags = size | (1 << QCOM_SHM_BRIDGE_NUM_VM_SHIFT);
> +	if (qcom_scm_shm_bridge_create(pfn_and_ns_perm, ipfn_and_s_perm,
> +				       size_and_flags, QCOM_SCM_VMID_HLOS,
> +				       handle))

Can we add a debug log here to ease debugging in future?
Something like this can also work.

pr_err("Shm bridge creation failed, ret: %d, NS PA|Perm: 0x%llx,
size|flags: 0x%llx\n", ret, pfn_and_ns_perm_flags, size_and_flags);

> +		return -EINVAL;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(qcom_tzmem_shm_bridge_create);

-- 
Regards
Kuldeep