| Message ID | 20240911-tzmem-null-ptr-v2-2-7c61b1a1b463@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | firmware: qcom: scm: fix SMC calls on ARM32 | expand |
On Wed, Sep 11, 2024 at 11:07:04AM +0200, Bartosz Golaszewski wrote: > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > > Older platforms don't have an actual SCM device tied into the driver > model and so there's no struct device which to use with the TZ Mem API. > We need to fall-back to kcalloc() when allocating the buffer for > additional SMC arguments on such platforms which don't even probe the SCM > driver and never create the TZMem pool. > > Fixes: 449d0d84bcd8 ("firmware: qcom: scm: smc: switch to using the SCM allocator") > Reported-by: Rudraksha Gupta <guptarud@gmail.com> > Closes: https://lore.kernel.org/lkml/692cfe9a-8c05-4ce4-813e-82b3f310019a@gmail.com/ > Tested-by: Rudraksha Gupta <guptarud@gmail.com> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > --- > drivers/firmware/qcom/qcom_scm-smc.c | 28 ++++++++++++++++++++++++---- > 1 file changed, 24 insertions(+), 4 deletions(-) > > diff --git a/drivers/firmware/qcom/qcom_scm-smc.c b/drivers/firmware/qcom/qcom_scm-smc.c > index 2b4c2826f572..88652c38c9a0 100644 > --- a/drivers/firmware/qcom/qcom_scm-smc.c > +++ b/drivers/firmware/qcom/qcom_scm-smc.c > [...] > @@ -173,9 +182,20 @@ int __scm_smc_call(struct device *dev, const struct qcom_scm_desc *desc, > smc.args[i + SCM_SMC_FIRST_REG_IDX] = desc->args[i]; > > if (unlikely(arglen > SCM_SMC_N_REG_ARGS)) { > - args_virt = qcom_tzmem_alloc(mempool, > - SCM_SMC_N_EXT_ARGS * sizeof(u64), > - flag); > + /* > + * Older platforms don't have an entry for SCM in device-tree > + * and so no device is bound to the SCM driver. This means there > + * is no struct device for the TZ Mem API. Fall back to > + * kcalloc() on such platforms. > + */ > + if (mempool) > + args_virt = qcom_tzmem_alloc( > + mempool, > + SCM_SMC_N_EXT_ARGS * sizeof(u64), > + flag); > + else > + args_virt = kcalloc(SCM_SMC_N_EXT_ARGS, sizeof(u64), > + flag); I'm afraid this won't work. For kcalloc, we would need to flush the cache since it returns cached memory. In v6.10 this was done using the dma_map_single() call that you removed when moving to the tzmem allocator. Actually, taking only the first patch in this series should be enough to fix the crash Rudraksha reported. None of the older platforms should ever reach into this if statement. I think the rough story is: 1. The crash Rudraksha reported happens in qcom_scm_set_cold_boot_addr() during SMP CPU core boot-up. That code runs very early, AFAIK even before the device model is initialized. There is no way to get a device pointer at that point. Even if you add the scm node to DT. 2. AFAIK all the ARM32 platforms without PSCI support implement the legacy calling convention (see qcom_scm-legacy.c). They will only reach qcom_scm-smc.c once during convention detection (see __get_convention()). This is a SCM call with just a single argument that won't go inside the if (unlikely(arglen > SCM_SMC_N_REG_ARGS)). And qcom_scm-legacy.c does not use the tzmem allocator (yet?). 3. qcom_scm-legacy.c does use the device pointer for dma_map_single(), so it already needs a scm node in the DT. I suspect MSM8960 does not hit an error there only because it does not have enough functionality enabled to actually reach a non-atomic SCM call. This means: Whoever adds that functionality should also add the scm node in the DT. It would be good to add explicit checks for the device pointer where needed, instead of crashing. But other than that I think we should be good with just the first patch of this series? Thanks, Stephan
diff --git a/drivers/firmware/qcom/qcom_scm-smc.c b/drivers/firmware/qcom/qcom_scm-smc.c index 2b4c2826f572..88652c38c9a0 100644 --- a/drivers/firmware/qcom/qcom_scm-smc.c +++ b/drivers/firmware/qcom/qcom_scm-smc.c @@ -147,6 +147,15 @@ static int __scm_smc_do(struct device *dev, struct arm_smccc_args *smc, return 0; } +static void smc_args_free(void *ptr) +{ + if (likely(qcom_scm_get_tzmem_pool())) + qcom_tzmem_free(ptr); + else + kfree(ptr); +} + +DEFINE_FREE(smc_args, void *, if (!IS_ERR_OR_NULL(_T)) smc_args_free(_T)); int __scm_smc_call(struct device *dev, const struct qcom_scm_desc *desc, enum qcom_scm_convention qcom_convention, @@ -155,7 +164,7 @@ int __scm_smc_call(struct device *dev, const struct qcom_scm_desc *desc, struct qcom_tzmem_pool *mempool = qcom_scm_get_tzmem_pool(); int arglen = desc->arginfo & 0xf; int i, ret; - void *args_virt __free(qcom_tzmem) = NULL; + void *args_virt __free(smc_args) = NULL; gfp_t flag = atomic ? GFP_ATOMIC : GFP_KERNEL; u32 smccc_call_type = atomic ? ARM_SMCCC_FAST_CALL : ARM_SMCCC_STD_CALL; u32 qcom_smccc_convention = (qcom_convention == SMC_CONVENTION_ARM_32) ? @@ -173,9 +182,20 @@ int __scm_smc_call(struct device *dev, const struct qcom_scm_desc *desc, smc.args[i + SCM_SMC_FIRST_REG_IDX] = desc->args[i]; if (unlikely(arglen > SCM_SMC_N_REG_ARGS)) { - args_virt = qcom_tzmem_alloc(mempool, - SCM_SMC_N_EXT_ARGS * sizeof(u64), - flag); + /* + * Older platforms don't have an entry for SCM in device-tree + * and so no device is bound to the SCM driver. This means there + * is no struct device for the TZ Mem API. Fall back to + * kcalloc() on such platforms. + */ + if (mempool) + args_virt = qcom_tzmem_alloc( + mempool, + SCM_SMC_N_EXT_ARGS * sizeof(u64), + flag); + else + args_virt = kcalloc(SCM_SMC_N_EXT_ARGS, sizeof(u64), + flag); if (!args_virt) return -ENOMEM;