From: Shyam Sundar S K Date: Tue, 10 Oct 2023 14:50:02 +0000 (+0530) Subject: platform/x86/amd/pmc: Handle overflow cases where the num_samples range is higher X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b136225746a9793bdff9c78b215eac4f64bf21f2;p=linux.git platform/x86/amd/pmc: Handle overflow cases where the num_samples range is higher In amd_pmc_stb_debugfs_open_v2(), the stb buffer is created based on the num_samples and the read/write pointer offset. This holds good when the num_samples reported by PMFW is less than S2D_TELEMETRY_BYTES_MAX; where the stb buffer gets filled from 0th position until S2D_TELEMETRY_BYTES_MAX - 1 based on the read/write pointer offset. But when the num_samples exceeds the S2D_TELEMETRY_BYTES_MAX, the current code does not handle it well as it does not account for the cases where the stb buffer has to filled up as a circular buffer. Handle this scenario into two cases, where first memcpy will have the samples from location: (num_samples % S2D_TELEMETRY_BYTES_MAX) - (S2D_TELEMETRY_BYTES_MAX - 1) and next memcpy will have the newest ones i.e. 0 - (num_samples % S2D_TELEMETRY_BYTES_MAX - 1) Suggested-by: Hans de Goede Reviewed-by: Hans de Goede Signed-off-by: Sanket Goswami Signed-off-by: Shyam Sundar S K Link: https://lore.kernel.org/r/20231010145003.139932-2-Shyam-sundar.S-k@amd.com [ij: renamed flex_arr -> stb_data_arr] Reviewed-by: Ilpo Järvinen Signed-off-by: Ilpo Järvinen --- diff --git a/drivers/platform/x86/amd/pmc/pmc.c b/drivers/platform/x86/amd/pmc/pmc.c index 77dca9a1f00f5..bc254e1fa71a5 100644 --- a/drivers/platform/x86/amd/pmc/pmc.c +++ b/drivers/platform/x86/amd/pmc/pmc.c @@ -276,16 +276,23 @@ static int amd_pmc_stb_debugfs_open_v2(struct inode *inode, struct file *filp) stb_data_arr->size = fsize; - /* Start capturing data from the last push location */ + /* + * Start capturing data from the last push location. + * This is for general cases, where the stb limits + * are meant for standard usage. + */ if (num_samples > S2D_TELEMETRY_BYTES_MAX) { - fsize = S2D_TELEMETRY_BYTES_MAX; - stb_rdptr_offset = num_samples - fsize; + /* First read oldest data starting 1 behind last write till end of ringbuffer */ + stb_rdptr_offset = num_samples % S2D_TELEMETRY_BYTES_MAX; + fsize = S2D_TELEMETRY_BYTES_MAX - stb_rdptr_offset; + + memcpy_fromio(stb_data_arr->data, dev->stb_virt_addr + stb_rdptr_offset, fsize); + /* Second copy the newer samples from offset 0 - last write */ + memcpy_fromio(stb_data_arr->data + fsize, dev->stb_virt_addr, stb_rdptr_offset); } else { - fsize = num_samples; - stb_rdptr_offset = 0; + memcpy_fromio(stb_data_arr->data, dev->stb_virt_addr, fsize); } - memcpy_fromio(stb_data_arr->data, dev->stb_virt_addr + stb_rdptr_offset, fsize); filp->private_data = stb_data_arr; return 0;