ACK: [PATCH][SRU][D][V2] UBUNTU: SAUCE: ACPI: sysfs: copy ACPI data using io memory copying

[Andrea Righi]

On Tue, Apr 28, 2020 at 11:48:58AM +0100, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1866772
> 
> Reading ACPI data on ARM64 at a non-aligned offset from
> /sys/firmware/acpi/tables/data/BERT will cause a splat because
> the data is I/O memory mapped and being read with just a memcpy.
> Fix this by introducing an I/O variant of memory_read_from_buffer
> and using I/O memory mapped copies instead.
> 
> Fixes the following splat:
> 
> [  439.789355] Unable to handle kernel paging request at virtual address ffff800041ac0007
> [  439.797275] Mem abort info:
> [  439.800078]   ESR = 0x96000021
> [  439.803131]   EC = 0x25: DABT (current EL), IL = 32 bits
> [  439.808437]   SET = 0, FnV = 0
> [  439.811486]   EA = 0, S1PTW = 0
> [  439.814621] Data abort info:
> [  439.817489]   ISV = 0, ISS = 0x00000021
> [  439.821319]   CM = 0, WnR = 0
> [  439.824282] swapper pgtable: 4k pages, 48-bit VAs, pgdp=00000000817fc000
> [  439.830979] [ffff800041ac0007] pgd=000000bffcfff003, pud=0000009f27cee003, pmd=000000bf4b993003, pte=0068000080280703
> [  439.841584] Internal error: Oops: 96000021 [#1] SMP
> [  439.846449] Modules linked in: nls_iso8859_1 dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua ipmi_ssif input_leds joydev ipmi_devintf ipmi_msghandler thunderx2_pmu sch_fq_codel ip_tables x_tables autofs4 btrfs zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor xor_neon raid6_pq libcrc32c raid1 raid0 multipath linear i2c_smbus ast i2c_algo_bit crct10dif_ce drm_vram_helper uas ttm ghash_ce drm_kms_helper sha2_ce syscopyarea sha256_arm64 qede sysfillrect mpt3sas sha1_ce sysimgblt fb_sys_fops raid_class qed drm scsi_transport_sas usb_storage ahci crc8 gpio_xlp i2c_xlp9xx hid_generic usbhid hid aes_neon_bs aes_neon_blk aes_ce_blk crypto_simd cryptd aes_ce_cipher
> [  439.908474] CPU: 2 PID: 3926 Comm: a.out Not tainted 5.4.0-14-generic #17-Ubuntu
> [  439.915855] Hardware name: To be filled by O.E.M. Saber/Saber, BIOS 0ACKL027 07/01/2019
> [  439.923844] pstate: 80400009 (Nzcv daif +PAN -UAO)
> [  439.928625] pc : __memcpy+0x90/0x180
> [  439.932192] lr : memory_read_from_buffer+0x64/0x88
> [  439.936968] sp : ffff8000350dbc70
> [  439.940270] x29: ffff8000350dbc70 x28: ffff009e9c444b00
> [  439.945568] x27: 0000000000000000 x26: 0000000000000000
> [  439.950866] x25: 0000000056000000 x24: ffff800041ac0000
> [  439.956164] x23: ffff009ea163f980 x22: 0000000000000007
> [  439.961462] x21: ffff8000350dbce8 x20: 000000000000000e
> [  439.966760] x19: 0000000000000007 x18: ffff8000112f64a8
> [  439.972058] x17: 0000000000000000 x16: 0000000000000000
> [  439.977355] x15: 0000000080280000 x14: ffff800041aed000
> [  439.982653] x13: ffff009ee9fa2840 x12: ffff800041ad1000
> [  439.987951] x11: ffff8000115e1360 x10: ffff8000115e1360
> [  439.993248] x9 : 0000000000010000 x8 : ffff800011ad2658
> [  439.998546] x7 : ffff800041ac0000 x6 : ffff009ea163f980
> [  440.003844] x5 : 0140000000000000 x4 : 0000000000010000
> [  440.009141] x3 : ffff800041ac0000 x2 : 0000000000000007
> [  440.014439] x1 : ffff800041ac0007 x0 : ffff009ea163f980
> [  440.019737] Call trace:
> [  440.022173]  __memcpy+0x90/0x180
> [  440.025392]  acpi_data_show+0x54/0x80
> [  440.029044]  sysfs_kf_bin_read+0x6c/0xa8
> [  440.032954]  kernfs_file_direct_read+0x90/0x2d0
> [  440.037470]  kernfs_fop_read+0x68/0x78
> [  440.041210]  __vfs_read+0x48/0x90
> [  440.044511]  vfs_read+0xd0/0x1a0
> [  440.047726]  ksys_read+0x78/0x100
> [  440.051028]  __arm64_sys_read+0x24/0x30
> [  440.054852]  el0_svc_common.constprop.0+0xdc/0x1d8
> [  440.059629]  el0_svc_handler+0x34/0xa0
> [  440.063366]  el0_svc+0x10/0x14
> [  440.066411] Code: 36180062 f8408423 f80084c3 36100062 (b8404423)
> [  440.072492] ---[ end trace 45fb374e8d2d800e ]---
> 
> A simple reproducer is as follows:
> 
> int main(void)
> {
>         int fd;
>         char buffer[7];
>         ssize_t n;
> 
>         fd = open("/sys/firmware/acpi/tables/data/BERT", O_RDONLY);
>         if (fd < 0) {
>                 perror("open failed");
>                 return -1;
>         }
>         do {
>                 n = read(fd, buffer, sizeof(buffer));
>         } while (n > 0);
> 
>         return 0;
> }
> 
> Link: https://bugs.launchpad.net/bugs/1866772
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>

Looks good, thanks!

Acked-by: Andrea Righi <andrea.righi at canonical.com>