• Chris Wilson's avatar
    drm/i915: Deconstruct struct sgt_dma initialiser · 5684514b
    Chris Wilson authored
    gcc-4.4 complains about:
    
    	struct sgt_dma iter = {
    		.sg = vma->pages->sgl,
    		.dma = sg_dma_address(iter.sg),
    		.max = iter.dma + iter.sg->length,
    	};
    
    drivers/gpu/drm/i915/i915_gem_gtt.c: In function ‘gen8_ppgtt_insert_4lvl’:
    drivers/gpu/drm/i915/i915_gem_gtt.c:938: error: ‘iter.sg’ is used uninitialized in this function
    drivers/gpu/drm/i915/i915_gem_gtt.c:939: error: ‘iter.dma’ is used uninitialized in this function
    
    and worse generates invalid code that triggers a GPF:
    
    BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
    IP: gen8_ppgtt_insert_4lvl+0x1b/0x1e0 [i915]
    PGD 0
    Oops: 0000 [#1] SMP
    Modules linked in: snd_aloop nf_conntrack_ipv6 nf_defrag_ipv6 nf_log_ipv6 ip6table_filter ip6_tables ctr ccm xt_state nf_log_ipv4
    nf_log_common xt_LOG xt_limit xt_recent xt_owner xt_addrtype iptable_filter ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat
    nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack libcrc32c ip_tables dm_mod vhost_net macvtap macvlan vhost tun kvm_intel kvm
    irqbypass uas usb_storage hid_multitouch btusb btrtl uvcvideo videobuf2_v4l2 videobuf2_core videodev media videobuf2_vmalloc videobuf2_memops
    sg ppdev dell_wmi sparse_keymap mei_wdt sd_mod iTCO_wdt iTCO_vendor_support rtsx_pci_ms memstick rtsx_pci_sdmmc mmc_core dell_smm_hwmon hwmon
    dell_laptop dell_smbios dcdbas joydev input_leds hci_uart btintel btqca btbcm bluetooth parport_pc parport i2c_hid
      intel_lpss_acpi intel_lpss pcspkr wmi int3400_thermal acpi_thermal_rel dell_rbtn mei_me mei snd_hda_codec_hdmi snd_hda_codec_realtek
    snd_hda_codec_generic ahci libahci acpi_pad xhci_pci xhci_hcd snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_seq snd_seq_device
    snd_pcm snd_timer snd soundcore int3403_thermal arc4 e1000e ptp pps_core i2c_i801 iwlmvm mac80211 rtsx_pci iwlwifi cfg80211 rfkill
    intel_pch_thermal processor_thermal_device int340x_thermal_zone intel_soc_dts_iosf i915 video fjes
    CPU: 2 PID: 2408 Comm: X Not tainted 4.10.0-rc5+ #1
    Hardware name: Dell Inc. Latitude E7470/0T6HHJ, BIOS 1.11.3 11/09/2016
    task: ffff880219fe4740 task.stack: ffffc90005f98000
    RIP: 0010:gen8_ppgtt_insert_4lvl+0x1b/0x1e0 [i915]
    RSP: 0018:ffffc90005f9b8c8 EFLAGS: 00010246
    RAX: 0000000000000000 RBX: ffff8802167d8000 RCX: 0000000000000001
    RDX: 00000000ffff7000 RSI: ffff880219f94140 RDI: ffff880228444000
    RBP: ffffc90005f9b948 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000080
    R13: 0000000000000001 R14: ffffc90005f9bcd7 R15: ffff88020c9a83c0
    FS:  00007fb53e1ee920(0000) GS:ffff88024dd00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000000000010 CR3: 000000022ef95000 CR4: 00000000003406e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
      ppgtt_bind_vma+0x40/0x50 [i915]
      i915_vma_bind+0xcb/0x1c0 [i915]
      __i915_vma_do_pin+0x6e/0xd0 [i915]
      i915_gem_execbuffer_reserve_vma+0x162/0x1d0 [i915]
      i915_gem_execbuffer_reserve+0x4fc/0x510 [i915]
      ? __kmalloc+0x134/0x250
      ? i915_gem_wait_for_error+0x25/0x100 [i915]
      ? i915_gem_wait_for_error+0x25/0x100 [i915]
      i915_gem_do_execbuffer+0x2df/0xa00 [i915]
      ? drm_malloc_gfp.clone.0+0x42/0x80 [i915]
      ? path_put+0x22/0x30
      ? __check_object_size+0x62/0x1f0
      ? terminate_walk+0x44/0x90
      i915_gem_execbuffer2+0x95/0x1e0 [i915]
      drm_ioctl+0x243/0x490
      ? handle_pte_fault+0x1d7/0x220
      ? i915_gem_do_execbuffer+0xa00/0xa00 [i915]
      ? handle_mm_fault+0x10d/0x2a0
      vfs_ioctl+0x18/0x30
      do_vfs_ioctl+0x14b/0x3f0
      SyS_ioctl+0x92/0xa0
      entry_SYSCALL_64_fastpath+0x1a/0xa9
    RIP: 0033:0x7fb53b4fcb77
    RSP: 002b:00007ffe0c572898 EFLAGS: 00003246 ORIG_RAX: 0000000000000010
    RAX: ffffffffffffffda RBX: 00007fb53e17c038 RCX: 00007fb53b4fcb77
    RDX: 00007ffe0c572900 RSI: 0000000040406469 RDI: 000000000000000b
    RBP: 00007fb5376d67e0 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000028 R11: 0000000000003246 R12: 0000000000000000
    R13: 0000000000000000 R14: 000055eecb314d00 R15: 000055eecb315460
    Code: 0f 84 5d ff ff ff eb a2 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 ec 58 0f 1f 44 00 00 31 c0 89 4d b0 <4c>
    8b 60 10 44 8b 70 0c 48 89 d0 4c 8b 2e 48 c1 e8 27 25 ff 01
    RIP: gen8_ppgtt_insert_4lvl+0x1b/0x1e0 [i915] RSP: ffffc90005f9b8c8
    CR2: 0000000000000010
    
    Recent gccs, such as 4.9, 6.3 or 7.2, do not generate the warning nor do
    they explode on use. If we manually create the struct using locals from
    the stack, this should eliminate this issue, and does not alter code
    generation with gcc-7.2.
    
    Fixes: 894ccebe ("drm/i915: Micro-optimise gen8_ppgtt_insert_entries()")
    Reported-by: default avatarKelly French <kfrench@federalhill.net>
    Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Cc: Kelly French <kfrench@federalhill.net>
    Cc: Mika Kuoppala <mika.kuoppala@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20171106211128.12538-1-chris@chris-wilson.co.ukTested-by: default avatarKelly French <kfrench@federalhill.net>
    Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
    5684514b
i915_gem_gtt.c 105 KB