LoongArch: BPF: Don't sign extend function return value
[ Upstream commit 5d47ec2e ] The `cls_redirect` test triggers a kernel panic like: # ./test_progs -t cls_redirect Can't find bpf_testmod.ko kernel module: -2 WARNING! Selftests relying on bpf_testmod.ko will be skipped. [ 30.938489] CPU 3 Unable to handle kernel paging request at virtual address fffffffffd814de0, era == ffff800002009fb8, ra == ffff800002009f9c [ 30.939331] Oops[#1]: [ 30.939513] CPU: 3 PID: 1260 Comm: test_progs Not tainted 6.7.0-rc2-loong-devel-g2f56bb0d2327 #35 a896aca3f4164f09cc346f89f2e09832e07be5f6 [ 30.939732] Hardware name: QEMU QEMU Virtual Machine, BIOS unknown 2/2/2022 [ 30.939901] pc ffff800002009fb8 ra ffff800002009f9c tp 9000000104da4000 sp 9000000104da7ab0 [ 30.940038] a0 fffffffffd814de0 a1 9000000104da7a68 a2 0000000000000000 a3 9000000104da7c10 [ 30.940183] a4 9000000104da7c14 a5 0000000000000002 a6 0000000000000021 a7 00005555904d7f90 [ 30.940321] t0 0000000000000110 t1 0000000000000000 t2 fffffffffd814de0 t3 0004c4b400000000 [ 30.940456] t4 ffffffffffffffff t5 00000000c3f63600 t6 0000000000000000 t7 0000000000000000 [ 30.940590] t8 000000000006d803 u0 0000000000000020 s9 9000000104da7b10 s0 900000010504c200 [ 30.940727] s1 fffffffffd814de0 s2 900000010504c200 s3 9000000104da7c10 s4 9000000104da7ad0 [ 30.940866] s5 0000000000000000 s6 90000000030e65bc s7 9000000104da7b44 s8 90000000044f6fc0 [ 30.941015] ra: ffff800002009f9c bpf_prog_846803e5ae81417f_cls_redirect+0xa0/0x590 [ 30.941535] ERA: ffff800002009fb8 bpf_prog_846803e5ae81417f_cls_redirect+0xbc/0x590 [ 30.941696] CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) [ 30.942224] PRMD: 00000004 (PPLV0 +PIE -PWE) [ 30.942330] EUEN: 00000003 (+FPE +SXE -ASXE -BTE) [ 30.942453] ECFG: 00071c1c (LIE=2-4,10-12 VS=7) [ 30.942612] ESTAT: 00010000 [PIL] (IS= ECode=1 EsubCode=0) [ 30.942764] BADV: fffffffffd814de0 [ 30.942854] PRID: 0014c010 (Loongson-64bit, Loongson-3A5000) [ 30.942974] Modules linked in: [ 30.943078] Process test_progs (pid: 1260, threadinfo=00000000ce303226, task=000000007d10bb76) [ 30.943306] Stack : 900000010a064000 90000000044f6fc0 9000000104da7b48 0000000000000000 [ 30.943495] 0000000000000000 9000000104da7c14 9000000104da7c10 900000010504c200 [ 30.943626] 0000000000000001 ffff80001b88c000 9000000104da7b70 90000000030e6668 [ 30.943785] 0000000000000000 9000000104da7b58 ffff80001b88c048 9000000003d05000 [ 30.943936] 900000000303ac88 0000000000000000 0000000000000000 9000000104da7b70 [ 30.944091] 0000000000000000 0000000000000001 0000000731eeab00 0000000000000000 [ 30.944245] ffff80001b88c000 0000000000000000 0000000000000000 54b99959429f83b8 [ 30.944402] ffff80001b88c000 90000000044f6fc0 9000000101d70000 ffff80001b88c000 [ 30.944538] 000000000000005a 900000010504c200 900000010a064000 900000010a067000 [ 30.944697] 9000000104da7d88 0000000000000000 9000000003d05000 90000000030e794c [ 30.944852] ... [ 30.944924] Call Trace: [ 30.945120] [<ffff800002009fb8>] bpf_prog_846803e5ae81417f_cls_redirect+0xbc/0x590 [ 30.945650] [<90000000030e6668>] bpf_test_run+0x1ec/0x2f8 [ 30.945958] [<90000000030e794c>] bpf_prog_test_run_skb+0x31c/0x684 [ 30.946065] [<90000000026d4f68>] __sys_bpf+0x678/0x2724 [ 30.946159] [<90000000026d7288>] sys_bpf+0x20/0x2c [ 30.946253] [<90000000032dd224>] do_syscall+0x7c/0x94 [ 30.946343] [<9000000002541c5c>] handle_syscall+0xbc/0x158 [ 30.946492] [ 30.946549] Code: 0015030e 5c0009c0 5001d000 <28c00304> 02c00484 29c00304 00150009 2a42d2e4 0280200d [ 30.946793] [ 30.946971] ---[ end trace 0000000000000000 ]--- [ 32.093225] Kernel panic - not syncing: Fatal exception in interrupt [ 32.093526] Kernel relocated by 0x2320000 [ 32.093630] .text @ 0x9000000002520000 [ 32.093725] .data @ 0x9000000003400000 [ 32.093792] .bss @ 0x9000000004413200 [ 34.971998] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]--- This is because we signed-extend function return values. When subprog mode is enabled, we have: cls_redirect() -> get_global_metrics() returns pcpu ptr 0xfffffefffc00b480 The pointer returned is later signed-extended to 0xfffffffffc00b480 at `BPF_JMP | BPF_EXIT`. During BPF prog run, this triggers unhandled page fault and a kernel panic. Drop the unnecessary signed-extension on return values like other architectures do. With this change, we have: # ./test_progs -t cls_redirect Can't find bpf_testmod.ko kernel module: -2 WARNING! Selftests relying on bpf_testmod.ko will be skipped. #51/1 cls_redirect/cls_redirect_inlined:OK #51/2 cls_redirect/IPv4 TCP accept unknown (no hops, flags: SYN):OK #51/3 cls_redirect/IPv6 TCP accept unknown (no hops, flags: SYN):OK #51/4 cls_redirect/IPv4 TCP accept unknown (no hops, flags: ACK):OK #51/5 cls_redirect/IPv6 TCP accept unknown (no hops, flags: ACK):OK #51/6 cls_redirect/IPv4 TCP forward unknown (one hop, flags: ACK):OK #51/7 cls_redirect/IPv6 TCP forward unknown (one hop, flags: ACK):OK #51/8 cls_redirect/IPv4 TCP accept known (one hop, flags: ACK):OK #51/9 cls_redirect/IPv6 TCP accept known (one hop, flags: ACK):OK #51/10 cls_redirect/IPv4 UDP accept unknown (no hops, flags: none):OK #51/11 cls_redirect/IPv6 UDP accept unknown (no hops, flags: none):OK #51/12 cls_redirect/IPv4 UDP forward unknown (one hop, flags: none):OK #51/13 cls_redirect/IPv6 UDP forward unknown (one hop, flags: none):OK #51/14 cls_redirect/IPv4 UDP accept known (one hop, flags: none):OK #51/15 cls_redirect/IPv6 UDP accept known (one hop, flags: none):OK #51/16 cls_redirect/cls_redirect_subprogs:OK #51/17 cls_redirect/IPv4 TCP accept unknown (no hops, flags: SYN):OK #51/18 cls_redirect/IPv6 TCP accept unknown (no hops, flags: SYN):OK #51/19 cls_redirect/IPv4 TCP accept unknown (no hops, flags: ACK):OK #51/20 cls_redirect/IPv6 TCP accept unknown (no hops, flags: ACK):OK #51/21 cls_redirect/IPv4 TCP forward unknown (one hop, flags: ACK):OK #51/22 cls_redirect/IPv6 TCP forward unknown (one hop, flags: ACK):OK #51/23 cls_redirect/IPv4 TCP accept known (one hop, flags: ACK):OK #51/24 cls_redirect/IPv6 TCP accept known (one hop, flags: ACK):OK #51/25 cls_redirect/IPv4 UDP accept unknown (no hops, flags: none):OK #51/26 cls_redirect/IPv6 UDP accept unknown (no hops, flags: none):OK #51/27 cls_redirect/IPv4 UDP forward unknown (one hop, flags: none):OK #51/28 cls_redirect/IPv6 UDP forward unknown (one hop, flags: none):OK #51/29 cls_redirect/IPv4 UDP accept known (one hop, flags: none):OK #51/30 cls_redirect/IPv6 UDP accept known (one hop, flags: none):OK #51/31 cls_redirect/cls_redirect_dynptr:OK #51/32 cls_redirect/IPv4 TCP accept unknown (no hops, flags: SYN):OK #51/33 cls_redirect/IPv6 TCP accept unknown (no hops, flags: SYN):OK #51/34 cls_redirect/IPv4 TCP accept unknown (no hops, flags: ACK):OK #51/35 cls_redirect/IPv6 TCP accept unknown (no hops, flags: ACK):OK #51/36 cls_redirect/IPv4 TCP forward unknown (one hop, flags: ACK):OK #51/37 cls_redirect/IPv6 TCP forward unknown (one hop, flags: ACK):OK #51/38 cls_redirect/IPv4 TCP accept known (one hop, flags: ACK):OK #51/39 cls_redirect/IPv6 TCP accept known (one hop, flags: ACK):OK #51/40 cls_redirect/IPv4 UDP accept unknown (no hops, flags: none):OK #51/41 cls_redirect/IPv6 UDP accept unknown (no hops, flags: none):OK #51/42 cls_redirect/IPv4 UDP forward unknown (one hop, flags: none):OK #51/43 cls_redirect/IPv6 UDP forward unknown (one hop, flags: none):OK #51/44 cls_redirect/IPv4 UDP accept known (one hop, flags: none):OK #51/45 cls_redirect/IPv6 UDP accept known (one hop, flags: none):OK #51 cls_redirect:OK Summary: 1/45 PASSED, 0 SKIPPED, 0 FAILED Fixes: 5dc61552 ("LoongArch: Add BPF JIT support") Signed-off-by:Hengqi Chen <hengqi.chen@gmail.com> Signed-off-by:
Please register or sign in to comment