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Puranjay Mohan says: ==================== bpf: report arena faults to BPF streams Changes in v6->v7: v6: https://lore.kernel.org/all/20250908163638.23150-1-puranjay@kernel.org/ - Added comments about the usage of arena_reg in x86 and arm64 jits. (Alexei) - Used clear_lo32() for clearing the lower 32-bits of user_vm_start. (Alexei) - Moved update of the old tests to use __stderr to a separate commit (Eduard) - Used test__skip() in prog_tests/stream.c (Eduard) - Start a sub-test for read / write Changes in v5->v6: v5: https://lore.kernel.org/all/20250901193730.43543-1-puranjay@kernel.org/ - Introduces __stderr and __stdout for easy testing of bpf streams (Eduard) - Add more test cases for arena fault reporting (subprog and callback) - Fix main_prog_aux usage and return main_prog from find_from_stack_cb (Kumar) - Properly fix the build issue reported by kernel test robot Changes in v4->v5: v4: https://lore.kernel.org/all/20250827153728.28115-1-puranjay@kernel.org/ - Added patch 2 to introducing main_prog_aux for easier access to streams. - Fixed bug in fault handlers when arena_reg == dst_reg - Updated selftest to check test above edge case. - Added comments about the usage of barrier_var() in code and commit message. Changes in v3->v4: v3: https://lore.kernel.org/all/20250827150113.15763-1-puranjay@kernel.org/ - Fixed a build issue when CONFIG_BPF_JIT=y and # CONFIG_BPF_SYSCALL is not set Changes in v2->v3: v2: https://lore.kernel.org/all/20250811111828.13836-1-puranjay@kernel.org/ - Improved the selftest to check the exact fault address - Dropped BPF_NO_KFUNC_PROTOTYPES and bpf_arena_alloc/free_pages() usage - Rebased on bpf-next/master Changes in v1->v2: v1: https://lore.kernel.org/all/20250806085847.18633-1-puranjay@kernel.org/ - Changed variable and mask names for consistency (Yonghong) - Added Acked-by: Yonghong Song <yonghong.song@linux.dev> on two patches This set adds the support of reporting page faults inside arena to BPF stderr stream. The reported address is the one that a user would expect to see if they pass it to bpf_printk(); Here is an example output from the stderr stream and bpf_printk() ERROR: Arena WRITE access at unmapped address 0xdeaddead0000 CPU: 9 UID: 0 PID: 502 Comm: test_progs Call trace: bpf_stream_stage_dump_stack+0xc0/0x150 bpf_prog_report_arena_violation+0x98/0xf0 ex_handler_bpf+0x5c/0x78 fixup_exception+0xf8/0x160 __do_kernel_fault+0x40/0x188 do_bad_area+0x70/0x88 do_translation_fault+0x54/0x98 do_mem_abort+0x4c/0xa8 el1_abort+0x44/0x70 el1h_64_sync_handler+0x50/0x108 el1h_64_sync+0x6c/0x70 bpf_prog_a64a9778d31b8e88_stream_arena_write_fault+0x84/0xc8 *(page) = 1; @ stream.c:100 bpf_prog_test_run_syscall+0x100/0x328 __sys_bpf+0x508/0xb98 __arm64_sys_bpf+0x2c/0x48 invoke_syscall+0x50/0x120 el0_svc_common.constprop.0+0x48/0xf8 do_el0_svc+0x28/0x40 el0_svc+0x48/0xf8 el0t_64_sync_handler+0xa0/0xe8 el0t_64_sync+0x198/0x1a0 Same address is printed by bpf_printk(): 1389.078831: bpf_trace_printk: Read Address: 0xdeaddead0000 To make this possible, some extra metadata has to be passed to the bpf exception handler, so the bpf exception handling mechanism for both x86-64 and arm64 have been improved in this set. The streams selftest has been updated to test this new feature. ==================== Link: https://patch.msgid.link/20250911145808.58042-1-puranjay@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
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