Add a test to verify that destination register of a 32-bit cmpxchg
operating on an arena pointer is explicitly zero extended.
W/o patch #1 this did not happen.
Reported-by: Nicholas Carlini <npc@anthropic.com>
Suggested-by: Nicholas Carlini <npc@anthropic.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260903171542.1438050-3-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Includes the following test cases:
- a test showing that zero extension flags do not propagate through
state pruning in the unpatched kernel.
- a 32-bit subregister consumed by MOV32 and ALU32 operations
(never zext'ed);
- a 64-bit MOV (never zext'ed);
- a narrow (32-bit) BPF_LDX load whose result is read as 64-bit;
- 32-bit atomic fetch_add and cmpxchg whose result is read as 64-bit;
- a CFG case where a 32-bit definition's upper half is used only on one
of two branches;
- no zext for dead registers;
- LD_ABS defines only lower 32 bits, hence needs zext when the result
is used as 64-bits;
- helper, kfunc and subprogram parameters are considered to use full
64 bits;
- a 32-bit subregister consumed by JMP32 (X/K) operations;
- a 32-bit subregister consumed by JMP (X/K) operations;
- a 64-bit register consumed by both JMP and JMP32 operations
(never zext'ed);
- ALU64 and address space cast operations on arena pointers;
- memory loads using BPF_PROBE_MEM instructions.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20260807-static-zext-v4-7-b6c270013c77@gmail.com
