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06096d19ee
Libbpf has a somewhat obscure feature of automatically adjusting the "size" of LDX/STX/ST instruction (memory store and load instructions), based on originally recorded access size (u8, u16, u32, or u64) and the actual size of the field on target kernel. This is meant to facilitate using BPF CO-RE on 32-bit architectures (pointers are always 64-bit in BPF, but host kernel's BTF will have it as 32-bit type), as well as generally supporting safe type changes (unsigned integer type changes can be transparently "relocated"). One issue that surfaced only now, 5 years after this logic was implemented, is how this all works when dealing with fields that are arrays. This isn't all that easy and straightforward to hit (see selftests that reproduce this condition), but one of sched_ext BPF programs did hit it with innocent looking loop. Long story short, libbpf used to calculate entire array size, instead of making sure to only calculate array's element size. But it's the element that is loaded by LDX/STX/ST instructions (1, 2, 4, or 8 bytes), so that's what libbpf should check. This patch adjusts the logic for arrays and fixed the issue. Reported-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20250207014809.1573841-1-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
History
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| .. | ||
| api | ||
| bpf | ||
| perf | ||
| subcmd | ||
| symbol | ||
| thermal | ||
| argv_split.c | ||
| bitmap.c | ||
| cmdline.c | ||
| ctype.c | ||
| find_bit.c | ||
| hweight.c | ||
| list_sort.c | ||
| rbtree.c | ||
| slab.c | ||
| str_error_r.c | ||
| string.c | ||
| vsprintf.c | ||
| zalloc.c | ||