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b126882672
In order to be able to generate loader program in the later patches change the order of data and text relocations. Also improve the test to include data relos. If the kernel supports "FD array" the map_fd relocations can be processed before text relos since generated loader program won't need to manually patch ld_imm64 insns with map_fd. But ksym and kfunc relocations can only be processed after all calls are relocated, since loader program will consist of a sequence of calls to bpf_btf_find_by_name_kind() followed by patching of btf_id and btf_obj_fd into corresponding ld_imm64 insns. The locations of those ld_imm64 insns are specified in relocations. Hence process all data relocations (maps, ksym, kfunc) together after call relos. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20210514003623.28033-12-alexei.starovoitov@gmail.com
117 lines
2.4 KiB
C
117 lines
2.4 KiB
C
#include "vmlinux.h"
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_core_read.h>
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const char LICENSE[] SEC("license") = "GPL";
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struct {
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__uint(type, BPF_MAP_TYPE_ARRAY);
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__uint(max_entries, 1);
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__type(key, __u32);
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__type(value, __u64);
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} array SEC(".maps");
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__noinline int sub1(int x)
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{
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int key = 0;
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bpf_map_lookup_elem(&array, &key);
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return x + 1;
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}
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static __noinline int sub5(int v);
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__noinline int sub2(int y)
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{
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return sub5(y + 2);
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}
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static __noinline int sub3(int z)
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{
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return z + 3 + sub1(4);
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}
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static __noinline int sub4(int w)
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{
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int key = 0;
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bpf_map_lookup_elem(&array, &key);
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return w + sub3(5) + sub1(6);
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}
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/* sub5() is an identitify function, just to test weirder functions layout and
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* call patterns
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*/
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static __noinline int sub5(int v)
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{
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return sub1(v) - 1; /* compensates sub1()'s + 1 */
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}
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/* unfortunately verifier rejects `struct task_struct *t` as an unkown pointer
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* type, so we need to accept pointer as integer and then cast it inside the
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* function
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*/
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__noinline int get_task_tgid(uintptr_t t)
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{
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/* this ensures that CO-RE relocs work in multi-subprogs .text */
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return BPF_CORE_READ((struct task_struct *)(void *)t, tgid);
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}
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int res1 = 0;
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int res2 = 0;
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int res3 = 0;
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int res4 = 0;
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SEC("raw_tp/sys_enter")
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int prog1(void *ctx)
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{
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/* perform some CO-RE relocations to ensure they work with multi-prog
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* sections correctly
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*/
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struct task_struct *t = (void *)bpf_get_current_task();
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if (!BPF_CORE_READ(t, pid) || !get_task_tgid((uintptr_t)t))
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return 1;
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res1 = sub1(1) + sub3(2); /* (1 + 1) + (2 + 3 + (4 + 1)) = 12 */
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return 0;
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}
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SEC("raw_tp/sys_exit")
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int prog2(void *ctx)
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{
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struct task_struct *t = (void *)bpf_get_current_task();
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if (!BPF_CORE_READ(t, pid) || !get_task_tgid((uintptr_t)t))
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return 1;
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res2 = sub2(3) + sub3(4); /* (3 + 2) + (4 + 3 + (4 + 1)) = 17 */
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return 0;
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}
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/* prog3 has the same section name as prog1 */
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SEC("raw_tp/sys_enter")
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int prog3(void *ctx)
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{
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struct task_struct *t = (void *)bpf_get_current_task();
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if (!BPF_CORE_READ(t, pid) || !get_task_tgid((uintptr_t)t))
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return 1;
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res3 = sub3(5) + 6; /* (5 + 3 + (4 + 1)) + 6 = 19 */
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return 0;
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}
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/* prog4 has the same section name as prog2 */
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SEC("raw_tp/sys_exit")
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int prog4(void *ctx)
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{
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struct task_struct *t = (void *)bpf_get_current_task();
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if (!BPF_CORE_READ(t, pid) || !get_task_tgid((uintptr_t)t))
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return 1;
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res4 = sub4(7) + sub1(8); /* (7 + (5 + 3 + (4 + 1)) + (6 + 1)) + (8 + 1) = 36 */
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return 0;
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}
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