The vsyscall is a legacy API for fast execution of system calls. It maps a page at address VSYSCALL_ADDR into the userspace program. This address is in the top 10MB of the address space: ffffffffff600000 - ffffffffff600fff | 4 kB | legacy vsyscall ABI The last commit fixes the x86-64 BPF JIT to skip accessing addresses in this memory region. Add this address to bpf_testmod_return_ptr() so we can make sure that it is fixed. After this change and without the previous commit, subprogs_extable selftest will crash the kernel. Signed-off-by: Puranjay Mohan <puranjay@xxxxxxxxxx> --- tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c index 39ad96a18123..edcd26106557 100644 --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c @@ -205,6 +205,9 @@ __weak noinline struct file *bpf_testmod_return_ptr(int arg) case 5: return (void *)~(1ull << 30); /* trigger extable */ case 6: return &f; /* valid addr */ case 7: return (void *)((long)&f | 1); /* kernel tricks */ +#ifdef CONFIG_X86_64 + case 8: return (void *)VSYSCALL_ADDR; /* vsyscall page address */ +#endif default: return NULL; } } -- 2.40.1
