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selftests/bpf: Test PROBE_MEM of VSYSCALL_ADDR on x86-64

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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@kernel.org>
Link: https://lore.kernel.org/r/20240424100210.11982-4-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Puranjay Mohan 2024-04-24 10:02:10 +00:00 committed by Alexei Starovoitov
parent b599d7d26d
commit 7cd6750d9a
1 changed files with 3 additions and 0 deletions
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3
tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
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@ -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;
}
}