Commit 7cd6750d authored by Puranjay Mohan's avatar Puranjay Mohan Committed by Alexei Starovoitov
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selftests/bpf: Test PROBE_MEM of VSYSCALL_ADDR on x86-64 



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: default avatarPuranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20240424100210.11982-4-puranjay@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent b599d7d2

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c

+3 −0
Original line number Diff line number Diff line
@@ -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;

	}

}