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powerpc/uprobes: Validation for prefixed instruction

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As per ISA 3.1, prefixed instruction should not cross 64-byte
boundary. So don't allow Uprobe on such prefixed instruction.

There are two ways probed instruction is changed in mapped pages.
First, when Uprobe is activated, it searches for all the relevant
pages and replace instruction in them. In this case, if that probe
is on the 64-byte unaligned prefixed instruction, error out
directly. Second, when Uprobe is already active and user maps a
relevant page via mmap(), instruction is replaced via mmap() code
path. But because Uprobe is invalid, entire mmap() operation can
not be stopped. In this case just print an error and continue.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210311091538.368590-1-ravi.bangoria@linux.ibm.com
This commit is contained in:
Ravi Bangoria 2021-03-11 14:45:38 +05:30 committed by Michael Ellerman
parent d3ccc97815
commit d943bc742a
1 changed files with 7 additions and 0 deletions
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7
arch/powerpc/kernel/uprobes.c
View file

@ -41,6 +41,13 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
if (addr & 0x03)
return -EINVAL;
if (cpu_has_feature(CPU_FTR_ARCH_31) &&
ppc_inst_prefixed(auprobe->insn) &&
(addr & 0x3f) == 60) {
pr_info_ratelimited("Cannot register a uprobe on 64 byte unaligned prefixed instruction\n");
return -EINVAL;
}
return 0;
}