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UPSTREAM: signal: define the SA_EXPOSE_TAGBITS bit in sa_flags

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Architectures that support address tagging, such as arm64, may want to
expose fault address tag bits to the signal handler to help diagnose
memory errors. However, these bits have not been previously set,
and their presence may confuse unaware user applications. Therefore,
introduce a SA_EXPOSE_TAGBITS flag bit in sa_flags that a signal
handler may use to explicitly request that the bits are set.

The generic signal handler APIs expect to receive tagged addresses.
Architectures may specify how to untag addresses in the case where
SA_EXPOSE_TAGBITS is clear by defining the arch_untagged_si_addr
function.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://linux-review.googlesource.com/id/I16dd0ed2081f091fce97be0190cb8caa874c26cb
Link: https://lkml.kernel.org/r/13cf24d00ebdd8e1f55caf1821c7c29d54100191.1605904350.git.pcc@google.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
(cherry picked from commit 6ac05e832a9e96f9b1c42a8917cdd317d7b6c8fa)
Bug: 135772972
Change-Id: I16dd0ed2081f091fce97be0190cb8caa874c26cb
This commit is contained in:
Peter Collingbourne
2020-11-20 12:33:45 -08:00
parent 4225576f6a
commit a30c848d10
4 changed files with 42 additions and 1 deletions
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24
kernel/signal.c
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@@ -2542,6 +2542,26 @@ static int ptrace_signal(int signr, kernel_siginfo_t *info)
return signr;
}
static void hide_si_addr_tag_bits(struct ksignal *ksig)
{
switch (siginfo_layout(ksig->sig, ksig->info.si_code)) {
case SIL_FAULT:
case SIL_FAULT_MCEERR:
case SIL_FAULT_BNDERR:
case SIL_FAULT_PKUERR:
ksig->info.si_addr = arch_untagged_si_addr(
ksig->info.si_addr, ksig->sig, ksig->info.si_code);
break;
case SIL_KILL:
case SIL_TIMER:
case SIL_POLL:
case SIL_CHLD:
case SIL_RT:
case SIL_SYS:
break;
}
}
bool get_signal(struct ksignal *ksig)
{
struct sighand_struct *sighand = current->sighand;
@@ -2779,6 +2799,10 @@ relock:
spin_unlock_irq(&sighand->siglock);
ksig->sig = signr;
if (!(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
hide_si_addr_tag_bits(ksig);
return ksig->sig > 0;
}