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| author |  Nicholas Piggin <npiggin@gmail.com>
| 2020-05-07 22:13:32 +1000 |
|---|---|---|
| committer |  Michael Ellerman <mpe@ellerman.id.au>
| 2020-05-15 11:58:54 +1000 |
| commit | 4e0e45b07d790253643ee05300784ab2156e2d5e (patch) | |
| tree | 8945f0e66bed685345be9fa12472e21893db7a41 /arch/powerpc/kernel/signal_64.c | |
| parent | powerpc: trap_is_syscall() helper to hide syscall trap number (diff) | |
| download | linux-4e0e45b07d790253643ee05300784ab2156e2d5e.tar.gz linux-4e0e45b07d790253643ee05300784ab2156e2d5e.tar.bz2 linux-4e0e45b07d790253643ee05300784ab2156e2d5e.zip | |
powerpc: Use trap metadata to prevent double restart rather than zeroing trap
It's not very nice to zero trap for this, because then system calls no
longer have trap_is_syscall(regs) invariant, and we can't distinguish
between sc and scv system calls (in a later patch).
Take one last unused bit from the low bits of the pt_regs.trap word
for this instead. There is not a really good reason why it should be
in trap as opposed to another field, but trap has some concept of
flags and it exists. Ideally I think we would move trap to 2-byte
field and have 2 more bytes available independently.
Add a selftests case for this, which can be seen to fail if
trap_norestart() is changed to return false.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Make them static inlines]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200507121332.2233629-4-mpe@ellerman.id.au
Diffstat (limited to 'arch/powerpc/kernel/signal_64.c')
| -rw-r--r-- | arch/powerpc/kernel/signal_64.c | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c index adfde59cf4ba..77061915897f 100644 --- a/arch/powerpc/kernel/signal_64.c +++ b/arch/powerpc/kernel/signal_64.c @@ -350,8 +350,8 @@ static long restore_sigcontext(struct task_struct *tsk, sigset_t *set, int sig, err |= __get_user(regs->link, &sc->gp_regs[PT_LNK]); err |= __get_user(regs->xer, &sc->gp_regs[PT_XER]); err |= __get_user(regs->ccr, &sc->gp_regs[PT_CCR]); - /* skip SOFTE */ - regs->trap = 0; + /* Don't allow userspace to set SOFTE */ + set_trap_norestart(regs); err |= __get_user(regs->dar, &sc->gp_regs[PT_DAR]); err |= __get_user(regs->dsisr, &sc->gp_regs[PT_DSISR]); err |= __get_user(regs->result, &sc->gp_regs[PT_RESULT]); @@ -472,10 +472,8 @@ static long restore_tm_sigcontexts(struct task_struct *tsk, &sc->gp_regs[PT_XER]); err |= __get_user(tsk->thread.ckpt_regs.ccr, &sc->gp_regs[PT_CCR]); - - /* Don't allow userspace to set the trap value */ - regs->trap = 0; - + /* Don't allow userspace to set SOFTE */ + set_trap_norestart(regs); /* These regs are not checkpointed; they can go in 'regs'. */ err |= __get_user(regs->dar, &sc->gp_regs[PT_DAR]); err |= __get_user(regs->dsisr, &sc->gp_regs[PT_DSISR]); |