diff options
| author | Marc Zyngier <marc.zyngier@arm.com> | 2018-10-01 13:19:43 +0200 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2018-10-01 17:52:24 +0200 |
| commit | c219bc4e920518feb025749bdf9623aa57e94b64 (patch) | |
| tree | bf2043211dbd9423e10005d6872d348065fb40cb /arch/arm64/kernel | |
| parent | arm64: docs: Document SSBS HWCAP (diff) | |
| download | linux-c219bc4e920518feb025749bdf9623aa57e94b64.tar.xz linux-c219bc4e920518feb025749bdf9623aa57e94b64.zip | |
arm64: Trap WFI executed in userspace
It recently came to light that userspace can execute WFI, and that
the arm64 kernel doesn't trap this event. This sounds rather benign,
but the kernel should decide when it wants to wait for an interrupt,
and not userspace.
Let's trap WFI and immediately return after having skipped the
instruction. This effectively makes WFI a rather expensive NOP.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kernel')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 1 | ||||
| -rw-r--r-- | arch/arm64/kernel/traps.c | 11 |
2 files changed, 12 insertions, 0 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index f0a0464d4809..039144ecbcb2 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -665,6 +665,7 @@ el0_sync: cmp x24, #ESR_ELx_EC_FP_EXC64 // FP/ASIMD exception b.eq el0_fpsimd_exc cmp x24, #ESR_ELx_EC_SYS64 // configurable trap + ccmp x24, #ESR_ELx_EC_WFx, #4, ne b.eq el0_sys cmp x24, #ESR_ELx_EC_SP_ALIGN // stack alignment exception b.eq el0_sp_pc diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 58134a97928f..4066da7f1e5e 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -508,6 +508,11 @@ static void mrs_handler(unsigned int esr, struct pt_regs *regs) force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc); } +static void wfi_handler(unsigned int esr, struct pt_regs *regs) +{ + arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE); +} + struct sys64_hook { unsigned int esr_mask; unsigned int esr_val; @@ -544,6 +549,12 @@ static struct sys64_hook sys64_hooks[] = { .esr_val = ESR_ELx_SYS64_ISS_SYS_MRS_OP_VAL, .handler = mrs_handler, }, + { + /* Trap WFI instructions executed in userspace */ + .esr_mask = ESR_ELx_WFx_MASK, + .esr_val = ESR_ELx_WFx_WFI_VAL, + .handler = wfi_handler, + }, {}, }; |