From bfe298745afc9548ad9344a9a3f26c81fd1a76c4 Mon Sep 17 00:00:00 2001 From: James Morse Date: Fri, 25 Oct 2019 17:42:16 +0100 Subject: [PATCH] arm64: entry-common: don't touch daif before bp-hardening The previous patches mechanically transformed the assembly version of entry.S to entry-common.c for synchronous exceptions. The C version of local_daif_restore() doesn't quite do the same thing as the assembly versions if pseudo-NMI is in use. In particular, | local_daif_restore(DAIF_PROCCTX_NOIRQ) will still allow pNMI to be delivered. This is not the behaviour do_el0_ia_bp_hardening() and do_sp_pc_abort() want as it should not be possible for the PMU handler to run as an NMI until the bp-hardening sequence has run. The bp-hardening calls were placed where they are because this was the first C code to run after the relevant exceptions. As we've now moved that point earlier, move the checks and calls earlier too. This makes it clearer that this stuff runs before any kind of exception, and saves modifying PSTATE twice. Signed-off-by: James Morse Reviewed-by: Mark Rutland Cc: Julien Thierry Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/processor.h | 14 ++++++++++++ arch/arm64/kernel/entry-common.c | 18 ++++++++++++--- arch/arm64/mm/fault.c | 36 +----------------------------- 3 files changed, 30 insertions(+), 38 deletions(-) diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 5623685c7d13..8899d26f73ff 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -26,10 +26,12 @@ #include #include #include +#include #include #include #include +#include #include #include #include @@ -214,6 +216,18 @@ static inline void start_thread(struct pt_regs *regs, unsigned long pc, regs->sp = sp; } +static inline bool is_ttbr0_addr(unsigned long addr) +{ + /* entry assembly clears tags for TTBR0 addrs */ + return addr < TASK_SIZE; +} + +static inline bool is_ttbr1_addr(unsigned long addr) +{ + /* TTBR1 addresses may have a tag if KASAN_SW_TAGS is in use */ + return arch_kasan_reset_tag(addr) >= PAGE_OFFSET; +} + #ifdef CONFIG_COMPAT static inline void compat_start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index 2c318e41d84b..5dce5e56995a 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -14,6 +14,7 @@ #include #include #include +#include #include static void notrace el1_abort(struct pt_regs *regs, unsigned long esr) @@ -112,9 +113,17 @@ static void notrace el0_ia(struct pt_regs *regs, unsigned long esr) { unsigned long far = read_sysreg(far_el1); + /* + * We've taken an instruction abort from userspace and not yet + * re-enabled IRQs. If the address is a kernel address, apply + * BP hardening prior to enabling IRQs and pre-emption. + */ + if (!is_ttbr0_addr(far)) + arm64_apply_bp_hardening(); + user_exit_irqoff(); - local_daif_restore(DAIF_PROCCTX_NOIRQ); - do_el0_ia_bp_hardening(far, esr, regs); + local_daif_restore(DAIF_PROCCTX); + do_mem_abort(far, esr, regs); } NOKPROBE_SYMBOL(el0_ia); @@ -154,8 +163,11 @@ static void notrace el0_pc(struct pt_regs *regs, unsigned long esr) { unsigned long far = read_sysreg(far_el1); + if (!is_ttbr0_addr(instruction_pointer(regs))) + arm64_apply_bp_hardening(); + user_exit_irqoff(); - local_daif_restore(DAIF_PROCCTX_NOIRQ); + local_daif_restore(DAIF_PROCCTX); do_sp_pc_abort(far, esr, regs); } NOKPROBE_SYMBOL(el0_pc); diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index cb13f4daa878..1bb2e3737e51 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -32,8 +32,8 @@ #include #include #include -#include #include +#include #include #include #include @@ -102,18 +102,6 @@ static void mem_abort_decode(unsigned int esr) data_abort_decode(esr); } -static inline bool is_ttbr0_addr(unsigned long addr) -{ - /* entry assembly clears tags for TTBR0 addrs */ - return addr < TASK_SIZE; -} - -static inline bool is_ttbr1_addr(unsigned long addr) -{ - /* TTBR1 addresses may have a tag if KASAN_SW_TAGS is in use */ - return arch_kasan_reset_tag(addr) >= PAGE_OFFSET; -} - static inline unsigned long mm_to_pgd_phys(struct mm_struct *mm) { /* Either init_pg_dir or swapper_pg_dir */ @@ -758,30 +746,8 @@ void do_el0_irq_bp_hardening(void) } NOKPROBE_SYMBOL(do_el0_irq_bp_hardening); -void do_el0_ia_bp_hardening(unsigned long addr, unsigned int esr, - struct pt_regs *regs) -{ - /* - * We've taken an instruction abort from userspace and not yet - * re-enabled IRQs. If the address is a kernel address, apply - * BP hardening prior to enabling IRQs and pre-emption. - */ - if (!is_ttbr0_addr(addr)) - arm64_apply_bp_hardening(); - - local_daif_restore(DAIF_PROCCTX); - do_mem_abort(addr, esr, regs); -} -NOKPROBE_SYMBOL(do_el0_ia_bp_hardening); - void do_sp_pc_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) { - if (user_mode(regs)) { - if (!is_ttbr0_addr(instruction_pointer(regs))) - arm64_apply_bp_hardening(); - local_daif_restore(DAIF_PROCCTX); - } - arm64_notify_die("SP/PC alignment exception", regs, SIGBUS, BUS_ADRALN, (void __user *)addr, esr); } -- 2.20.1