From 27a921e75711d924617269e0ba4adb8bae9fd0d1 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 10 Aug 2017 13:58:16 +0100 Subject: [PATCH] arm64: mm: Fix and re-enable ARM64_SW_TTBR0_PAN With the ASID now installed in TTBR1, we can re-enable ARM64_SW_TTBR0_PAN by ensuring that we switch to a reserved ASID of zero when disabling user access and restore the active user ASID on the uaccess enable path. Reviewed-by: Mark Rutland Tested-by: Laura Abbott Tested-by: Shanker Donthineni Signed-off-by: Will Deacon --- arch/arm64/Kconfig | 1 - arch/arm64/include/asm/asm-uaccess.h | 25 +++++++++++++++++-------- arch/arm64/include/asm/uaccess.h | 21 +++++++++++++++++---- arch/arm64/kernel/entry.S | 4 ++-- arch/arm64/lib/clear_user.S | 2 +- arch/arm64/lib/copy_from_user.S | 2 +- arch/arm64/lib/copy_in_user.S | 2 +- arch/arm64/lib/copy_to_user.S | 2 +- arch/arm64/mm/cache.S | 2 +- arch/arm64/xen/hypercall.S | 2 +- 10 files changed, 42 insertions(+), 21 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 7e7d7fd152c4..a93339f5178f 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -910,7 +910,6 @@ endif config ARM64_SW_TTBR0_PAN bool "Emulate Privileged Access Never using TTBR0_EL1 switching" - depends on BROKEN # Temporary while switch_mm is reworked help Enabling this option prevents the kernel from accessing user-space memory directly by pointing TTBR0_EL1 to a reserved diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h index b3da6c886835..21b8cf304028 100644 --- a/arch/arm64/include/asm/asm-uaccess.h +++ b/arch/arm64/include/asm/asm-uaccess.h @@ -16,11 +16,20 @@ add \tmp1, \tmp1, #SWAPPER_DIR_SIZE // reserved_ttbr0 at the end of swapper_pg_dir msr ttbr0_el1, \tmp1 // set reserved TTBR0_EL1 isb + sub \tmp1, \tmp1, #SWAPPER_DIR_SIZE + bic \tmp1, \tmp1, #(0xffff << 48) + msr ttbr1_el1, \tmp1 // set reserved ASID + isb .endm - .macro __uaccess_ttbr0_enable, tmp1 + .macro __uaccess_ttbr0_enable, tmp1, tmp2 get_thread_info \tmp1 ldr \tmp1, [\tmp1, #TSK_TI_TTBR0] // load saved TTBR0_EL1 + mrs \tmp2, ttbr1_el1 + extr \tmp2, \tmp2, \tmp1, #48 + ror \tmp2, \tmp2, #16 + msr ttbr1_el1, \tmp2 // set the active ASID + isb msr ttbr0_el1, \tmp1 // set the non-PAN TTBR0_EL1 isb .endm @@ -31,18 +40,18 @@ alternative_if_not ARM64_HAS_PAN alternative_else_nop_endif .endm - .macro uaccess_ttbr0_enable, tmp1, tmp2 + .macro uaccess_ttbr0_enable, tmp1, tmp2, tmp3 alternative_if_not ARM64_HAS_PAN - save_and_disable_irq \tmp2 // avoid preemption - __uaccess_ttbr0_enable \tmp1 - restore_irq \tmp2 + save_and_disable_irq \tmp3 // avoid preemption + __uaccess_ttbr0_enable \tmp1, \tmp2 + restore_irq \tmp3 alternative_else_nop_endif .endm #else .macro uaccess_ttbr0_disable, tmp1 .endm - .macro uaccess_ttbr0_enable, tmp1, tmp2 + .macro uaccess_ttbr0_enable, tmp1, tmp2, tmp3 .endm #endif @@ -56,8 +65,8 @@ alternative_if ARM64_ALT_PAN_NOT_UAO alternative_else_nop_endif .endm - .macro uaccess_enable_not_uao, tmp1, tmp2 - uaccess_ttbr0_enable \tmp1, \tmp2 + .macro uaccess_enable_not_uao, tmp1, tmp2, tmp3 + uaccess_ttbr0_enable \tmp1, \tmp2, \tmp3 alternative_if ARM64_ALT_PAN_NOT_UAO SET_PSTATE_PAN(0) alternative_else_nop_endif diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index fc0f9eb66039..750a3b76a01c 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -107,15 +107,19 @@ static inline void __uaccess_ttbr0_disable(void) { unsigned long ttbr; + ttbr = read_sysreg(ttbr1_el1); /* reserved_ttbr0 placed at the end of swapper_pg_dir */ - ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE; - write_sysreg(ttbr, ttbr0_el1); + write_sysreg(ttbr + SWAPPER_DIR_SIZE, ttbr0_el1); + isb(); + /* Set reserved ASID */ + ttbr &= ~(0xffffUL << 48); + write_sysreg(ttbr, ttbr1_el1); isb(); } static inline void __uaccess_ttbr0_enable(void) { - unsigned long flags; + unsigned long flags, ttbr0, ttbr1; /* * Disable interrupts to avoid preemption between reading the 'ttbr0' @@ -123,7 +127,16 @@ static inline void __uaccess_ttbr0_enable(void) * roll-over and an update of 'ttbr0'. */ local_irq_save(flags); - write_sysreg(current_thread_info()->ttbr0, ttbr0_el1); + ttbr0 = current_thread_info()->ttbr0; + + /* Restore active ASID */ + ttbr1 = read_sysreg(ttbr1_el1); + ttbr1 |= ttbr0 & (0xffffUL << 48); + write_sysreg(ttbr1, ttbr1_el1); + isb(); + + /* Restore user page table */ + write_sysreg(ttbr0, ttbr0_el1); isb(); local_irq_restore(flags); } diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 804e43c9cb0b..d454d8ed45e4 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -184,7 +184,7 @@ alternative_if ARM64_HAS_PAN alternative_else_nop_endif .if \el != 0 - mrs x21, ttbr0_el1 + mrs x21, ttbr1_el1 tst x21, #0xffff << 48 // Check for the reserved ASID orr x23, x23, #PSR_PAN_BIT // Set the emulated PAN in the saved SPSR b.eq 1f // TTBR0 access already disabled @@ -248,7 +248,7 @@ alternative_else_nop_endif tbnz x22, #22, 1f // Skip re-enabling TTBR0 access if the PSR_PAN_BIT is set .endif - __uaccess_ttbr0_enable x0 + __uaccess_ttbr0_enable x0, x1 .if \el == 0 /* diff --git a/arch/arm64/lib/clear_user.S b/arch/arm64/lib/clear_user.S index e88fb99c1561..8f9c4641e706 100644 --- a/arch/arm64/lib/clear_user.S +++ b/arch/arm64/lib/clear_user.S @@ -30,7 +30,7 @@ * Alignment fixed up by hardware. */ ENTRY(__clear_user) - uaccess_enable_not_uao x2, x3 + uaccess_enable_not_uao x2, x3, x4 mov x2, x1 // save the size for fixup return subs x1, x1, #8 b.mi 2f diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S index 4b5d826895ff..69d86a80f3e2 100644 --- a/arch/arm64/lib/copy_from_user.S +++ b/arch/arm64/lib/copy_from_user.S @@ -64,7 +64,7 @@ end .req x5 ENTRY(__arch_copy_from_user) - uaccess_enable_not_uao x3, x4 + uaccess_enable_not_uao x3, x4, x5 add end, x0, x2 #include "copy_template.S" uaccess_disable_not_uao x3 diff --git a/arch/arm64/lib/copy_in_user.S b/arch/arm64/lib/copy_in_user.S index b24a830419ad..e442b531252a 100644 --- a/arch/arm64/lib/copy_in_user.S +++ b/arch/arm64/lib/copy_in_user.S @@ -65,7 +65,7 @@ end .req x5 ENTRY(raw_copy_in_user) - uaccess_enable_not_uao x3, x4 + uaccess_enable_not_uao x3, x4, x5 add end, x0, x2 #include "copy_template.S" uaccess_disable_not_uao x3 diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S index 351f0766f7a6..318f15d5c336 100644 --- a/arch/arm64/lib/copy_to_user.S +++ b/arch/arm64/lib/copy_to_user.S @@ -63,7 +63,7 @@ end .req x5 ENTRY(__arch_copy_to_user) - uaccess_enable_not_uao x3, x4 + uaccess_enable_not_uao x3, x4, x5 add end, x0, x2 #include "copy_template.S" uaccess_disable_not_uao x3 diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S index 7f1dbe962cf5..6cd20a8c0952 100644 --- a/arch/arm64/mm/cache.S +++ b/arch/arm64/mm/cache.S @@ -49,7 +49,7 @@ ENTRY(flush_icache_range) * - end - virtual end address of region */ ENTRY(__flush_cache_user_range) - uaccess_ttbr0_enable x2, x3 + uaccess_ttbr0_enable x2, x3, x4 dcache_line_size x2, x3 sub x3, x2, #1 bic x4, x0, x3 diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S index 401ceb71540c..acdbd2c9e899 100644 --- a/arch/arm64/xen/hypercall.S +++ b/arch/arm64/xen/hypercall.S @@ -101,7 +101,7 @@ ENTRY(privcmd_call) * need the explicit uaccess_enable/disable if the TTBR0 PAN emulation * is enabled (it implies that hardware UAO and PAN disabled). */ - uaccess_ttbr0_enable x6, x7 + uaccess_ttbr0_enable x6, x7, x8 hvc XEN_IMM /*