From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Thu, 26 Feb 2015 15:29:06 +0000 Subject: [RFC PATCH 2/3] arm64: make ID map shareable with EL2 In-Reply-To: <1424964547-2118-1-git-send-email-ard.biesheuvel@linaro.org> References: <1424964547-2118-1-git-send-email-ard.biesheuvel@linaro.org> Message-ID: <1424964547-2118-3-git-send-email-ard.biesheuvel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org This changes the ID map creation in head.S so that it can be reused by KVM to ID map the HYP init code in EL2. Since the architecture defines the AP[1] bit as RES1 in page table entries used at EL2, we must ensure that the HYP init code is mapped with the AP[1] bit set. However, AP[1] means 'writable at EL0' when set at EL1, which automatically implies PXN == 1 (rendering the entire ID map non-executable) unless we also set AP[2], which means read-only at both EL0 and EL1. To prevent having to make the entire ID map read-only, we split the ID map in two regions, and only set AP[2:1] == 0b11 for the first part, that covers the HYP .text section. Note that this also moves it to before _stext, which removes it from the runtime executable at EL1 region. This is a nice bonus, in fact, since this code should never be executable at EL1 anyway. Signed-off-by: Ard Biesheuvel --- arch/arm64/kernel/head.S | 22 ++++++++++++++++++---- arch/arm64/kernel/vmlinux.lds.S | 2 +- 2 files changed, 19 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index a3612eadab3c..0b3fb672640c 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -79,8 +79,10 @@ #ifdef CONFIG_ARM64_64K_PAGES #define MM_MMUFLAGS PTE_ATTRINDX(MT_NORMAL) | PTE_FLAGS +#define MM_MMUFLAGS_HYP MM_MMUFLAGS | PTE_HYP | PTE_RDONLY #else #define MM_MMUFLAGS PMD_ATTRINDX(MT_NORMAL) | PMD_FLAGS +#define MM_MMUFLAGS_HYP MM_MMUFLAGS | PMD_HYP | PMD_SECT_RDONLY #endif /* @@ -379,8 +381,6 @@ __create_page_tables: cmp x0, x6 b.lo 1b - ldr x7, =MM_MMUFLAGS - /* * Create the identity mapping. */ @@ -426,9 +426,23 @@ __create_page_tables: #endif create_pgd_entry x0, x3, x5, x6 - ldr x6, =KERNEL_END + + /* + * Map the first region -which also contains the HYP text sections- with + * HYP compatible attributes, so that we can share the ID map with KVM. + */ + ldr x7, =MM_MMUFLAGS_HYP + adrp x6, _stext // __pa(_stext) mov x5, x3 // __pa(KERNEL_START) - add x6, x6, x28 // __pa(KERNEL_END) + create_block_map x0, x7, x3, x5, x6 + + /* + * Map everything else with the default attributes. + */ + ldr x7, =MM_MMUFLAGS + adrp x3, (_stext + BLOCK_SIZE - 1) // next block after _stext + adrp x6, KERNEL_END + mov x5, x3 create_block_map x0, x7, x3, x5, x6 /* diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 17383c257a7d..4874ebca4b3e 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -83,6 +83,7 @@ SECTIONS .head.text : { _text = .; HEAD_TEXT + HYPERVISOR_TEXT } ALIGN_DEBUG_RO .text : { /* Real text segment */ @@ -94,7 +95,6 @@ SECTIONS TEXT_TEXT SCHED_TEXT LOCK_TEXT - HYPERVISOR_TEXT *(.fixup) *(.gnu.warning) . = ALIGN(16); -- 1.8.3.2