From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-hardening@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Kees Cook <keescook@chromium.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Brown <broonie@kernel.org>,
Anshuman Khandual <anshuman.khandual@arm.com>
Subject: [PATCH v4 11/26] arm64: head: add helper function to remap regions in early page tables
Date: Mon, 13 Jun 2022 16:45:35 +0200 [thread overview]
Message-ID: <20220613144550.3760857-12-ardb@kernel.org> (raw)
In-Reply-To: <20220613144550.3760857-1-ardb@kernel.org>
The asm macros used to create the initial ID map and kernel mappings
don't support randomly remapping parts of the address space after it has
been populated. What we can do, however, given that all block or page
mappings are created at the final level, is take a subset of the mapped
range and update its attributes or output address. This will permit us
to make parts of these page tables read-only, or remap a part of it to
cover the device tree.
So add a helper that encapsulates this.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/kernel/head.S | 33 ++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 70c462bbd6bf..7397555f8437 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -263,6 +263,39 @@ SYM_FUNC_END(clear_page_tables)
populate_entries \tbl, \rtbl, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp
.endm
+/*
+ * Remap a subregion created with the map_memory macro with modified attributes
+ * or output address. The entire remapped region must have been covered in the
+ * invocation of map_memory.
+ *
+ * x0: last level table address (returned in first argument to map_memory)
+ * x1: start VA of the existing mapping
+ * x2: start VA of the region to update
+ * x3: end VA of the region to update (exclusive)
+ * x4: start PA associated with the region to update
+ * x5: attributes to set on the updated region
+ * x6: order of the last level mappings
+ */
+SYM_FUNC_START_LOCAL(remap_region)
+ sub x3, x3, #1 // make end inclusive
+
+ // Get the index offset for the start of the last level table
+ lsr x1, x1, x6
+ bfi x1, xzr, #0, #PAGE_SHIFT - 3
+
+ // Derive the start and end indexes into the last level table
+ // associated with the provided region
+ lsr x2, x2, x6
+ lsr x3, x3, x6
+ sub x2, x2, x1
+ sub x3, x3, x1
+
+ mov x1, #1
+ lsl x6, x1, x6 // block size at this level
+
+ populate_entries x0, x4, x2, x3, x5, x6, x7
+ ret
+SYM_FUNC_END(remap_region)
SYM_FUNC_START_LOCAL(create_idmap)
adrp x0, idmap_pg_dir
--
2.30.2
next prev parent reply other threads:[~2022-06-13 18:31 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-13 14:45 [PATCH v4 00/26] arm64: refactor boot flow and add support for WXN Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 01/26] arm64: head: move kimage_vaddr variable into C file Ard Biesheuvel
2022-06-14 8:26 ` Anshuman Khandual
2022-06-13 14:45 ` [PATCH v4 02/26] arm64: mm: make vabits_actual a build time constant if possible Ard Biesheuvel
2022-06-14 8:25 ` Anshuman Khandual
2022-06-14 8:34 ` Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 03/26] arm64: head: move assignment of idmap_t0sz to C code Ard Biesheuvel
2022-06-14 9:22 ` Anshuman Khandual
2022-06-14 9:34 ` Ard Biesheuvel
2022-06-24 12:36 ` Will Deacon
2022-06-24 12:57 ` Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 04/26] arm64: head: drop idmap_ptrs_per_pgd Ard Biesheuvel
2022-06-15 4:07 ` Anshuman Khandual
2022-06-13 14:45 ` [PATCH v4 05/26] arm64: head: simplify page table mapping macros (slightly) Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 06/26] arm64: head: switch to map_memory macro for the extended ID map Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 07/26] arm64: head: split off idmap creation code Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 08/26] arm64: kernel: drop unnecessary PoC cache clean+invalidate Ard Biesheuvel
2022-06-15 4:32 ` Anshuman Khandual
2022-06-13 14:45 ` [PATCH v4 09/26] arm64: head: pass ID map root table address to __enable_mmu() Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 10/26] arm64: mm: provide idmap pointer to cpu_replace_ttbr1() Ard Biesheuvel
2022-06-13 14:45 ` Ard Biesheuvel [this message]
2022-06-13 14:45 ` [PATCH v4 12/26] arm64: head: cover entire kernel image in initial ID map Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 13/26] arm64: head: use relative references to the RELA and RELR tables Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 14/26] arm64: head: create a temporary FDT mapping in the initial ID map Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 15/26] arm64: idreg-override: use early FDT mapping in " Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 16/26] arm64: head: factor out TTBR1 assignment into a macro Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 17/26] arm64: head: populate kernel page tables with MMU and caches on Ard Biesheuvel
2022-06-24 12:56 ` Will Deacon
2022-06-24 13:07 ` Ard Biesheuvel
2022-06-24 13:29 ` Will Deacon
2022-06-24 14:07 ` Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 18/26] arm64: head: record CPU boot mode after enabling the MMU Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 19/26] arm64: kaslr: defer initialization to late initcall where permitted Ard Biesheuvel
2022-06-24 13:08 ` Will Deacon
2022-06-24 13:09 ` Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 20/26] arm64: head: avoid relocating the kernel twice for KASLR Ard Biesheuvel
2022-06-24 13:16 ` Will Deacon
2022-06-24 13:17 ` Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 21/26] arm64: setup: drop early FDT pointer helpers Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 22/26] arm64: mm: move ro_after_init section into the data segment Ard Biesheuvel
2022-06-13 17:00 ` Kees Cook
2022-06-13 17:16 ` Ard Biesheuvel
2022-06-13 23:38 ` Kees Cook
2022-06-16 11:31 ` Ard Biesheuvel
2022-06-16 16:18 ` Kees Cook
2022-06-16 16:31 ` Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 23/26] arm64: head: remap the kernel text/inittext region read-only Ard Biesheuvel
2022-06-13 16:57 ` Kees Cook
2022-06-13 14:45 ` [PATCH v4 24/26] mm: add arch hook to validate mmap() prot flags Ard Biesheuvel
2022-06-13 16:37 ` Kees Cook
2022-06-13 16:44 ` Ard Biesheuvel
2022-06-13 14:45 ` [PATCH v4 25/26] arm64: mm: add support for WXN memory translation attribute Ard Biesheuvel
2022-06-13 16:51 ` Kees Cook
2022-06-13 14:45 ` [PATCH v4 26/26] arm64: kernel: move ID map out of .text mapping Ard Biesheuvel
2022-06-13 16:52 ` Kees Cook
2022-06-24 13:19 ` [PATCH v4 00/26] arm64: refactor boot flow and add support for WXN Will Deacon
2022-06-24 14:40 ` Ard Biesheuvel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220613144550.3760857-12-ardb@kernel.org \
--to=ardb@kernel.org \
--cc=anshuman.khandual@arm.com \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=keescook@chromium.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-hardening@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=maz@kernel.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).