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Message-Id: <20200907131613.12703-17-joro@8bytes.org>
Date: Mon, 7 Sep 2020 15:15:17 +0200
From: Joerg Roedel <joro@...tes.org>
To: x86@...nel.org
Cc: Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
Kees Cook <keescook@...omium.org>, hpa@...or.com,
Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Jiri Slaby <jslaby@...e.cz>,
Dan Williams <dan.j.williams@...el.com>,
Tom Lendacky <thomas.lendacky@....com>,
Juergen Gross <jgross@...e.com>,
David Rientjes <rientjes@...gle.com>,
Cfir Cohen <cfir@...gle.com>,
Erdem Aktas <erdemaktas@...gle.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mike Stunes <mstunes@...are.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Martin Radev <martin.b.radev@...il.com>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
virtualization@...ts.linux-foundation.org
Subject: [PATCH v7 16/72] x86/boot/compressed/64: Always switch to own page-table
From: Joerg Roedel <jroedel@...e.de>
When booted through startup_64 the kernel keeps running on the EFI
page-table until the KASLR code sets up its own page-table. Without
KASLR the pre-decompression boot code never switches off the EFI
page-table. Change that by unconditionally switching to a kernel
controlled page-table after relocation.
This makes sure we can make changes to the mapping when necessary, for
example map pages unencrypted in SEV and SEV-ES guests.
Also remove the debug_putstr() calls in initialize_identity_maps()
because the function now runs before console_init() is called.
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
arch/x86/boot/compressed/head_64.S | 3 +-
arch/x86/boot/compressed/ident_map_64.c | 51 +++++++++++++++----------
arch/x86/boot/compressed/kaslr.c | 3 --
3 files changed, 32 insertions(+), 25 deletions(-)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 1fffaec1c069..37c8c2c8f8b6 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -533,10 +533,11 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
rep stosq
/*
- * Load stage2 IDT
+ * Load stage2 IDT and switch to our own page-table
*/
pushq %rsi
call load_stage2_idt
+ call initialize_identity_maps
popq %rsi
/*
diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
index e3d980ae9c2b..ecf9353b064d 100644
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -86,9 +86,31 @@ phys_addr_t physical_mask = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
*/
static struct x86_mapping_info mapping_info;
+/*
+ * Adds the specified range to what will become the new identity mappings.
+ * Once all ranges have been added, the new mapping is activated by calling
+ * finalize_identity_maps() below.
+ */
+void add_identity_map(unsigned long start, unsigned long size)
+{
+ unsigned long end = start + size;
+
+ /* Align boundary to 2M. */
+ start = round_down(start, PMD_SIZE);
+ end = round_up(end, PMD_SIZE);
+ if (start >= end)
+ return;
+
+ /* Build the mapping. */
+ kernel_ident_mapping_init(&mapping_info, (pgd_t *)top_level_pgt,
+ start, end);
+}
+
/* Locates and clears a region for a new top level page table. */
void initialize_identity_maps(void)
{
+ unsigned long start, size;
+
/* If running as an SEV guest, the encryption mask is required. */
set_sev_encryption_mask();
@@ -121,37 +143,24 @@ void initialize_identity_maps(void)
*/
top_level_pgt = read_cr3_pa();
if (p4d_offset((pgd_t *)top_level_pgt, 0) == (p4d_t *)_pgtable) {
- debug_putstr("booted via startup_32()\n");
pgt_data.pgt_buf = _pgtable + BOOT_INIT_PGT_SIZE;
pgt_data.pgt_buf_size = BOOT_PGT_SIZE - BOOT_INIT_PGT_SIZE;
memset(pgt_data.pgt_buf, 0, pgt_data.pgt_buf_size);
} else {
- debug_putstr("booted via startup_64()\n");
pgt_data.pgt_buf = _pgtable;
pgt_data.pgt_buf_size = BOOT_PGT_SIZE;
memset(pgt_data.pgt_buf, 0, pgt_data.pgt_buf_size);
top_level_pgt = (unsigned long)alloc_pgt_page(&pgt_data);
}
-}
-/*
- * Adds the specified range to what will become the new identity mappings.
- * Once all ranges have been added, the new mapping is activated by calling
- * finalize_identity_maps() below.
- */
-void add_identity_map(unsigned long start, unsigned long size)
-{
- unsigned long end = start + size;
-
- /* Align boundary to 2M. */
- start = round_down(start, PMD_SIZE);
- end = round_up(end, PMD_SIZE);
- if (start >= end)
- return;
-
- /* Build the mapping. */
- kernel_ident_mapping_init(&mapping_info, (pgd_t *)top_level_pgt,
- start, end);
+ /*
+ * New page-table is set up - map the kernel image and load it
+ * into cr3.
+ */
+ start = (unsigned long)_head;
+ size = _end - _head;
+ add_identity_map(start, size);
+ write_cr3(top_level_pgt);
}
/*
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index e27de98ed038..82662869c4cb 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -861,9 +861,6 @@ void choose_random_location(unsigned long input,
boot_params->hdr.loadflags |= KASLR_FLAG;
- /* Prepare to add new identity pagetables on demand. */
- initialize_identity_maps();
-
if (IS_ENABLED(CONFIG_X86_32))
mem_limit = KERNEL_IMAGE_SIZE;
else
--
2.28.0
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