diff mbox series

[stable:PATCH,v4.19.235,12/22] arm64: entry: Allow the trampoline text to occupy multiple pages

Message ID 20220318174842.2321061-13-james.morse@arm.com
State New
Headers show
Series arm64: Mitigate spectre style branch history side channels | expand

Commit Message

James Morse March 18, 2022, 5:48 p.m. UTC 
commit a9c406e6462ff14956d690de7bbe5131a5677dc9 upstream.

Adding a second set of vectors to .entry.tramp.text will make it
larger than a single 4K page.

Allow the trampoline text to occupy up to three pages by adding two
more fixmap slots. Previous changes to tramp_valias allowed it to reach
beyond a single page.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/arm64/include/asm/fixmap.h   |  6 ++++--
 arch/arm64/include/asm/sections.h |  5 +++++
 arch/arm64/kernel/entry.S         |  2 +-
 arch/arm64/kernel/vmlinux.lds.S   |  2 +-
 arch/arm64/mm/mmu.c               | 12 +++++++++---
 5 files changed, 20 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index c0cfc6d3bf9f..3c962ef081f8 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -59,9 +59,11 @@  enum fixed_addresses {
 #endif /* CONFIG_ACPI_APEI_GHES */
 
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
-	FIX_ENTRY_TRAMP_TEXT,
+	FIX_ENTRY_TRAMP_TEXT3,
+	FIX_ENTRY_TRAMP_TEXT2,
+	FIX_ENTRY_TRAMP_TEXT1,
 	FIX_ENTRY_TRAMP_DATA,
-#define TRAMP_VALIAS		(__fix_to_virt(FIX_ENTRY_TRAMP_TEXT))
+#define TRAMP_VALIAS		(__fix_to_virt(FIX_ENTRY_TRAMP_TEXT1))
 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
 	__end_of_permanent_fixed_addresses,
 
diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h
index caab039d6305..8d3f1eab58e0 100644
--- a/arch/arm64/include/asm/sections.h
+++ b/arch/arm64/include/asm/sections.h
@@ -30,4 +30,9 @@  extern char __irqentry_text_start[], __irqentry_text_end[];
 extern char __mmuoff_data_start[], __mmuoff_data_end[];
 extern char __entry_tramp_text_start[], __entry_tramp_text_end[];
 
+static inline size_t entry_tramp_text_size(void)
+{
+	return __entry_tramp_text_end - __entry_tramp_text_start;
+}
+
 #endif /* __ASM_SECTIONS_H */
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 50843161607e..22d39c941a6d 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -966,7 +966,7 @@  alternative_else_nop_endif
 	.endm
 
 	.macro tramp_data_page	dst
-	adr	\dst, .entry.tramp.text
+	adr_l	\dst, .entry.tramp.text
 	sub	\dst, \dst, PAGE_SIZE
 	.endm
 
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 69e7c8d4a00f..370089455d38 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -259,7 +259,7 @@  ASSERT(__hibernate_exit_text_end - (__hibernate_exit_text_start & ~(SZ_4K - 1))
 	<= SZ_4K, "Hibernate exit text too big or misaligned")
 #endif
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
-ASSERT((__entry_tramp_text_end - __entry_tramp_text_start) == PAGE_SIZE,
+ASSERT((__entry_tramp_text_end - __entry_tramp_text_start) <= 3*PAGE_SIZE,
 	"Entry trampoline text too big")
 #endif
 /*
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 0fa558176fb1..b0a83dbed2dc 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -541,6 +541,8 @@  early_param("rodata", parse_rodata);
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 static int __init map_entry_trampoline(void)
 {
+	int i;
+
 	pgprot_t prot = rodata_enabled ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
 	phys_addr_t pa_start = __pa_symbol(__entry_tramp_text_start);
 
@@ -549,11 +551,15 @@  static int __init map_entry_trampoline(void)
 
 	/* Map only the text into the trampoline page table */
 	memset(tramp_pg_dir, 0, PGD_SIZE);
-	__create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS, PAGE_SIZE,
-			     prot, pgd_pgtable_alloc, 0);
+	__create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS,
+			     entry_tramp_text_size(), prot, pgd_pgtable_alloc,
+			     0);
 
 	/* Map both the text and data into the kernel page table */
-	__set_fixmap(FIX_ENTRY_TRAMP_TEXT, pa_start, prot);
+	for (i = 0; i < DIV_ROUND_UP(entry_tramp_text_size(), PAGE_SIZE); i++)
+		__set_fixmap(FIX_ENTRY_TRAMP_TEXT1 - i,
+			     pa_start + i * PAGE_SIZE, prot);
+
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
 		extern char __entry_tramp_data_start[];