[PATCH v3 2/7] arm64: kernel: move ID map out of .text mapping

Ard Biesheuvel
2022-08-27T15:59:12Z

Reorganize the ID map slightly so that only code that is executed via
the 1:1 mapping remains. This allows us to move the ID map out of the
.text segment, as it will no longer need executable permissions via the
kernel mapping.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/kernel/head.S | 5 ++++-
arch/arm64/kernel/vmlinux.lds.S | 2 +-
arch/arm64/mm/proc.S | 2 --
3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index bd7c04f1f993..cfc7ba25bf87 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -474,7 +474,7 @@ SYM_FUNC_END(__primary_switched)
* end early head section, begin head code that is also used for
* hotplug and needs to have the same protections as the text region
*/
- .section ".idmap.text","awx"
+ .text

/*
* Starting from EL2 or EL1, configure the CPU to execute at the highest
@@ -554,6 +554,7 @@ SYM_FUNC_START_LOCAL(set_cpu_boot_mode_flag)
ret
SYM_FUNC_END(set_cpu_boot_mode_flag)

+ .section ".idmap.text","awx"
/*
* This provides a "holding pen" for platforms to hold all secondary
* cores are held until we're ready for them to initialise.
@@ -598,6 +599,7 @@ SYM_FUNC_START_LOCAL(secondary_startup)
br x8
SYM_FUNC_END(secondary_startup)

+ .text
SYM_FUNC_START_LOCAL(__secondary_switched)
mov x0, x20
bl set_cpu_boot_mode_flag
@@ -657,6 +659,7 @@ SYM_FUNC_END(__secondary_too_slow)
* Checks if the selected granule size is supported by the CPU.
* If it isn't, park the CPU
*/
+ .section ".idmap.text","awx"
SYM_FUNC_START(__enable_mmu)
mrs x3, ID_AA64MMFR0_EL1
ubfx x3, x3, #ID_AA64MMFR0_TGRAN_SHIFT, 4
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 0efccdf52be2..5002d869fa7f 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -168,7 +168,6 @@ SECTIONS
LOCK_TEXT
KPROBES_TEXT
HYPERVISOR_TEXT
- IDMAP_TEXT
*(.gnu.warning)
. = ALIGN(16);
*(.got) /* Global offset table */
@@ -195,6 +194,7 @@ SECTIONS
TRAMP_TEXT
HIBERNATE_TEXT
KEXEC_TEXT
+ IDMAP_TEXT
. = ALIGN(PAGE_SIZE);
}

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 7837a69524c5..113a4fedf5b8 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -107,7 +107,6 @@ SYM_FUNC_END(cpu_do_suspend)
*
* x0: Address of context pointer
*/
- .pushsection ".idmap.text", "awx"
SYM_FUNC_START(cpu_do_resume)
ldp x2, x3, [x0]
ldp x4, x5, [x0, #16]
@@ -163,7 +162,6 @@ alternative_else_nop_endif
isb
ret
SYM_FUNC_END(cpu_do_resume)
- .popsection
#endif

.pushsection ".idmap.text", "awx"
--
2.35.1