From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: mark.rutland@arm.com, catalin.marinas@arm.com,
james.morse@arm.com, mark.brown@arm.com, will@kernel.org,
Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH v2] arm64/entry: deduplicate SW PAN entry/exit routines
Date: Tue, 21 Jul 2020 10:33:15 +0200 [thread overview]
Message-ID: <20200721083315.4816-1-ardb@kernel.org> (raw)
Factor the 12 copies of the SW PAN entry and exit code into callable
subroutines, and use alternatives patching to either emit a 'bl'
instruction to call them, or a NOP if h/w PAN is found to be available
at runtime.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
v2: use tail call to invoke post_ttbr_update_workaround
arch/arm64/kernel/entry.S | 95 ++++++++++----------
1 file changed, 47 insertions(+), 48 deletions(-)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 35de8ba60e3d..5fe49b1b620f 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -226,28 +226,9 @@ alternative_else_nop_endif
add x29, sp, #S_STACKFRAME
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
- /*
- * Set the TTBR0 PAN bit in SPSR. When the exception is taken from
- * EL0, there is no need to check the state of TTBR0_EL1 since
- * accesses are always enabled.
- * Note that the meaning of this bit differs from the ARMv8.1 PAN
- * feature as all TTBR0_EL1 accesses are disabled, not just those to
- * user mappings.
- */
-alternative_if ARM64_HAS_PAN
- b 1f // skip TTBR0 PAN
+alternative_if_not ARM64_HAS_PAN
+ bl __swpan_entry_el\el
alternative_else_nop_endif
-
- .if \el != 0
- mrs x21, ttbr0_el1
- tst x21, #TTBR_ASID_MASK // Check for the reserved ASID
- orr x23, x23, #PSR_PAN_BIT // Set the emulated PAN in the saved SPSR
- b.eq 1f // TTBR0 access already disabled
- and x23, x23, #~PSR_PAN_BIT // Clear the emulated PAN in the saved SPSR
- .endif
-
- __uaccess_ttbr0_disable x21
-1:
#endif
stp x22, x23, [sp, #S_PC]
@@ -301,34 +282,9 @@ alternative_else_nop_endif
.endif
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
- /*
- * Restore access to TTBR0_EL1. If returning to EL0, no need for SPSR
- * PAN bit checking.
- */
-alternative_if ARM64_HAS_PAN
- b 2f // skip TTBR0 PAN
+alternative_if_not ARM64_HAS_PAN
+ bl __swpan_exit_el\el
alternative_else_nop_endif
-
- .if \el != 0
- tbnz x22, #22, 1f // Skip re-enabling TTBR0 access if the PSR_PAN_BIT is set
- .endif
-
- __uaccess_ttbr0_enable x0, x1
-
- .if \el == 0
- /*
- * Enable errata workarounds only if returning to user. The only
- * workaround currently required for TTBR0_EL1 changes are for the
- * Cavium erratum 27456 (broadcast TLBI instructions may cause I-cache
- * corruption).
- */
- bl post_ttbr_update_workaround
- .endif
-1:
- .if \el != 0
- and x22, x22, #~PSR_PAN_BIT // ARMv8.0 CPUs do not understand this bit
- .endif
-2:
#endif
.if \el == 0
@@ -401,6 +357,49 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
sb
.endm
+#ifdef CONFIG_ARM64_SW_TTBR0_PAN
+ /*
+ * Set the TTBR0 PAN bit in SPSR. When the exception is taken from
+ * EL0, there is no need to check the state of TTBR0_EL1 since
+ * accesses are always enabled.
+ * Note that the meaning of this bit differs from the ARMv8.1 PAN
+ * feature as all TTBR0_EL1 accesses are disabled, not just those to
+ * user mappings.
+ */
+SYM_CODE_START_LOCAL(__swpan_entry_el1)
+ mrs x21, ttbr0_el1
+ tst x21, #TTBR_ASID_MASK // Check for the reserved ASID
+ orr x23, x23, #PSR_PAN_BIT // Set the emulated PAN in the saved SPSR
+ b.eq 1f // TTBR0 access already disabled
+ and x23, x23, #~PSR_PAN_BIT // Clear the emulated PAN in the saved SPSR
+SYM_INNER_LABEL(__swpan_entry_el0, SYM_L_LOCAL)
+ __uaccess_ttbr0_disable x21
+1: ret
+SYM_CODE_END(__swpan_entry_el1)
+
+ /*
+ * Restore access to TTBR0_EL1. If returning to EL0, no need for SPSR
+ * PAN bit checking.
+ */
+SYM_CODE_START_LOCAL(__swpan_exit_el1)
+ tbnz x22, #22, 1f // Skip re-enabling TTBR0 access if the PSR_PAN_BIT is set
+ __uaccess_ttbr0_enable x0, x1
+1: and x22, x22, #~PSR_PAN_BIT // ARMv8.0 CPUs do not understand this bit
+ ret
+SYM_CODE_END(__swpan_exit_el1)
+
+SYM_CODE_START_LOCAL(__swpan_exit_el0)
+ __uaccess_ttbr0_enable x0, x1
+ /*
+ * Enable errata workarounds only if returning to user. The only
+ * workaround currently required for TTBR0_EL1 changes are for the
+ * Cavium erratum 27456 (broadcast TLBI instructions may cause I-cache
+ * corruption).
+ */
+ b post_ttbr_update_workaround
+SYM_CODE_END(__swpan_exit_el0)
+#endif
+
.macro irq_stack_entry
mov x19, sp // preserve the original sp
#ifdef CONFIG_SHADOW_CALL_STACK
--
2.20.1
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