From: Mark Rutland mark.rutland@arm.com
mainline inclusion from mainline-v5.11-rc1 commit d87a8e65b5101123a24cddeb7a8a2c7b45f7b60c category: bugfix bugzilla: 189556
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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As with SCTLR_ELx and other control registers, some PSTATE bits are UNKNOWN out-of-reset, and we may not be able to rely on hardware or firmware to initialize them to our liking prior to entry to the kernel, e.g. in the primary/secondary boot paths and return from idle/suspend.
It would be more robust (and easier to reason about) if we consistently initialized PSTATE to a default value, as we do with control registers. This will ensure that the kernel is not adversely affected by bits it is not aware of, e.g. when support for a feature such as PAN/UAO is disabled.
This patch ensures that PSTATE is consistently initialized at boot time via an ERET. This is not intended to relax the existing requirements (e.g. DAIF bits must still be set prior to entering the kernel). For features detected dynamically (which may require system-wide support), it is still necessary to subsequently modify PSTATE.
As ERET is not always a Context Synchronization Event, an ISB is placed before each exception return to ensure updates to control registers have taken effect. This handles the kernel being entered with SCTLR_ELx.EOS clear (or any future control bits being in an UNKNOWN state).
Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Christoph Hellwig hch@lst.de Cc: James Morse james.morse@arm.com Cc: Will Deacon will@kernel.org Link: https://lore.kernel.org/r/20201113124937.20574-6-mark.rutland@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Conflicts: arch/arm64/kernel/head.S Signed-off-by: Li Zetao lizetao1@huawei.com --- arch/arm64/include/asm/ptrace.h | 5 +++++ arch/arm64/kernel/head.S | 32 +++++++++++++++++++++----------- 2 files changed, 26 insertions(+), 11 deletions(-)
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index 27fee85c3c2b..e58568f94b5e 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -16,6 +16,11 @@ #define CurrentEL_EL1 (1 << 2) #define CurrentEL_EL2 (2 << 2)
+#define INIT_PSTATE_EL1 \ + (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT | PSR_MODE_EL1h) +#define INIT_PSTATE_EL2 \ + (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT | PSR_MODE_EL2h) + /* * PMR values used to mask/unmask interrupts. * diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index ad1e45abfe6c..91890de6cefa 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -531,21 +531,29 @@ EXPORT_SYMBOL(kimage_vaddr) * If we're fortunate enough to boot at EL2, ensure that the world is * sane before dropping to EL1. * + * Since we cannot always rely on ERET synchronizing writes to sysregs (e.g. if + * SCTLR_ELx.EOS is clear), we place an ISB prior to ERET. + * * Returns either BOOT_CPU_MODE_EL1 or BOOT_CPU_MODE_EL2 in w0 if * booted in EL1 or EL2 respectively. */ SYM_FUNC_START(el2_setup) - msr SPsel, #1 // We want to use SP_EL{1,2} mrs x0, CurrentEL cmp x0, #CurrentEL_EL2 - b.eq 1f + b.eq init_el2 + +SYM_INNER_LABEL(init_el1, SYM_L_LOCAL) mov_q x0, INIT_SCTLR_EL1_MMU_OFF msr sctlr_el1, x0 - mov w0, #BOOT_CPU_MODE_EL1 // This cpu booted in EL1 isb - ret + mov_q x0, INIT_PSTATE_EL1 + msr spsr_el1, x0 + msr elr_el1, lr + mov w0, #BOOT_CPU_MODE_EL1 + eret
-1: mov_q x0, INIT_SCTLR_EL2_MMU_OFF +SYM_INNER_LABEL(init_el2, SYM_L_LOCAL) + mov_q x0, INIT_SCTLR_EL2_MMU_OFF msr sctlr_el2, x0
#ifdef CONFIG_ARM64_VHE @@ -657,9 +665,12 @@ set_hcr:
cbz x2, install_el2_stub
- mov w0, #BOOT_CPU_MODE_EL2 // This CPU booted in EL2 isb - ret + mov_q x0, INIT_PSTATE_EL2 + msr spsr_el2, x0 + msr elr_el2, lr + mov w0, #BOOT_CPU_MODE_EL2 + eret
/* Disable any fine grained traps */ .macro __init_el2_fgt @@ -778,12 +789,11 @@ SYM_INNER_LABEL(install_el2_stub, SYM_L_LOCAL) 7: adr_l x0, __hyp_stub_vectors msr vbar_el2, x0
- /* spsr */ - mov x0, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\ - PSR_MODE_EL1h) + isb + mov x0, #INIT_PSTATE_EL1 msr spsr_el2, x0 msr elr_el2, lr - mov w0, #BOOT_CPU_MODE_EL2 // This CPU booted in EL2 + mov w0, #BOOT_CPU_MODE_EL2 eret SYM_FUNC_END(el2_setup)