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[Xen-devel] [PATCH v4 01/19] xen/arm: Save ESR_EL2 to avoid using mismatched value in syndrome check

To: <xen-devel@xxxxxxxxxxxxx>

From: Wei Chen <Wei.Chen@xxxxxxx>

Date: Wed, 5 Apr 2017 17:09:03 +0800

Cc: sstabellini@xxxxxxxxxx, wei.chen@xxxxxxx, steve.capper@xxxxxxx, Kaly.Xin@xxxxxxx, julien.grall@xxxxxxx, nd@xxxxxxx

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List-id: Xen developer discussion <xen-devel.lists.xen.org>

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Xen will do exception syndrome check while some types of exception take place in EL2. The syndrome check code read the ESR_EL2 register directly, but in some situation this register maybe overridden by nested exception. For example, if we re-enable IRQ before reading ESR_EL2 which means Xen may enter in IRQ exception mode and return the processor with clobbered ESR_EL2 (See ARM ARM DDI 0487A.j D7.2.25) In this case the guest exception syndrome has been overridden, we will check the syndrome for guest sync exception with an incorrect ESR_EL2 value. So we want to save ESR_EL2 to cpu_user_regs as soon as the exception takes place in EL2 to avoid using an incorrect syndrome value. In order to save ESR_EL2, we added a 32-bit member hsr to cpu_user_regs. But while saving registers in trap entry, we use stp to save ELR and CPSR at the same time through 64-bit general registers. If we keep this code, the hsr will be overridden by upper 32-bit of CPSR. So adjust the code to use str to save ELR in a separate instruction and use stp to save CPSR and HSR at the same time through 32-bit general registers. This change affects the registers restore in trap exit, we can't use the ldp to restore ELR and CPSR from stack at the same time. We have to use ldr to restore them separately. Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx> Reviewed-by: Julien Grall <julien.grall@xxxxxxx> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> --- xen/arch/arm/arm32/asm-offsets.c | 1 + xen/arch/arm/arm32/entry.S | 3 +++ xen/arch/arm/arm64/asm-offsets.c | 1 + xen/arch/arm/arm64/entry.S | 13 +++++++++---- xen/arch/arm/arm64/traps.c | 2 +- xen/arch/arm/traps.c | 4 ++-- xen/include/asm-arm/arm32/processor.h | 2 +- xen/include/asm-arm/arm64/processor.h | 3 +-- 8 files changed, 19 insertions(+), 10 deletions(-) diff --git a/xen/arch/arm/arm32/asm-offsets.c b/xen/arch/arm/arm32/asm-offsets.c index f8e6b53..5b543ab 100644 --- a/xen/arch/arm/arm32/asm-offsets.c +++ b/xen/arch/arm/arm32/asm-offsets.c @@ -26,6 +26,7 @@ void __dummy__(void) OFFSET(UREGS_lr, struct cpu_user_regs, lr); OFFSET(UREGS_pc, struct cpu_user_regs, pc); OFFSET(UREGS_cpsr, struct cpu_user_regs, cpsr); + OFFSET(UREGS_hsr, struct cpu_user_regs, hsr); OFFSET(UREGS_LR_usr, struct cpu_user_regs, lr_usr); OFFSET(UREGS_SP_usr, struct cpu_user_regs, sp_usr); diff --git a/xen/arch/arm/arm32/entry.S b/xen/arch/arm/arm32/entry.S index 2a6f4f0..2187226 100644 --- a/xen/arch/arm/arm32/entry.S +++ b/xen/arch/arm/arm32/entry.S @@ -23,6 +23,9 @@ add r11, sp, #UREGS_kernel_sizeof+4; \ str r11, [sp, #UREGS_sp]; \ \ + mrc CP32(r11, HSR); /* Save exception syndrome */ \ + str r11, [sp, #UREGS_hsr]; \ + \ mrs r11, SPSR_hyp; \ str r11, [sp, #UREGS_cpsr]; \ and r11, #PSR_MODE_MASK; \ diff --git a/xen/arch/arm/arm64/asm-offsets.c b/xen/arch/arm/arm64/asm-offsets.c index 69ea92a..ce24e44 100644 --- a/xen/arch/arm/arm64/asm-offsets.c +++ b/xen/arch/arm/arm64/asm-offsets.c @@ -27,6 +27,7 @@ void __dummy__(void) OFFSET(UREGS_SP, struct cpu_user_regs, sp); OFFSET(UREGS_PC, struct cpu_user_regs, pc); OFFSET(UREGS_CPSR, struct cpu_user_regs, cpsr); + OFFSET(UREGS_ESR_el2, struct cpu_user_regs, hsr); OFFSET(UREGS_SPSR_el1, struct cpu_user_regs, spsr_el1); diff --git a/xen/arch/arm/arm64/entry.S b/xen/arch/arm/arm64/entry.S index c181b5e..02802c0 100644 --- a/xen/arch/arm/arm64/entry.S +++ b/xen/arch/arm/arm64/entry.S @@ -121,9 +121,13 @@ lr .req x30 // link register stp lr, x21, [sp, #UREGS_LR] - mrs x22, elr_el2 - mrs x23, spsr_el2 - stp x22, x23, [sp, #UREGS_PC] + mrs x21, elr_el2 + str x21, [sp, #UREGS_PC] + + add x21, sp, #UREGS_CPSR + mrs x22, spsr_el2 + mrs x23, esr_el2 + stp w22, w23, [x21] .endm @@ -307,7 +311,8 @@ ENTRY(return_to_new_vcpu64) return_from_trap: msr daifset, #2 /* Mask interrupts */ - ldp x21, x22, [sp, #UREGS_PC] // load ELR, SPSR + ldr x21, [sp, #UREGS_PC] // load ELR + ldr w22, [sp, #UREGS_CPSR] // load SPSR pop x0, x1 pop x2, x3 diff --git a/xen/arch/arm/arm64/traps.c b/xen/arch/arm/arm64/traps.c index 8e89376..36b3a30 100644 --- a/xen/arch/arm/arm64/traps.c +++ b/xen/arch/arm/arm64/traps.c @@ -32,7 +32,7 @@ static const char *handler[]= { asmlinkage void do_bad_mode(struct cpu_user_regs *regs, int reason) { - union hsr hsr = { .bits = READ_SYSREG32(ESR_EL2) }; + union hsr hsr = { .bits = regs->hsr }; printk("Bad mode in %s handler detected\n", handler[reason]); printk("ESR=0x%08"PRIx32": EC=%"PRIx32", IL=%"PRIx32", ISS=%"PRIx32"\n", diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c index b7d5fb6..f7fca37 100644 --- a/xen/arch/arm/traps.c +++ b/xen/arch/arm/traps.c @@ -864,7 +864,7 @@ static void _show_registers(struct cpu_user_regs *regs, printk(" HCR_EL2: %016"PRIregister"\n", READ_SYSREG(HCR_EL2)); printk(" TTBR0_EL2: %016"PRIx64"\n", READ_SYSREG64(TTBR0_EL2)); printk("\n"); - printk(" ESR_EL2: %08"PRIx32"\n", READ_SYSREG32(ESR_EL2)); + printk(" ESR_EL2: %08"PRIx32"\n", regs->hsr); printk(" HPFAR_EL2: %016"PRIregister"\n", READ_SYSREG(HPFAR_EL2)); #ifdef CONFIG_ARM_32 @@ -2694,7 +2694,7 @@ static void enter_hypervisor_head(struct cpu_user_regs *regs) asmlinkage void do_trap_hypervisor(struct cpu_user_regs *regs) { - const union hsr hsr = { .bits = READ_SYSREG32(ESR_EL2) }; + const union hsr hsr = { .bits = regs->hsr }; enter_hypervisor_head(regs); diff --git a/xen/include/asm-arm/arm32/processor.h b/xen/include/asm-arm/arm32/processor.h index db3b17b..f6d5df3 100644 --- a/xen/include/asm-arm/arm32/processor.h +++ b/xen/include/asm-arm/arm32/processor.h @@ -37,7 +37,7 @@ struct cpu_user_regs uint32_t pc, pc32; }; uint32_t cpsr; /* Return mode */ - uint32_t pad0; /* Doubleword-align the kernel half of the frame */ + uint32_t hsr; /* Exception Syndrome */ /* Outer guest frame only from here on... */ diff --git a/xen/include/asm-arm/arm64/processor.h b/xen/include/asm-arm/arm64/processor.h index b0726ff..24f836b 100644 --- a/xen/include/asm-arm/arm64/processor.h +++ b/xen/include/asm-arm/arm64/processor.h @@ -66,8 +66,7 @@ struct cpu_user_regs /* Return address and mode */ __DECL_REG(pc, pc32); /* ELR_EL2 */ uint32_t cpsr; /* SPSR_EL2 */ - - uint32_t pad0; /* Align end of kernel frame. */ + uint32_t hsr; /* ESR_EL2 */ /* Outer guest frame only from here on... */ -- 2.7.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel

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