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arm64: kill ESR_LNX_EXEC 

Currently we treat ESR_EL1 bit 24 as software-defined for distinguishing
instruction aborts from data aborts, but this bit is architecturally
RES0 for instruction aborts, and could be allocated for an arbitrary
purpose in future. Additionally, we hard-code the value in entry.S
without the mnemonic, making the code difficult to understand.

Instead, remove ESR_LNX_EXEC, and distinguish aborts based on the esr,
which we already pass to the sole use of ESR_LNX_EXEC. A new helper,
is_el0_instruction_abort() is added to make the logic clear. Any
instruction aborts taken from EL1 will already have been handled by
bad_mode, so we need not handle that case in the helper.

For consistency, the existing permission_fault helper is renamed to
is_permission_fault, and the return type is changed to bool. There
should be no functional changes as the return value was a boolean
expression, and the result is only used in another boolean expression.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Dave P Martin <dave.martin@arm.com>
Cc: Huang Shijie <shijie.huang@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Rutland 2016-05-31 12:33:03 +01:00 committed by Catalin Marinas
parent 561454e25d
commit 541ec870ef
2 changed files with 9 additions and 6 deletions
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2
arch/arm64/kernel/entry.S
View File

@ -532,7 +532,7 @@ el0_ia:
enable_dbg_and_irq
ct_user_exit
mov x0, x26
orr x1, x25, #1 << 24 // use reserved ISS bit for instruction aborts
mov x1, x25
mov x2, sp
bl do_mem_abort
b ret_to_user

13
arch/arm64/mm/fault.c
View File

@ -202,8 +202,6 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re
#define VM_FAULT_BADMAP 0x010000
#define VM_FAULT_BADACCESS 0x020000
#define ESR_LNX_EXEC (1 << 24)
static int __do_page_fault(struct mm_struct *mm, unsigned long addr,
unsigned int mm_flags, unsigned long vm_flags,
struct task_struct *tsk)
@ -242,7 +240,7 @@ static int __do_page_fault(struct mm_struct *mm, unsigned long addr,
return fault;
}
static inline int permission_fault(unsigned int esr)
static inline bool is_permission_fault(unsigned int esr)
{
unsigned int ec = ESR_ELx_EC(esr);
unsigned int fsc_type = esr & ESR_ELx_FSC_TYPE;
@ -250,6 +248,11 @@ static inline int permission_fault(unsigned int esr)
return (ec == ESR_ELx_EC_DABT_CUR && fsc_type == ESR_ELx_FSC_PERM);
}
static bool is_el0_instruction_abort(unsigned int esr)
{
return ESR_ELx_EC(esr) == ESR_ELx_EC_IABT_LOW;
}
static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
@ -272,14 +275,14 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
if (user_mode(regs))
mm_flags |= FAULT_FLAG_USER;
if (esr & ESR_LNX_EXEC) {
if (is_el0_instruction_abort(esr)) {
vm_flags = VM_EXEC;
} else if ((esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM)) {
vm_flags = VM_WRITE;
mm_flags |= FAULT_FLAG_WRITE;
}
if (permission_fault(esr) && (addr < USER_DS)) {
if (is_permission_fault(esr) && (addr < USER_DS)) {
if (get_fs() == KERNEL_DS)
die("Accessing user space memory with fs=KERNEL_DS", regs, esr);