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ARM: 7208/1: Add condition code checking to SWP emulation handler.

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This patch fixes two separate issues with the SWP emulation handler:
1: Certain processors implementing ARMv7-A can (legally) take an
   undef exception even when the condition code would have meant that
   the instruction should not have been executed.
2: Opcodes with all flags set (condition code = 0xf) have been reused
   in recent, and not-so-recent, versions of the ARM architecture to
   implement unconditional extensions to the instruction set. The
   existing code would still have processed any undefs triggered by
   executing an opcode with such a value.

This patch uses the new generic ARM instruction set condition code
checks to implement proper handling of these situations.

Signed-off-by: Leif Lindholm <leif.lindholm@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Leif Lindholm 2011-12-12 19:45:24 +01:00 committed by Russell King
parent e7f626db83
commit c245dcd326
1 changed files with 16 additions and 0 deletions
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16
arch/arm/kernel/swp_emulate.c
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@ -25,6 +25,7 @@
#include <linux/syscalls.h>
#include <linux/perf_event.h>
#include <asm/opcodes.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
@ -185,6 +186,21 @@ static int swp_handler(struct pt_regs *regs, unsigned int instr)
perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc);
res = arm_check_condition(instr, regs->ARM_cpsr);
switch (res) {
case ARM_OPCODE_CONDTEST_PASS:
break;
case ARM_OPCODE_CONDTEST_FAIL:
/* Condition failed - return to next instruction */
regs->ARM_pc += 4;
return 0;
case ARM_OPCODE_CONDTEST_UNCOND:
/* If unconditional encoding - not a SWP, undef */
return -EFAULT;
default:
return -EINVAL;
}
if (current->pid != previous_pid) {
pr_debug("\"%s\" (%ld) uses deprecated SWP{B} instruction\n",
current->comm, (unsigned long)current->pid);