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arm64: Emulate SETEND for AArch32 tasks

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Emulate deprecated 'setend' instruction for AArch32 bit tasks.

	setend [le/be] - Sets the endianness of EL0

On systems with CPUs which support mixed endian at EL0, the hardware
support for the instruction can be enabled by setting the SCTLR_EL1.SED
bit. Like the other emulated instructions it is controlled by an entry in
/proc/sys/abi/. For more information see :
	Documentation/arm64/legacy_instructions.txt

The instruction is emulated by setting/clearing the SPSR_EL1.E bit, which
will be reflected in the PSTATE.E in AArch32 context.

This patch also restores the native endianness for the execution of signal
handlers, since the process could have changed the endianness.

Note: All CPUs on the system must have mixed endian support at EL0. Once the
handler is registered, hotplugging a CPU which doesn't support mixed endian,
could lead to unexpected results/behavior in applications.

Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Suzuki K. Poulose
2015-01-21 12:43:11 +00:00
committed by Catalin Marinas
parent 736d474f0f
commit 2d888f48e0
6 changed files with 119 additions and 1 deletions
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5
arch/arm64/kernel/signal32.c
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@@ -440,7 +440,7 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
{
compat_ulong_t handler = ptr_to_compat(ka->sa.sa_handler);
compat_ulong_t retcode;
compat_ulong_t spsr = regs->pstate & ~PSR_f;
compat_ulong_t spsr = regs->pstate & ~(PSR_f | COMPAT_PSR_E_BIT);
int thumb;
/* Check if the handler is written for ARM or Thumb */
@@ -454,6 +454,9 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
/* The IT state must be cleared for both ARM and Thumb-2 */
spsr &= ~COMPAT_PSR_IT_MASK;
/* Restore the original endianness */
spsr |= COMPAT_PSR_ENDSTATE;
if (ka->sa.sa_flags & SA_RESTORER) {
retcode = ptr_to_compat(ka->sa.sa_restorer);
} else {