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Commit f045269b authored by Marc Zyngier's avatar Marc Zyngier Committed by Isaac J. Manjarres
Browse files

arm64: Call ARCH_WORKAROUND_2 on transitions between EL0 and EL1 



In order for the kernel to protect itself, let's call the SSBD mitigation
implemented by the higher exception level (either hypervisor or firmware)
on each transition between userspace and kernel.

We must take the PSCI conduit into account in order to target the
right exception level, hence the introduction of a runtime patching
callback.

Change-Id: Ic4cc012d804dd0c68b557ba58e34e1b8031f1ae2
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarJulien Grall <julien.grall@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Git-commit: 8e2906245f1e3b0d027169d9f2e55ce0548cb96e
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[isaacm@codeaurora.org: remove code for alternative_cb, as
 that is not present. Instead, since the psci conduit is
 smc, replace the alternative_cb reference with the smc
 call it would be anyway.]
Signed-off-by: default avatarIsaac J. Manjarres <isaacm@codeaurora.org>
parent 04ff63a3

arch/arm64/kernel/entry.S

+20 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */



#include <linux/arm-smccc.h>

#include <linux/init.h>

#include <linux/linkage.h>
@@ -137,6 +138,16 @@ alternative_else_nop_endif 
	add	\dst, \dst, #(\sym - .entry.tramp.text)

	.endm



	// This macro corrupts x0-x3. It is the caller's duty

	// to save/restore them if required.

	.macro	apply_ssbd, state

#ifdef CONFIG_ARM64_SSBD

	mov	w0, #ARM_SMCCC_ARCH_WORKAROUND_2

	mov	w1, #\state

	smc	#0

#endif

	.endm



	.macro	kernel_entry, el, regsize = 64

	.if	\regsize == 32

	mov	w0, w0				// zero upper 32 bits of x0
@@ -163,6 +174,13 @@ alternative_else_nop_endif 
	ldr	x19, [tsk, #TSK_TI_FLAGS]	// since we can unmask debug

	disable_step_tsk x19, x20		// exceptions when scheduling.



	apply_ssbd 1



#ifdef CONFIG_ARM64_SSBD

	ldp	x0, x1, [sp, #16 * 0]

	ldp	x2, x3, [sp, #16 * 1]

#endif



	mov	x29, xzr			// fp pointed to user-space

	.else

	add	x21, sp, #S_FRAME_SIZE
@@ -301,6 +319,8 @@ alternative_if ARM64_WORKAROUND_845719 
alternative_else_nop_endif

#endif

3:

	apply_ssbd 0



	.endif



	msr	elr_el1, x21			// set up the return data

include/linux/arm-smccc.h

+5 −0
Original line number Diff line number Diff line
@@ -80,6 +80,11 @@ 
			   ARM_SMCCC_SMC_32,				\

			   0, 0x8000)



#define ARM_SMCCC_ARCH_WORKAROUND_2					\

	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\

			   ARM_SMCCC_SMC_32,				\

			   0, 0x7fff)



#ifndef __ASSEMBLY__



#include <linux/linkage.h>