iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

arm64: don't reload GPRs after apply_ssbd

Browse Source 
Now that all of the syscall logic works on the saved pt_regs, apply_ssbd
can safely corrupt x0-x3 in the entry paths, and we no longer need to
restore them. So let's remove the logic doing so.

With that logic gone, we can fold the branch target into the macro, so
that callers need not deal with this. GAS provides \@, which provides a
unique value per macro invocation, which we can use to create a unique
label.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Mark Rutland 2018-07-11 14:56:47 +01:00 committed by Will Deacon
parent d9be03256d
commit 99ed3ed08d
1 changed files with 7 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
arch/arm64/kernel/entry.S
View File

@ -130,20 +130,21 @@ alternative_else_nop_endif
// This macro corrupts x0-x3. It is the caller's duty
// to save/restore them if required.
.macro apply_ssbd, state, targ, tmp1, tmp2
.macro apply_ssbd, state, tmp1, tmp2
#ifdef CONFIG_ARM64_SSBD
alternative_cb arm64_enable_wa2_handling
b \targ
b .L__asm_ssbd_skip\@
alternative_cb_end
ldr_this_cpu \tmp2, arm64_ssbd_callback_required, \tmp1
cbz \tmp2, \targ
cbz \tmp2, .L__asm_ssbd_skip\@
ldr \tmp2, [tsk, #TSK_TI_FLAGS]
tbnz \tmp2, #TIF_SSBD, \targ
tbnz \tmp2, #TIF_SSBD, .L__asm_ssbd_skip\@
mov w0, #ARM_SMCCC_ARCH_WORKAROUND_2
mov w1, #\state
alternative_cb arm64_update_smccc_conduit
nop // Patched to SMC/HVC #0
alternative_cb_end
.L__asm_ssbd_skip\@:
#endif
.endm
@ -173,13 +174,7 @@ alternative_cb_end
ldr x19, [tsk, #TSK_TI_FLAGS] // since we can unmask debug
disable_step_tsk x19, x20 // exceptions when scheduling.
apply_ssbd 1, 1f, x22, x23
#ifdef CONFIG_ARM64_SSBD
ldp x0, x1, [sp, #16 * 0]
ldp x2, x3, [sp, #16 * 1]
#endif
1:
apply_ssbd 1, x22, x23
mov x29, xzr // fp pointed to user-space
.else
@ -321,8 +316,7 @@ alternative_if ARM64_WORKAROUND_845719
alternative_else_nop_endif
#endif
3:
apply_ssbd 0, 5f, x0, x1
5:
apply_ssbd 0, x0, x1
.endif
msr elr_el1, x21 // set up the return data