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authorJames Morse <james.morse@arm.com>2019-07-22 16:11:48 +0100
committerWill Deacon <will@kernel.org>2019-07-22 16:22:34 +0100
commit40ca0ce56d4bb889dc43b455c55398468115569a (patch)
tree7a9676958df8994374788b5f1fa92502e0e6192e /arch
parentcbdf8a189a66001c36007bf0f5c975d0376c5c3a (diff)
downloadlinux-40ca0ce56d4bb889dc43b455c55398468115569a.tar.bz2
arm64: entry: SP Alignment Fault doesn't write to FAR_EL1
Comparing the arm-arm's pseudocode for AArch64.PCAlignmentFault() with AArch64.SPAlignmentFault() shows that SP faults don't copy the faulty-SP to FAR_EL1, but this is where we read from, and the address we provide to user-space with the BUS_ADRALN signal. For user-space this value will be UNKNOWN due to the previous ERET to user-space. If the last value is preserved, on systems with KASLR or KPTI this will be the user-space link-register left in FAR_EL1 by tramp_exit(). Fix this to retrieve the original sp_el0 value, and pass this to do_sp_pc_fault(). SP alignment faults from EL1 will cause us to take the fault again when trying to store the pt_regs. This eventually takes us to the overflow stack. Remove the ESR_ELx_EC_SP_ALIGN check as we will never make it this far. Fixes: 60ffc30d5652 ("arm64: Exception handling") Signed-off-by: James Morse <james.morse@arm.com> [will: change label name and fleshed out comment] Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/kernel/entry.S22
1 files changed, 13 insertions, 9 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 9cdc4592da3e..320a30dbe35e 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -586,10 +586,8 @@ el1_sync:
b.eq el1_ia
cmp x24, #ESR_ELx_EC_SYS64 // configurable trap
b.eq el1_undef
- cmp x24, #ESR_ELx_EC_SP_ALIGN // stack alignment exception
- b.eq el1_sp_pc
cmp x24, #ESR_ELx_EC_PC_ALIGN // pc alignment exception
- b.eq el1_sp_pc
+ b.eq el1_pc
cmp x24, #ESR_ELx_EC_UNKNOWN // unknown exception in EL1
b.eq el1_undef
cmp x24, #ESR_ELx_EC_BREAKPT_CUR // debug exception in EL1
@@ -611,9 +609,11 @@ el1_da:
bl do_mem_abort
kernel_exit 1
-el1_sp_pc:
+el1_pc:
/*
- * Stack or PC alignment exception handling
+ * PC alignment exception handling. We don't handle SP alignment faults,
+ * since we will have hit a recursive exception when trying to push the
+ * initial pt_regs.
*/
mrs x0, far_el1
inherit_daif pstate=x23, tmp=x2
@@ -732,9 +732,9 @@ el0_sync:
ccmp x24, #ESR_ELx_EC_WFx, #4, ne
b.eq el0_sys
cmp x24, #ESR_ELx_EC_SP_ALIGN // stack alignment exception
- b.eq el0_sp_pc
+ b.eq el0_sp
cmp x24, #ESR_ELx_EC_PC_ALIGN // pc alignment exception
- b.eq el0_sp_pc
+ b.eq el0_pc
cmp x24, #ESR_ELx_EC_UNKNOWN // unknown exception in EL0
b.eq el0_undef
cmp x24, #ESR_ELx_EC_BREAKPT_LOW // debug exception in EL0
@@ -758,7 +758,7 @@ el0_sync_compat:
cmp x24, #ESR_ELx_EC_FP_EXC32 // FP/ASIMD exception
b.eq el0_fpsimd_exc
cmp x24, #ESR_ELx_EC_PC_ALIGN // pc alignment exception
- b.eq el0_sp_pc
+ b.eq el0_pc
cmp x24, #ESR_ELx_EC_UNKNOWN // unknown exception in EL0
b.eq el0_undef
cmp x24, #ESR_ELx_EC_CP15_32 // CP15 MRC/MCR trap
@@ -858,11 +858,15 @@ el0_fpsimd_exc:
mov x1, sp
bl do_fpsimd_exc
b ret_to_user
+el0_sp:
+ ldr x26, [sp, #S_SP]
+ b el0_sp_pc
+el0_pc:
+ mrs x26, far_el1
el0_sp_pc:
/*
* Stack or PC alignment exception handling
*/
- mrs x26, far_el1
gic_prio_kentry_setup tmp=x0
enable_da_f
#ifdef CONFIG_TRACE_IRQFLAGS