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Revert "FROMLIST: arm64: implement Shadow Call Stack"

Browse Source 
Shadow call stack is now merged upstream for 5.9, so revert the patches
cherry-picked into android-mainline in preparation for pulling the upstream
version instead.

This reverts commit 084cffa679.

Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: Ie0f0e3a32948f68082ed23e67535529035a16300
This commit is contained in:
Will Deacon
2020-06-09 12:44:53 +01:00
parent 6103983f46
commit 239f5f1767
12 changed files with 2 additions and 139 deletions
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5
arch/arm64/Kconfig
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@@ -65,7 +65,6 @@ config ARM64
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_QUEUED_SPINLOCKS
select ARCH_SUPPORTS_MEMORY_FAILURE
select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
select ARCH_SUPPORTS_LTO_CLANG
select ARCH_SUPPORTS_THINLTO
select ARCH_SUPPORTS_ATOMIC_RMW
@@ -1029,10 +1028,6 @@ config ARCH_HAS_CACHE_LINE_SIZE
config ARCH_ENABLE_SPLIT_PMD_PTLOCK
def_bool y if PGTABLE_LEVELS > 2
# Supported by clang >= 7.0
config CC_HAVE_SHADOW_CALL_STACK
def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
config SECCOMP
bool "Enable seccomp to safely compute untrusted bytecode"
---help---

37
arch/arm64/include/asm/scs.h
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@@ -1,37 +0,0 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_SCS_H
#define _ASM_SCS_H
#ifndef __ASSEMBLY__
#include <linux/scs.h>
#ifdef CONFIG_SHADOW_CALL_STACK
extern void scs_init_irq(void);
static __always_inline void scs_save(struct task_struct *tsk)
{
void *s;
asm volatile("mov %0, x18" : "=r" (s));
task_set_scs(tsk, s);
}
static inline void scs_overflow_check(struct task_struct *tsk)
{
if (unlikely(scs_corrupted(tsk)))
panic("corrupted shadow stack detected inside scheduler\n");
}
#else /* CONFIG_SHADOW_CALL_STACK */
static inline void scs_init_irq(void) {}
static inline void scs_save(struct task_struct *tsk) {}
static inline void scs_overflow_check(struct task_struct *tsk) {}
#endif /* CONFIG_SHADOW_CALL_STACK */
#endif /* __ASSEMBLY __ */
#endif /* _ASM_SCS_H */

4
arch/arm64/include/asm/stacktrace.h
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@@ -68,10 +68,6 @@ extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk);
DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
#ifdef CONFIG_SHADOW_CALL_STACK
DECLARE_PER_CPU(unsigned long *, irq_shadow_call_stack_ptr);
#endif
static inline bool on_irq_stack(unsigned long sp,
struct stack_info *info)
{

3
arch/arm64/include/asm/thread_info.h
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@@ -41,9 +41,6 @@ struct thread_info {
#endif
} preempt;
};
#ifdef CONFIG_SHADOW_CALL_STACK
void *shadow_call_stack;
#endif
};
#define thread_saved_pc(tsk) \

1
arch/arm64/kernel/Makefile
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@@ -63,7 +63,6 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
obj-$(CONFIG_ARM64_SSBD) += ssbd.o
obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o
obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o
obj-y += vdso/ probes/
obj-$(CONFIG_COMPAT_VDSO) += vdso32/

3
arch/arm64/kernel/asm-offsets.c
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@@ -33,9 +33,6 @@ int main(void)
DEFINE(TSK_TI_ADDR_LIMIT, offsetof(struct task_struct, thread_info.addr_limit));
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
DEFINE(TSK_TI_TTBR0, offsetof(struct task_struct, thread_info.ttbr0));
#endif
#ifdef CONFIG_SHADOW_CALL_STACK
DEFINE(TSK_TI_SCS, offsetof(struct task_struct, thread_info.shadow_call_stack));
#endif
DEFINE(TSK_STACK, offsetof(struct task_struct, stack));
#ifdef CONFIG_STACKPROTECTOR

31
arch/arm64/kernel/entry.S
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@@ -178,10 +178,6 @@ alternative_cb_end
apply_ssbd 1, x22, x23
#ifdef CONFIG_SHADOW_CALL_STACK
ldr x18, [tsk, #TSK_TI_SCS] // Restore shadow call stack
str xzr, [tsk, #TSK_TI_SCS] // Limit visibility of saved SCS
#endif
ptrauth_keys_install_kernel tsk, 1, x20, x22, x23
.else
add x21, sp, #S_FRAME_SIZE
@@ -284,12 +280,6 @@ alternative_else_nop_endif
ct_user_enter
.endif
#ifdef CONFIG_SHADOW_CALL_STACK
.if \el == 0
str x18, [tsk, #TSK_TI_SCS] // Save shadow call stack
.endif
#endif
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
/*
* Restore access to TTBR0_EL1. If returning to EL0, no need for SPSR
@@ -398,9 +388,6 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
.macro irq_stack_entry
mov x19, sp // preserve the original sp
#ifdef CONFIG_SHADOW_CALL_STACK
mov x20, x18 // preserve the original shadow stack
#endif
/*
* Compare sp with the base of the task stack.
@@ -418,24 +405,15 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
/* switch to the irq stack */
mov sp, x26
#ifdef CONFIG_SHADOW_CALL_STACK
/* also switch to the irq shadow stack */
ldr_this_cpu x18, irq_shadow_call_stack_ptr, x26
#endif
9998:
.endm
/*
* The callee-saved regs (x19-x29) should be preserved between
* irq_stack_entry and irq_stack_exit.
* x19 should be preserved between irq_stack_entry and
* irq_stack_exit.
*/
.macro irq_stack_exit
mov sp, x19
#ifdef CONFIG_SHADOW_CALL_STACK
mov x18, x20
#endif
.endm
/* GPRs used by entry code */
@@ -922,11 +900,6 @@ SYM_FUNC_START(cpu_switch_to)
ldr lr, [x8]
mov sp, x9
msr sp_el0, x1
#ifdef CONFIG_SHADOW_CALL_STACK
str x18, [x0, #TSK_TI_SCS]
ldr x18, [x1, #TSK_TI_SCS]
str xzr, [x1, #TSK_TI_SCS] // limit visibility of saved SCS
#endif
ptrauth_keys_install_kernel x1, 1, x8, x9, x10
ret
SYM_FUNC_END(cpu_switch_to)

9
arch/arm64/kernel/head.S
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@@ -27,7 +27,6 @@
#include <asm/pgtable-hwdef.h>
#include <asm/pgtable.h>
#include <asm/page.h>
#include <asm/scs.h>
#include <asm/smp.h>
#include <asm/sysreg.h>
#include <asm/thread_info.h>
@@ -425,10 +424,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
stp xzr, x30, [sp, #-16]!
mov x29, sp
#ifdef CONFIG_SHADOW_CALL_STACK
adr_l x18, init_shadow_call_stack // Set shadow call stack
#endif
str_l x21, __fdt_pointer, x5 // Save FDT pointer
ldr_l x4, kimage_vaddr // Save the offset between
@@ -742,10 +737,6 @@ SYM_FUNC_START_LOCAL(__secondary_switched)
ldr x2, [x0, #CPU_BOOT_TASK]
cbz x2, __secondary_too_slow
msr sp_el0, x2
#ifdef CONFIG_SHADOW_CALL_STACK
ldr x18, [x2, #TSK_TI_SCS] // set shadow call stack
str xzr, [x2, #TSK_TI_SCS] // limit visibility of saved SCS
#endif
mov x29, #0
mov x30, #0
b secondary_start_kernel

2
arch/arm64/kernel/irq.c
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@@ -21,7 +21,6 @@
#include <linux/vmalloc.h>
#include <asm/daifflags.h>
#include <asm/vmap_stack.h>
#include <asm/scs.h>
unsigned long irq_err_count;
@@ -64,7 +63,6 @@ static void init_irq_stacks(void)
void __init init_IRQ(void)
{
init_irq_stacks();
scs_init_irq();
irqchip_init();
if (!handle_arch_irq)
panic("No interrupt controller found.");

2
arch/arm64/kernel/process.c
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@@ -52,7 +52,6 @@
#include <asm/mmu_context.h>
#include <asm/processor.h>
#include <asm/pointer_auth.h>
#include <asm/scs.h>
#include <asm/stacktrace.h>
#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK)
@@ -516,7 +515,6 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
entry_task_switch(next);
uao_thread_switch(next);
ssbs_thread_switch(next);
scs_overflow_check(next);
/*
* Complete any pending TLB or cache maintenance on this CPU in case

40
arch/arm64/kernel/scs.c
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@@ -1,40 +0,0 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Shadow Call Stack support.
*
* Copyright (C) 2019 Google LLC
*/
#include <linux/percpu.h>
#include <linux/vmalloc.h>
#include <asm/pgtable.h>
#include <asm/scs.h>
DEFINE_PER_CPU(unsigned long *, irq_shadow_call_stack_ptr);
#ifndef CONFIG_SHADOW_CALL_STACK_VMAP
DEFINE_PER_CPU(unsigned long [SCS_SIZE/sizeof(long)], irq_shadow_call_stack)
__aligned(SCS_SIZE);
#endif
void scs_init_irq(void)
{
int cpu;
for_each_possible_cpu(cpu) {
#ifdef CONFIG_SHADOW_CALL_STACK_VMAP
unsigned long *p;
p = __vmalloc_node_range(PAGE_SIZE, SCS_SIZE,
VMALLOC_START, VMALLOC_END,
GFP_SCS, PAGE_KERNEL,
0, cpu_to_node(cpu),
__builtin_return_address(0));
per_cpu(irq_shadow_call_stack_ptr, cpu) = p;
#else
per_cpu(irq_shadow_call_stack_ptr, cpu) =
per_cpu(irq_shadow_call_stack, cpu);
#endif /* CONFIG_SHADOW_CALL_STACK_VMAP */
}
}

4
arch/arm64/kernel/smp.c
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@@ -46,7 +46,6 @@
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/processor.h>
#include <asm/scs.h>
#include <asm/smp_plat.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>
@@ -371,9 +370,6 @@ void cpu_die(void)
unsigned int cpu = smp_processor_id();
const struct cpu_operations *ops = get_cpu_ops(cpu);
/* Save the shadow stack pointer before exiting the idle task */
scs_save(current);
idle_task_exit();
local_daif_mask();