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arm64: sdei: Add trampoline code for remapping the kernel

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When CONFIG_UNMAP_KERNEL_AT_EL0 is set the SDEI entry point and the rest
of the kernel may be unmapped when we take an event. If this may be the
case, use an entry trampoline that can switch to the kernel page tables.

We can't use the provided PSTATE to determine whether to switch page
tables as we may have interrupted the kernel's entry trampoline, (or a
normal-priority event that interrupted the kernel's entry trampoline).
Instead test for a user ASID in ttbr1_el1.

Save a value in regs->addr_limit to indicate whether we need to restore
the original ASID when returning from this event. This value is only used
by do_page_fault(), which we don't call with the SDEI regs.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
James Morse
2018-01-08 15:38:18 +00:00
committed by Catalin Marinas
parent 83f8ee3a73
commit 79e9aa59dc
4 changed files with 113 additions and 14 deletions
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20
arch/arm64/kernel/sdei.c
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@@ -10,7 +10,9 @@
#include <asm/alternative.h>
#include <asm/kprobes.h>
#include <asm/mmu.h>
#include <asm/ptrace.h>
#include <asm/sections.h>
#include <asm/sysreg.h>
#include <asm/vmap_stack.h>
@@ -124,7 +126,18 @@ unsigned long sdei_arch_get_entry_point(int conduit)
}
sdei_exit_mode = (conduit == CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC;
return (unsigned long)__sdei_asm_handler;
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
if (arm64_kernel_unmapped_at_el0()) {
unsigned long offset;
offset = (unsigned long)__sdei_asm_entry_trampoline -
(unsigned long)__entry_tramp_text_start;
return TRAMP_VALIAS + offset;
} else
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
return (unsigned long)__sdei_asm_handler;
}
/*
@@ -138,11 +151,14 @@ static __kprobes unsigned long _sdei_handler(struct pt_regs *regs,
{
u32 mode;
int i, err = 0;
const int clobbered_registers = 4;
int clobbered_registers = 4;
u64 elr = read_sysreg(elr_el1);
u32 kernel_mode = read_sysreg(CurrentEL) | 1; /* +SPSel */
unsigned long vbar = read_sysreg(vbar_el1);
if (arm64_kernel_unmapped_at_el0())
clobbered_registers++;
/* Retrieve the missing registers values */
for (i = 0; i < clobbered_registers; i++) {
/* from within the handler, this call always succeeds */