[PATCH] Arm64: convert soft_restart() to assembly code

Arun Chandran
2014-08-12T12:42:45Z

soft_restart() will fail on arm64 systems that does not
quarantee the flushing of cache to PoC with flush_cache_all().

soft_restart(addr)
{
push_to_stack(addr);

Do mm setup for restart;
Flush&turnoff D-cache;

pop_from_stack(addr); --> fails here as addr is not at PoC
cpu_reset(addr) --> Jumps to invalid address
}

So convert the whole code to assembly to make sure that addr
is not pushed to stack.

Signed-off-by: Arun Chandran <achandran@mvista.com>
---
arch/arm64/include/asm/proc-fns.h | 1 +
arch/arm64/include/asm/system_misc.h | 1 -
arch/arm64/kernel/process.c | 38 ++--------------------------------
arch/arm64/mm/proc.S | 34 ++++++++++++++++++++++++++++++
4 files changed, 37 insertions(+), 37 deletions(-)

diff --git a/arch/arm64/include/asm/proc-fns.h b/arch/arm64/include/asm/proc-fns.h
index 0c657bb..e18d5d0 100644
--- a/arch/arm64/include/asm/proc-fns.h
+++ b/arch/arm64/include/asm/proc-fns.h
@@ -32,6 +32,7 @@ extern void cpu_cache_off(void);
extern void cpu_do_idle(void);
extern void cpu_do_switch_mm(unsigned long pgd_phys, struct mm_struct *mm);
extern void cpu_reset(unsigned long addr) __attribute__((noreturn));
+extern void cpu_soft_restart(unsigned long addr) __attribute__((noreturn));
extern void cpu_do_suspend(struct cpu_suspend_ctx *ptr);
extern u64 cpu_do_resume(phys_addr_t ptr, u64 idmap_ttbr);

diff --git a/arch/arm64/include/asm/system_misc.h b/arch/arm64/include/asm/system_misc.h
index 7a18fab..659fbf5 100644
--- a/arch/arm64/include/asm/system_misc.h
+++ b/arch/arm64/include/asm/system_misc.h
@@ -41,7 +41,6 @@ struct mm_struct;
extern void show_pte(struct mm_struct *mm, unsigned long addr);
extern void __show_regs(struct pt_regs *);

-void soft_restart(unsigned long);
extern void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);

#define UDBG_UNDEFINED (1 << 0)
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 1309d64..3ca1ade 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -57,40 +57,6 @@ unsigned long __stack_chk_guard __read_mostly;
EXPORT_SYMBOL(__stack_chk_guard);
#endif

-static void setup_restart(void)
-{
- /*
- * Tell the mm system that we are going to reboot -
- * we may need it to insert some 1:1 mappings so that
- * soft boot works.
- */
- setup_mm_for_reboot();
-
- /* Clean and invalidate caches */
- flush_cache_all();
-
- /* Turn D-cache off */
- cpu_cache_off();
-
- /* Push out any further dirty data, and ensure cache is empty */
- flush_cache_all();
-}
-
-void soft_restart(unsigned long addr)
-{
- typedef void (*phys_reset_t)(unsigned long);
- phys_reset_t phys_reset;
-
- setup_restart();
-
- /* Switch to the identity mapping */
- phys_reset = (phys_reset_t)virt_to_phys(cpu_reset);
- phys_reset(addr);
-
- /* Should never get here */
- BUG();
-}
-
/*
* Function pointers to optional machine specific functions
*/
@@ -162,8 +128,8 @@ void machine_power_off(void)

/*
* Restart requires that the secondary CPUs stop performing any activity
- * while the primary CPU resets the system. Systems with a single CPU can
- * use soft_restart() as their machine descriptor's .restart hook, since that
+ * while the primary CPU resets the system. Systems with a single CPU can use
+ * cpu_soft_restart() as their machine descriptor's .restart hook, since that
* will cause the only available CPU to reset. Systems with multiple CPUs must
* provide a HW restart implementation, to ensure that all CPUs reset@once.
* This is required so that any code running after reset on the primary CPU
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 7736779..a7c3fce 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -76,6 +76,40 @@ ENTRY(cpu_reset)
ret x0
ENDPROC(cpu_reset)

+ .align 3
+1: .quad memstart_addr
+
+ENTRY(cpu_soft_restart)
+ adr x1, cpu_reset
+ adr x2, 1b
+
+ /* virt_to_phys(cpu_reset) */
+ ldr x3, [x2]
+ ldr x3, [x3]
+ mov x4, #1
+ lsl x4, x4, #(VA_BITS - 1)
+ add x1, x1, x4
+ add x1, x1, x3
+
+ /* Save it; We can't use stack as it is going to run with caches OFF */
+ mov x19, x0
+ mov x20, x1
+
+ bl setup_mm_for_reboot
+
+ bl flush_cache_all
+ /* Turn D-cache off */
+ bl cpu_cache_off
+ /* Push out any further dirty data, and ensure cache is empty */
+ bl flush_cache_all
+
+ mov x0, x19
+
+ br x20
+ /* It should never come back */
+ bl panic
+ENDPROC(cpu_soft_restart)
+
/*
* cpu_do_idle()
*
--
1.7.9.5