linux/arch/arm/include/asm/processor.h

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/*
* arch/arm/include/asm/processor.h
*
* Copyright (C) 1995-1999 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef __ASM_ARM_PROCESSOR_H
#define __ASM_ARM_PROCESSOR_H
/*
* Default implementation of macro that returns current
* instruction pointer ("program counter").
*/
#define current_text_addr() ({ __label__ _l; _l: &&_l;})
#ifdef __KERNEL__
#include <asm/hw_breakpoint.h>
#include <asm/ptrace.h>
#include <asm/types.h>
#include <asm/unified.h>
#ifdef __KERNEL__
#define STACK_TOP ((current->personality & ADDR_LIMIT_32BIT) ? \
TASK_SIZE : TASK_SIZE_26)
#define STACK_TOP_MAX TASK_SIZE
#endif
struct debug_info {
#ifdef CONFIG_HAVE_HW_BREAKPOINT
struct perf_event *hbp[ARM_MAX_HBP_SLOTS];
#endif
};
struct thread_struct {
/* fault info */
unsigned long address;
unsigned long trap_no;
unsigned long error_code;
/* debugging */
struct debug_info debug;
};
#define INIT_THREAD { }
#ifdef CONFIG_MMU
#define nommu_start_thread(regs) do { } while (0)
#else
#define nommu_start_thread(regs) regs->ARM_r10 = current->mm->start_data
#endif
#define start_thread(regs,pc,sp) \
({ \
memset(regs->uregs, 0, sizeof(regs->uregs)); \
if (current->personality & ADDR_LIMIT_32BIT) \
regs->ARM_cpsr = USR_MODE; \
else \
regs->ARM_cpsr = USR26_MODE; \
if (elf_hwcap & HWCAP_THUMB && pc & 1) \
regs->ARM_cpsr |= PSR_T_BIT; \
regs->ARM_cpsr |= PSR_ENDSTATE; \
regs->ARM_pc = pc & ~1; /* pc */ \
regs->ARM_sp = sp; /* sp */ \
nommu_start_thread(regs); \
})
/* Forward declaration, a strange C thing */
struct task_struct;
/* Free all resources held by a thread. */
extern void release_thread(struct task_struct *);
unsigned long get_wchan(struct task_struct *p);
#if __LINUX_ARM_ARCH__ == 6 || defined(CONFIG_ARM_ERRATA_754327)
#define cpu_relax() smp_mb()
#else
#define cpu_relax() barrier()
#endif
#define task_pt_regs(p) \
((struct pt_regs *)(THREAD_START_SP + task_stack_page(p)) - 1)
#define KSTK_EIP(tsk) task_pt_regs(tsk)->ARM_pc
#define KSTK_ESP(tsk) task_pt_regs(tsk)->ARM_sp
#ifdef CONFIG_SMP
#define __ALT_SMP_ASM(smp, up) \
"9998: " smp "\n" \
" .pushsection \".alt.smp.init\", \"a\"\n" \
" .long 9998b\n" \
" " up "\n" \
" .popsection\n"
#else
#define __ALT_SMP_ASM(smp, up) up
#endif
/*
* Prefetching support - only ARMv5.
*/
#if __LINUX_ARM_ARCH__ >= 5
#define ARCH_HAS_PREFETCH
[ARM] 4016/1: prefetch macro is wrong wrt gcc's "delete-null-pointer-checks" optimization The gcc manual says: |`-fdelete-null-pointer-checks' | Use global dataflow analysis to identify and eliminate useless | checks for null pointers. The compiler assumes that dereferencing | a null pointer would have halted the program. If a pointer is | checked after it has already been dereferenced, it cannot be null. | Enabled at levels `-O2', `-O3', `-Os'. Now the problem can be seen with this test case: #include <linux/prefetch.h> extern void bar(char *x); void foo(char *x) { prefetch(x); if (x) bar(x); } Because the constraint to the inline asm used in the prefetch() macro is a memory operand, gcc assumes that the asm code does dereference the pointer and the delete-null-pointer-checks optimization kicks in. Inspection of generated assembly for the above example shows that bar() is indeed called unconditionally without any test on the value of x. Of course in the prefetch case there is no real dereference and it cannot be assumed that a null pointer would have been caught at that point. This causes kernel oopses with constructs like hlist_for_each_entry() where the list's 'next' content is prefetched before the pointer is tested against NULL, and only when gcc feels like applying this optimization which doesn't happen all the time with more complex code. It appears that the way to prevent delete-null-pointer-checks optimization to occur in this case is to make prefetch() into a static inline function instead of a macro. At least this is what is done on x86_64 where a similar inline asm memory operand is used (I presume they would have seen the same problem if it didn't work) and resulting code for the above example confirms that. An alternative would consist of replacing the memory operand by a register operand containing the pointer, and use the addressing mode explicitly in the asm template. But that would be less optimal than an offsettable memory reference. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2006-12-13 17:39:26 +00:00
static inline void prefetch(const void *ptr)
{
__asm__ __volatile__(
"pld\t%a0"
:: "p" (ptr));
[ARM] 4016/1: prefetch macro is wrong wrt gcc's "delete-null-pointer-checks" optimization The gcc manual says: |`-fdelete-null-pointer-checks' | Use global dataflow analysis to identify and eliminate useless | checks for null pointers. The compiler assumes that dereferencing | a null pointer would have halted the program. If a pointer is | checked after it has already been dereferenced, it cannot be null. | Enabled at levels `-O2', `-O3', `-Os'. Now the problem can be seen with this test case: #include <linux/prefetch.h> extern void bar(char *x); void foo(char *x) { prefetch(x); if (x) bar(x); } Because the constraint to the inline asm used in the prefetch() macro is a memory operand, gcc assumes that the asm code does dereference the pointer and the delete-null-pointer-checks optimization kicks in. Inspection of generated assembly for the above example shows that bar() is indeed called unconditionally without any test on the value of x. Of course in the prefetch case there is no real dereference and it cannot be assumed that a null pointer would have been caught at that point. This causes kernel oopses with constructs like hlist_for_each_entry() where the list's 'next' content is prefetched before the pointer is tested against NULL, and only when gcc feels like applying this optimization which doesn't happen all the time with more complex code. It appears that the way to prevent delete-null-pointer-checks optimization to occur in this case is to make prefetch() into a static inline function instead of a macro. At least this is what is done on x86_64 where a similar inline asm memory operand is used (I presume they would have seen the same problem if it didn't work) and resulting code for the above example confirms that. An alternative would consist of replacing the memory operand by a register operand containing the pointer, and use the addressing mode explicitly in the asm template. But that would be less optimal than an offsettable memory reference. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2006-12-13 17:39:26 +00:00
}
#if __LINUX_ARM_ARCH__ >= 7 && defined(CONFIG_SMP)
#define ARCH_HAS_PREFETCHW
static inline void prefetchw(const void *ptr)
{
__asm__ __volatile__(
".arch_extension mp\n"
__ALT_SMP_ASM(
WASM(pldw) "\t%a0",
WASM(pld) "\t%a0"
)
:: "p" (ptr));
}
#endif
#endif
#define HAVE_ARCH_PICK_MMAP_LAYOUT
#endif
#endif /* __ASM_ARM_PROCESSOR_H */