Re: [PATCH] x86: Clean up stack access code in irq_32.c

From: H. Peter Anvin
Date: Sun Oct 12 2014 - 12:48:15 EST


We changed this to asm because the C broke some compilers. Why are you changing it back?

On October 12, 2014 9:43:53 AM PDT, Chuck Ebbert <cebbert.lkml@xxxxxxxxx> wrote:
>Use C instead of asm for accessing the stack pointer. And define some
>macros to make the code easier to understand.
>
>Signed-off-by: Chuck Ebbert <cebbert.lkml@xxxxxxxxx>
>
>diff --git a/arch/x86/include/asm/page_32_types.h
>b/arch/x86/include/asm/page_32_types.h
>index f48b17d..a8ca0cb 100644
>--- a/arch/x86/include/asm/page_32_types.h
>+++ b/arch/x86/include/asm/page_32_types.h
>@@ -19,6 +19,8 @@
>
> #define THREAD_SIZE_ORDER 1
> #define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
>+#define THREAD_SIZE_MASK (THREAD_SIZE - 1)
>+#define CURRENT_MASK (~THREAD_SIZE_MASK)
>
> #define STACKFAULT_STACK 0
> #define DOUBLEFAULT_STACK 1
>diff --git a/arch/x86/include/asm/page_64_types.h
>b/arch/x86/include/asm/page_64_types.h
>index 6782051..ded89b0 100644
>--- a/arch/x86/include/asm/page_64_types.h
>+++ b/arch/x86/include/asm/page_64_types.h
>@@ -2,8 +2,9 @@
> #define _ASM_X86_PAGE_64_DEFS_H
>
> #define THREAD_SIZE_ORDER 2
>-#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
>-#define CURRENT_MASK (~(THREAD_SIZE - 1))
>+#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
>+#define THREAD_SIZE_MASK (THREAD_SIZE - 1)
>+#define CURRENT_MASK (~THREAD_SIZE_MASK)
>
> #define EXCEPTION_STACK_ORDER 0
> #define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)
>diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
>index 63ce838..bef90fc 100644
>--- a/arch/x86/kernel/irq_32.c
>+++ b/arch/x86/kernel/irq_32.c
>@@ -27,6 +27,12 @@ EXPORT_PER_CPU_SYMBOL(irq_stat);
> DEFINE_PER_CPU(struct pt_regs *, irq_regs);
> EXPORT_PER_CPU_SYMBOL(irq_regs);
>
>+/* how to get the current stack pointer from C */
>+#define current_stack_pointer ({ \
>+ register unsigned long sp asm("esp"); \
>+ sp; \
>+})
>+
> #ifdef CONFIG_DEBUG_STACKOVERFLOW
>
> int sysctl_panic_on_stackoverflow __read_mostly;
>@@ -34,12 +40,8 @@ int sysctl_panic_on_stackoverflow __read_mostly;
> /* Debugging check for stack overflow: is there less than 1KB free? */
> static int check_stack_overflow(void)
> {
>- long sp;
>-
>- __asm__ __volatile__("andl %%esp,%0" :
>- "=r" (sp) : "0" (THREAD_SIZE - 1));
>-
>- return sp < (sizeof(struct thread_info) + STACK_WARN);
>+ return (current_stack_pointer & THREAD_SIZE_MASK)
>+ < sizeof(struct thread_info) + STACK_WARN;
> }
>
> static void print_stack_overflow(void)
>@@ -69,16 +71,9 @@ static void call_on_stack(void *func, void *stack)
> : "memory", "cc", "edx", "ecx", "eax");
> }
>
>-/* how to get the current stack pointer from C */
>-#define current_stack_pointer ({ \
>- unsigned long sp; \
>- asm("mov %%esp,%0" : "=g" (sp)); \
>- sp; \
>-})
>-
> static inline void *current_stack(void)
> {
>- return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
>+ return (void *)(current_stack_pointer & CURRENT_MASK);
> }
>
> static inline int

--
Sent from my mobile phone. Please pardon brevity and lack of formatting.
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