Commit 947e76cd authored by Brian Gerst's avatar Brian Gerst Committed by Tejun Heo
Browse files

x86: move stack_canary into irq_stack



Impact: x86_64 percpu area layout change, irq_stack now at the beginning

Now that the PDA is empty except for the stack canary, it can be removed.
The irqstack is moved to the start of the per-cpu section.  If the stack
protector is enabled, the canary overlaps the bottom 48 bytes of the irqstack.

tj: * updated subject
    * dropped asm relocation of irq_stack_ptr
    * updated comments a bit
    * rebased on top of stack canary changes
Signed-off-by: default avatarBrian Gerst <brgerst@gmail.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 8c7e58e6
......@@ -17,9 +17,6 @@ struct x8664_pda {
unsigned long unused4;
int unused5;
unsigned int unused6; /* 36 was cpunumber */
unsigned long stack_canary; /* 40 stack canary value */
/* gcc-ABI: this canary MUST be at
offset 40!!! */
short in_bootmem; /* pda lives in bootmem */
} ____cacheline_aligned_in_smp;
......
......@@ -133,12 +133,6 @@ do { \
/* We can use this directly for local CPU (faster). */
DECLARE_PER_CPU(unsigned long, this_cpu_off);
#ifdef CONFIG_X86_64
extern void load_pda_offset(int cpu);
#else
static inline void load_pda_offset(int cpu) { }
#endif
#endif /* !__ASSEMBLY__ */
#ifdef CONFIG_SMP
......
......@@ -379,8 +379,29 @@ union thread_xstate {
#ifdef CONFIG_X86_64
DECLARE_PER_CPU(struct orig_ist, orig_ist);
DECLARE_PER_CPU(char[IRQ_STACK_SIZE], irq_stack);
union irq_stack_union {
char irq_stack[IRQ_STACK_SIZE];
/*
* GCC hardcodes the stack canary as %gs:40. Since the
* irq_stack is the object at %gs:0, we reserve the bottom
* 48 bytes of the irq stack for the canary.
*/
struct {
char gs_base[40];
unsigned long stack_canary;
};
};
DECLARE_PER_CPU(union irq_stack_union, irq_stack_union);
DECLARE_PER_CPU(char *, irq_stack_ptr);
static inline void load_gs_base(int cpu)
{
/* Memory clobbers used to order pda/percpu accesses */
mb();
wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));
mb();
}
#endif
extern void print_cpu_info(struct cpuinfo_x86 *);
......
......@@ -2,7 +2,7 @@
#define _ASM_STACKPROTECTOR_H 1
#include <asm/tsc.h>
#include <asm/pda.h>
#include <asm/processor.h>
/*
* Initialize the stackprotector canary value.
......@@ -19,7 +19,7 @@ static __always_inline void boot_init_stack_canary(void)
* Build time only check to make sure the stack_canary is at
* offset 40 in the pda; this is a gcc ABI requirement
*/
BUILD_BUG_ON(offsetof(struct x8664_pda, stack_canary) != 40);
BUILD_BUG_ON(offsetof(union irq_stack_union, stack_canary) != 40);
/*
* We both use the random pool and the current TSC as a source
......@@ -32,7 +32,7 @@ static __always_inline void boot_init_stack_canary(void)
canary += tsc + (tsc << 32UL);
current->stack_canary = canary;
write_pda(stack_canary, canary);
percpu_write(irq_stack_union.stack_canary, canary);
}
#endif
......@@ -89,10 +89,10 @@ do { \
#ifdef CONFIG_CC_STACKPROTECTOR
#define __switch_canary \
"movq %P[task_canary](%%rsi),%%r8\n\t" \
"movq %%r8,%%gs:%P[pda_canary]\n\t"
"movq %%r8,%%gs:%P[gs_canary]\n\t"
#define __switch_canary_param \
, [task_canary] "i" (offsetof(struct task_struct, stack_canary)) \
, [pda_canary] "i" (offsetof(struct x8664_pda, stack_canary))
, [gs_canary] "i" (offsetof(union irq_stack_union, stack_canary))
#else /* CC_STACKPROTECTOR */
#define __switch_canary
#define __switch_canary_param
......
......@@ -48,10 +48,6 @@ int main(void)
#endif
BLANK();
#undef ENTRY
#define ENTRY(entry) DEFINE(pda_ ## entry, offsetof(struct x8664_pda, entry))
DEFINE(pda_size, sizeof(struct x8664_pda));
BLANK();
#undef ENTRY
#ifdef CONFIG_PARAVIRT
BLANK();
OFFSET(PARAVIRT_enabled, pv_info, paravirt_enabled);
......
......@@ -881,12 +881,13 @@ __setup("clearcpuid=", setup_disablecpuid);
#ifdef CONFIG_X86_64
struct desc_ptr idt_descr = { 256 * 16 - 1, (unsigned long) idt_table };
DEFINE_PER_CPU_PAGE_ALIGNED(char[IRQ_STACK_SIZE], irq_stack);
DEFINE_PER_CPU_FIRST(union irq_stack_union,
irq_stack_union) __aligned(PAGE_SIZE);
#ifdef CONFIG_SMP
DEFINE_PER_CPU(char *, irq_stack_ptr); /* will be set during per cpu init */
#else
DEFINE_PER_CPU(char *, irq_stack_ptr) =
per_cpu_var(irq_stack) + IRQ_STACK_SIZE - 64;
per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE - 64;
#endif
DEFINE_PER_CPU(unsigned long, kernel_stack) =
......@@ -960,7 +961,7 @@ void __cpuinit cpu_init(void)
loadsegment(fs, 0);
loadsegment(gs, 0);
load_pda_offset(cpu);
load_gs_base(cpu);
#ifdef CONFIG_NUMA
if (cpu != 0 && percpu_read(node_number) == 0 &&
......
......@@ -242,13 +242,10 @@ ENTRY(secondary_startup_64)
/* Set up %gs.
*
* On SMP, %gs should point to the per-cpu area. For initial
* boot, make %gs point to the init data section. For a
* secondary CPU,initial_gs should be set to its pda address
* before the CPU runs this code.
*
* On UP, initial_gs points to PER_CPU_VAR(__pda) and doesn't
* change.
* The base of %gs always points to the bottom of the irqstack
* union. If the stack protector canary is enabled, it is
* located at %gs:40. Note that, on SMP, the boot cpu uses
* init data section till per cpu areas are set up.
*/
movl $MSR_GS_BASE,%ecx
movq initial_gs(%rip),%rax
......@@ -281,7 +278,7 @@ ENTRY(secondary_startup_64)
#ifdef CONFIG_SMP
.quad __per_cpu_load
#else
.quad PER_CPU_VAR(__pda)
.quad PER_CPU_VAR(irq_stack_union)
#endif
__FINITDATA
......
......@@ -77,30 +77,6 @@ static void __init setup_node_to_cpumask_map(void);
static inline void setup_node_to_cpumask_map(void) { }
#endif
/*
* Define load_pda_offset() and per-cpu __pda for x86_64.
* load_pda_offset() is responsible for loading the offset of pda into
* %gs.
*
* On SMP, pda offset also duals as percpu base address and thus it
* should be at the start of per-cpu area. To achieve this, it's
* preallocated in vmlinux_64.lds.S directly instead of using
* DEFINE_PER_CPU().
*/
#ifdef CONFIG_X86_64
void __cpuinit load_pda_offset(int cpu)
{
/* Memory clobbers used to order pda/percpu accesses */
mb();
wrmsrl(MSR_GS_BASE, cpu_pda(cpu));
mb();
}
#ifndef CONFIG_SMP
DEFINE_PER_CPU(struct x8664_pda, __pda);
#endif
EXPORT_PER_CPU_SYMBOL(__pda);
#endif /* CONFIG_SMP && CONFIG_X86_64 */
#ifdef CONFIG_X86_64
/* correctly size the local cpu masks */
......@@ -207,15 +183,13 @@ void __init setup_per_cpu_areas(void)
per_cpu(cpu_number, cpu) = cpu;
#ifdef CONFIG_X86_64
per_cpu(irq_stack_ptr, cpu) =
(char *)per_cpu(irq_stack, cpu) + IRQ_STACK_SIZE - 64;
per_cpu(irq_stack_union.irq_stack, cpu) + IRQ_STACK_SIZE - 64;
/*
* CPU0 modified pda in the init data area, reload pda
* offset for CPU0 and clear the area for others.
* Up to this point, CPU0 has been using .data.init
* area. Reload %gs offset for CPU0.
*/
if (cpu == 0)
load_pda_offset(0);
else
memset(cpu_pda(cpu), 0, sizeof(*cpu_pda(cpu)));
load_gs_base(cpu);
#endif
DBG("PERCPU: cpu %4d %p\n", cpu, ptr);
......
......@@ -220,8 +220,7 @@ SECTIONS
* so that it can be accessed as a percpu variable.
*/
. = ALIGN(PAGE_SIZE);
PERCPU_VADDR_PREALLOC(0, :percpu, pda_size)
per_cpu____pda = __per_cpu_start;
PERCPU_VADDR(0, :percpu)
#else
PERCPU(PAGE_SIZE)
#endif
......@@ -262,3 +261,8 @@ SECTIONS
*/
ASSERT((_end - _text <= KERNEL_IMAGE_SIZE),
"kernel image bigger than KERNEL_IMAGE_SIZE")
#ifdef CONFIG_SMP
ASSERT((per_cpu__irq_stack_union == 0),
"irq_stack_union is not at start of per-cpu area");
#endif
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment