2008-08-15 16:21:19

by Alex Nixon

Subject: [PATCH] change init_gdt to update the gdt via write_gdt, rather than a direct write.

From: Alex Nixon <[email protected]>
Date: Fri, 15 Aug 2008 11:21:56 +0100
Subject: [PATCH] change init_gdt to update the gdt via write_gdt, rather than a direct write.

By writing directly, a memory access violation can occur whilst hotplugging a CPU if the entry was previously marked read-only.

Signed-off-by: Alex Nixon <[email protected]>
---
arch/x86/kernel/smpcommon.c | 8 ++++----
1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/smpcommon.c b/arch/x86/kernel/smpcommon.c
index 99941b3..29f8bf0 100644
--- a/arch/x86/kernel/smpcommon.c
+++ b/arch/x86/kernel/smpcommon.c
@@ -13,13 +13,13 @@ EXPORT_PER_CPU_SYMBOL(this_cpu_off);
secondary which will soon come up. */
__cpuinit void init_gdt(int cpu)
{
- struct desc_struct *gdt = get_cpu_gdt_table(cpu);
+ struct desc_struct gdt;

- pack_descriptor(&gdt[GDT_ENTRY_PERCPU],
- __per_cpu_offset[cpu], 0xFFFFF,
+ pack_descriptor(&gdt, __per_cpu_offset[cpu], 0xFFFFF,
0x2 | DESCTYPE_S, 0x8);
+ gdt.s = 1;

- gdt[GDT_ENTRY_PERCPU].s = 1;
+ write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PERCPU, &gdt, DESCTYPE_S);

per_cpu(this_cpu_off, cpu) = __per_cpu_offset[cpu];
per_cpu(cpu_number, cpu) = cpu;
--
1.5.4.3

2008-08-15 16:58:47

by Ingo Molnar

Subject: Re: [PATCH] change init_gdt to update the gdt via write_gdt, rather than a direct write.

* Alex Nixon <[email protected]> wrote:

> From: Alex Nixon <[email protected]>
> Date: Fri, 15 Aug 2008 11:21:56 +0100
> Subject: [PATCH] change init_gdt to update the gdt via write_gdt, rather than a direct write.
>
> By writing directly, a memory access violation can occur whilst
> hotplugging a CPU if the entry was previously marked read-only.

applied to tip/x86/urgent - thanks Alex.

Ingo