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change init_gdt to update the gdt via write_gdt, rather than a direct write.

PATCH Applied Alex Nixon 2 participants 2 messages Aug 15, 2008 x86

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Alex Nixon

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PATCH 1/1 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(-)
arch/x86/kernel/smpcommon.c +4 -4
index 99941b3..29f8bf0 100644
@@ -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;
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1.5.4.3
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Quoted 6 lines · Alex Nixon

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.

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