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lguest: fix guest crash on non-linear addresses in gdt pvops

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Fixes guest crash 'lguest: bad read address 0x4800000 len 256'

The new per-cpu allocator ends up handing a non-linear address to
write_gdt_entry.  We do __pa() on it, and hand it to the host, which
kills us.

I've long wanted to make the hypercall "LOAD_GDT_ENTRY" to match the IDT
code, but had no pressing reason until now.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: lguest@ozlabs.org
This commit is contained in:
Rusty Russell
2009-04-19 23:14:00 -06:00
parent 88df781afb
commit a489f0b555
5 changed files with 21 additions and 17 deletions
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13
drivers/lguest/segments.c
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@@ -144,18 +144,19 @@ void copy_gdt(const struct lg_cpu *cpu, struct desc_struct *gdt)
gdt[i] = cpu->arch.gdt[i];
}
/*H:620 This is where the Guest asks us to load a new GDT (LHCALL_LOAD_GDT).
* We copy it from the Guest and tweak the entries. */
void load_guest_gdt(struct lg_cpu *cpu, unsigned long table, u32 num)
/*H:620 This is where the Guest asks us to load a new GDT entry
* (LHCALL_LOAD_GDT_ENTRY). We tweak the entry and copy it in. */
void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi)
{
/* We assume the Guest has the same number of GDT entries as the
* Host, otherwise we'd have to dynamically allocate the Guest GDT. */
if (num > ARRAY_SIZE(cpu->arch.gdt))
kill_guest(cpu, "too many gdt entries %i", num);
/* We read the whole thing in, then fix it up. */
__lgread(cpu, cpu->arch.gdt, table, num * sizeof(cpu->arch.gdt[0]));
fixup_gdt_table(cpu, 0, ARRAY_SIZE(cpu->arch.gdt));
/* Set it up, then fix it. */
cpu->arch.gdt[num].a = lo;
cpu->arch.gdt[num].b = hi;
fixup_gdt_table(cpu, num, num+1);
/* Mark that the GDT changed so the core knows it has to copy it again,
* even if the Guest is run on the same CPU. */
cpu->changed |= CHANGED_GDT;