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[Qemu-devel] [PATCH] target-i386: fix segment limit check in ljmp
From: |
andrew |
Subject: |
[Qemu-devel] [PATCH] target-i386: fix segment limit check in ljmp |
Date: |
Wed, 15 Aug 2018 21:19:03 -0400 |
From: Andrew Oates <address@hidden>
The current implementation has three bugs,
* segment limits are not enforced in protected mode if the L bit is set
in the target segment descriptor[1]
* segment limits are not enforced in compatability mode (ljmp to 32-bit
code segment in long mode)
* #GP(new_cs) is generated rather than #GP(0)
Now the segment limits are enforced if we're not in long mode OR the
target code segment doesn't have the L bit set.
[1] this is an invalid configuration (in protected mode the L bit is
reserved and should be set to zero), but qemu doesn't enforce that.
Signed-off-by: Andrew Oates <address@hidden>
---
The limit check is still incorrect for ljmp-through-call-gate in 64-bit
mode. That's a larger fix I'm still working on.
target/i386/seg_helper.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/target/i386/seg_helper.c b/target/i386/seg_helper.c
index 00301a0c04..975365fd30 100644
--- a/target/i386/seg_helper.c
+++ b/target/i386/seg_helper.c
@@ -1628,8 +1628,8 @@ void helper_ljmp_protected(CPUX86State *env, int new_cs,
target_ulong new_eip,
}
limit = get_seg_limit(e1, e2);
if (new_eip > limit &&
- !(env->hflags & HF_LMA_MASK) && !(e2 & DESC_L_MASK)) {
- raise_exception_err_ra(env, EXCP0D_GPF, new_cs & 0xfffc, GETPC());
+ (!(env->hflags & HF_LMA_MASK) || !(e2 & DESC_L_MASK))) {
+ raise_exception_err_ra(env, EXCP0D_GPF, 0, GETPC());
}
cpu_x86_load_seg_cache(env, R_CS, (new_cs & 0xfffc) | cpl,
get_seg_base(e1, e2), limit, e2);
--
2.17.0
- [Qemu-devel] [PATCH] target-i386: fix segment limit check in ljmp,
andrew <=