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[Qemu-devel] [PULL 35/74] target-i386: fix segment limit check in ljmp

From: Paolo Bonzini
Subject: [Qemu-devel] [PULL 35/74] target-i386: fix segment limit check in ljmp
Date: Tue, 21 Aug 2018 19:02:07 +0200

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
 * segment limits are not enforced in compatibility 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.

Signed-off-by: Andrew Oates <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
 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 b2adddc..d1cbc6e 100644
--- a/target/i386/seg_helper.c
+++ b/target/i386/seg_helper.c
@@ -1633,8 +1633,8 @@ 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);

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