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authorBill Paul <wpaul@windriver.com>2015-03-09 15:48:01 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2015-03-10 11:18:24 +0100
commitac57622985220de064059971f9ccb00905e9bd04 (patch)
tree0a50e0158c2c9b073881b8d2661ee90384bb8143 /target-i386
parentae071cc851d7150d3a9950c642570830bb85729e (diff)
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x86: fix SS selector in SYSRET
According to my reading of the Intel documentation, the SYSRET instruction is supposed to force the RPL bits of the %ss register to 3 when returning to user mode. The actual sequence is: SS.Selector <-- (IA32_STAR[63:48]+8) OR 3; (* RPL forced to 3 *) However, the code in helper_sysret() leaves them at 0 (in other words, the "OR 3" part of the above sequence is missing). It does set the privilege level bits of %cs correctly though. This has caused me trouble with some of my VxWorks development: code that runs okay on real hardware will crash on QEMU, unless I apply the patch below. Signed-off-by: Bill Paul <wpaul@windriver.com> Message-Id: <201503091548.01462.wpaul@windriver.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'target-i386')
-rw-r--r--target-i386/seg_helper.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/target-i386/seg_helper.c b/target-i386/seg_helper.c
index fa374d0..2bc757a 100644
--- a/target-i386/seg_helper.c
+++ b/target-i386/seg_helper.c
@@ -1043,7 +1043,7 @@ void helper_sysret(CPUX86State *env, int dflag)
DESC_CS_MASK | DESC_R_MASK | DESC_A_MASK);
env->eip = (uint32_t)env->regs[R_ECX];
}
- cpu_x86_load_seg_cache(env, R_SS, selector + 8,
+ cpu_x86_load_seg_cache(env, R_SS, (selector + 8) | 3,
0, 0xffffffff,
DESC_G_MASK | DESC_B_MASK | DESC_P_MASK |
DESC_S_MASK | (3 << DESC_DPL_SHIFT) |
@@ -1056,7 +1056,7 @@ void helper_sysret(CPUX86State *env, int dflag)
DESC_S_MASK | (3 << DESC_DPL_SHIFT) |
DESC_CS_MASK | DESC_R_MASK | DESC_A_MASK);
env->eip = (uint32_t)env->regs[R_ECX];
- cpu_x86_load_seg_cache(env, R_SS, selector + 8,
+ cpu_x86_load_seg_cache(env, R_SS, (selector + 8) | 3,
0, 0xffffffff,
DESC_G_MASK | DESC_B_MASK | DESC_P_MASK |
DESC_S_MASK | (3 << DESC_DPL_SHIFT) |