diff options
| author | Bill Paul <wpaul@windriver.com> | 2015-03-09 15:48:01 -0700 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2015-03-10 11:18:24 +0100 |
| commit | ac57622985220de064059971f9ccb00905e9bd04 (patch) | |
| tree | 0a50e0158c2c9b073881b8d2661ee90384bb8143 | |
| parent | ae071cc851d7150d3a9950c642570830bb85729e (diff) | |
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>
| -rw-r--r-- | target-i386/seg_helper.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/target-i386/seg_helper.c b/target-i386/seg_helper.c index fa374d0c0b..2bc757af31 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) | |