Hi Bill,
sending text only e-mails might help. Usually git send-email is better
than using KMail or other mail software.
Use tools like git gui to get a correct signature. Any optional personal
comments should come directly after
the line with ---. Could you please re-send your patch? Check it before
sending with scripts/checkpatch.pl.
Maybe this looks like much regulations to fix a bug, but some rules are
necessary to keep a project
like QEMU alive.
Cc'ing Paolo and Richard because this might be an important bug fix for
the next release.
(scripts/get_maintainer.pl tells which maintainers should be cc'ed).
Regards
Stefan
Am 09.03.2015 um 23:02 schrieb Bill Paul:
Nobody has commented on this yet. 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.
Can someone confirm that this is in fact a real bug? The Intel
architecture manual seems quite clear about the SYSRET behavior. The
bug seems to have been around as far back as QEMU 0.10.5.
I am using QEMU 2.2.0 on FreeBSD/amd64 9.1-RELEASE.
-Bill
Signed-off-by: Bill Paul <wp...@windriver.com>
---
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 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) |
--
1.8.0
--
=============================================================================
-Bill Paul (510) 749-2329 | Senior Member of Technical Staff,
wp...@windriver.com | Master of Unix-Fu - Wind River Systems
=============================================================================
"I put a dollar in a change machine. Nothing changed." - George Carlin
=============================================================================
