diff options
| author | Peter Maydell <peter.maydell@linaro.org> | 2016-03-04 11:30:16 +0000 |
|---|---|---|
| committer | Peter Maydell <peter.maydell@linaro.org> | 2016-03-04 11:30:16 +0000 |
| commit | 8c4f0eb94cc65ee32a12feba88d0b32e3665d5ea (patch) | |
| tree | 81d58dad781a1e87f2e41094dd721178083b0fb3 /target-arm/helper.c | |
| parent | 2d3b7c0164e1b9287304bc70dd6ed071ba3e8dfc (diff) | |
target-arm: Correct handling of writes to CPSR mode bits from gdb in usermode
In helper.c the expression
(env->uncached_cpsr & CPSR_M) != CPSR_USER
is always true; the right hand side was supposed to be ARM_CPU_MODE_USR
(an error in commit cb01d391).
Since the incorrect expression was always true, this just meant that
commit cb01d391 had no effect.
However simply changing the RHS here would reveal a logic error: if
the mode is USR we wish to completely ignore the attempt to set the
mode bits, which means that we must clear the CPSR_M bits from mask
to avoid the uncached_cpsr bits being updated at the end of the
function.
Move the condition into the correct place in the code, fix its RHS
constant, and add a comment about the fact that we must be doing a
gdbstub write if we're in user mode.
Fixes: https://bugs.launchpad.net/qemu/+bug/1550503
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Sergey Fedorov <serge.fdrv@gmail.com>
Message-id: 1456764438-30015-1-git-send-email-peter.maydell@linaro.org
Diffstat (limited to 'target-arm/helper.c')
| -rw-r--r-- | target-arm/helper.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/target-arm/helper.c b/target-arm/helper.c index 18c82967d3..935f13b7ed 100644 --- a/target-arm/helper.c +++ b/target-arm/helper.c @@ -5490,9 +5490,16 @@ void cpsr_write(CPUARMState *env, uint32_t val, uint32_t mask, env->daif |= val & CPSR_AIF & mask; if (write_type != CPSRWriteRaw && - (env->uncached_cpsr & CPSR_M) != CPSR_USER && ((env->uncached_cpsr ^ val) & mask & CPSR_M)) { - if (bad_mode_switch(env, val & CPSR_M, write_type)) { + if ((env->uncached_cpsr & CPSR_M) == ARM_CPU_MODE_USR) { + /* Note that we can only get here in USR mode if this is a + * gdb stub write; for this case we follow the architectural + * behaviour for guest writes in USR mode of ignoring an attempt + * to switch mode. (Those are caught by translate.c for writes + * triggered by guest instructions.) + */ + mask &= ~CPSR_M; + } else if (bad_mode_switch(env, val & CPSR_M, write_type)) { /* Attempt to switch to an invalid mode: this is UNPREDICTABLE in * v7, and has defined behaviour in v8: * + leave CPSR.M untouched |