| Message ID | ZMNJ+Ga7A4zDXjAg@p100 (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] linux-user/armeb: Fix __kernel_cmpxchg() for armeb | expand |
Nitpick: the bug was introduced between 6.2.0 and 7.0.0, so "qemu >= v7.0.0" ~Markus On 2023-07-28 06:54, Helge Deller wrote: > Commit 7f4f0d9ea870 ("linux-user/arm: Implement __kernel_cmpxchg with host > atomics") switched to use qatomic_cmpxchg() to swap a word with the memory > content, but missed to endianess-swap the oldval and newval values when > emulating an armeb CPU, which expects words to be stored in big endian in > the guest memory. > > The bug can be verified with qemu >= v7.2 on any little-endian host, when > starting the armeb binary of the upx program, which just hangs without > this patch. > > Signed-off-by: Helge Deller <deller@gmx.de> > Cc: Richard Henderson <richard.henderson@linaro.org> > Cc: Peter Maydell <peter.maydell@linaro.org> > Cc: qemu-stable@nongnu.org > Reported-by: "Markus F.X.J. Oberhumer" <markus@oberhumer.com> > Reported-by: John Reiser <jreiser@BitWagon.com> > Closes: https://github.com/upx/upx/issues/687 > > -- > v2: > - add tswap32() in arm_kernel_cmpxchg64_helper() > > > diff --git a/linux-user/arm/cpu_loop.c b/linux-user/arm/cpu_loop.c > index a992423257..0907cd8c15 100644 > --- a/linux-user/arm/cpu_loop.c > +++ b/linux-user/arm/cpu_loop.c > @@ -117,8 +117,9 @@ static void arm_kernel_cmpxchg32_helper(CPUARMState *env) > { > uint32_t oldval, newval, val, addr, cpsr, *host_addr; > > - oldval = env->regs[0]; > - newval = env->regs[1]; > + /* endianess-swap if emulating armeb */ > + oldval = tswap32(env->regs[0]); > + newval = tswap32(env->regs[1]); > addr = env->regs[2]; > > mmap_lock(); > @@ -174,6 +175,10 @@ static void arm_kernel_cmpxchg64_helper(CPUARMState *env) > return; > } > > + /* endianess-swap if emulating armeb */ > + oldval = tswap32(oldval); > + newval = tswap32(newval); > + > #ifdef CONFIG_ATOMIC64 > val = qatomic_cmpxchg__nocheck(host_addr, oldval, newval); > cpsr = (val == oldval) * CPSR_C; >
The fix in arm_kernel_cmpxchg64_helper probably should use tswap64() instead of tswap32(). ~Markus On 2023-07-28 06:54, Helge Deller wrote: > Commit 7f4f0d9ea870 ("linux-user/arm: Implement __kernel_cmpxchg with host > atomics") switched to use qatomic_cmpxchg() to swap a word with the memory > content, but missed to endianess-swap the oldval and newval values when > emulating an armeb CPU, which expects words to be stored in big endian in > the guest memory. > > The bug can be verified with qemu >= v7.2 on any little-endian host, when > starting the armeb binary of the upx program, which just hangs without > this patch. > > Signed-off-by: Helge Deller <deller@gmx.de> > Cc: Richard Henderson <richard.henderson@linaro.org> > Cc: Peter Maydell <peter.maydell@linaro.org> > Cc: qemu-stable@nongnu.org > Reported-by: "Markus F.X.J. Oberhumer" <markus@oberhumer.com> > Reported-by: John Reiser <jreiser@BitWagon.com> > Closes: https://github.com/upx/upx/issues/687 > > -- > v2: > - add tswap32() in arm_kernel_cmpxchg64_helper() > > > diff --git a/linux-user/arm/cpu_loop.c b/linux-user/arm/cpu_loop.c > index a992423257..0907cd8c15 100644 > --- a/linux-user/arm/cpu_loop.c > +++ b/linux-user/arm/cpu_loop.c > @@ -117,8 +117,9 @@ static void arm_kernel_cmpxchg32_helper(CPUARMState *env) > { > uint32_t oldval, newval, val, addr, cpsr, *host_addr; > > - oldval = env->regs[0]; > - newval = env->regs[1]; > + /* endianess-swap if emulating armeb */ > + oldval = tswap32(env->regs[0]); > + newval = tswap32(env->regs[1]); > addr = env->regs[2]; > > mmap_lock(); > @@ -174,6 +175,10 @@ static void arm_kernel_cmpxchg64_helper(CPUARMState *env) > return; > } > > + /* endianess-swap if emulating armeb */ > + oldval = tswap32(oldval); > + newval = tswap32(newval); > + > #ifdef CONFIG_ATOMIC64 > val = qatomic_cmpxchg__nocheck(host_addr, oldval, newval); > cpsr = (val == oldval) * CPSR_C; >
On 7/27/23 21:54, Helge Deller wrote: > @@ -174,6 +175,10 @@ static void arm_kernel_cmpxchg64_helper(CPUARMState *env) > return; > } > > + /* endianess-swap if emulating armeb */ > + oldval = tswap32(oldval); > + newval = tswap32(newval); Must be tswap64. r~
On 7/28/23 17:35, Richard Henderson wrote: > On 7/27/23 21:54, Helge Deller wrote: >> @@ -174,6 +175,10 @@ static void arm_kernel_cmpxchg64_helper(CPUARMState *env) >> return; >> } >> >> + /* endianess-swap if emulating armeb */ >> + oldval = tswap32(oldval); >> + newval = tswap32(newval); > > Must be tswap64. Oh, of course! I send a v3. Helge
diff --git a/linux-user/arm/cpu_loop.c b/linux-user/arm/cpu_loop.c index a992423257..0907cd8c15 100644 --- a/linux-user/arm/cpu_loop.c +++ b/linux-user/arm/cpu_loop.c @@ -117,8 +117,9 @@ static void arm_kernel_cmpxchg32_helper(CPUARMState *env) { uint32_t oldval, newval, val, addr, cpsr, *host_addr; - oldval = env->regs[0]; - newval = env->regs[1]; + /* endianess-swap if emulating armeb */ + oldval = tswap32(env->regs[0]); + newval = tswap32(env->regs[1]); addr = env->regs[2]; mmap_lock(); @@ -174,6 +175,10 @@ static void arm_kernel_cmpxchg64_helper(CPUARMState *env) return; } + /* endianess-swap if emulating armeb */ + oldval = tswap32(oldval); + newval = tswap32(newval); + #ifdef CONFIG_ATOMIC64 val = qatomic_cmpxchg__nocheck(host_addr, oldval, newval); cpsr = (val == oldval) * CPSR_C;
Commit 7f4f0d9ea870 ("linux-user/arm: Implement __kernel_cmpxchg with host atomics") switched to use qatomic_cmpxchg() to swap a word with the memory content, but missed to endianess-swap the oldval and newval values when emulating an armeb CPU, which expects words to be stored in big endian in the guest memory. The bug can be verified with qemu >= v7.2 on any little-endian host, when starting the armeb binary of the upx program, which just hangs without this patch. Signed-off-by: Helge Deller <deller@gmx.de> Cc: Richard Henderson <richard.henderson@linaro.org> Cc: Peter Maydell <peter.maydell@linaro.org> Cc: qemu-stable@nongnu.org Reported-by: "Markus F.X.J. Oberhumer" <markus@oberhumer.com> Reported-by: John Reiser <jreiser@BitWagon.com> Closes: https://github.com/upx/upx/issues/687 -- v2: - add tswap32() in arm_kernel_cmpxchg64_helper()