| Message ID | 1370352705-27590-1-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | Accepted |
| Headers | show |
Ping! thanks -- PMM On 4 June 2013 14:31, Peter Maydell <peter.maydell@linaro.org> wrote: > In the ARM implementation of cpu_signal_handler(), set is_write > correctly using the FSR value which the kernel passes us in the > error_code field of uc_mcontext. Since the WnR bit of the FSR was > only introduced in ARMv6, this means that v5 cores will continue > to behave as before this patch, but they are not really supported > as hosts for linux-user mode anyway since they do not have the > modern behaviour for unaligned accesses. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > Without this linux-user won't work very well. In particular after > fork() bash will segfault, with this in the QEMU_STRACE output > immediately preceding: > sigreturn(18,4390912,1082130608,0,0,0) = -1 errno=255 (Unknown error 255) > at least for PPC and MIPSEL guests. > > user-exec.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/user-exec.c b/user-exec.c > index 71bd6c5..336ac70 100644 > --- a/user-exec.c > +++ b/user-exec.c > @@ -20,6 +20,7 @@ > #include "cpu.h" > #include "disas/disas.h" > #include "tcg.h" > +#include "qemu/bitops.h" > > #undef EAX > #undef ECX > @@ -441,8 +442,11 @@ int cpu_signal_handler(int host_signum, void *pinfo, > #else > pc = uc->uc_mcontext.arm_pc; > #endif > - /* XXX: compute is_write */ > - is_write = 0; > + > + /* error_code is the FSR value, in which bit 11 is WnR (assuming a v6 or > + * later processor; on v5 we will always report this as a read). > + */ > + is_write = extract32(uc->uc_mcontext.error_code, 11, 1); > return handle_cpu_signal(pc, (unsigned long)info->si_addr, > is_write, > &uc->uc_sigmask, puc); > -- > 1.7.9.5 > >
Am 04.06.2013 15:31, schrieb Peter Maydell: > In the ARM implementation of cpu_signal_handler(), set is_write > correctly using the FSR value which the kernel passes us in the > error_code field of uc_mcontext. Since the WnR bit of the FSR was > only introduced in ARMv6, this means that v5 cores will continue > to behave as before this patch, but they are not really supported > as hosts for linux-user mode anyway since they do not have the > modern behaviour for unaligned accesses. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > Without this linux-user won't work very well. In particular after > fork() bash will segfault, with this in the QEMU_STRACE output > immediately preceding: > sigreturn(18,4390912,1082130608,0,0,0) = -1 errno=255 (Unknown error 255) > at least for PPC and MIPSEL guests. > > user-exec.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/user-exec.c b/user-exec.c > index 71bd6c5..336ac70 100644 > --- a/user-exec.c > +++ b/user-exec.c > @@ -20,6 +20,7 @@ > #include "cpu.h" > #include "disas/disas.h" > #include "tcg.h" > +#include "qemu/bitops.h" > > #undef EAX > #undef ECX > @@ -441,8 +442,11 @@ int cpu_signal_handler(int host_signum, void *pinfo, > #else > pc = uc->uc_mcontext.arm_pc; > #endif > - /* XXX: compute is_write */ > - is_write = 0; > + > + /* error_code is the FSR value, in which bit 11 is WnR (assuming a v6 or > + * later processor; on v5 we will always report this as a read). > + */ > + is_write = extract32(uc->uc_mcontext.error_code, 11, 1); You seem to be relying on v5 and earlier reading zero here - wondering if that is true for all implementations (OMAP, PXA, etc.)? Safer and closer to the comment might be an explicit check for v6+ if that were possible. Cheers, Andreas > return handle_cpu_signal(pc, (unsigned long)info->si_addr, > is_write, > &uc->uc_sigmask, puc);
On 27 June 2013 17:59, Andreas Färber <afaerber@suse.de> wrote: > Am 04.06.2013 15:31, schrieb Peter Maydell: >> + /* error_code is the FSR value, in which bit 11 is WnR (assuming a v6 or >> + * later processor; on v5 we will always report this as a read). >> + */ >> + is_write = extract32(uc->uc_mcontext.error_code, 11, 1); > > You seem to be relying on v5 and earlier reading zero here - wondering > if that is true for all implementations (OMAP, PXA, etc.)? Safer and > closer to the comment might be an explicit check for v6+ if that were > possible. The kernel will clear bit 11 if on a v4 or v5 core, eg: http://lxr.linux.no/#linux+v3.9.7/arch/arm/mm/abort-ev5t.S#L24 As I say in the commit message, v5 hosts are going to be badly broken (or possibly just hideously inefficient) because of the unaligned access thing anyway. thanks -- PMM
On 04.06.2013, at 15:31, Peter Maydell wrote: > In the ARM implementation of cpu_signal_handler(), set is_write > correctly using the FSR value which the kernel passes us in the > error_code field of uc_mcontext. Since the WnR bit of the FSR was > only introduced in ARMv6, this means that v5 cores will continue > to behave as before this patch, but they are not really supported > as hosts for linux-user mode anyway since they do not have the > modern behaviour for unaligned accesses. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Acked-by: Alexander Graf <agraf@suse.de> Alex > --- > Without this linux-user won't work very well. In particular after > fork() bash will segfault, with this in the QEMU_STRACE output > immediately preceding: > sigreturn(18,4390912,1082130608,0,0,0) = -1 errno=255 (Unknown error 255) > at least for PPC and MIPSEL guests. > > user-exec.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/user-exec.c b/user-exec.c > index 71bd6c5..336ac70 100644 > --- a/user-exec.c > +++ b/user-exec.c > @@ -20,6 +20,7 @@ > #include "cpu.h" > #include "disas/disas.h" > #include "tcg.h" > +#include "qemu/bitops.h" > > #undef EAX > #undef ECX > @@ -441,8 +442,11 @@ int cpu_signal_handler(int host_signum, void *pinfo, > #else > pc = uc->uc_mcontext.arm_pc; > #endif > - /* XXX: compute is_write */ > - is_write = 0; > + > + /* error_code is the FSR value, in which bit 11 is WnR (assuming a v6 or > + * later processor; on v5 we will always report this as a read). > + */ > + is_write = extract32(uc->uc_mcontext.error_code, 11, 1); > return handle_cpu_signal(pc, (unsigned long)info->si_addr, > is_write, > &uc->uc_sigmask, puc); > -- > 1.7.9.5 > >
diff --git a/user-exec.c b/user-exec.c index 71bd6c5..336ac70 100644 --- a/user-exec.c +++ b/user-exec.c @@ -20,6 +20,7 @@ #include "cpu.h" #include "disas/disas.h" #include "tcg.h" +#include "qemu/bitops.h" #undef EAX #undef ECX @@ -441,8 +442,11 @@ int cpu_signal_handler(int host_signum, void *pinfo, #else pc = uc->uc_mcontext.arm_pc; #endif - /* XXX: compute is_write */ - is_write = 0; + + /* error_code is the FSR value, in which bit 11 is WnR (assuming a v6 or + * later processor; on v5 we will always report this as a read). + */ + is_write = extract32(uc->uc_mcontext.error_code, 11, 1); return handle_cpu_signal(pc, (unsigned long)info->si_addr, is_write, &uc->uc_sigmask, puc);
In the ARM implementation of cpu_signal_handler(), set is_write correctly using the FSR value which the kernel passes us in the error_code field of uc_mcontext. Since the WnR bit of the FSR was only introduced in ARMv6, this means that v5 cores will continue to behave as before this patch, but they are not really supported as hosts for linux-user mode anyway since they do not have the modern behaviour for unaligned accesses. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- Without this linux-user won't work very well. In particular after fork() bash will segfault, with this in the QEMU_STRACE output immediately preceding: sigreturn(18,4390912,1082130608,0,0,0) = -1 errno=255 (Unknown error 255) at least for PPC and MIPSEL guests. user-exec.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)