| Message ID | 20200318170116.1922-1-vfazio@xes-inc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/1] target/ppc: don't byte swap ELFv2 signal handler | expand |
On 3/18/20 10:01 AM, Vincent Fazio wrote: > From: Vincent Fazio <vfazio@gmail.com> > > Previously, the signal handler would be byte swapped if the target and > host CPU used different endianness. This would cause a SIGSEGV when > attempting to translate the opcode pointed to by the swapped address. > > Thread 1 "qemu-ppc64" received signal SIGSEGV, Segmentation fault. > 0x00000000600a9257 in ldl_he_p (ptr=0x4c2c061000000000) at qemu/include/qemu/bswap.h:351 > 351 __builtin_memcpy(&r, ptr, sizeof(r)); > > #0 0x00000000600a9257 in ldl_he_p (ptr=0x4c2c061000000000) at qemu/include/qemu/bswap.h:351 > #1 0x00000000600a92fe in ldl_be_p (ptr=0x4c2c061000000000) at qemu/include/qemu/bswap.h:449 > #2 0x00000000600c0790 in translator_ldl_swap at qemu/include/exec/translator.h:201 > #3 0x000000006011c1ab in ppc_tr_translate_insn at qemu/target/ppc/translate.c:7856 > #4 0x000000006005ae70 in translator_loop at qemu/accel/tcg/translator.c:102 > > Now, no swap is performed and execution continues properly. > > Signed-off-by: Vincent Fazio <vfazio@gmail.com> > Reviewed-by: Laurent Vivier <laurent@vivier.eu> > --- > Changes since v1: > - Drop host/target endianness callouts > - Drop unnecessary pointer cast > - Clarify commit message Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
On Wed, Mar 18, 2020 at 12:01:16PM -0500, Vincent Fazio wrote: > From: Vincent Fazio <vfazio@gmail.com> > > Previously, the signal handler would be byte swapped if the target and > host CPU used different endianness. This would cause a SIGSEGV when > attempting to translate the opcode pointed to by the swapped address. > > Thread 1 "qemu-ppc64" received signal SIGSEGV, Segmentation fault. > 0x00000000600a9257 in ldl_he_p (ptr=0x4c2c061000000000) at qemu/include/qemu/bswap.h:351 > 351 __builtin_memcpy(&r, ptr, sizeof(r)); > > #0 0x00000000600a9257 in ldl_he_p (ptr=0x4c2c061000000000) at qemu/include/qemu/bswap.h:351 > #1 0x00000000600a92fe in ldl_be_p (ptr=0x4c2c061000000000) at qemu/include/qemu/bswap.h:449 > #2 0x00000000600c0790 in translator_ldl_swap at qemu/include/exec/translator.h:201 > #3 0x000000006011c1ab in ppc_tr_translate_insn at qemu/target/ppc/translate.c:7856 > #4 0x000000006005ae70 in translator_loop at qemu/accel/tcg/translator.c:102 > > Now, no swap is performed and execution continues properly. Patch is good, but the message still needs some work. It should point out that the necessary swap is already done at sigaction() time by the __get_user(). > > Signed-off-by: Vincent Fazio <vfazio@gmail.com> > Reviewed-by: Laurent Vivier <laurent@vivier.eu> > --- > Changes since v1: > - Drop host/target endianness callouts > - Drop unnecessary pointer cast > - Clarify commit message > > linux-user/ppc/signal.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c > index 5b82af6cb6..b8613c5e1b 100644 > --- a/linux-user/ppc/signal.c > +++ b/linux-user/ppc/signal.c > @@ -567,10 +567,8 @@ void setup_rt_frame(int sig, struct target_sigaction *ka, > env->nip = tswapl(handler->entry); > env->gpr[2] = tswapl(handler->toc); > } else { > - /* ELFv2 PPC64 function pointers are entry points, but R12 > - * must also be set */ > - env->nip = tswapl((target_ulong) ka->_sa_handler); > - env->gpr[12] = env->nip; > + /* ELFv2 PPC64 function pointers are entry points. R12 must also be set. */ > + env->gpr[12] = env->nip = ka->_sa_handler; > } > #else > env->nip = (target_ulong) ka->_sa_handler;
diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c index 5b82af6cb6..b8613c5e1b 100644 --- a/linux-user/ppc/signal.c +++ b/linux-user/ppc/signal.c @@ -567,10 +567,8 @@ void setup_rt_frame(int sig, struct target_sigaction *ka, env->nip = tswapl(handler->entry); env->gpr[2] = tswapl(handler->toc); } else { - /* ELFv2 PPC64 function pointers are entry points, but R12 - * must also be set */ - env->nip = tswapl((target_ulong) ka->_sa_handler); - env->gpr[12] = env->nip; + /* ELFv2 PPC64 function pointers are entry points. R12 must also be set. */ + env->gpr[12] = env->nip = ka->_sa_handler; } #else env->nip = (target_ulong) ka->_sa_handler;