| Message ID | 20210803221606.150103-1-iii@linux.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] accel/tcg/user-exec: Fix read-modify-write of code on s390 hosts | expand |
On 8/3/21 12:16 PM, Ilya Leoshkevich wrote: > x86_64 dotnet/runtime uses cmpxchg for code patching. When running it > under s390x qemu-linux user, cpu_signal_handler() does not recognize > this as a write and does not restore PAGE_WRITE cleared by > tb_page_add(), incorrectly forwarding the signal to the guest code. > > Signed-off-by: Ilya Leoshkevich<iii@linux.ibm.com> > --- > > v1:https://lists.nongnu.org/archive/html/qemu-devel/2021-08/msg00464.html > v1 -> v2: Fix comment style, fix CSST detection (Richard). > > accel/tcg/user-exec.c | 48 ++++++++++++++++++++++++++++++++++++------- > 1 file changed, 41 insertions(+), 7 deletions(-) Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
On Wed, 2021-08-04 at 00:16 +0200, Ilya Leoshkevich wrote: > x86_64 dotnet/runtime uses cmpxchg for code patching. When running it > under s390x qemu-linux user, cpu_signal_handler() does not recognize > this as a write and does not restore PAGE_WRITE cleared by > tb_page_add(), incorrectly forwarding the signal to the guest code. > > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> > --- > > v1: > https://lists.nongnu.org/archive/html/qemu-devel/2021-08/msg00464.html > v1 -> v2: Fix comment style, fix CSST detection (Richard). > > accel/tcg/user-exec.c | 48 ++++++++++++++++++++++++++++++++++++----- > -- > 1 file changed, 41 insertions(+), 7 deletions(-) > > diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c > index 90d1a2d327..8fed542622 100644 > --- a/accel/tcg/user-exec.c > +++ b/accel/tcg/user-exec.c > @@ -680,18 +680,26 @@ int cpu_signal_handler(int host_signum, void > *pinfo, > > pc = uc->uc_mcontext.psw.addr; > > - /* ??? On linux, the non-rt signal handler has 4 (!) arguments > instead > - of the normal 2 arguments. The 3rd argument contains the > "int_code" > - from the hardware which does in fact contain the is_write > value. > - The rt signal handler, as far as I can tell, does not give > this value > - at all. Not that we could get to it from here even if it > were. */ > - /* ??? This is not even close to complete, since it ignores all > - of the read-modify-write instructions. */ > + /* > + * ??? On linux, the non-rt signal handler has 4 (!) arguments > instead > + * of the normal 2 arguments. The 4th argument contains the > "Translation- > + * Exception Identification for DAT Exceptions" from the > hardware (aka > + * "int_parm_long"), which does in fact contain the is_write > value. > + * The rt signal handler, as far as I can tell, does not give > this value > + * at all. Not that we could get to it from here even if it > were. > + * So fall back to parsing instructions. Treat read-modify- > write ones as > + * writes, which is not fully correct, but for tracking self- > modifying code > + * this is better than treating them as reads. Checking si_addr > page flags > + * might be a viable improvement, albeit a racy one. > + */ > + /* ??? This is not even close to complete. */ > pinsn = (uint16_t *)pc; > switch (pinsn[0] >> 8) { > case 0x50: /* ST */ > case 0x42: /* STC */ > case 0x40: /* STH */ > + case 0xba: /* CS */ > + case 0xbb: /* CDS */ > is_write = 1; > break; > case 0xc4: /* RIL format insns */ > @@ -702,6 +710,12 @@ int cpu_signal_handler(int host_signum, void > *pinfo, > is_write = 1; > } > break; > + case 0xc8: /* SSF format insns */ > + switch (pinsn[0] & 0xf) { > + case 0x2: /* CSST */ > + is_write = 1; > + } > + break; > case 0xe3: /* RXY format insns */ > switch (pinsn[2] & 0xff) { > case 0x50: /* STY */ > @@ -715,7 +729,27 @@ int cpu_signal_handler(int host_signum, void > *pinfo, > is_write = 1; > } > break; > + case 0xeb: /* RSY format insns */ > + switch (pinsn[2] & 0xff) { > + case 0x14: /* CSY */ > + case 0x30: /* CSG */ > + case 0x31: /* CDSY */ > + case 0x3e: /* CDSG */ > + case 0xe4: /* LANG */ > + case 0xe6: /* LAOG */ > + case 0xe7: /* LAXG */ > + case 0xe8: /* LAAG */ > + case 0xea: /* LAALG */ > + case 0xf4: /* LAN */ > + case 0xf6: /* LAO */ > + case 0xf7: /* LAX */ > + case 0xfa: /* LAAL */ > + case 0xf8: /* LAA */ > + is_write = 1; > + } > + break; > } > + > return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask); > } > Hello, Richard has reviewed this patch a while ago - is there anything else that needs to be done before it can be picked up? Best regards, Ilya
On 8/3/21 3:16 PM, Ilya Leoshkevich wrote: > x86_64 dotnet/runtime uses cmpxchg for code patching. When running it > under s390x qemu-linux user, cpu_signal_handler() does not recognize > this as a write and does not restore PAGE_WRITE cleared by > tb_page_add(), incorrectly forwarding the signal to the guest code. > > Signed-off-by: Ilya Leoshkevich<iii@linux.ibm.com> > --- > > v1:https://lists.nongnu.org/archive/html/qemu-devel/2021-08/msg00464.html > v1 -> v2: Fix comment style, fix CSST detection (Richard). > > accel/tcg/user-exec.c | 48 ++++++++++++++++++++++++++++++++++++------- > 1 file changed, 41 insertions(+), 7 deletions(-) Queued, thanks. r~
diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c index 90d1a2d327..8fed542622 100644 --- a/accel/tcg/user-exec.c +++ b/accel/tcg/user-exec.c @@ -680,18 +680,26 @@ int cpu_signal_handler(int host_signum, void *pinfo, pc = uc->uc_mcontext.psw.addr; - /* ??? On linux, the non-rt signal handler has 4 (!) arguments instead - of the normal 2 arguments. The 3rd argument contains the "int_code" - from the hardware which does in fact contain the is_write value. - The rt signal handler, as far as I can tell, does not give this value - at all. Not that we could get to it from here even if it were. */ - /* ??? This is not even close to complete, since it ignores all - of the read-modify-write instructions. */ + /* + * ??? On linux, the non-rt signal handler has 4 (!) arguments instead + * of the normal 2 arguments. The 4th argument contains the "Translation- + * Exception Identification for DAT Exceptions" from the hardware (aka + * "int_parm_long"), which does in fact contain the is_write value. + * The rt signal handler, as far as I can tell, does not give this value + * at all. Not that we could get to it from here even if it were. + * So fall back to parsing instructions. Treat read-modify-write ones as + * writes, which is not fully correct, but for tracking self-modifying code + * this is better than treating them as reads. Checking si_addr page flags + * might be a viable improvement, albeit a racy one. + */ + /* ??? This is not even close to complete. */ pinsn = (uint16_t *)pc; switch (pinsn[0] >> 8) { case 0x50: /* ST */ case 0x42: /* STC */ case 0x40: /* STH */ + case 0xba: /* CS */ + case 0xbb: /* CDS */ is_write = 1; break; case 0xc4: /* RIL format insns */ @@ -702,6 +710,12 @@ int cpu_signal_handler(int host_signum, void *pinfo, is_write = 1; } break; + case 0xc8: /* SSF format insns */ + switch (pinsn[0] & 0xf) { + case 0x2: /* CSST */ + is_write = 1; + } + break; case 0xe3: /* RXY format insns */ switch (pinsn[2] & 0xff) { case 0x50: /* STY */ @@ -715,7 +729,27 @@ int cpu_signal_handler(int host_signum, void *pinfo, is_write = 1; } break; + case 0xeb: /* RSY format insns */ + switch (pinsn[2] & 0xff) { + case 0x14: /* CSY */ + case 0x30: /* CSG */ + case 0x31: /* CDSY */ + case 0x3e: /* CDSG */ + case 0xe4: /* LANG */ + case 0xe6: /* LAOG */ + case 0xe7: /* LAXG */ + case 0xe8: /* LAAG */ + case 0xea: /* LAALG */ + case 0xf4: /* LAN */ + case 0xf6: /* LAO */ + case 0xf7: /* LAX */ + case 0xfa: /* LAAL */ + case 0xf8: /* LAA */ + is_write = 1; + } + break; } + return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask); }
x86_64 dotnet/runtime uses cmpxchg for code patching. When running it under s390x qemu-linux user, cpu_signal_handler() does not recognize this as a write and does not restore PAGE_WRITE cleared by tb_page_add(), incorrectly forwarding the signal to the guest code. Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> --- v1: https://lists.nongnu.org/archive/html/qemu-devel/2021-08/msg00464.html v1 -> v2: Fix comment style, fix CSST detection (Richard). accel/tcg/user-exec.c | 48 ++++++++++++++++++++++++++++++++++++------- 1 file changed, 41 insertions(+), 7 deletions(-)