| Message ID | 1469172468-12892-1-git-send-email-npiggin@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Fri, 2016-07-22 at 17:27 +1000, Nicholas Piggin wrote: > tabort_syscall runs with RI=1, so a nested recoverable machine > check will load the paca into r13 and overwrite what we loaded > it with, because exceptions returning to privileged mode do not > restore r13. > > This has survived testing with sc instruction inside transaction > (bare sc, not glibc syscall because glibc can tabort before sc). > Verified the transaction is failing failing with with > TM_CAUSE_SYSCALL. > > Signed-off-by: Nick Piggin <npiggin@gmail.com> Thanks. This looks good, but should probably be cc: stable from when the syscall tm abort went in. There are some random whitespace changes in here too, which if we avoid will make the patch smaller (and easier to read). Mikey > Cc: Michael Neuling <mikey@neuling.org> > Cc: Sam Bobroff <sam.bobroff@au1.ibm.com> > Cc: Michael Ellerman <mpe@ellerman.id.au> > > --- > > arch/powerpc/kernel/entry_64.S | 20 ++++++++++---------- > 1 file changed, 10 insertions(+), 10 deletions(-) > > diff --git a/arch/powerpc/kernel/entry_64.S > b/arch/powerpc/kernel/entry_64.S > index 73e461a..387dee3 100644 > --- a/arch/powerpc/kernel/entry_64.S > +++ b/arch/powerpc/kernel/entry_64.S > @@ -368,13 +368,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) > tabort_syscall: > /* Firstly we need to enable TM in the kernel */ > mfmsr r10 > - li r13, 1 > - rldimi r10, r13, MSR_TM_LG, 63-MSR_TM_LG > - mtmsrd r10, 0 > + li r9,1 > + rldimi r10,r9,MSR_TM_LG,63-MSR_TM_LG > + mtmsrd r10,0 > > /* tabort, this dooms the transaction, nothing else */ > - li r13, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT) > - TABORT(R13) > + li r9,(TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT) > + TABORT(R9) > > /* > * Return directly to userspace. We have corrupted user register > state, > @@ -382,11 +382,11 @@ tabort_syscall: > * resume after the tbegin of the aborted transaction with the > * checkpointed register state. > */ > - li r13, MSR_RI > - andc r10, r10, r13 > - mtmsrd r10, 1 > - mtspr SPRN_SRR0, r11 > - mtspr SPRN_SRR1, r12 > + li r9,MSR_RI > + andc r10,r10,r9 > + mtmsrd r10,1 > + mtspr SPRN_SRR0,r11 > + mtspr SPRN_SRR1,r12 > > rfid > b . /* prevent speculative execution */
On Fri, 2016-07-22 at 17:27 +1000, Nicholas Piggin wrote: > tabort_syscall runs with RI=1, so a nested recoverable machine > check will load the paca into r13 and overwrite what we loaded > it with, because exceptions returning to privileged mode do not > restore r13. > > This has survived testing with sc instruction inside transaction > (bare sc, not glibc syscall because glibc can tabort before sc). > Verified the transaction is failing failing with with > TM_CAUSE_SYSCALL. > > Signed-off-by: Nick Piggin <npiggin@gmail.com> > Cc: Michael Neuling <mikey@neuling.org> FWIW Acked-by: Michael Neuling <mikey@neuling.org> > Cc: Sam Bobroff <sam.bobroff@au1.ibm.com> > Cc: Michael Ellerman <mpe@ellerman.id.au> > > --- > > arch/powerpc/kernel/entry_64.S | 20 ++++++++++---------- > 1 file changed, 10 insertions(+), 10 deletions(-) > > diff --git a/arch/powerpc/kernel/entry_64.S > b/arch/powerpc/kernel/entry_64.S > index 73e461a..387dee3 100644 > --- a/arch/powerpc/kernel/entry_64.S > +++ b/arch/powerpc/kernel/entry_64.S > @@ -368,13 +368,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) > tabort_syscall: > /* Firstly we need to enable TM in the kernel */ > mfmsr r10 > - li r13, 1 > - rldimi r10, r13, MSR_TM_LG, 63-MSR_TM_LG > - mtmsrd r10, 0 > + li r9,1 > + rldimi r10,r9,MSR_TM_LG,63-MSR_TM_LG > + mtmsrd r10,0 > > /* tabort, this dooms the transaction, nothing else */ > - li r13, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT) > - TABORT(R13) > + li r9,(TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT) > + TABORT(R9) > > /* > * Return directly to userspace. We have corrupted user register > state, > @@ -382,11 +382,11 @@ tabort_syscall: > * resume after the tbegin of the aborted transaction with the > * checkpointed register state. > */ > - li r13, MSR_RI > - andc r10, r10, r13 > - mtmsrd r10, 1 > - mtspr SPRN_SRR0, r11 > - mtspr SPRN_SRR1, r12 > + li r9,MSR_RI > + andc r10,r10,r9 > + mtmsrd r10,1 > + mtspr SPRN_SRR0,r11 > + mtspr SPRN_SRR1,r12 > > rfid > b . /* prevent speculative execution */
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 73e461a..387dee3 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -368,13 +368,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) tabort_syscall: /* Firstly we need to enable TM in the kernel */ mfmsr r10 - li r13, 1 - rldimi r10, r13, MSR_TM_LG, 63-MSR_TM_LG - mtmsrd r10, 0 + li r9,1 + rldimi r10,r9,MSR_TM_LG,63-MSR_TM_LG + mtmsrd r10,0 /* tabort, this dooms the transaction, nothing else */ - li r13, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT) - TABORT(R13) + li r9,(TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT) + TABORT(R9) /* * Return directly to userspace. We have corrupted user register state, @@ -382,11 +382,11 @@ tabort_syscall: * resume after the tbegin of the aborted transaction with the * checkpointed register state. */ - li r13, MSR_RI - andc r10, r10, r13 - mtmsrd r10, 1 - mtspr SPRN_SRR0, r11 - mtspr SPRN_SRR1, r12 + li r9,MSR_RI + andc r10,r10,r9 + mtmsrd r10,1 + mtspr SPRN_SRR0,r11 + mtspr SPRN_SRR1,r12 rfid b . /* prevent speculative execution */
tabort_syscall runs with RI=1, so a nested recoverable machine check will load the paca into r13 and overwrite what we loaded it with, because exceptions returning to privileged mode do not restore r13. This has survived testing with sc instruction inside transaction (bare sc, not glibc syscall because glibc can tabort before sc). Verified the transaction is failing failing with with TM_CAUSE_SYSCALL. Signed-off-by: Nick Piggin <npiggin@gmail.com> Cc: Michael Neuling <mikey@neuling.org> Cc: Sam Bobroff <sam.bobroff@au1.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> --- arch/powerpc/kernel/entry_64.S | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)