From f144e7c7272bf527c380bffaa5e789dc28a09d8d Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 10 Mar 2007 03:23:03 -0500 Subject: [PATCH 1/3] [POWERPC] Fix atomicity of TIF update in flush_thread() Fix atomicity of TIF update in flush_thread() for powerpc Fixes it correctly with *_ti_thread_flag. Race : parent process executing : sys_ptrace() (lock_kernel()) (ptrace_get_task_struct(pid)) arch_ptrace() ptrace_detach() ptrace_disable(child); clear_singlestep(child); clear_tsk_thread_flag(child, TIF_SINGLESTEP); (which clears the TIF_SINGLESTEP flag atomically from a different process) (put_task_struct(child)) (unlock_kernel()) And at the same time, in the child process : sys_execve() do_execve() search_binary_handler() load_elf_binary() flush_old_exec() flush_thread() doing a non-atomic thread flag update Applies on 2.6.20. Signed-off-by: Mathieu Desnoyers Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/process.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index f3d4dd580dd6..e53b2988d1bf 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -465,8 +465,13 @@ void flush_thread(void) #ifdef CONFIG_PPC64 struct thread_info *t = current_thread_info(); - if (t->flags & _TIF_ABI_PENDING) - t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT); + if (test_ti_thread_flag(t, TIF_ABI_PENDING)) { + clear_ti_thread_flag(t, TIF_ABI_PENDING); + if (test_ti_thread_flag(t, TIF_32BIT)) + clear_ti_thread_flag(t, TIF_32BIT); + else + set_ti_thread_flag(t, TIF_32BIT); + } #endif discard_lazy_cpu_state(); From b4aea36b7956eeebfc56314ce0944db1441255ce Mon Sep 17 00:00:00 2001 From: Mohan Kumar M Date: Wed, 21 Mar 2007 11:21:32 +0530 Subject: [PATCH 2/3] [POWERPC] Avoid hypervisor statistics calculation in real mode kexec invokes plpar_hcall hypervisor call in real mode. plpar_hcall refers to per cpu variables for accounting hypervisor statistics. These variables may not be in the RMO region, so accesses to them in real mode may result in a data storage exception. This fixes this problem by using a new plpar_hcall_raw function which does not update the hypervisor call statistics. Thanks to Anton for suggesting this idea. Signed-off-by: Mohan Kumar M Signed-off-by: Paul Mackerras --- arch/powerpc/platforms/pseries/hvCall.S | 34 +++++++++++++++++++ arch/powerpc/platforms/pseries/lpar.c | 2 +- .../platforms/pseries/plpar_wrappers.h | 16 +++++++++ include/asm-powerpc/hvcall.h | 14 ++++++++ 4 files changed, 65 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/platforms/pseries/hvCall.S b/arch/powerpc/platforms/pseries/hvCall.S index 5c7e38789897..1501b0a9e749 100644 --- a/arch/powerpc/platforms/pseries/hvCall.S +++ b/arch/powerpc/platforms/pseries/hvCall.S @@ -123,6 +123,40 @@ _GLOBAL(plpar_hcall) blr /* return r3 = status */ +/* + * plpar_hcall_raw can be called in real mode. kexec/kdump need some + * hypervisor calls to be executed in real mode. So plpar_hcall_raw + * does not access the per cpu hypervisor call statistics variables, + * since these variables may not be present in the RMO region. + */ +_GLOBAL(plpar_hcall_raw) + HMT_MEDIUM + + mfcr r0 + stw r0,8(r1) + + std r4,STK_PARM(r4)(r1) /* Save ret buffer */ + + mr r4,r5 + mr r5,r6 + mr r6,r7 + mr r7,r8 + mr r8,r9 + mr r9,r10 + + HVSC /* invoke the hypervisor */ + + ld r12,STK_PARM(r4)(r1) + std r4, 0(r12) + std r5, 8(r12) + std r6, 16(r12) + std r7, 24(r12) + + lwz r0,8(r1) + mtcrf 0xff,r0 + + blr /* return r3 = status */ + _GLOBAL(plpar_hcall9) HMT_MEDIUM diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 7496005566ef..843ee9643211 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -378,7 +378,7 @@ static void pSeries_lpar_hptab_clear(void) /* TODO: Use bulk call */ for (i = 0; i < hpte_count; i++) - plpar_pte_remove(0, i, 0, &dummy1, &dummy2); + plpar_pte_remove_raw(0, i, 0, &dummy1, &dummy2); } /* diff --git a/arch/powerpc/platforms/pseries/plpar_wrappers.h b/arch/powerpc/platforms/pseries/plpar_wrappers.h index 3eb7b294d92f..2e4d10c9eea8 100644 --- a/arch/powerpc/platforms/pseries/plpar_wrappers.h +++ b/arch/powerpc/platforms/pseries/plpar_wrappers.h @@ -78,6 +78,22 @@ static inline long plpar_pte_remove(unsigned long flags, unsigned long ptex, return rc; } +/* plpar_pte_remove_raw can be called in real mode. It calls plpar_hcall_raw */ +static inline long plpar_pte_remove_raw(unsigned long flags, unsigned long ptex, + unsigned long avpn, unsigned long *old_pteh_ret, + unsigned long *old_ptel_ret) +{ + long rc; + unsigned long retbuf[PLPAR_HCALL_BUFSIZE]; + + rc = plpar_hcall_raw(H_REMOVE, retbuf, flags, ptex, avpn); + + *old_pteh_ret = retbuf[0]; + *old_ptel_ret = retbuf[1]; + + return rc; +} + static inline long plpar_pte_read(unsigned long flags, unsigned long ptex, unsigned long *old_pteh_ret, unsigned long *old_ptel_ret) { diff --git a/include/asm-powerpc/hvcall.h b/include/asm-powerpc/hvcall.h index 60977806d2f4..62efd9d7a43d 100644 --- a/include/asm-powerpc/hvcall.h +++ b/include/asm-powerpc/hvcall.h @@ -236,6 +236,20 @@ long plpar_hcall_norets(unsigned long opcode, ...); #define PLPAR_HCALL_BUFSIZE 4 long plpar_hcall(unsigned long opcode, unsigned long *retbuf, ...); +/** + * plpar_hcall_raw: - Make a hypervisor call without calculating hcall stats + * @opcode: The hypervisor call to make. + * @retbuf: Buffer to store up to 4 return arguments in. + * + * This call supports up to 6 arguments and 4 return arguments. Use + * PLPAR_HCALL_BUFSIZE to size the return argument buffer. + * + * Used when phyp interface needs to be called in real mode. Similar to + * plpar_hcall, but plpar_hcall_raw works in real mode and does not + * calculate hypervisor call statistics. + */ +long plpar_hcall_raw(unsigned long opcode, unsigned long *retbuf, ...); + /** * plpar_hcall9: - Make a pseries hypervisor call with up to 9 return arguments * @opcode: The hypervisor call to make. From 4f5fa2fb1259f506d20e8af447117ec3ec426a53 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Tue, 20 Mar 2007 14:29:54 -0500 Subject: [PATCH 3/3] [POWERPC] Bypass hcall stats until cpu features have run I noticed that we execute hcalls before cpu feature code has run (eg for setting up the bolted kernel region). This means that we may be executing code that is not appropriate for the processor we have. Create an unconditional branch that we nop out all the time to fix this. Signed-off-by: Anton Blanchard Signed-off-by: Paul Mackerras --- arch/powerpc/platforms/pseries/hvCall.S | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/platforms/pseries/hvCall.S b/arch/powerpc/platforms/pseries/hvCall.S index 1501b0a9e749..c1427b3634ec 100644 --- a/arch/powerpc/platforms/pseries/hvCall.S +++ b/arch/powerpc/platforms/pseries/hvCall.S @@ -30,9 +30,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_PURR); /* * postcall is performed immediately before function return which - * allows liberal use of volatile registers. + * allows liberal use of volatile registers. We branch around this + * in early init (eg when populating the MMU hashtable) by using an + * unconditional cpu feature. */ #define HCALL_INST_POSTCALL \ +BEGIN_FTR_SECTION; \ + b 1f; \ +END_FTR_SECTION(0, 1); \ ld r4,STK_PARM(r3)(r1); /* validate opcode */ \ cmpldi cr7,r4,MAX_HCALL_OPCODE; \ bgt- cr7,1f; \