[PATCH 0/5] make *_gate_vma accept mm_struct instead of task_struct
Morally, the question of whether an address lies in a gate vma should be asked with respect to an mm, not a particular task. Practically, dropping the dependency on task_struct will help make current and future operations on mm's more flexible and convenient. In particular, it allows some code paths to avoid the need to hold task_lock. The only architecture this change impacts in any significant way is x86_64. The principle change on that architecture is to mirror TIF_IA32 via a new flag in mm_context_t. This is the first of a two part series that implements safe writes to /proc/pid/mem. I will be posting the second series to lkml shortly. These patches are based on v2.6.38-rc8. The general approach used here was suggested to me by Alexander Viro, but any mistakes present in these patches are entirely my own. -- steve Stephen Wilson (5): x86: add context tag to mark mm when running a task in 32-bit compatibility mode x86: mark associated mm when running a task in 32 bit compatibility mode mm: arch: make get_gate_vma take an mm_struct instead of a task_struct mm: arch: make in_gate_area take an mm_struct instead of a task_struct mm: arch: rename in_gate_area_no_task to in_gate_area_no_mm arch/powerpc/kernel/vdso.c |6 +++--- arch/s390/kernel/vdso.c|6 +++--- arch/sh/kernel/vsyscall/vsyscall.c |6 +++--- arch/x86/ia32/ia32_aout.c |1 + arch/x86/include/asm/mmu.h |6 ++ arch/x86/kernel/process_64.c |8 arch/x86/mm/init_64.c | 16 arch/x86/vdso/vdso32-setup.c | 15 --- fs/binfmt_elf.c|2 +- fs/proc/task_mmu.c |8 +--- include/linux/mm.h | 10 +- kernel/kallsyms.c |4 ++-- mm/memory.c|8 mm/mlock.c |4 ++-- mm/nommu.c |2 +- 15 files changed, 61 insertions(+), 42 deletions(-) ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[PATCH 2/5] x86: mark associated mm when running a task in 32 bit compatibility mode
This patch simply follows the same practice as for setting the TIF_IA32 flag. In particular, an mm is marked as holding 32-bit tasks when a 32-bit binary is exec'ed. Both ELF and a.out formats are updated. Signed-off-by: Stephen Wilson --- arch/x86/ia32/ia32_aout.c|1 + arch/x86/kernel/process_64.c |8 2 files changed, 9 insertions(+), 0 deletions(-) diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c index 2d93bdb..95cde43 100644 --- a/arch/x86/ia32/ia32_aout.c +++ b/arch/x86/ia32/ia32_aout.c @@ -298,6 +298,7 @@ static int load_aout_binary(struct linux_binprm *bprm, struct pt_regs *regs) /* OK, This is the point of no return */ set_personality(PER_LINUX); set_thread_flag(TIF_IA32); + current->mm->context.compat = 1; setup_new_exec(bprm); diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index bd387e8..35f1221 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -501,6 +501,10 @@ void set_personality_64bit(void) /* Make sure to be in 64bit mode */ clear_thread_flag(TIF_IA32); + /* Ensure the corresponding mm is not marked. */ + if (current->mm) + current->mm->context.compat = 0; + /* TBD: overwrites user setup. Should have two bits. But 64bit processes have always behaved this way, so it's not too bad. The main problem is just that @@ -516,6 +520,10 @@ void set_personality_ia32(void) set_thread_flag(TIF_IA32); current->personality |= force_personality32; + /* Mark the associated mm as containing 32-bit tasks. */ + if (current->mm) + current->mm->context.compat = 1; + /* Prepare the first "return" to user space */ current_thread_info()->status |= TS_COMPAT; } -- 1.7.3.5 ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[PATCH 1/5] x86: add context tag to mark mm when running a task in 32-bit compatibility mode
This tag is intended to mirror the thread info TIF_IA32 flag. Will be used to identify mm's which support 32 bit tasks running in compatibility mode without requiring a reference to the task itself. Signed-off-by: Stephen Wilson --- arch/x86/include/asm/mmu.h |6 ++ 1 files changed, 6 insertions(+), 0 deletions(-) diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index 80a1dee..8a2e5b4 100644 --- a/arch/x86/include/asm/mmu.h +++ b/arch/x86/include/asm/mmu.h @@ -13,6 +13,12 @@ typedef struct { int size; struct mutex lock; void *vdso; + +#ifdef CONFIG_X86_64 + /* True if mm supports a task running in 32 bit compatibility mode. */ + unsigned short compat; +#endif + } mm_context_t; #ifdef CONFIG_SMP -- 1.7.3.5 ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[PATCH 3/5] mm: arch: make get_gate_vma take an mm_struct instead of a task_struct
Morally, the presence of a gate vma is more an attribute of a particular mm than a particular task. Moreover, dropping the dependency on task_struct will help make both existing and future operations on mm's more flexible and convenient. Signed-off-by: Stephen Wilson --- arch/powerpc/kernel/vdso.c |2 +- arch/s390/kernel/vdso.c|2 +- arch/sh/kernel/vsyscall/vsyscall.c |2 +- arch/x86/mm/init_64.c |6 +++--- arch/x86/vdso/vdso32-setup.c | 11 ++- fs/binfmt_elf.c|2 +- fs/proc/task_mmu.c |8 +--- include/linux/mm.h |2 +- mm/memory.c|4 ++-- mm/mlock.c |4 ++-- 10 files changed, 23 insertions(+), 20 deletions(-) diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c index fd87287..6169f17 100644 --- a/arch/powerpc/kernel/vdso.c +++ b/arch/powerpc/kernel/vdso.c @@ -830,7 +830,7 @@ int in_gate_area(struct task_struct *task, unsigned long addr) return 0; } -struct vm_area_struct *get_gate_vma(struct task_struct *tsk) +struct vm_area_struct *get_gate_vma(struct mm_struct *mm) { return NULL; } diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c index f438d74..d19f305 100644 --- a/arch/s390/kernel/vdso.c +++ b/arch/s390/kernel/vdso.c @@ -347,7 +347,7 @@ int in_gate_area(struct task_struct *task, unsigned long addr) return 0; } -struct vm_area_struct *get_gate_vma(struct task_struct *tsk) +struct vm_area_struct *get_gate_vma(struct mm_struct *mm) { return NULL; } diff --git a/arch/sh/kernel/vsyscall/vsyscall.c b/arch/sh/kernel/vsyscall/vsyscall.c index 242117c..3f9b6f4 100644 --- a/arch/sh/kernel/vsyscall/vsyscall.c +++ b/arch/sh/kernel/vsyscall/vsyscall.c @@ -94,7 +94,7 @@ const char *arch_vma_name(struct vm_area_struct *vma) return NULL; } -struct vm_area_struct *get_gate_vma(struct task_struct *task) +struct vm_area_struct *get_gate_vma(struct mm_struct *mm) { return NULL; } diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 71a5929..2c1799f 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -870,10 +870,10 @@ static struct vm_area_struct gate_vma = { .vm_flags = VM_READ | VM_EXEC }; -struct vm_area_struct *get_gate_vma(struct task_struct *tsk) +struct vm_area_struct *get_gate_vma(struct mm_struct *mm) { #ifdef CONFIG_IA32_EMULATION - if (test_tsk_thread_flag(tsk, TIF_IA32)) + if (!mm || mm->context.compat) return NULL; #endif return &gate_vma; @@ -881,7 +881,7 @@ struct vm_area_struct *get_gate_vma(struct task_struct *tsk) int in_gate_area(struct task_struct *task, unsigned long addr) { - struct vm_area_struct *vma = get_gate_vma(task); + struct vm_area_struct *vma = get_gate_vma(task->mm); if (!vma) return 0; diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c index 36df991..1f651f6 100644 --- a/arch/x86/vdso/vdso32-setup.c +++ b/arch/x86/vdso/vdso32-setup.c @@ -417,11 +417,12 @@ const char *arch_vma_name(struct vm_area_struct *vma) return NULL; } -struct vm_area_struct *get_gate_vma(struct task_struct *tsk) +struct vm_area_struct *get_gate_vma(struct mm_struct *mm) { - struct mm_struct *mm = tsk->mm; - - /* Check to see if this task was created in compat vdso mode */ + /* +* Check to see if the corresponding task was created in compat vdso +* mode. +*/ if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE) return &gate_vma; return NULL; @@ -429,7 +430,7 @@ struct vm_area_struct *get_gate_vma(struct task_struct *tsk) int in_gate_area(struct task_struct *task, unsigned long addr) { - const struct vm_area_struct *vma = get_gate_vma(task); + const struct vm_area_struct *vma = get_gate_vma(task->mm); return vma && addr >= vma->vm_start && addr < vma->vm_end; } diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index d5b640b..bbabdcc 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1906,7 +1906,7 @@ static int elf_core_dump(struct coredump_params *cprm) segs = current->mm->map_count; segs += elf_core_extra_phdrs(); - gate_vma = get_gate_vma(current); + gate_vma = get_gate_vma(current->mm); if (gate_vma != NULL) segs++; diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 60b9148..bb548d4 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -126,7 +126,7 @@ static void *m_start(struct seq_file *m, loff_t *pos) return NULL; down_read(&mm->mmap_sem); - tail_vma = get_gate_vma(priv->task); + tail_vma = get_gate_vma(priv->task->mm); priv->tail_vma = tail_vma; /* Star
[PATCH 4/5] mm: arch: make in_gate_area take an mm_struct instead of a task_struct
Morally, the question of whether an address lies in a gate vma should be asked with respect to an mm, not a particular task. Moreover, dropping the dependency on task_struct will help make existing and future operations on mm's more flexible and convenient. Signed-off-by: Stephen Wilson --- arch/powerpc/kernel/vdso.c |2 +- arch/s390/kernel/vdso.c|2 +- arch/sh/kernel/vsyscall/vsyscall.c |2 +- arch/x86/mm/init_64.c |4 ++-- arch/x86/vdso/vdso32-setup.c |4 ++-- include/linux/mm.h |4 ++-- mm/memory.c|2 +- 7 files changed, 10 insertions(+), 10 deletions(-) diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c index 6169f17..467aa9e 100644 --- a/arch/powerpc/kernel/vdso.c +++ b/arch/powerpc/kernel/vdso.c @@ -825,7 +825,7 @@ int in_gate_area_no_task(unsigned long addr) return 0; } -int in_gate_area(struct task_struct *task, unsigned long addr) +int in_gate_area(struct mm_struct *mm, unsigned long addr) { return 0; } diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c index d19f305..9006e96 100644 --- a/arch/s390/kernel/vdso.c +++ b/arch/s390/kernel/vdso.c @@ -342,7 +342,7 @@ int in_gate_area_no_task(unsigned long addr) return 0; } -int in_gate_area(struct task_struct *task, unsigned long addr) +int in_gate_area(struct mm_struct *mm, unsigned long addr) { return 0; } diff --git a/arch/sh/kernel/vsyscall/vsyscall.c b/arch/sh/kernel/vsyscall/vsyscall.c index 3f9b6f4..62c36a8 100644 --- a/arch/sh/kernel/vsyscall/vsyscall.c +++ b/arch/sh/kernel/vsyscall/vsyscall.c @@ -99,7 +99,7 @@ struct vm_area_struct *get_gate_vma(struct mm_struct *mm) return NULL; } -int in_gate_area(struct task_struct *task, unsigned long address) +int in_gate_area(struct mm_struct *mm, unsigned long address) { return 0; } diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 2c1799f..3af0da3 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -879,9 +879,9 @@ struct vm_area_struct *get_gate_vma(struct mm_struct *mm) return &gate_vma; } -int in_gate_area(struct task_struct *task, unsigned long addr) +int in_gate_area(struct mm_struct *mm, unsigned long addr) { - struct vm_area_struct *vma = get_gate_vma(task->mm); + struct vm_area_struct *vma = get_gate_vma(mm); if (!vma) return 0; diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c index 1f651f6..f849bb2 100644 --- a/arch/x86/vdso/vdso32-setup.c +++ b/arch/x86/vdso/vdso32-setup.c @@ -428,9 +428,9 @@ struct vm_area_struct *get_gate_vma(struct mm_struct *mm) return NULL; } -int in_gate_area(struct task_struct *task, unsigned long addr) +int in_gate_area(struct mm_struct *mm, unsigned long addr) { - const struct vm_area_struct *vma = get_gate_vma(task->mm); + const struct vm_area_struct *vma = get_gate_vma(mm); return vma && addr >= vma->vm_start && addr < vma->vm_end; } diff --git a/include/linux/mm.h b/include/linux/mm.h index b571921..c700bbb 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1571,10 +1571,10 @@ static inline bool kernel_page_present(struct page *page) { return true; } extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm); #ifdef __HAVE_ARCH_GATE_AREA int in_gate_area_no_task(unsigned long addr); -int in_gate_area(struct task_struct *task, unsigned long addr); +int in_gate_area(struct mm_struct *mm, unsigned long addr); #else int in_gate_area_no_task(unsigned long addr); -#define in_gate_area(task, addr) ({(void)task; in_gate_area_no_task(addr);}) +#define in_gate_area(mm, addr) ({(void)mm; in_gate_area_no_task(addr);}) #endif /* __HAVE_ARCH_GATE_AREA */ int drop_caches_sysctl_handler(struct ctl_table *, int, diff --git a/mm/memory.c b/mm/memory.c index aec7cbd..d1347ac 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1437,7 +1437,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, struct vm_area_struct *vma; vma = find_extend_vma(mm, start); - if (!vma && in_gate_area(tsk, start)) { + if (!vma && in_gate_area(tsk->mm, start)) { unsigned long pg = start & PAGE_MASK; struct vm_area_struct *gate_vma = get_gate_vma(tsk->mm); pgd_t *pgd; -- 1.7.3.5 ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[PATCH 5/5] mm: arch: rename in_gate_area_no_task to in_gate_area_no_mm
Now that gate vma's are referenced with respect to a particular mm and not a particular task it only makes sense to propagate the change to this predicate as well. Signed-off-by: Stephen Wilson --- arch/powerpc/kernel/vdso.c |2 +- arch/s390/kernel/vdso.c|2 +- arch/sh/kernel/vsyscall/vsyscall.c |2 +- arch/x86/mm/init_64.c |8 arch/x86/vdso/vdso32-setup.c |2 +- include/linux/mm.h |6 +++--- kernel/kallsyms.c |4 ++-- mm/memory.c|2 +- mm/nommu.c |2 +- 9 files changed, 15 insertions(+), 15 deletions(-) diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c index 467aa9e..142ab10 100644 --- a/arch/powerpc/kernel/vdso.c +++ b/arch/powerpc/kernel/vdso.c @@ -820,7 +820,7 @@ static int __init vdso_init(void) } arch_initcall(vdso_init); -int in_gate_area_no_task(unsigned long addr) +int in_gate_area_no_mm(unsigned long addr) { return 0; } diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c index 9006e96..d73630b 100644 --- a/arch/s390/kernel/vdso.c +++ b/arch/s390/kernel/vdso.c @@ -337,7 +337,7 @@ static int __init vdso_init(void) } arch_initcall(vdso_init); -int in_gate_area_no_task(unsigned long addr) +int in_gate_area_no_mm(unsigned long addr) { return 0; } diff --git a/arch/sh/kernel/vsyscall/vsyscall.c b/arch/sh/kernel/vsyscall/vsyscall.c index 62c36a8..1d6d51a 100644 --- a/arch/sh/kernel/vsyscall/vsyscall.c +++ b/arch/sh/kernel/vsyscall/vsyscall.c @@ -104,7 +104,7 @@ int in_gate_area(struct mm_struct *mm, unsigned long address) return 0; } -int in_gate_area_no_task(unsigned long address) +int in_gate_area_no_mm(unsigned long address) { return 0; } diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 3af0da3..d3b5e2c 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -890,11 +890,11 @@ int in_gate_area(struct mm_struct *mm, unsigned long addr) } /* - * Use this when you have no reliable task/vma, typically from interrupt - * context. It is less reliable than using the task's vma and may give - * false positives: + * Use this when you have no reliable mm, typically from interrupt + * context. It is less reliable than using a task's mm and may give + * false positives. */ -int in_gate_area_no_task(unsigned long addr) +int in_gate_area_no_mm(unsigned long addr) { return (addr >= VSYSCALL_START) && (addr < VSYSCALL_END); } diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c index f849bb2..468d591 100644 --- a/arch/x86/vdso/vdso32-setup.c +++ b/arch/x86/vdso/vdso32-setup.c @@ -435,7 +435,7 @@ int in_gate_area(struct mm_struct *mm, unsigned long addr) return vma && addr >= vma->vm_start && addr < vma->vm_end; } -int in_gate_area_no_task(unsigned long addr) +int in_gate_area_no_mm(unsigned long addr) { return 0; } diff --git a/include/linux/mm.h b/include/linux/mm.h index c700bbb..694512d 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1570,11 +1570,11 @@ static inline bool kernel_page_present(struct page *page) { return true; } extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm); #ifdef __HAVE_ARCH_GATE_AREA -int in_gate_area_no_task(unsigned long addr); +int in_gate_area_no_mm(unsigned long addr); int in_gate_area(struct mm_struct *mm, unsigned long addr); #else -int in_gate_area_no_task(unsigned long addr); -#define in_gate_area(mm, addr) ({(void)mm; in_gate_area_no_task(addr);}) +int in_gate_area_no_mm(unsigned long addr); +#define in_gate_area(mm, addr) ({(void)mm; in_gate_area_no_mm(addr);}) #endif /* __HAVE_ARCH_GATE_AREA */ int drop_caches_sysctl_handler(struct ctl_table *, int, diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 6f6d091..b9d0fd1 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -64,14 +64,14 @@ static inline int is_kernel_text(unsigned long addr) if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) || arch_is_kernel_text(addr)) return 1; - return in_gate_area_no_task(addr); + return in_gate_area_no_mm(addr); } static inline int is_kernel(unsigned long addr) { if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end) return 1; - return in_gate_area_no_task(addr); + return in_gate_area_no_mm(addr); } static int is_ksym_addr(unsigned long addr) diff --git a/mm/memory.c b/mm/memory.c index d1347ac..3863e86 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3448,7 +3448,7 @@ struct vm_area_struct *get_gate_vma(struct mm_struct *mm) #endif } -int in_gate_area_no_task(unsigned long addr) +int in_gate_area_no_mm(unsigned long addr) { #ifdef AT_SYSINFO_EHDR if ((addr >= FIXADDR_USER_START) && (addr
Re: [PATCH 0/5] make *_gate_vma accept mm_struct instead of task_struct
On Wed, Mar 09, 2011 at 05:09:09AM -0800, Michel Lespinasse wrote: > On Tue, Mar 8, 2011 at 4:31 PM, Stephen Wilson wrote: > > Morally, the question of whether an address lies in a gate vma should be > > asked > > with respect to an mm, not a particular task. > > > > Practically, dropping the dependency on task_struct will help make current > > and > > future operations on mm's more flexible and convenient. In particular, it > > allows some code paths to avoid the need to hold task_lock. > > Reviewed-by: Michel Lespinasse > > May I suggest ia32_compat instead of just compat for the flag name ? Yes, sounds good to me. Will change in the next iteration. Thanks for the review! > -- > Michel "Walken" Lespinasse > A program is never fully debugged until the last user dies. -- steve ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/5] make *_gate_vma accept mm_struct instead of task_struct
On Thu, Mar 10, 2011 at 08:00:32AM -0800, Andi Kleen wrote: > On Tue, Mar 08, 2011 at 07:31:56PM -0500, Stephen Wilson wrote: > > > > Morally, the question of whether an address lies in a gate vma should be > > asked > > with respect to an mm, not a particular task. > > > > Practically, dropping the dependency on task_struct will help make current > > and > > future operations on mm's more flexible and convenient. In particular, it > > allows some code paths to avoid the need to hold task_lock. > > > > The only architecture this change impacts in any significant way is x86_64. > > The principle change on that architecture is to mirror TIF_IA32 via > > a new flag in mm_context_t. > > The problem is -- you're adding a likely cache miss on mm_struct for > every 32bit compat syscall now, even if they don't need mm_struct > currently (and a lot of them do not) Unless there's a very good > justification to make up for this performance issue elsewhere > (including numbers) this seems like a bad idea. I do not think this will result in cache misses on the scale you suggest. I am simply mirroring the *state* of the TIF_IA32 flag in mm_struct, not testing/accessing it in the same way. The only place where this flag is accessed (outside the exec() syscall path) is in x86/mm/init_64.c, get_gate_vma(), which in turn is needed by a few, relatively heavy weight, page locking/pinning routines on the mm side (get_user_pages, for example). Patches 3 and 4 in the series show the extent of the change. Or am I missing something? > > /proc/pid/mem. I will be posting the second series to lkml shortly. These > > Making every syscall slower for /proc/pid/mem doesn't seem like a good > tradeoff to me. Please solve this in some other way. > > -Andi -- steve ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH 0/5] make *_gate_vma accept mm_struct instead of task_struct II
On Thu, Mar 10, 2011 at 08:38:09AM -0800, Andi Kleen wrote: > On Thu, Mar 10, 2011 at 08:00:32AM -0800, Andi Kleen wrote: > > On Tue, Mar 08, 2011 at 07:31:56PM -0500, Stephen Wilson wrote: > > > The only architecture this change impacts in any significant way is > > > x86_64. > > > The principle change on that architecture is to mirror TIF_IA32 via > > > a new flag in mm_context_t. > > > > The problem is -- you're adding a likely cache miss on mm_struct for > > every 32bit compat syscall now, even if they don't need mm_struct > > currently (and a lot of them do not) Unless there's a very good > > justification to make up for this performance issue elsewhere > > (including numbers) this seems like a bad idea. > > Hmm I see you're only setting it on exec time actually on rereading > the patches. I thought you were changing TS_COMPAT which is in > the syscall path. > > Never mind. I have no problems with doing such a change on exec > time. OK. Great! Does this mean I have your ACK'ed by or reviewed by? Thanks for taking a look! -- steve ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev