MPX-enabled application will possibly create a lot of bounds tables in process address space to save bounds information. These tables can take up huge swaths of memory (as much as 80% of the memory on the system) even if we clean them up aggressively. Being this huge, we need a way to track their memory use. If we want to track them, we essentially have two options:
1. walk the multi-GB (in virtual space) bounds directory to locate all the VMAs and walk them 2. Find a way to distinguish MPX bounds-table VMAs from normal anonymous VMAs and use some existing mechanism to walk them We expect (1) will be prohibitively expensive. For (2), we only need a single bit, and we've chosen to use a VM_ flag. We understand that they are scarce and are open to other options. There is one potential hybrid approach: check the bounds directory entry for any anonymous VMA that could possibly contain a bounds table. This is less expensive than (1), but still requires reading a pointer out of userspace for every VMA that we iterate over. Signed-off-by: Qiaowei Ren <[email protected]> --- arch/x86/mm/init_64.c | 2 ++ fs/proc/task_mmu.c | 1 + include/linux/mm.h | 2 ++ 3 files changed, 5 insertions(+), 0 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index f35c66c..2d41679 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1223,6 +1223,8 @@ int in_gate_area_no_mm(unsigned long addr) const char *arch_vma_name(struct vm_area_struct *vma) { + if (vma->vm_flags & VM_MPX) + return "[mpx]"; if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso) return "[vdso]"; if (vma == &gate_vma) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 442177b..09266bd 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -543,6 +543,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma) [ilog2(VM_GROWSDOWN)] = "gd", [ilog2(VM_PFNMAP)] = "pf", [ilog2(VM_DENYWRITE)] = "dw", + [ilog2(VM_MPX)] = "mp", [ilog2(VM_LOCKED)] = "lo", [ilog2(VM_IO)] = "io", [ilog2(VM_SEQ_READ)] = "sr", diff --git a/include/linux/mm.h b/include/linux/mm.h index d677706..029c716 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -127,6 +127,8 @@ extern unsigned int kobjsize(const void *objp); #define VM_HUGETLB 0x00400000 /* Huge TLB Page VM */ #define VM_NONLINEAR 0x00800000 /* Is non-linear (remap_file_pages) */ #define VM_ARCH_1 0x01000000 /* Architecture-specific flag */ +/* MPX specific bounds table or bounds directory (x86) */ +#define VM_MPX 0x02000000 #define VM_DONTDUMP 0x04000000 /* Do not include in the core dump */ #ifdef CONFIG_MEM_SOFT_DIRTY -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
