Re: [RFC] procfs: Add VmFlags field in smaps output

From: Cyrill Gorcunov
Date: Fri Oct 19 2012 - 05:45:34 EST


On Fri, Oct 19, 2012 at 01:28:35AM +0400, Cyrill Gorcunov wrote:
> >
> > A common way in which we do this future-proofing is to display the info
> > in name:value tuples (eg, /proc/meminfo). So userspace parses for the
> > "name" rather than looking into a fixed position in the /proc output.
> >
> > So.... with this thought in mind, perhaps a better output format would
> > be something like:
> >
> > VmFlags: LO:1 GR:0 RA:0 SE:1 ...
> >
> > ie: a two-character "name" and a boolean "value". Something like that.
>
> OK, Andrew, I'll try to come with something like that tomorrow, thanks!

Does the format below looks well enough (i'll make docs update as well
once things settle down)? Also I thought maybe it should be protected
with CAP_SYS_ADMIN or something?
---
Index: linux-2.6.git/fs/proc/task_mmu.c
===================================================================
--- linux-2.6.git.orig/fs/proc/task_mmu.c
+++ linux-2.6.git/fs/proc/task_mmu.c
@@ -480,6 +480,33 @@ static int smaps_pte_range(pmd_t *pmd, u
return 0;
}

+static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
+{
+#define __VM_FLAG(_f) (!!(vma->vm_flags & (_f)))
+ seq_printf(m, "VmFlags: "
+ "RD:%d WR:%d EX:%d SH:%d MR:%d "
+ "MW:%d ME:%d MS:%d GD:%d PF:%d "
+ "DW:%d LO:%d IO:%d SR:%d RR:%d "
+ "DC:%d DE:%d AC:%d NR:%d HT:%d "
+ "NL:%d AR:%d DD:%d MM:%d HG:%d "
+ "NH:%d MG:%d\n",
+ __VM_FLAG(VM_READ), __VM_FLAG(VM_WRITE),
+ __VM_FLAG(VM_EXEC), __VM_FLAG(VM_SHARED),
+ __VM_FLAG(VM_MAYREAD), __VM_FLAG(VM_MAYWRITE),
+ __VM_FLAG(VM_MAYEXEC), __VM_FLAG(VM_MAYSHARE),
+ __VM_FLAG(VM_GROWSDOWN), __VM_FLAG(VM_PFNMAP),
+ __VM_FLAG(VM_DENYWRITE), __VM_FLAG(VM_LOCKED),
+ __VM_FLAG(VM_IO), __VM_FLAG(VM_SEQ_READ),
+ __VM_FLAG(VM_RAND_READ), __VM_FLAG(VM_DONTCOPY),
+ __VM_FLAG(VM_DONTEXPAND), __VM_FLAG(VM_ACCOUNT),
+ __VM_FLAG(VM_NORESERVE), __VM_FLAG(VM_HUGETLB),
+ __VM_FLAG(VM_NONLINEAR), __VM_FLAG(VM_ARCH_1),
+ __VM_FLAG(VM_DONTDUMP), __VM_FLAG(VM_MIXEDMAP),
+ __VM_FLAG(VM_HUGEPAGE), __VM_FLAG(VM_NOHUGEPAGE),
+ __VM_FLAG(VM_MERGEABLE));
+#undef __VM_FLAG
+}
+
static int show_smap(struct seq_file *m, void *v, int is_pid)
{
struct proc_maps_private *priv = m->private;
@@ -535,6 +562,8 @@ static int show_smap(struct seq_file *m,
seq_printf(m, "Nonlinear: %8lu kB\n",
mss.nonlinear >> 10);

+ show_smap_vma_flags(m, vma);
+
if (m->count < m->size) /* vma is copied successfully */
m->version = (vma != get_gate_vma(task->mm))
? vma->vm_start : 0;
--
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