Ram Pai [off-list ref] writes:

On Fri, Jan 19, 2018 at 10:09:41AM -0600, Eric W. Biederman wrote:

quoted

Ram Pai [off-list ref] writes:

quoted

Currently the  architecture  specific code is expected to
display  the  protection  keys  in  smap  for a given vma.
This can lead to redundant code and possibly to divergent
formats in which the key gets displayed.

This  patch  changes  the implementation. It displays the
pkey only if the architecture support pkeys.

x86 arch_show_smap() function is not needed anymore.
Delete it.

Signed-off-by: Ram Pai <redacted>
---
 arch/x86/kernel/setup.c |    8 --------
 fs/proc/task_mmu.c      |   11 ++++++-----
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 8af2e8d..ddf945a 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c

@@ -1326,11 +1326,3 @@ static int __init register_kernel_offset_dumper(void)
 	return 0;
 }
 __initcall(register_kernel_offset_dumper);
-
-void arch_show_smap(struct seq_file *m, struct vm_area_struct *vma)
-{
-	if (!boot_cpu_has(X86_FEATURE_OSPKE))
-		return;
-
-	seq_printf(m, "ProtectionKey:  %8u\n", vma_pkey(vma));
-}

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 0edd4da..4b39a94 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c

@@ -18,6 +18,7 @@
 #include <linux/page_idle.h>
 #include <linux/shmem_fs.h>
 #include <linux/uaccess.h>
+#include <linux/pkeys.h>
 
 #include <asm/elf.h>
 #include <asm/tlb.h>

@@ -728,10 +729,6 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
 }
 #endif /* HUGETLB_PAGE */
 
-void __weak arch_show_smap(struct seq_file *m, struct vm_area_struct *vma)
-{
-}
-
 static int show_smap(struct seq_file *m, void *v, int is_pid)
 {
 	struct proc_maps_private *priv = m->private;

@@ -851,9 +848,13 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
 			   (unsigned long)(mss->pss >> (10 + PSS_SHIFT)));
 
 	if (!rollup_mode) {
-		arch_show_smap(m, vma);
+#ifdef CONFIG_ARCH_HAS_PKEYS
+		if (arch_pkeys_enabled())
+			seq_printf(m, "ProtectionKey:  %8u\n", vma_pkey(vma));
+#endif

Would it be worth it making vma_pkey a noop on architectures that don't
support protection keys so that we don't need the #ifdef here?

You mean something like this?
	#define vma_pkey(vma)  
It will lead to compilation error.


I can make it
	#define vma_pkey(vma)  0

and that will work and get rid of the #ifdef

Yes the second is what I was thinking.

I don't know if it is worth it but #ifdefs can be problematic as the
result in code not being compile tested.

Eric