Re: [PATCH] target/riscv: Fix incorrect PTE merge in walk_pte

[Ralf Ramsauer]

On 01/04/2022 14:22, Ralf Ramsauer wrote:
Two non-subsequent PTEs can be mapped to subsequent paddrs. In this
case, walk_pte will erroneously merge them.

Enforce the split up, by tracking the virtual base address.

Let's say we have the mapping:
0x81200000 -> 0x89623000 (4K)
0x8120f000 -> 0x89624000 (4K)

Before, walk_pte would have shown:

vaddr            paddr            size             attr
---------------- ---------------- ---------------- -------
0000000081200000 0000000089623000 0000000000002000 rwxu-ad

as it only checks for subsequent paddrs. With this patch, it becomes:

vaddr            paddr            size             attr
---------------- ---------------- ---------------- -------
0000000081200000 0000000089623000 0000000000001000 rwxu-ad
000000008120f000 0000000089624000 0000000000001000 rwxu-ad

Signed-off-by: Ralf Ramsauer <ralf.ramsa...@oth-regensburg.de>
---
  target/riscv/monitor.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/target/riscv/monitor.c b/target/riscv/monitor.c
index 7efb4b62c1..60e3edd0ad 100644
--- a/target/riscv/monitor.c
+++ b/target/riscv/monitor.c
@@ -84,6 +84,7 @@ static void walk_pte(Monitor *mon, hwaddr base, target_ulong 
start,
  {
      hwaddr pte_addr;
      hwaddr paddr;
+    target_ulong last_start = -1;
      target_ulong pgsize;
      target_ulong pte;
      int ptshift;
@@ -116,13 +117,15 @@ static void walk_pte(Monitor *mon, hwaddr base, 
target_ulong start,
                   * contiguous mapped block details.
                   */
                  if ((*last_attr != attr) ||
-                    (*last_paddr + *last_size != paddr)) {
+                    (*last_paddr + *last_size != paddr) ||
+                    (last_start + *last_size != start)) {
                      print_pte(mon, va_bits, *vbase, *pbase,
                                *last_paddr + *last_size - *pbase, *last_attr);
  
                      *vbase = start;
                      *pbase = paddr;
                      *last_attr = attr;
+                    last_start = start;
                  }

Yikes, there's a small bug in my patch that I failed to see:
last_addr = start should be outside the curly brackets, otherwise it 
will rip up too much regions.

I'll return with a V2.

Thanks
  Ralf

  
                  *last_paddr = paddr;