xtensa: ldso: coalesce dl_mprotect address ranges

This noticeably lowers the number of mprotect calls at program startup,
e.g. for busybox: 7 calls vs 1835 calls.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

diff --git a/ldso/ldso/xtensa/dl-startup.h b/ldso/ldso/xtensa/dl-startup.h
index b135a4c..0c28d5e 100644 (file)
--- a/ldso/ldso/xtensa/dl-startup.h
+++ b/ldso/ldso/xtensa/dl-startup.h
@@ -83,6 +83,7 @@ do { \
        unsigned long l_addr = tpnt->loadaddr; \
        Elf32_Word relative_count; \
        unsigned long rel_addr; \
+       Elf32_Addr prev_got_start = 0, prev_got_end = 0; \
        int x; \
 \
        got_loc = (xtensa_got_location *) \
@@ -93,7 +94,24 @@ do { \
                got_start = got_loc[x].offset & ~(PAGE_SIZE - 1); \
                got_end = ((got_loc[x].offset + got_loc[x].length + PAGE_SIZE - 1) \
                                   & ~(PAGE_SIZE - 1)); \
-               _dl_mprotect ((void *)(got_start + l_addr), got_end - got_start, \
+               if (got_end >= prev_got_start && got_start <= prev_got_end) { \
+                       if (got_end > prev_got_end) \
+                               prev_got_end = got_end; \
+                       if (got_start < prev_got_start) \
+                               prev_got_start = got_start; \
+                       continue; \
+               } else if (prev_got_start != prev_got_end) { \
+                       _dl_mprotect ((void *)(prev_got_start + l_addr), \
+                                                 prev_got_end - prev_got_start, \
+                                                 PROT_READ | PROT_WRITE | PROT_EXEC); \
+               } \
+               prev_got_start = got_start; \
+               prev_got_end = got_end; \
+       } \
+\
+       if (prev_got_start != prev_got_end) { \
+               _dl_mprotect ((void *)(prev_got_start + l_addr), \
+                                         prev_got_end - prev_got_start, \
                                          PROT_READ | PROT_WRITE | PROT_EXEC); \
        } \
 \

diff --git a/ldso/ldso/xtensa/dl-sysdep.h b/ldso/ldso/xtensa/dl-sysdep.h
index a0ed4e5..5f8bcb0 100644 (file)
--- a/ldso/ldso/xtensa/dl-sysdep.h
+++ b/ldso/ldso/xtensa/dl-sysdep.h
@@ -36,6 +36,7 @@ typedef struct xtensa_got_location_struct {
   do {                                                                       \
     xtensa_got_location *got_loc;                                            \
     Elf32_Addr l_addr = MODULE->loadaddr;                                    \
+    Elf32_Addr prev_got_start = 0, prev_got_end = 0;                         \
     int x;                                                                   \
                                                                              \
     got_loc = (xtensa_got_location *)                                        \
@@ -47,7 +48,28 @@ typedef struct xtensa_got_location_struct {
        got_start = got_loc[x].offset & ~(PAGE_SIZE - 1);                     \
        got_end = ((got_loc[x].offset + got_loc[x].length + PAGE_SIZE - 1)    \
                   & ~(PAGE_SIZE - 1));                                       \
-       _dl_mprotect ((void *)(got_start + l_addr) , got_end - got_start,     \
+       if (got_end >= prev_got_start && got_start <= prev_got_end)           \
+         {                                                                   \
+           if (got_end > prev_got_end)                                       \
+               prev_got_end = got_end;                                       \
+           if (got_start < prev_got_start)                                   \
+               prev_got_start = got_start;                                   \
+           continue;                                                         \
+         }                                                                   \
+        else if (prev_got_start != prev_got_end)                             \
+         {                                                                   \
+           _dl_mprotect ((void *)(prev_got_start + l_addr),                  \
+                         prev_got_end - prev_got_start,                      \
+                         PROT_READ | PROT_WRITE | PROT_EXEC);                \
+          }                                                                  \
+        prev_got_start = got_start;                                          \
+        prev_got_end = got_end;                                                      \
+      }                                                                              \
+                                                                             \
+    if (prev_got_start != prev_got_end)                                              \
+      {                                                                              \
+        _dl_mprotect ((void *)(prev_got_start + l_addr),                     \
+                     prev_got_end - prev_got_start,                          \
                      PROT_READ | PROT_WRITE | PROT_EXEC);                    \
       }                                                                              \
                                                                              \