From: Robert Spalek <robert@ucw.cz>
Date: Thu, 24 Jun 2004 11:57:48 +0000 (+0000)
Subject: - lizard_alloc() turns on the wrapper for SIGSEGV and lizard_free() restores
X-Git-Tag: holmes-import~1038
X-Git-Url: http://mj.ucw.cz/gitweb/?a=commitdiff_plain;h=4deb7fd75ea1306e943ab414efca26b1951cfd23;p=libucw.git

- lizard_alloc() turns on the wrapper for SIGSEGV and lizard_free() restores
  its original value
- lizard_decompress_safe() registers quickly the SIGSEGV handler using the
  wrapper.  it saves 2 sys-calls.

- allocate 3 more bytes for unaligned memory access
---

diff --git a/lib/lizard-safe.c b/lib/lizard-safe.c
index 6bba2544..6d0b10c9 100644
--- a/lib/lizard-safe.c
+++ b/lib/lizard-safe.c
@@ -22,12 +22,13 @@ struct lizard_buffer *
 lizard_alloc(uns max_len)
 {
   struct lizard_buffer *buf = xmalloc(sizeof(struct lizard_buffer));
-  buf->len = ALIGN(max_len, PAGE_SIZE);
+  buf->len = ALIGN(max_len + 3, PAGE_SIZE);		// +3 due to the unaligned access
   buf->start = mmap(NULL, buf->len + PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
   if (buf->start == MAP_FAILED)
     die("mmap(anonymous): %m");
   if (mprotect(buf->start + buf->len, PAGE_SIZE, PROT_NONE) < 0)
     die("mprotect: %m");
+  buf->old_sigsegv_handler = handle_signal(SIGSEGV);
   return buf;
 }
 
@@ -35,12 +36,13 @@ void
 lizard_free(struct lizard_buffer *buf)
 {
   munmap(buf->start, buf->len + PAGE_SIZE);
+  signal(SIGSEGV, buf->old_sigsegv_handler);
   xfree(buf);
 }
 
 static jmp_buf safe_decompress_jump;
 static void
-sigsegv_handler(int UNUSED whatsit)
+sigsegv_handler(void)
 {
   log(L_ERROR, "SIGSEGV caught in lizard_decompress()");
   longjmp(safe_decompress_jump, 1);
@@ -59,7 +61,8 @@ lizard_decompress_safe(byte *in, struct lizard_buffer *buf, uns expected_length)
     errno = EFBIG;
     return -1;
   }
-  volatile sighandler_t old_handler = signal(SIGSEGV, sigsegv_handler);
+  volatile my_sighandler_t old_handler = signal_handler[SIGSEGV];
+  signal_handler[SIGSEGV] = sigsegv_handler;
   int len, err;
   if (!setjmp(safe_decompress_jump))
   {
@@ -73,7 +76,7 @@ lizard_decompress_safe(byte *in, struct lizard_buffer *buf, uns expected_length)
     len = -1;
     err = EFAULT;
   }
-  signal(SIGSEGV, old_handler);
+  signal_handler[SIGSEGV] = old_handler;
   errno = err;
   return len;
 }
diff --git a/lib/lizard.h b/lib/lizard.h
index e84b5119..35200c08 100644
--- a/lib/lizard.h
+++ b/lib/lizard.h
@@ -31,6 +31,7 @@ int lizard_decompress(byte *in, byte *out);
 struct lizard_buffer {
   uns len;
   void *start, *ptr;
+  void *old_sigsegv_handler;
 };
 
 struct lizard_buffer *lizard_alloc(uns max_len);