Building libgcj on Linux/Alpha

[Jeff Sturm <jsturm@sigma6.com>]

Below are patches necessary to build/use libgcj on Linux/Alpha.  Most
are GC issues.  The worst is that __data_start is no longer defined on
my RH 6.0 machine (is this a glibc2.1 problem, or binutils?) so I
included a workaround (based on /proc) to obtain the starting address
of the data segment.  I'll bring this up on gclist as well.  I'm not
sure the B-W-D collector is handling dynamic loading correctly for Alpha
yet, so I plan to run more tests.

Also I defined GC_test_and_set for Alpha, and __IEEE_LITTLE_ENDIAN in
ieeefp.h.

There is another small problem in boehm-gc... the alpha_mach_dep.s file
has preprocessor symbols, and the current Makefile runs
"as alpha_mach_dep.s" which fails on Linux.  I got past by renaming
it to alpha_mach_dep.S and compiling with "gcc -c alpha_mach_dep.S".
Since patch isn't very friendly to renaming files, is there a cleaner
workaround?

I noticed the current libgcj is based on 4.13alpha2... is there a plan
to migrate to 4.14?


diff -r -c libgcj.orig/boehm-gc/config.h libgcj/boehm-gc/config.h
*** libgcj.orig/boehm-gc/config.h       Fri Apr 16 05:56:29 1999
--- libgcj/boehm-gc/config.h    Sun Jun 20 09:03:55 1999
***************
*** 844,851 ****
  #       define CPP_WORDSZ 64
  #       define STACKBOTTOM ((ptr_t) 0x120000000)
  #       ifdef __ELF__
!             extern int __data_start;
! #           define DATASTART &__data_start
  #           define DYNAMIC_LOADING
  #       else
  #           define DATASTART ((ptr_t) 0x140000000)
--- 844,851 ----
  #       define CPP_WORDSZ 64
  #       define STACKBOTTOM ((ptr_t) 0x120000000)
  #       ifdef __ELF__
! #           define DATASTART GC_data_start
! #           define USE_PROC
  #           define DYNAMIC_LOADING
  #       else
  #           define DATASTART ((ptr_t) 0x140000000)
diff -r -c libgcj.orig/boehm-gc/gc_priv.h libgcj/boehm-gc/gc_priv.h
*** libgcj.orig/boehm-gc/gc_priv.h      Wed Apr  7 04:01:38 1999
--- libgcj/boehm-gc/gc_priv.h   Thu Jun 10 00:09:41 1999
***************
*** 442,451 ****
                : "0"(1), "m"(*(addr)));
          return oldval;
         }
  #    else
         -- > Need implementation of GC_test_and_set()
  #    endif
- #    define GC_clear(addr) (*(addr) = 0)

       extern volatile unsigned int GC_allocate_lock;
        /* This is not a mutex because mutexes that obey the (optional)
*/
--- 442,473 ----
                : "0"(1), "m"(*(addr)));
          return oldval;
         }
+        inline static void GC_clear(volatile unsigned int *addr) {
+           *(addr) = 0;
+        }
+ #    elif defined(__alpha__)
+        inline static int GC_test_and_set(volatile unsigned int *addr)
{
+         long oldval, temp;
+
+         __asm__ __volatile__(
+               "1:\tldl_l %0,%3\n"
+               "\tbne %0,2f\n"
+               "\tor $31,1,%1\n"
+               "\tstl_c %1,%2\n"
+               "\tbeq %1,1b\n"
+               "2:\tmb\n"
+               : "=&r"(oldval), "=&r"(temp), "=m"(*(addr))
+               : "m"(*(addr))
+               : "memory");
+         return (int)oldval;
+        }
+        inline static void GC_clear(volatile unsigned int *addr) {
+           __asm__ __volatile__("mb": : :"memory");
+           *(addr) = 0;
+        }
  #    else
         -- > Need implementation of GC_test_and_set()
  #    endif

       extern volatile unsigned int GC_allocate_lock;
        /* This is not a mutex because mutexes that obey the (optional)
*/
diff -r -c libgcj.orig/boehm-gc/misc.c libgcj/boehm-gc/misc.c
*** libgcj.orig/boehm-gc/misc.c Mon Apr 26 10:15:05 1999
--- libgcj/boehm-gc/misc.c      Sun Jun 20 09:02:04 1999
***************
*** 436,441 ****
--- 436,444 ----
  #   if defined(LINUX) && defined(POWERPC)
        GC_init_linuxppc();
  #   endif
+ #   if defined(LINUX) && defined(ALPHA)
+       GC_init_linuxalpha();
+ #   endif
  #   ifdef SOLARIS_THREADS
        GC_thr_init();
        /* We need dirty bits in order to find live stack sections.    
*/
diff -r -c libgcj.orig/boehm-gc/os_dep.c libgcj/boehm-gc/os_dep.c
*** libgcj.orig/boehm-gc/os_dep.c       Wed Apr 21 05:42:28 1999
--- libgcj/boehm-gc/os_dep.c    Sun Jun 20 09:21:58 1999
***************
*** 68,74 ****
  #   define NEED_FIND_LIMIT
  # endif

! # if defined(LINUX) && defined(POWERPC)
  #   define NEED_FIND_LIMIT
  # endif

--- 68,74 ----
  #   define NEED_FIND_LIMIT
  # endif

! # if defined(LINUX) && (defined(POWERPC) || defined(ALPHA))
  #   define NEED_FIND_LIMIT
  # endif

***************
*** 145,150 ****
--- 145,226 ----
        /* This may need to be environ, without the underscore, for    
*/
        /* some versions.                                              
*/
      GC_data_start = GC_find_limit((ptr_t)&_environ, FALSE);
+   }
+ #endif
+
+ #if defined(LINUX) && defined(ALPHA)
+   ptr_t GC_data_start;
+
+   void GC_init_linuxalpha()
+   {
+ # ifdef USE_PROC
+     FILE *fp = fopen("/proc/self/maps", "r");
+
+     if (fp) {
+       extern void *_etext;
+       ptr_t stacktop = 0, stackbottom = 0;
+       ptr_t textstart = 0, textend = 0;
+       ptr_t datastart = 0, dataend = 0;
+       ptr_t bssstart = 0, bssend = 0;
+
+       while (!feof(fp)) {
+         ptr_t start, end, offset;
+         unsigned short major, minor;
+         char r, w, x, p;
+         unsigned int inode;
+
+         int n = fscanf(fp, "%lx-%lx %c%c%c%c %lx %hx:%hx %d",
+           &start, &end, &r, &w, &x, &p, &offset, &major, &minor,
&inode);
+         if (n < 10) break;
+
+         /*
+          * If local variable lies within segment, it is stack.
+          * Else if segment lies below _end and is executable,
+          * it is text.  Otherwise, if segment start lies between
+          * _etext and _end and segment is writable and is mapped
+          * to the executable image it is data, otherwise bss.
+          */
+          if (start < (ptr_t)&fp && end > (ptr_t)&fp && w == 'w') {
+            stacktop = start;
+            stackbottom = end;
+          } else if (start < (ptr_t)&_end && w == '-' && x == 'x') {
+            textstart = start;
+            textend = end;
+          } else if (start >= (ptr_t)&_etext &&
+                       start < (ptr_t)&_end && w == 'w') {
+            if (inode > 0) {
+              datastart = start;
+              dataend = end;
+            } else {
+              bssstart = start;
+              bssend = end;
+            }
+          }
+
+          //printf("%016lx-%016lx %c%c%c%c %016lx %02hx:%02hx %d\n",
+          //      start, end, r, w, x, p, offset, major, minor, inode);
+
+          while (fgetc(fp) != '\n') ;
+        }
+        fclose(fp);
+
+        //fprintf(stderr, "text:  %lx-%lx\n", textstart, textend);
+        //fprintf(stderr, "data:  %lx-%lx\n", datastart, dataend);
+        //fprintf(stderr, "bss:   %lx-%lx\n", bssstart, bssend);
+        //fprintf(stderr, "stack: %lx-%lx\n", stacktop, stackbottom);
+
+        GC_data_start = datastart;
+      } else {
+ # endif
+        extern ptr_t GC_find_limit();
+        extern int _edata;
+        /* This may need to be environ, without the underscore, for */
+        /* some versions.  */
+        GC_data_start = GC_find_limit((ptr_t)&_edata, FALSE);
+ # ifdef USE_PROC
+      }
+ # endif
+      //fprintf(stderr, "GC_data_start = %p\n", GC_data_start);
    }
  #endif

diff -r -c libgcj.orig/libjava/java/lang/ieeefp.h
libgcj/libjava/java/lang/ieeefp.h
*** libgcj.orig/libjava/java/lang/ieeefp.h      Wed Apr  7 10:52:38 1999
--- libgcj/libjava/java/lang/ieeefp.h   Wed Jun  9 21:52:51 1999
***************
*** 1,6 ****
--- 1,10 ----
  #ifndef __IEEE_BIG_ENDIAN
  #ifndef __IEEE_LITTLE_ENDIAN

+ #ifdef __alpha__
+ #define __IEEE_LITTLE_ENDIAN
+ #endif
+
  #ifdef __arm__
  /* ARM always has big-endian words.  Within those words the byte
ordering
     appears to be big or little endian.  Newlib doesn't seem to care
about

-- 
Jeff Sturm
jsturm@sigma6.com