hipe segmentation fault

Serge Aleynikov <>
Thu Apr 6 21:53:57 CEST 2006


Mikael,

Thanks for the quick turnaround!

Serge

Mikael Pettersson wrote:
> Serge Aleynikov writes:
>  > Mikael,
>  > 
>  > Here's a bunch of info you requested.  Let's continue this discussion 
>  > outside of the mailing list's scope, and just post the resolution 
>  > when/if it's available.
>  > 
> [gdb session omitted]
> 
> Problem solved. According to the gdb session everything looked OK,
> yet the code couldn't be executed. It turns out that with the fairly
> new processor model Serge is using, the Linux kernel makes normal
> data memory non-executable by default. We've seen this long ago on
> AMD64 machines with 64-bit kernels, but never before on machines with
> 32-bit kernels. The solution is to adapt the specially written AMD64
> code memory allocation routines for use on x86 as well.
> 
> The patch below solves this problem. It's been checked in on the R11
> development branch and should be applied to R10B-10 as well.
> 
> /Mikael
> 
> --- otp-0330/erts/emulator/hipe/hipe_amd64.h.~1~	2005-12-15 12:29:52.000000000 +0100
> +++ otp-0330/erts/emulator/hipe/hipe_amd64.h	2006-04-06 17:46:19.000000000 +0200
> @@ -14,10 +14,6 @@
>  
>  #define hipe_arch_name	am_amd64
>  
> -/* for hipe_bifs_enter_code_2 */
> -extern void *hipe_alloc_code(Uint nrbytes, Eterm callees, Eterm *trampolines, Process *p);
> -#define HIPE_ALLOC_CODE(n,c,t,p) hipe_alloc_code((n),(c),(t),(p))
> -
>  extern const Uint sse2_fnegate_mask[];
>  
>  #endif /* HIPE_AMD64_H */
> --- otp-0330/erts/emulator/hipe/hipe_x86.c.~1~	2005-12-15 12:29:53.000000000 +0100
> +++ otp-0330/erts/emulator/hipe/hipe_x86.c	2006-04-06 19:23:59.000000000 +0200
> @@ -50,6 +50,114 @@
>      return 0;
>  }
>  
> +/*
> + * Memory allocator for executable code.
> + *
> + * This is required on x86 because some combinations
> + * of Linux kernels and CPU generations default to
> + * non-executable memory mappings, causing ordinary
> + * malloc() memory to be non-executable.
> + */
> +static unsigned int code_bytes;
> +static char *code_next;
> +
> +#if 0	/* change to non-zero to get allocation statistics at exit() */
> +static unsigned int total_mapped, nr_joins, nr_splits, total_alloc, nr_allocs, nr_large, total_lost;
> +static unsigned int atexit_done;
> +
> +static void alloc_code_stats(void)
> +{
> +    printf("\r\nalloc_code_stats: %u bytes mapped, %u joins, %u splits, %u bytes allocated, %u average alloc, %u large allocs, %u bytes lost\r\n",
> +	   total_mapped, nr_joins, nr_splits, total_alloc, nr_allocs ? total_alloc/nr_allocs : 0, nr_large, total_lost);
> +}
> +
> +static void atexit_alloc_code_stats(void)
> +{
> +    if (!atexit_done) {
> +	atexit_done = 1;
> +	(void)atexit(alloc_code_stats);
> +    }
> +}
> +
> +#define ALLOC_CODE_STATS(X)	do{X;}while(0)
> +#else
> +#define ALLOC_CODE_STATS(X)	do{}while(0)
> +#endif
> +
> +static void morecore(unsigned int alloc_bytes)
> +{
> +    unsigned int map_bytes;
> +    char *map_hint, *map_start;
> +
> +    /* Page-align the amount to allocate. */
> +    map_bytes = (alloc_bytes + 4095) & ~4095;
> +
> +    /* Round up small allocations. */
> +    if (map_bytes < 1024*1024)
> +	map_bytes = 1024*1024;
> +    else
> +	ALLOC_CODE_STATS(++nr_large);
> +
> +    /* Create a new memory mapping, ensuring it is executable
> +       and in the low 2GB of the address space. Also attempt
> +       to make it adjacent to the previous mapping. */
> +    map_hint = code_next + code_bytes;
> +    if ((unsigned long)map_hint & 4095)
> +	abort();
> +    map_start = mmap(map_hint, map_bytes,
> +		     PROT_EXEC|PROT_READ|PROT_WRITE,
> +		     MAP_PRIVATE|MAP_ANONYMOUS
> +#ifdef __x86_64__
> +		     |MAP_32BIT
> +#endif
> +		     ,
> +		     -1, 0);
> +    if (map_start == MAP_FAILED) {
> +	perror("mmap");
> +	abort();
> +    }
> +    ALLOC_CODE_STATS(total_mapped += map_bytes);
> +
> +    /* Merge adjacent mappings, so the trailing portion of the previous
> +       mapping isn't lost. In practice this is quite successful. */
> +    if (map_start == map_hint) {
> +	ALLOC_CODE_STATS(++nr_joins);
> +	code_bytes += map_bytes;
> +    } else {
> +	ALLOC_CODE_STATS(++nr_splits);
> +	ALLOC_CODE_STATS(total_lost += code_bytes);
> +	code_next = map_start;
> +	code_bytes = map_bytes;
> +    }
> +
> +    ALLOC_CODE_STATS(atexit_alloc_code_stats());
> +}
> +
> +static void *alloc_code(unsigned int alloc_bytes)
> +{
> +    void *res;
> +
> +    /* Align function entries. */
> +    alloc_bytes = (alloc_bytes + 3) & ~3;
> +
> +    if (code_bytes < alloc_bytes)
> +	morecore(alloc_bytes);
> +    ALLOC_CODE_STATS(++nr_allocs);
> +    ALLOC_CODE_STATS(total_alloc += alloc_bytes);
> +    res = code_next;
> +    code_next += alloc_bytes;
> +    code_bytes -= alloc_bytes;
> +    return res;
> +}
> +
> +void *hipe_alloc_code(Uint nrbytes, Eterm callees, Eterm *trampolines, Process *p)
> +{
> +    if (is_not_nil(callees))
> +	return NULL;
> +    *trampolines = NIL;
> +    return alloc_code(nrbytes);
> +}
> +
>  /* called from hipe_bif0.c:hipe_bifs_make_native_stub_2()
>     and hipe_bif0.c:hipe_make_stub() */
>  void *hipe_make_native_stub(void *beamAddress, unsigned int beamArity)
> @@ -76,7 +184,7 @@
>  	16 +	/* 16 when both offsets are 8-bit */
>  	(P_BEAM_IP >= 128 ? 3 : 0) +
>  	(P_ARITY >= 128 ? 3 : 0);
> -    codep = code = erts_alloc(ERTS_ALC_T_HIPE, codeSize);
> +    codep = code = alloc_code(codeSize);
>  
>      /* movl $beamAddress, P_BEAM_IP(%ebp); 3 or 6 bytes, plus 4 */
>      codep[0] = 0xc7;
> --- otp-0330/erts/emulator/hipe/hipe_x86.h.~1~	2005-12-15 12:29:53.000000000 +0100
> +++ otp-0330/erts/emulator/hipe/hipe_x86.h	2006-04-06 17:45:48.000000000 +0200
> @@ -39,4 +39,8 @@
>  extern void nbif_inc_stack_0(void);
>  extern void nbif_handle_fp_exception(void);
>  
> +/* for hipe_bifs_enter_code_2 */
> +extern void *hipe_alloc_code(Uint nrbytes, Eterm callees, Eterm *trampolines, Process *p);
> +#define HIPE_ALLOC_CODE(n,c,t,p) hipe_alloc_code((n),(c),(t),(p))
> +
>  #endif /* HIPE_X86_H */
> 

-- 
Serge Aleynikov
R&D Telecom, IDT Corp.
Tel: (973) 438-3436
Fax: (973) 438-1464




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