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IPA: Add alloc_jump_pad_buffer target hook. 

Targets may have various requirements on the required location of the jump
pad area.  Currently IPA allocates it at the lowest possible address,
so that it is reachable by branches from the executable.  However, this
fails on powerpc, which has executable link address (0x10000000) much
larger than branch reach (+/- 32MiB).

This makes jump pad buffer allocation a target hook instead.  The current
implementations are as follows:

- i386 and s390: Branches can reach anywhere, so just mmap it.  This
  avoids the linear search dance.
- x86_64: Branches have +/-2GiB of reach, and executable is loaded low,
  so just call mmap with MAP_32BIT.  Likewise avoids the linear search.
- aarch64: Branches have +-128MiB of reach, executable loaded at 4MiB.
  Do a linear search from 4MiB-size downwards to page_size.
- s390x: Branches have +-4GiB of reach, executable loaded at 2GiB.
  Do like on aarch64.

gdb/gdbserver/ChangeLog:

	* linux-aarch64-ipa.c: Add <sys/mman.h> and <sys/auxv.h> includes.
	(alloc_jump_pad_buffer): New function.
	* linux-amd64-ipa.c: Add <sys/mman.h> include.
	(alloc_jump_pad_buffer): New function.
	* linux-i386-ipa.c (alloc_jump_pad_buffer): New function.
	* linux-s390-ipa.c: Add <sys/mman.h> and <sys/auxv.h> includes.
	(alloc_jump_pad_buffer): New function.
	* tracepoint.c (getauxval) [!HAVE_GETAUXVAL]: New function.
	(initialize_tracepoint): Delegate to alloc_jump_pad_buffer.
	* tracepoint.h (alloc_jump_pad_buffer): New prototype.
	(getauxval) [!HAVE_GETAUXVAL]: New prototype.
This commit is contained in:
Marcin Kościelnicki 2016-03-13 00:30:11 +01:00
parent 0a191de984
commit a13c46966d
7 changed files with 194 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
gdb/gdbserver/ChangeLog
View File

@ -1,3 +1,17 @@
2016-03-31 Marcin Kościelnicki <koriakin@0x04.net>
* linux-aarch64-ipa.c: Add <sys/mman.h> and <sys/auxv.h> includes.
(alloc_jump_pad_buffer): New function.
* linux-amd64-ipa.c: Add <sys/mman.h> include.
(alloc_jump_pad_buffer): New function.
* linux-i386-ipa.c (alloc_jump_pad_buffer): New function.
* linux-s390-ipa.c: Add <sys/mman.h> and <sys/auxv.h> includes.
(alloc_jump_pad_buffer): New function.
* tracepoint.c (getauxval) [!HAVE_GETAUXVAL]: New function.
(initialize_tracepoint): Delegate to alloc_jump_pad_buffer.
* tracepoint.h (alloc_jump_pad_buffer): New prototype.
(getauxval) [!HAVE_GETAUXVAL]: New prototype.
2016-03-30 Marcin Kościelnicki <koriakin@0x04.net>
* linux-aarch64-ipa.c: Rename gdb_agent_get_raw_reg to get_raw_reg.

50
gdb/gdbserver/linux-aarch64-ipa.c
View File

@ -19,7 +19,11 @@
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "server.h"
#include <sys/mman.h>
#include "tracepoint.h"
#ifdef HAVE_GETAUXVAL
#include <sys/auxv.h>
#endif
/* Defined in auto-generated file aarch64.c. */
void init_registers_aarch64 (void);
@ -153,6 +157,52 @@ get_ipa_tdesc (int idx)
return tdesc_aarch64;
}
/* Allocate buffer for the jump pads. The branch instruction has a reach
of +/- 128MiB, and the executable is loaded at 0x400000 (4MiB).
To maximize the area of executable that can use tracepoints, try
allocating at 0x400000 - size initially, decreasing until we hit
a free area. */
void *
alloc_jump_pad_buffer (size_t size)
{
uintptr_t addr;
uintptr_t exec_base = getauxval (AT_PHDR);
int pagesize;
void *res;
if (exec_base == 0)
exec_base = 0x400000;
pagesize = sysconf (_SC_PAGE_SIZE);
if (pagesize == -1)
perror_with_name ("sysconf");
addr = exec_base - size;
/* size should already be page-aligned, but this can't hurt. */
addr &= ~(pagesize - 1);
/* Search for a free area. If we hit 0, we're out of luck. */
for (; addr; addr -= pagesize)
{
/* No MAP_FIXED - we don't want to zap someone's mapping. */
res = mmap ((void *) addr, size,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
/* If we got what we wanted, return. */
if ((uintptr_t) res == addr)
return res;
/* If we got a mapping, but at a wrong address, undo it. */
if (res != MAP_FAILED)
munmap (res, size);
}
return NULL;
}
void
initialize_low_tracepoint (void)
{

18
gdb/gdbserver/linux-amd64-ipa.c
View File

@ -19,6 +19,7 @@
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "server.h"
#include <sys/mman.h>
#include "tracepoint.h"
#include "linux-x86-tdesc.h"
@ -190,6 +191,23 @@ get_ipa_tdesc (int idx)
}
}
/* Allocate buffer for the jump pads. Since we're using 32-bit jumps
to reach them, and the executable is at low addresses, MAP_32BIT
works just fine. Shared libraries, being allocated at the top,
are unfortunately out of luck. */
void *
alloc_jump_pad_buffer (size_t size)
{
void *res = mmap (NULL, size, PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_32BIT, -1, 0);
if (res == MAP_FAILED)
return NULL;
return res;
}
void
initialize_low_tracepoint (void)
{

15
gdb/gdbserver/linux-i386-ipa.c
View File

@ -269,6 +269,21 @@ get_ipa_tdesc (int idx)
}
}
/* Allocate buffer for the jump pads. On i386, we can reach an arbitrary
address with a jump instruction, so just allocate normally. */
void *
alloc_jump_pad_buffer (size_t size)
{
void *res = mmap (NULL, size, PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (res == MAP_FAILED)
return NULL;
return res;
}
void
initialize_low_tracepoint (void)
{

59
gdb/gdbserver/linux-s390-ipa.c
View File

@ -19,8 +19,12 @@
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "server.h"
#include <sys/mman.h>
#include "tracepoint.h"
#include "linux-s390-tdesc.h"
#ifdef HAVE_GETAUXVAL
#include <sys/auxv.h>
#endif
#define FT_FPR(x) (0x000 + (x) * 0x10)
#define FT_VR(x) (0x000 + (x) * 0x10)
@ -370,6 +374,61 @@ get_ipa_tdesc (int idx)
}
}
/* Allocate buffer for the jump pads. On 31-bit, JG reaches everywhere,
so just allocate normally. On 64-bit, we have +/-4GiB of reach, and
the executable is usually mapped at 0x80000000 - aim for somewhere
below it. */
void *
alloc_jump_pad_buffer (size_t size)
{
#ifdef __s390x__
uintptr_t addr;
uintptr_t exec_base = getauxval (AT_PHDR);
int pagesize;
void *res;
if (exec_base == 0)
exec_base = 0x80000000;
pagesize = sysconf (_SC_PAGE_SIZE);
if (pagesize == -1)
perror_with_name ("sysconf");
addr = exec_base - size;
/* size should already be page-aligned, but this can't hurt. */
addr &= ~(pagesize - 1);
/* Search for a free area. If we hit 0, we're out of luck. */
for (; addr; addr -= pagesize)
{
/* No MAP_FIXED - we don't want to zap someone's mapping. */
res = mmap ((void *) addr, size,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
/* If we got what we wanted, return. */
if ((uintptr_t) res == addr)
return res;
/* If we got a mapping, but at a wrong address, undo it. */
if (res != MAP_FAILED)
munmap (res, size);
}
return NULL;
#else
void *res = mmap (NULL, size, PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (res == MAP_FAILED)
return NULL;
return res;
#endif
}
void
initialize_low_tracepoint (void)
{

53
gdb/gdbserver/tracepoint.c
View File

@ -216,6 +216,34 @@ static struct ipa_sym_addresses ipa_sym_addrs;
static int read_inferior_integer (CORE_ADDR symaddr, int *val);
#if !defined HAVE_GETAUXVAL && defined IN_PROCESS_AGENT
/* Retrieve the value of TYPE from the auxiliary vector. If TYPE is not
found, 0 is returned. This function is provided if glibc is too old. */
unsigned long
getauxval (unsigned long type)
{
unsigned long data[2];
FILE *f = fopen ("/proc/self/auxv", "r");
unsigned long value = 0;
if (f == NULL)
return 0;
while (fread (data, sizeof (data), 1, f) > 0)
{
if (data[0] == type)
{
value = data[1];
break;
}
}
fclose (f);
return value;
}
#endif
/* Returns true if both the in-process agent library and the static
tracepoints libraries are loaded in the inferior, and agent has
capability on static tracepoints. */
@ -7400,35 +7428,22 @@ initialize_tracepoint (void)
#ifdef IN_PROCESS_AGENT
{
uintptr_t addr;
int pagesize;
size_t jump_pad_size;
pagesize = sysconf (_SC_PAGE_SIZE);
if (pagesize == -1)
perror_with_name ("sysconf");
gdb_tp_heap_buffer = (char *) xmalloc (5 * 1024 * 1024);
#define SCRATCH_BUFFER_NPAGES 20
/* Allocate scratch buffer aligned on a page boundary, at a low
address (close to the main executable's code). */
for (addr = pagesize; addr != 0; addr += pagesize)
{
gdb_jump_pad_buffer
= (char *) mmap ((void *) addr,
pagesize * SCRATCH_BUFFER_NPAGES,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
-1, 0);
if (gdb_jump_pad_buffer != MAP_FAILED)
break;
}
jump_pad_size = pagesize * SCRATCH_BUFFER_NPAGES;
if (addr == 0)
gdb_tp_heap_buffer = (char *) xmalloc (5 * 1024 * 1024);
gdb_jump_pad_buffer = alloc_jump_pad_buffer (jump_pad_size);
if (gdb_jump_pad_buffer == NULL)
perror_with_name ("mmap");
gdb_jump_pad_buffer_end = gdb_jump_pad_buffer + pagesize * SCRATCH_BUFFER_NPAGES;
gdb_jump_pad_buffer_end = gdb_jump_pad_buffer + jump_pad_size;
}
gdb_trampoline_buffer = gdb_trampoline_buffer_end = 0;

4
gdb/gdbserver/tracepoint.h
View File

@ -132,6 +132,10 @@ void supply_static_tracepoint_registers (struct regcache *regcache,
CORE_ADDR pc);
void set_trampoline_buffer_space (CORE_ADDR begin, CORE_ADDR end,
char *errmsg);
void *alloc_jump_pad_buffer (size_t size);
#ifndef HAVE_GETAUXVAL
unsigned long getauxval (unsigned long type);
#endif
#else
void stop_tracing (void);