btrace: support 32-bit inferior on 64-bit host
The heuristic for filtering out kernel addressess in BTS trace checks the most significant bit in each address. This works fine for 32-bit and 64-bit mode. For 32-bit compatibility mode, i.e. a 32-bit inferior running on 64-bit host, we need to check bit 63 (or any bit bigger than 31), not bit 31. Use the machine field in struct utsname provided by a uname call to determine whether we are running on a 64-bit host. Thanks to Jan Kratochvil for reporting the issue. gdb/ * nat/linux-btrace.c: Include sys/utsname.h. (linux_determine_kernel_ptr_bits): New. (linux_enable_bts): Call linux_determine_kernel_ptr_bits. * x86-linux-nat.c (x86_linux_enable_btrace): Do not overwrite non-zero ptr_bits. gdbserver/ * linux-low.c (linux_low_enable_btrace): Do not overwrite non-zero ptr_bits.
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@ -1,3 +1,11 @@
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2015-03-03 Markus Metzger <markus.t.metzger@intel.com>
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* nat/linux-btrace.c: Include sys/utsname.h.
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(linux_determine_kernel_ptr_bits): New.
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(linux_enable_bts): Call linux_determine_kernel_ptr_bits.
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* x86-linux-nat.c (x86_linux_enable_btrace): Do not overwrite non-zero
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ptr_bits.
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2015-03-03 Markus Metzger <markus.t.metzger@intel.com>
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* btrace.c (ftrace_update_function): Treat return as tailcall for
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@ -1,3 +1,8 @@
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2015-03-03 Markus Metzger <markus.t.metzger@intel.com>
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* linux-low.c (linux_low_enable_btrace): Do not overwrite non-zero
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ptr_bits.
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2015-03-02 Andreas Arnez <arnez@linux.vnet.ibm.com>
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* Makefile.in (s390-vx-linux64.c, s390-tevx-linux64.c)
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@ -5956,7 +5956,7 @@ linux_low_enable_btrace (ptid_t ptid, const struct btrace_config *conf)
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tinfo = linux_enable_btrace (ptid, conf);
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if (tinfo != NULL)
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if (tinfo != NULL && tinfo->ptr_bits == 0)
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{
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struct thread_info *thread = find_thread_ptid (ptid);
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struct regcache *regcache = get_thread_regcache (thread, 0);
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@ -38,6 +38,7 @@
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#include <sys/ptrace.h>
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#include <sys/types.h>
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#include <signal.h>
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#include <sys/utsname.h>
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/* A branch trace record in perf_event. */
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struct perf_event_bts
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@ -102,6 +103,31 @@ perf_event_new_data (const struct perf_event_buffer *pev)
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return *pev->data_head != pev->last_head;
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}
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/* Try to determine the size of a pointer in bits for the OS.
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This is the same as the size of a pointer for the inferior process
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except when a 32-bit inferior is running on a 64-bit OS. */
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static int
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linux_determine_kernel_ptr_bits (void)
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{
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struct utsname utsn;
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int errcode;
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memset (&utsn, 0, sizeof (utsn));
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errcode = uname (&utsn);
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if (errcode < 0)
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return 0;
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/* We only need to handle the 64-bit host case, here. For 32-bit host,
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the pointer size can be filled in later based on the inferior. */
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if (strcmp (utsn.machine, "x86_64") == 0)
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return 64;
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return 0;
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}
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/* Check whether an address is in the kernel. */
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static inline int
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@ -434,7 +460,7 @@ linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
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tinfo = xzalloc (sizeof (*tinfo));
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tinfo->ptid = ptid;
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tinfo->ptr_bits = 0;
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tinfo->ptr_bits = linux_determine_kernel_ptr_bits ();
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tinfo->conf.format = BTRACE_FORMAT_BTS;
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bts = &tinfo->variant.bts;
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@ -450,9 +450,11 @@ x86_linux_enable_btrace (struct target_ops *self, ptid_t ptid,
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target_pid_to_str (ptid), safe_strerror (errno));
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/* Fill in the size of a pointer in bits. */
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gdbarch = target_thread_architecture (ptid);
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tinfo->ptr_bits = gdbarch_ptr_bit (gdbarch);
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if (tinfo->ptr_bits == 0)
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{
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gdbarch = target_thread_architecture (ptid);
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tinfo->ptr_bits = gdbarch_ptr_bit (gdbarch);
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}
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return tinfo;
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}
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