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Yao Qi
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Initialize target description early in IPA
Target descriptions are allocated lazily, that is fine in GDBserver, but it is not safe to call malloc in gdb_collect in IPA, because we can set a fast tracepoint in malloc, and when the tracepoint is hit, gdb_collect/malloc is called, deadlock or memory corruption may be triggered. #0 0xf7cfc200 in malloc () #1 0xf7efdc07 in operator new(unsigned int) () #2 0xf7ef7636 in allocate_target_description() () #3 0xf7efcbe1 in i386_create_target_description(unsigned long long, bool) () #4 0xf7efb474 in i386_linux_read_description(unsigned long long) () #5 0xf7efb190 in get_ipa_tdesc(int) () #6 0xf7ef9baa in gdb_collect () The fix is to initialize all target descriptions earlier, when the IPA is loaded. In order to guarantee malloc is not called in IPA in gdb_collect, I change the test to set a breakpoint on malloc, if IPA gdb_collect calls malloc, program will hit the breakpoint, and test fail. continue Continuing. Thread 1 "" hit Breakpoint 5, 0xf7cfc200 in malloc () (gdb) FAIL: gdb.trace/ftrace.exp: advance through tracing gdb/gdbserver: 2017-12-07 Yao Qi <yao.qi@linaro.org> * linux-aarch64-ipa.c (initialize_low_tracepoint): Call aarch64_linux_read_description. * linux-amd64-ipa.c (idx2mask): New array. (get_ipa_tdesc): Move idx2mask out. (initialize_low_tracepoint): Initialize target descriptions. * linux-i386-ipa.c (idx2mask): New array. (get_ipa_tdesc): Move idx2mask out. (initialize_low_tracepoint): Initialize target descriptions. gdb/testsuite: 2017-12-07 Yao Qi <yao.qi@linaro.org> * gdb.trace/ftrace.exp (run_trace_experiment): Set breakpoint on malloc and catch syscall.
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‎gdb/gdbserver/ChangeLog‎

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,14 @@
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2017-12-07 Yao Qi <yao.qi@linaro.org>
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* linux-aarch64-ipa.c (initialize_low_tracepoint): Call
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aarch64_linux_read_description.
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* linux-amd64-ipa.c (idx2mask): New array.
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(get_ipa_tdesc): Move idx2mask out.
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(initialize_low_tracepoint): Initialize target descriptions.
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* linux-i386-ipa.c (idx2mask): New array.
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(get_ipa_tdesc): Move idx2mask out.
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(initialize_low_tracepoint): Initialize target descriptions.
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2017-12-05 Simon Marchi <simon.marchi@polymtl.ca>
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* tdesc.c (struct tdesc_type): Change return type.

‎gdb/gdbserver/linux-aarch64-ipa.c‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -204,4 +204,5 @@ alloc_jump_pad_buffer (size_t size)
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void
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initialize_low_tracepoint (void)
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{
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aarch64_linux_read_description ();
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}

‎gdb/gdbserver/linux-amd64-ipa.c‎

Lines changed: 21 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -169,6 +169,19 @@ supply_static_tracepoint_registers (struct regcache *regcache,
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170170
#endif /* HAVE_UST */
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#if !defined __ILP32__
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/* Map the tdesc index to xcr0 mask. */
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static uint64_t idx2mask[X86_TDESC_LAST] = {
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X86_XSTATE_X87_MASK,
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X86_XSTATE_SSE_MASK,
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X86_XSTATE_AVX_MASK,
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X86_XSTATE_MPX_MASK,
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X86_XSTATE_AVX_MPX_MASK,
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X86_XSTATE_AVX_AVX512_MASK,
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X86_XSTATE_AVX_MPX_AVX512_PKU_MASK,
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};
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#endif
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/* Return target_desc to use for IPA, given the tdesc index passed by
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gdbserver. */
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@@ -194,17 +207,6 @@ get_ipa_tdesc (int idx)
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break;
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}
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#else
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/* Map the tdesc index to xcr0 mask. */
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uint64_t idx2mask[X86_TDESC_LAST] = {
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X86_XSTATE_X87_MASK,
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X86_XSTATE_SSE_MASK,
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X86_XSTATE_AVX_MASK,
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X86_XSTATE_MPX_MASK,
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X86_XSTATE_AVX_MPX_MASK,
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X86_XSTATE_AVX_AVX512_MASK,
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X86_XSTATE_AVX_MPX_AVX512_PKU_MASK,
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};
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return amd64_linux_read_description (idx2mask[idx], false);
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#endif
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@@ -276,4 +278,12 @@ alloc_jump_pad_buffer (size_t size)
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void
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initialize_low_tracepoint (void)
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{
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#if defined __ILP32__
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amd64_linux_read_description (X86_XSTATE_SSE_MASK, true);
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amd64_linux_read_description (X86_XSTATE_AVX_MASK, true);
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amd64_linux_read_description (X86_XSTATE_AVX_AVX512_MASK, true);
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#else
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for (auto i = 0; i < X86_TDESC_LAST; i++)
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amd64_linux_read_description (idx2mask[i], false);
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#endif
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}

‎gdb/gdbserver/linux-i386-ipa.c‎

Lines changed: 13 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -245,6 +245,17 @@ initialize_fast_tracepoint_trampoline_buffer (void)
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}
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}
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/* Map the tdesc index to xcr0 mask. */
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static uint64_t idx2mask[X86_TDESC_LAST] = {
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X86_XSTATE_X87_MASK,
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X86_XSTATE_SSE_MASK,
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X86_XSTATE_AVX_MASK,
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X86_XSTATE_MPX_MASK,
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X86_XSTATE_AVX_MPX_MASK,
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X86_XSTATE_AVX_AVX512_MASK,
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X86_XSTATE_AVX_MPX_AVX512_PKU_MASK,
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};
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/* Return target_desc to use for IPA, given the tdesc index passed by
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gdbserver. */
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@@ -256,18 +267,6 @@ get_ipa_tdesc (int idx)
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internal_error (__FILE__, __LINE__,
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"unknown ipa tdesc index: %d", idx);
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}
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/* Map the tdesc index to xcr0 mask. */
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uint64_t idx2mask[X86_TDESC_LAST] = {
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X86_XSTATE_X87_MASK,
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X86_XSTATE_SSE_MASK,
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X86_XSTATE_AVX_MASK,
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X86_XSTATE_MPX_MASK,
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X86_XSTATE_AVX_MPX_MASK,
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X86_XSTATE_AVX_AVX512_MASK,
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X86_XSTATE_AVX_MPX_AVX512_PKU_MASK,
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};
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return i386_linux_read_description (idx2mask[idx]);
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}
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@@ -290,4 +289,6 @@ void
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initialize_low_tracepoint (void)
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{
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initialize_fast_tracepoint_trampoline_buffer ();
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for (auto i = 0; i < X86_TDESC_LAST; i++)
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i386_linux_read_description (idx2mask[i]);
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}

‎gdb/testsuite/ChangeLog‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,8 @@
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2017-12-07 Yao Qi <yao.qi@linaro.org>
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* gdb.trace/ftrace.exp (run_trace_experiment): Set breakpoint on
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malloc and catch syscall.
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2017-12-07 Phil Muldoon <pmuldoon@redhat.com>
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* gdb.python/py-breakpoint.exp (test_bkpt_explicit_loc): Add new

‎gdb/testsuite/gdb.trace/ftrace.exp‎

Lines changed: 30 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -63,9 +63,36 @@ proc run_trace_experiment {} {
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gdb_test_no_output "tstart" "start trace experiment"
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gdb_test "continue" \
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".*Breakpoint \[0-9\]+, end .*" \
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"advance through tracing"
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# Fast tracepoint can be set in signal handler, so gdb_collect in
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# IPA shouldn't call any non-async-signal-safe functions. It is
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# impractical to list all non-async-signal-safe functions, and set
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# breakpoints on them, so choose malloc only in this test.
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gdb_test "b -q malloc"
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# Performance-wise, gdb_collect in IPA shouldn't call any syscall
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# in order to keep fast tracepoint fast enough.
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global gdb_prompt
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set test "catch syscall"
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gdb_test_multiple $test $test {
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-re "The feature \'catch syscall\' is not supported.*\r\n$gdb_prompt $" {
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}
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-re ".*$gdb_prompt $" {
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pass $test
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}
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}
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global decimal
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set test "advance through tracing"
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gdb_test_multiple "continue" $test {
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-re "Thread 2 .* hit Catchpoint $decimal \\(call to syscall .*\\).*\r\n$gdb_prompt $" {
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# IPA starts a helper thread, which calls accept. Ignore it.
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send_gdb "continue\n"
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exp_continue
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}
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-re "Breakpoint $decimal, end .*$gdb_prompt $" {
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pass $test
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}
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}
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gdb_test "tstatus" ".*Trace .*" "check on trace status"
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