[binutils-gdb] [gdb/testsuite] Add xfail in gdb.python/py-record-btrace.exp

[Tom de Vries <vries@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5bed9dc992a0136d403a7addb29a2ed822fd4fd2

commit 5bed9dc992a0136d403a7addb29a2ed822fd4fd2
Author: Tom de Vries <tdevries@suse.de>
Date:   Tue Feb 14 13:15:49 2023 +0100

    [gdb/testsuite] Add xfail in gdb.python/py-record-btrace.exp
    
    There's a HW bug affecting Processor Trace on some Intel processors
    (Ice Lake to Raptor Lake microarchitectures).
    
    The bug was exposed by linux kernel commit 670638477aed
    ("perf/x86/intel/pt: Opportunistically use single range output mode"),
    added in version v5.5.0, and was worked around by commit ce0d998be927
    ("perf/x86/intel/pt: Fix sampling using single range output") in version
    6.1.0.
    
    The bug manifests (on a Performance-core of an i7-1250U, an Alder Lake cpu) in
    a single test-case:
    ...
    (gdb) python insn = r.instruction_history^M
    warning: Decode error (-20) at instruction 33 (offset = 0x3d6a, \
      pc = 0x400501): compressed return without call.^M
    (gdb) FAIL: gdb.python/py-record-btrace.exp: prepare record: \
      python insn = r.instruction_history
    ...
    
    Add a corresponding XFAIL.
    
    Note that the i7-1250U has both Performance-cores and Efficient-cores, and on
    an Efficient-Core the test-case runs without any problems, so if the testsuite
    run is not pinned to a specific cpu, the test may either PASS or XFAIL.
    
    Tested on x86_64-linux:
    - openSUSE Leap 15.4 with linux kernel version 5.14.21
    - openSUSE Tumbleweed with linux kernel version 6.1.8
    
    PR testsuite/30075
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30075

Diff:
---
 gdb/testsuite/gdb.python/py-record-btrace.exp | 43 ++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/gdb.python/py-record-btrace.exp b/gdb/testsuite/gdb.python/py-record-btrace.exp
index 555b70ae336..c055a882f85 100644
--- a/gdb/testsuite/gdb.python/py-record-btrace.exp
+++ b/gdb/testsuite/gdb.python/py-record-btrace.exp
@@ -54,7 +54,48 @@ with_test_prefix "prepare record" {
     gdb_test "python print(r.method)" "btrace"
     gdb_test "python print(r.format)" "pt|bts"
     gdb_test "stepi 100" ".*"
-    gdb_test_no_output "python insn = r.instruction_history"
+
+    # There's a HW bug affecting Processor Trace on some Intel processors.
+    # The bug was exposed by linux kernel commit 670638477aed
+    # ("perf/x86/intel/pt: Opportunistically use single range output mode"),
+    # added in version v5.5.0, and was worked around by commit ce0d998be927
+    # ("perf/x86/intel/pt: Fix sampling using single range output") in version
+    # 6.1.0.  Detect the kernel version range for which the problem may
+    # manifest.
+    set have_xfail 0
+    set v [linux_kernel_version]
+    if { $v != {} } {
+	set have_xfail \
+	    [expr [version_compare [list 5 5 0] <= $v] \
+		 && [version_compare $v < [list 6 1 0]]]
+    }
+    set nonl_re \[^\r\n\]
+    set xfail_re \
+	[join \
+	     [list \
+		  "warning: Decode error \\($nonl_re*\\) at instruction $decimal" \
+		  "\\(offset = $hex, pc = $hex\\):" \
+		  "$nonl_re*\\."]]
+
+    set got_xfail 0
+    set cmd "python insn = r.instruction_history"
+    gdb_test_multiple $cmd "" {
+	-re "^[string_to_regexp $cmd]\r\n$::gdb_prompt $" {
+	    pass $gdb_test_name
+	}
+	-re -wrap "$xfail_re" {
+	    if { $have_xfail } {
+		xfail $gdb_test_name
+		set got_xfail 1
+	    } else {
+		fail $gdb_test_name
+	    }
+	}
+    }
+    if { $got_xfail } {
+	return
+    }
+
     gdb_test_no_output "python call = r.function_call_history"
     gdb_test_no_output "python i = insn\[0\]"
     gdb_test_no_output "python c = call\[0\]"