When adding new featureset words, it is convenient to split the work into
several patches. However, GCC 12 spotted that the way we prefer to split the
work results in a real (transient) breakage whereby the policy <-> featureset
helpers perform out-of-bounds accesses on the featureset array.
Fix this by having gen-cpuid.py calculate FEATURESET_NR_ENTRIES from the
comments describing the word blocks, rather than from the XEN_CPUFEATURE()
with the greatest value.
For simplicty, require that the word blocks appear in order. This can be
revisted if we find a good reason to have blocks out of order.
No functional change.
Reported-by: Jan Beulich <jbeul...@suse.com>
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
CC: Roger Pau Monné <roger....@citrix.com>
CC: Wei Liu <w...@xen.org>
This supercedes the entire "x86: Fix transient build breakage with featureset
additions" series, but doesn't really feel as if it ought to be labelled v2
---
xen/tools/gen-cpuid.py | 42 ++++++++++++++++++++++++++++++++++++------
1 file changed, 36 insertions(+), 6 deletions(-)
diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
index 0edb7d4a19f8..e0664e0defe1 100755
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -50,13 +50,37 @@ def parse_definitions(state):
"\s+([\s\d]+\*[\s\d]+\+[\s\d]+)\)"
"\s+/\*([\w!]*) .*$")
+ word_regex = re.compile(
+ r"^/\* .* word (\d*) \*/$")
+ last_word = -1
+
this = sys.modules[__name__]
for l in state.input.readlines():
- # Short circuit the regex...
- if not l.startswith("XEN_CPUFEATURE("):
+
+ # Short circuit the regexes...
+ if not (l.startswith("XEN_CPUFEATURE(") or
+ l.startswith("/* ")):
continue
+ # Handle /* ... word $N */ lines
+ if l.startswith("/* "):
+
+ res = word_regex.match(l)
+ if res is None:
+ continue # Some other comment
+
+ word = int(res.groups()[0])
+
+ if word != last_word + 1:
+ raise Fail("Featureset word %u out of order (last word %u)"
+ % (word, last_word))
+
+ last_word = word
+ state.nr_entries = word + 1
+ continue
+
+ # Handle XEN_CPUFEATURE( lines
res = feat_regex.match(l)
if res is None:
@@ -94,6 +118,15 @@ def parse_definitions(state):
if len(state.names) == 0:
raise Fail("No features found")
+ if state.nr_entries == 0:
+ raise Fail("No featureset word info found")
+
+ max_val = max(state.names.keys())
+ if (max_val >> 5) + 1 > state.nr_entries:
+ max_name = state.names[max_val]
+ raise Fail("Feature %s (%d*32+%d) exceeds FEATURESET_NR_ENTRIES (%d)"
+ % (max_name, max_val >> 5, max_val & 31, state.nr_entries))
+
def featureset_to_uint32s(fs, nr):
""" Represent a featureset as a list of C-compatible uint32_t's """
@@ -122,9 +155,6 @@ def format_uint32s(state, featureset, indent):
def crunch_numbers(state):
- # Size of bitmaps
- state.nr_entries = nr_entries = (max(state.names.keys()) >> 5) + 1
-
# Features common between 1d and e1d.
common_1d = (FPU, VME, DE, PSE, TSC, MSR, PAE, MCE, CX8, APIC,
MTRR, PGE, MCA, CMOV, PAT, PSE36, MMX, FXSR)
@@ -328,7 +358,7 @@ def crunch_numbers(state):
state.nr_deep_deps = len(state.deep_deps.keys())
# Calculate the bitfield name declarations
- for word in range(nr_entries):
+ for word in range(state.nr_entries):
names = []
for bit in range(32):
--
2.30.2
