https://bugs.kde.org/show_bug.cgi?id=495112
Bug ID: 495112
Summary: s390x: GCC miscompiles coredump-elf.c
Classification: Developer tools
Product: valgrind
Version: unspecified
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: jsew...@acm.org
Reporter: flo2...@eich-krohm.de
Target Milestone: ---
Created attachment 175067
--> https://bugs.kde.org/attachment.cgi?id=175067&action=edit
Reproducer
The symptom is this compiler warning:
In function ‘fill_prstatus’,
inlined from ‘dump_one_thread’ at m_coredump/coredump-elf.c:804:7:
m_coredump/coredump-elf.c:451:32: warning: array subscript ‘struct
vki_user_regs_struct[0]
’ is partly outside array bounds of ‘struct vki_elf_prstatus[1]’
[-Warray-bounds=]
451 | # define DO(n) regs->gprs[n] = arch->vex.guest_r##n
| ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
m_coredump/coredump-elf.c:452:4: note: in expansion of macro ‘DO’
452 | DO(0); DO(1); DO(2); DO(3); DO(4); DO(5); DO(6); DO(7);
| ^~
m_coredump/coredump-elf.c: In function ‘dump_one_thread’:
m_coredump/coredump-elf.c:774:28: note: at offset 112 into object ‘prstatus’ of
size 336
774 | struct vki_elf_prstatus prstatus;
| ^~~~~~~~
....
and many more for every invocation of the DO macro.
The warning is incorrect because it is not struct vki_user_regs_struct that
is being indexed but vki_user_regs_struct::gprs. I condensed a small
reproducer.
Taking a closer look it turns out that the reproducer gets miscompiled.
In the .s file there should be a reference to the global variable "vexstuff"
but
it is missing. I guess it's reasonable to conclude that coredump-elf.c will get
miscompiled as well.
This occurs both with gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0 as well
as stock 14.2.0 (latest released version). One of the folks at IBM maintaining
the
s390x backend for GCC confirmed that this is a known bug.
The fix is to reduce the optimisation level with a function attribute like so:
diff --git a/coregrind/m_coredump/coredump-elf.c
b/coregrind/m_coredump/coredump-elf.c
index a4632d9e2..22c6d4946 100644
--- a/coregrind/m_coredump/coredump-elf.c
+++ b/coregrind/m_coredump/coredump-elf.c
@@ -241,6 +241,9 @@ static void fill_prpsinfo(const ThreadState *tst,
}
#endif
+#if __GNUC__*10000 + __GNUC_MINOR__*100 + __GNUC__PATCHLEVEL__ <= 140200
+__attribute__((optimize(1)))
+#endif
static void fill_prstatus(const ThreadState *tst,
/*OUT*/struct vki_elf_prstatus *prs,
const vki_siginfo_t *si)
--
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