From 770207ffdd3db77bdae7f1640be0d3d0de0f0a64 Mon Sep 17 00:00:00 2001
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From: Joseph Myers <joseph@codesourcery.com>
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Date: Fri, 30 Oct 2020 21:38:31 +0000
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Subject: [PATCH 05/19] Disable spurious -Wstringop-overflow for setjmp/longjmp
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(bug 26647)
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Building glibc with GCC 11 fails with (among other warnings) spurious
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-Wstringop-overflow warnings from calls to setjmp and longjmp with a
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pointer to a pthread_unwind_buf that is smaller than jmp_buf. As
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discussed in bug 26647, the warning in libc-start.c is a false
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positive, because setjmp and longjmp do not access anything (the
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signal mask) beyond the common prefix of the two structures, so this
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patch disables the warning for that call to setjmp, as well as for two
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calls in NPTL code that produce the same warning and look like false
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positives for the same reason.
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Tested with build-many-glibcs.py for arm-linux-gnueabi, where this
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allows the build to get further.
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Reviewed-by: DJ Delorie <dj@redhat.com>
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(cherry picked from commit 2098d4034d398cbde6ccd4a2aaac52c518374698)
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Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
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---
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csu/libc-start.c | 10 ++++++++++
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nptl/pthread_create.c | 10 ++++++++++
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nptl/unwind.c | 10 ++++++++++
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3 files changed, 30 insertions(+)
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diff --git a/csu/libc-start.c b/csu/libc-start.c
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index 5d9c3675..9450fb80 100644
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--- a/csu/libc-start.c
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+++ b/csu/libc-start.c
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@@ -21,6 +21,7 @@
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#include <unistd.h>
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#include <ldsodefs.h>
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#include <exit-thread.h>
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+#include <libc-diag.h>
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#include <libc-internal.h>
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#include <elf/dl-tunables.h>
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@@ -292,7 +293,16 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
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struct pthread_unwind_buf unwind_buf;
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int not_first_call;
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+ DIAG_PUSH_NEEDS_COMMENT;
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+#if __GNUC_PREREQ (7, 0)
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+ /* This call results in a -Wstringop-overflow warning because struct
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+ pthread_unwind_buf is smaller than jmp_buf. setjmp and longjmp
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+ do not use anything beyond the common prefix (they never access
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+ the saved signal mask), so that is a false positive. */
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+ DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overflow=");
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+#endif
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not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
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+ DIAG_POP_NEEDS_COMMENT;
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if (__glibc_likely (! not_first_call))
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{
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struct pthread *self = THREAD_SELF;
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diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
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index 2bd2b107..574d5787 100644
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--- a/nptl/pthread_create.c
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+++ b/nptl/pthread_create.c
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@@ -26,6 +26,7 @@
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#include <hp-timing.h>
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#include <ldsodefs.h>
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#include <atomic.h>
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+#include <libc-diag.h>
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#include <libc-internal.h>
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#include <resolv.h>
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#include <kernel-features.h>
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@@ -429,7 +430,16 @@ START_THREAD_DEFN
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struct pthread_unwind_buf unwind_buf;
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int not_first_call;
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+ DIAG_PUSH_NEEDS_COMMENT;
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+#if __GNUC_PREREQ (7, 0)
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+ /* This call results in a -Wstringop-overflow warning because struct
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+ pthread_unwind_buf is smaller than jmp_buf. setjmp and longjmp
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+ do not use anything beyond the common prefix (they never access
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+ the saved signal mask), so that is a false positive. */
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+ DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overflow=");
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+#endif
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not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
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+ DIAG_POP_NEEDS_COMMENT;
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/* No previous handlers. NB: This must be done after setjmp since the
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private space in the unwind jump buffer may overlap space used by
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diff --git a/nptl/unwind.c b/nptl/unwind.c
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index 911fa99b..24bafa2c 100644
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--- a/nptl/unwind.c
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+++ b/nptl/unwind.c
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@@ -23,6 +23,7 @@
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#include <string.h>
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#include <unistd.h>
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#include "pthreadP.h"
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+#include <libc-diag.h>
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#include <jmpbuf-unwind.h>
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#ifdef _STACK_GROWS_DOWN
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@@ -90,8 +91,17 @@ unwind_stop (int version, _Unwind_Action actions,
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}
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}
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+ DIAG_PUSH_NEEDS_COMMENT;
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+#if __GNUC_PREREQ (7, 0)
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+ /* This call results in a -Wstringop-overflow warning because struct
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+ pthread_unwind_buf is smaller than jmp_buf. setjmp and longjmp
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+ do not use anything beyond the common prefix (they never access
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+ the saved signal mask), so that is a false positive. */
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+ DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overflow=");
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+#endif
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if (do_longjump)
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__libc_unwind_longjmp ((struct __jmp_buf_tag *) buf->cancel_jmp_buf, 1);
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+ DIAG_POP_NEEDS_COMMENT;
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return _URC_NO_REASON;
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}
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--
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2.20.1
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