From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.3 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 27597 invoked from network); 11 Aug 2020 18:11:45 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 11 Aug 2020 18:11:45 -0000 Received: (qmail 15790 invoked by uid 550); 11 Aug 2020 18:11:29 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 15527 invoked from network); 11 Aug 2020 18:11:28 -0000 From: Alexander Monakov To: musl@lists.openwall.com Date: Tue, 11 Aug 2020 21:11:14 +0300 Message-Id: <20200811181116.8433-1-amonakov@ispras.ru> X-Mailer: git-send-email 2.11.0 Subject: [musl] [PATCH 1/3] setjmp: fix x86-64 longjmp argument adjustment longjmp 'val' argument is an int, but the assembly is referencing 64-bit registers as if the argument was a long, or the caller was responsible for extending the argument. Though the psABI is not clear on this, the interpretation in GCC is that high bits may be arbitrary and the callee is responsible for sign/zero-extending the value as needed (likewise for return values: callers must anticipate that high bits may be garbage). Therefore testing %rax is a functional bug: setjmp would wrongly return zero if longjmp was called with val==0, but high bits of %rsi happened to be non-zero. Rewrite the prologue to refer to 32-bit registers. In passing, change 'test' to use %rsi, as there's no advantage to using %rax and the new form is cheaper on processors that do not perform move elimination. --- src/setjmp/x32/longjmp.s | 6 +++--- src/setjmp/x86_64/longjmp.s | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/src/setjmp/x32/longjmp.s b/src/setjmp/x32/longjmp.s index e175a4b9..e709acad 100644 --- a/src/setjmp/x32/longjmp.s +++ b/src/setjmp/x32/longjmp.s @@ -5,10 +5,10 @@ .type longjmp,@function _longjmp: longjmp: - mov %rsi,%rax /* val will be longjmp return */ - test %rax,%rax + mov %esi,%eax /* val will be longjmp return */ + test %esi,%esi jnz 1f - inc %rax /* if val==0, val=1 per longjmp semantics */ + inc %eax /* if val==0, val=1 per longjmp semantics */ 1: mov (%rdi),%rbx /* rdi is the jmp_buf, restore regs from it */ mov 8(%rdi),%rbp diff --git a/src/setjmp/x86_64/longjmp.s b/src/setjmp/x86_64/longjmp.s index e175a4b9..e709acad 100644 --- a/src/setjmp/x86_64/longjmp.s +++ b/src/setjmp/x86_64/longjmp.s @@ -5,10 +5,10 @@ .type longjmp,@function _longjmp: longjmp: - mov %rsi,%rax /* val will be longjmp return */ - test %rax,%rax + mov %esi,%eax /* val will be longjmp return */ + test %esi,%esi jnz 1f - inc %rax /* if val==0, val=1 per longjmp semantics */ + inc %eax /* if val==0, val=1 per longjmp semantics */ 1: mov (%rdi),%rbx /* rdi is the jmp_buf, restore regs from it */ mov 8(%rdi),%rbp -- 2.11.0