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* [Bug string/28895] New: Wrong result in strncmp-avx2 and strncmp-evex @ 2022-02-15 13:37 goldstein.w.n at gmail dot com 2022-02-15 13:56 ` [Bug string/28895] " fweimer at redhat dot com ` (6 more replies) 0 siblings, 7 replies; 8+ messages in thread From: goldstein.w.n at gmail dot com @ 2022-02-15 13:37 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=28895 Bug ID: 28895 Summary: Wrong result in strncmp-avx2 and strncmp-evex Product: glibc Version: 2.36 Status: UNCONFIRMED Severity: normal Priority: P2 Component: string Assignee: unassigned at sourceware dot org Reporter: goldstein.w.n at gmail dot com Target Milestone: --- Wrong result for strncmp-avx2 and strncmp-evex when it hits the page cross case followed by the loop page cross case immediately afterwards with a short length. See following test case: ``` #include <assert.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> #include <wchar.h> #define PAGE_SIZE 4096 static void * make_buf(uint64_t sz) { void * p = mmap(NULL, 2 * PAGE_SIZE + sz, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); assert(p != NULL); assert(!mprotect(p + PAGE_SIZE, sz, PROT_READ | PROT_WRITE)); return p + PAGE_SIZE; } int main(int argc, char ** argv) { char * s1 = make_buf(0xd000 + 0x4000); char * s2 = make_buf(0xd000 + 0x4000); s1 += 0xffa; s2 += 0xfed; strcpy(s1, "tst-tlsmod%"); strcpy(s2, "tst-tls-manydynamic73mod"); if (strncmp(s1, s2, 10) != 0) { printf("Error!\n"); } } ``` Issue (for both evex and avx2) ``` .p2align 4,, 10 L(return_page_cross_end_check): tzcntl %ecx, %ecx ``` `ecx` can have garbabe in it from before the start of the string. Fix is to use the `r10` mask to and off these bad matches (strcmp was doing so. It was an oversight not to to do so in strncmp). -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug string/28895] Wrong result in strncmp-avx2 and strncmp-evex 2022-02-15 13:37 [Bug string/28895] New: Wrong result in strncmp-avx2 and strncmp-evex goldstein.w.n at gmail dot com @ 2022-02-15 13:56 ` fweimer at redhat dot com 2022-02-15 15:43 ` hjl.tools at gmail dot com ` (5 subsequent siblings) 6 siblings, 0 replies; 8+ messages in thread From: fweimer at redhat dot com @ 2022-02-15 13:56 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=28895 Florian Weimer <fweimer at redhat dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |fweimer at redhat dot com -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug string/28895] Wrong result in strncmp-avx2 and strncmp-evex 2022-02-15 13:37 [Bug string/28895] New: Wrong result in strncmp-avx2 and strncmp-evex goldstein.w.n at gmail dot com 2022-02-15 13:56 ` [Bug string/28895] " fweimer at redhat dot com @ 2022-02-15 15:43 ` hjl.tools at gmail dot com 2022-02-15 15:43 ` hjl.tools at gmail dot com ` (4 subsequent siblings) 6 siblings, 0 replies; 8+ messages in thread From: hjl.tools at gmail dot com @ 2022-02-15 15:43 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=28895 --- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> --- Created attachment 13979 --> https://sourceware.org/bugzilla/attachment.cgi?id=13979&action=edit A patch to add a testcase -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug string/28895] Wrong result in strncmp-avx2 and strncmp-evex 2022-02-15 13:37 [Bug string/28895] New: Wrong result in strncmp-avx2 and strncmp-evex goldstein.w.n at gmail dot com 2022-02-15 13:56 ` [Bug string/28895] " fweimer at redhat dot com 2022-02-15 15:43 ` hjl.tools at gmail dot com @ 2022-02-15 15:43 ` hjl.tools at gmail dot com 2022-02-15 15:57 ` goldstein.w.n at gmail dot com ` (3 subsequent siblings) 6 siblings, 0 replies; 8+ messages in thread From: hjl.tools at gmail dot com @ 2022-02-15 15:43 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=28895 H.J. Lu <hjl.tools at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |hjl.tools at gmail dot com -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug string/28895] Wrong result in strncmp-avx2 and strncmp-evex 2022-02-15 13:37 [Bug string/28895] New: Wrong result in strncmp-avx2 and strncmp-evex goldstein.w.n at gmail dot com ` (2 preceding siblings ...) 2022-02-15 15:43 ` hjl.tools at gmail dot com @ 2022-02-15 15:57 ` goldstein.w.n at gmail dot com 2022-02-16 10:41 ` goldstein.w.n at gmail dot com ` (2 subsequent siblings) 6 siblings, 0 replies; 8+ messages in thread From: goldstein.w.n at gmail dot com @ 2022-02-15 15:57 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=28895 --- Comment #2 from Noah Goldstein <goldstein.w.n at gmail dot com> --- I have patch with test + fix. Just testing on build-many which takes a bit. -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug string/28895] Wrong result in strncmp-avx2 and strncmp-evex 2022-02-15 13:37 [Bug string/28895] New: Wrong result in strncmp-avx2 and strncmp-evex goldstein.w.n at gmail dot com ` (3 preceding siblings ...) 2022-02-15 15:57 ` goldstein.w.n at gmail dot com @ 2022-02-16 10:41 ` goldstein.w.n at gmail dot com 2022-02-16 12:05 ` fweimer at redhat dot com 2022-02-16 12:24 ` goldstein.w.n at gmail dot com 6 siblings, 0 replies; 8+ messages in thread From: goldstein.w.n at gmail dot com @ 2022-02-16 10:41 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=28895 Noah Goldstein <goldstein.w.n at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |FIXED Status|UNCONFIRMED |RESOLVED --- Comment #3 from Noah Goldstein <goldstein.w.n at gmail dot com> --- Fix has been pushed: https://sourceware.org/git/?p=glibc.git;a=commit;h=e108c02a5e23c8c88ce66d8705d4a24bb6b9a8bf -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug string/28895] Wrong result in strncmp-avx2 and strncmp-evex 2022-02-15 13:37 [Bug string/28895] New: Wrong result in strncmp-avx2 and strncmp-evex goldstein.w.n at gmail dot com ` (4 preceding siblings ...) 2022-02-16 10:41 ` goldstein.w.n at gmail dot com @ 2022-02-16 12:05 ` fweimer at redhat dot com 2022-02-16 12:24 ` goldstein.w.n at gmail dot com 6 siblings, 0 replies; 8+ messages in thread From: fweimer at redhat dot com @ 2022-02-16 12:05 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=28895 --- Comment #4 from Florian Weimer <fweimer at redhat dot com> --- Thanks. Which commit introduced the problem? Do we need to backport this to release branches? -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug string/28895] Wrong result in strncmp-avx2 and strncmp-evex 2022-02-15 13:37 [Bug string/28895] New: Wrong result in strncmp-avx2 and strncmp-evex goldstein.w.n at gmail dot com ` (5 preceding siblings ...) 2022-02-16 12:05 ` fweimer at redhat dot com @ 2022-02-16 12:24 ` goldstein.w.n at gmail dot com 6 siblings, 0 replies; 8+ messages in thread From: goldstein.w.n at gmail dot com @ 2022-02-16 12:24 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=28895 --- Comment #5 from Noah Goldstein <goldstein.w.n at gmail dot com> --- Commits: EVEX: https://sourceware.org/git/?p=glibc.git;a=commit;h=8418eb3ff4b781d31c4ed5dc6c0bd7356bc45db9 AVX2: https://sourceware.org/git/?p=glibc.git;a=commit;h=b77b06e0e296f1a2276c27a67e1d44f2cfa38d45 No need to backport. We waited until after 2.35 release to push. -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-02-16 12:24 UTC | newest] Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-02-15 13:37 [Bug string/28895] New: Wrong result in strncmp-avx2 and strncmp-evex goldstein.w.n at gmail dot com 2022-02-15 13:56 ` [Bug string/28895] " fweimer at redhat dot com 2022-02-15 15:43 ` hjl.tools at gmail dot com 2022-02-15 15:43 ` hjl.tools at gmail dot com 2022-02-15 15:57 ` goldstein.w.n at gmail dot com 2022-02-16 10:41 ` goldstein.w.n at gmail dot com 2022-02-16 12:05 ` fweimer at redhat dot com 2022-02-16 12:24 ` goldstein.w.n at gmail dot com
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