| Message ID | 20230804233748.218935-3-iii@linux.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | target/s390x: Fix the "ignored match" case in VSTRS | expand |
On 05.08.23 01:03, Ilya Leoshkevich wrote: > Currently the emulation of VSTRS recognizes partial matches in presence > of \0 in the haystack, which, according to PoP, is not correct: > > If the ZS flag is one and a zero byte was detected > in the second operand, then there can not be a > partial match ... > > Add a check for this. While at it, fold a number of explicitly handled > special cases into the generic logic. Can we split that off? Or doesn't it make sense to split it off after fixing the issue?
On 8/5/23 01:03, Ilya Leoshkevich wrote: > Currently the emulation of VSTRS recognizes partial matches in presence > of \0 in the haystack, which, according to PoP, is not correct: > > If the ZS flag is one and a zero byte was detected > in the second operand, then there can not be a > partial match ... > > Add a check for this. While at it, fold a number of explicitly handled > special cases into the generic logic. > > Cc: qemu-stable@nongnu.org > Reported-by: Claudio Fontana <cfontana@suse.de> > Closes: https://lists.gnu.org/archive/html/qemu-devel/2023-08/msg00633.html > Fixes: 1d706f314191 ("target/s390x: vxeh2: vector string search") > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> verified that it fixes the problem I encountered, Tested-by: Claudio Fontana <cfontana@suse.de> > --- > target/s390x/tcg/vec_string_helper.c | 54 +++++++++------------------- > 1 file changed, 17 insertions(+), 37 deletions(-) > > diff --git a/target/s390x/tcg/vec_string_helper.c b/target/s390x/tcg/vec_string_helper.c > index 9b85becdfbf..a19f429768f 100644 > --- a/target/s390x/tcg/vec_string_helper.c > +++ b/target/s390x/tcg/vec_string_helper.c > @@ -474,9 +474,9 @@ DEF_VSTRC_CC_RT_HELPER(32) > static int vstrs(S390Vector *v1, const S390Vector *v2, const S390Vector *v3, > const S390Vector *v4, uint8_t es, bool zs) > { > - int substr_elen, substr_0, str_elen, i, j, k, cc; > + int substr_elen, i, j, k, cc; > int nelem = 16 >> es; > - bool eos = false; > + int str_leftmost_0; > > substr_elen = s390_vec_read_element8(v4, 7) >> es; > > @@ -498,47 +498,20 @@ static int vstrs(S390Vector *v1, const S390Vector *v2, const S390Vector *v3, > } > > /* If ZS, look for eos in the searched string. */ > + str_leftmost_0 = nelem; > if (zs) { > for (k = 0; k < nelem; k++) { > if (s390_vec_read_element(v2, k, es) == 0) { > - eos = true; > + str_leftmost_0 = k; > break; > } > } > - str_elen = k; > - } else { > - str_elen = nelem; > } > > - substr_0 = s390_vec_read_element(v3, 0, es); > - > - for (k = 0; ; k++) { > - for (; k < str_elen; k++) { > - if (s390_vec_read_element(v2, k, es) == substr_0) { > - break; > - } > - } > - > - /* If we reached the end of the string, no match. */ > - if (k == str_elen) { > - cc = eos; /* no match (with or without zero char) */ > - goto done; > - } > - > - /* If the substring is only one char, match. */ > - if (substr_elen == 1) { > - cc = 2; /* full match */ > - goto done; > - } > - > - /* If the match begins at the last char, we have a partial match. */ > - if (k == str_elen - 1) { > - cc = 3; /* partial match */ > - goto done; > - } > - > + cc = str_leftmost_0 == nelem ? 0 : 1; /* No match. */ > + for (k = 0; k < nelem; k++) { > i = MIN(nelem, k + substr_elen); > - for (j = k + 1; j < i; j++) { > + for (j = k; j < i; j++) { > uint32_t e2 = s390_vec_read_element(v2, j, es); > uint32_t e3 = s390_vec_read_element(v3, j - k, es); > if (e2 != e3) { > @@ -546,9 +519,16 @@ static int vstrs(S390Vector *v1, const S390Vector *v2, const S390Vector *v3, > } > } > if (j == i) { > - /* Matched up until "end". */ > - cc = i - k == substr_elen ? 2 : 3; /* full or partial match */ > - goto done; > + /* All elements matched. */ > + if (k > str_leftmost_0) { > + cc = 1; /* Ignored match. */ > + k = nelem; > + } else if (i - k == substr_elen) { > + cc = 2; /* Full match. */ > + } else { > + cc = 3; /* Partial match. */ > + } > + break; > } > } >
On Sat, 2023-08-05 at 10:02 +0200, David Hildenbrand wrote: > On 05.08.23 01:03, Ilya Leoshkevich wrote: > > Currently the emulation of VSTRS recognizes partial matches in > > presence > > of \0 in the haystack, which, according to PoP, is not correct: > > > > If the ZS flag is one and a zero byte was detected > > in the second operand, then there can not be a > > partial match ... > > > > Add a check for this. While at it, fold a number of explicitly > > handled > > special cases into the generic logic. > > Can we split that off? Or doesn't it make sense to split it off after > fixing the issue? I could do this if this is important, e.g., for stable, but I came to the conclusion that I needed to get rid of the special cases after I had to add the new check to more than one place.
On 07.08.23 10:10, Ilya Leoshkevich wrote: > On Sat, 2023-08-05 at 10:02 +0200, David Hildenbrand wrote: >> On 05.08.23 01:03, Ilya Leoshkevich wrote: >>> Currently the emulation of VSTRS recognizes partial matches in >>> presence >>> of \0 in the haystack, which, according to PoP, is not correct: >>> >>> If the ZS flag is one and a zero byte was detected >>> in the second operand, then there can not be a >>> partial match ... >>> >>> Add a check for this. While at it, fold a number of explicitly >>> handled >>> special cases into the generic logic. >> >> Can we split that off? Or doesn't it make sense to split it off after >> fixing the issue? > > I could do this if this is important, e.g., for stable, but I came to > the conclusion that I needed to get rid of the special cases after I > had to add the new check to more than one place. Okay, so let's keep it as is. Fortunately you heavily test that code! :) Acked-by: David Hildenbrand <david@redhat.com>
diff --git a/target/s390x/tcg/vec_string_helper.c b/target/s390x/tcg/vec_string_helper.c index 9b85becdfbf..a19f429768f 100644 --- a/target/s390x/tcg/vec_string_helper.c +++ b/target/s390x/tcg/vec_string_helper.c @@ -474,9 +474,9 @@ DEF_VSTRC_CC_RT_HELPER(32) static int vstrs(S390Vector *v1, const S390Vector *v2, const S390Vector *v3, const S390Vector *v4, uint8_t es, bool zs) { - int substr_elen, substr_0, str_elen, i, j, k, cc; + int substr_elen, i, j, k, cc; int nelem = 16 >> es; - bool eos = false; + int str_leftmost_0; substr_elen = s390_vec_read_element8(v4, 7) >> es; @@ -498,47 +498,20 @@ static int vstrs(S390Vector *v1, const S390Vector *v2, const S390Vector *v3, } /* If ZS, look for eos in the searched string. */ + str_leftmost_0 = nelem; if (zs) { for (k = 0; k < nelem; k++) { if (s390_vec_read_element(v2, k, es) == 0) { - eos = true; + str_leftmost_0 = k; break; } } - str_elen = k; - } else { - str_elen = nelem; } - substr_0 = s390_vec_read_element(v3, 0, es); - - for (k = 0; ; k++) { - for (; k < str_elen; k++) { - if (s390_vec_read_element(v2, k, es) == substr_0) { - break; - } - } - - /* If we reached the end of the string, no match. */ - if (k == str_elen) { - cc = eos; /* no match (with or without zero char) */ - goto done; - } - - /* If the substring is only one char, match. */ - if (substr_elen == 1) { - cc = 2; /* full match */ - goto done; - } - - /* If the match begins at the last char, we have a partial match. */ - if (k == str_elen - 1) { - cc = 3; /* partial match */ - goto done; - } - + cc = str_leftmost_0 == nelem ? 0 : 1; /* No match. */ + for (k = 0; k < nelem; k++) { i = MIN(nelem, k + substr_elen); - for (j = k + 1; j < i; j++) { + for (j = k; j < i; j++) { uint32_t e2 = s390_vec_read_element(v2, j, es); uint32_t e3 = s390_vec_read_element(v3, j - k, es); if (e2 != e3) { @@ -546,9 +519,16 @@ static int vstrs(S390Vector *v1, const S390Vector *v2, const S390Vector *v3, } } if (j == i) { - /* Matched up until "end". */ - cc = i - k == substr_elen ? 2 : 3; /* full or partial match */ - goto done; + /* All elements matched. */ + if (k > str_leftmost_0) { + cc = 1; /* Ignored match. */ + k = nelem; + } else if (i - k == substr_elen) { + cc = 2; /* Full match. */ + } else { + cc = 3; /* Partial match. */ + } + break; } }
Currently the emulation of VSTRS recognizes partial matches in presence of \0 in the haystack, which, according to PoP, is not correct: If the ZS flag is one and a zero byte was detected in the second operand, then there can not be a partial match ... Add a check for this. While at it, fold a number of explicitly handled special cases into the generic logic. Cc: qemu-stable@nongnu.org Reported-by: Claudio Fontana <cfontana@suse.de> Closes: https://lists.gnu.org/archive/html/qemu-devel/2023-08/msg00633.html Fixes: 1d706f314191 ("target/s390x: vxeh2: vector string search") Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> --- target/s390x/tcg/vec_string_helper.c | 54 +++++++++------------------- 1 file changed, 17 insertions(+), 37 deletions(-)