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Message-ID: <20250824022637.GK1827@brightrain.aerifal.cx>
Date: Sat, 23 Aug 2025 22:26:38 -0400
From: Rich Felker <dalias@...c.org>
To: tombo <hulata@...art.tech>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH v3] vdso: add support for GNU hash tables
On Sat, Aug 23, 2025 at 12:54:04AM +0200, tombo wrote:
> Hi Rich, thanks for the review. Hopefully this version addresses all the points.
>
> ---
> src/internal/vdso.c | 28 ++++++++++++++++++++++++++--
> 1 file changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/src/internal/vdso.c b/src/internal/vdso.c
> index d46d3228..2b6e1ae2 100644
> --- a/src/internal/vdso.c
> +++ b/src/internal/vdso.c
> @@ -40,6 +40,24 @@ static int checkver(Verdef *def, int vsym, const char *vername, char *strings)
> #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
> #define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK | 1<<STB_GNU_UNIQUE)
>
> +static size_t count_syms_gnu(uint32_t *gh)
> +{
> + size_t nsym, i;
> + uint32_t *buckets = gh + 4 + (gh[2]*sizeof(size_t)/4);
> + uint32_t *hashval;
> + for (i = nsym = 0; i < gh[0]; i++) {
> + if (buckets[i] > nsym)
> + nsym = buckets[i];
> + }
> + if (nsym) {
> + hashval = buckets + gh[0] + (nsym - gh[1]);
> + do nsym++;
> + while (!(*hashval++ & 1));
> + }
> + return nsym;
> +}
> +
> +
> void *__vdsosym(const char *vername, const char *name)
> {
> size_t i;
> @@ -60,6 +78,7 @@ void *__vdsosym(const char *vername, const char *name)
> char *strings = 0;
> Sym *syms = 0;
> Elf_Symndx *hashtab = 0;
> + uint32_t *ghashtab = 0;
> uint16_t *versym = 0;
> Verdef *verdef = 0;
>
> @@ -69,15 +88,20 @@ void *__vdsosym(const char *vername, const char *name)
> case DT_STRTAB: strings = p; break;
> case DT_SYMTAB: syms = p; break;
> case DT_HASH: hashtab = p; break;
> + case DT_GNU_HASH: ghashtab = p; break;
> case DT_VERSYM: versym = p; break;
> case DT_VERDEF: verdef = p; break;
> }
> }
>
> - if (!strings || !syms || !hashtab) return 0;
> + if (!strings || !syms) return 0;
> if (!verdef) versym = 0;
> + size_t nsym = 0;
> +
> + if (hashtab) nsym = hashtab[1];
> + else if (ghashtab) nsym = count_syms_gnu(ghashtab);
>
> - for (i=0; i<hashtab[1]; i++) {
> + for (i=0; i<nsym; i++) {
> if (!(1<<(syms[i].st_info&0xf) & OK_TYPES)) continue;
> if (!(1<<(syms[i].st_info>>4) & OK_BINDS)) continue;
> if (!syms[i].st_shndx) continue;
> --
> 2.46.0
Thanks! I don't see anything obviously wrong with this. I'll take a
more detailed look over it soon. Are you hoping to get it included in
this release cycle?
Rich
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