| Message ID | 20250507142110.3452012-5-adhemerval.zanella@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | Add initial support for --enable-ubsan | expand |
* Adhemerval Zanella: > From: Richard Henderson <rth@twiddle.net> > > When building with --enable-ubsan, the relocation code triggers: > > UBSAN: Undefined behaviour in get-dynamic-info.h:56:30 left shift of 1879047925 by 1 cannot be represented in type 'int' > > Originally from > https://sourceware.org/pipermail/libc-alpha/2015-August/063015.html. > --- > elf/elf.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/elf/elf.h b/elf/elf.h > index 1e1a59c14d..d48cf47b9a 100644 > --- a/elf/elf.h > +++ b/elf/elf.h > @@ -995,7 +995,7 @@ typedef struct > range. Be compatible. */ > #define DT_AUXILIARY 0x7ffffffd /* Shared object to load before self */ > #define DT_FILTER 0x7fffffff /* Shared object to get values from */ > -#define DT_EXTRATAGIDX(tag) ((Elf32_Word)-((Elf32_Sword) (tag) <<1>>1)-1) > +#define DT_EXTRATAGIDX(tag) (-((Elf32_Sword)((Elf32_Word)(tag) * 2) / 2 + 1)) > #define DT_EXTRANUM 3 > > /* Values of `d_un.d_val' in the DT_FLAGS entry. */ Doesn't this change the type of the constant? And rely on a GCC extension? Thanks, Florian
On 20/05/25 09:48, Florian Weimer wrote: > * Adhemerval Zanella: > >> From: Richard Henderson <rth@twiddle.net> >> >> When building with --enable-ubsan, the relocation code triggers: >> >> UBSAN: Undefined behaviour in get-dynamic-info.h:56:30 left shift of 1879047925 by 1 cannot be represented in type 'int' >> >> Originally from >> https://sourceware.org/pipermail/libc-alpha/2015-August/063015.html. >> --- >> elf/elf.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/elf/elf.h b/elf/elf.h >> index 1e1a59c14d..d48cf47b9a 100644 >> --- a/elf/elf.h >> +++ b/elf/elf.h >> @@ -995,7 +995,7 @@ typedef struct >> range. Be compatible. */ >> #define DT_AUXILIARY 0x7ffffffd /* Shared object to load before self */ >> #define DT_FILTER 0x7fffffff /* Shared object to get values from */ >> -#define DT_EXTRATAGIDX(tag) ((Elf32_Word)-((Elf32_Sword) (tag) <<1>>1)-1) >> +#define DT_EXTRATAGIDX(tag) (-((Elf32_Sword)((Elf32_Word)(tag) * 2) / 2 + 1)) >> #define DT_EXTRANUM 3 >> >> /* Values of `d_un.d_val' in the DT_FLAGS entry. */ > > Doesn't this change the type of the constant? And rely on a GCC > extension? Indeed, I think an extra cast to Elf32_Word should keep the same type. Wrt to GCC extension, this definition is already gated through _GNU_SOURCE and afaik only used internally on glibc (I couldn't find any other project that actually uses it), so I think it should be fine to rely on it.
* Adhemerval Zanella Netto: > On 20/05/25 09:48, Florian Weimer wrote: >> * Adhemerval Zanella: >> >>> From: Richard Henderson <rth@twiddle.net> >>> >>> When building with --enable-ubsan, the relocation code triggers: >>> >>> UBSAN: Undefined behaviour in get-dynamic-info.h:56:30 left shift of 1879047925 by 1 cannot be represented in type 'int' >>> >>> Originally from >>> https://sourceware.org/pipermail/libc-alpha/2015-August/063015.html. >>> --- >>> elf/elf.h | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/elf/elf.h b/elf/elf.h >>> index 1e1a59c14d..d48cf47b9a 100644 >>> --- a/elf/elf.h >>> +++ b/elf/elf.h >>> @@ -995,7 +995,7 @@ typedef struct >>> range. Be compatible. */ >>> #define DT_AUXILIARY 0x7ffffffd /* Shared object to load before self */ >>> #define DT_FILTER 0x7fffffff /* Shared object to get values from */ >>> -#define DT_EXTRATAGIDX(tag) ((Elf32_Word)-((Elf32_Sword) (tag) <<1>>1)-1) >>> +#define DT_EXTRATAGIDX(tag) (-((Elf32_Sword)((Elf32_Word)(tag) * 2) / 2 + 1)) >>> #define DT_EXTRANUM 3 >>> >>> /* Values of `d_un.d_val' in the DT_FLAGS entry. */ >> >> Doesn't this change the type of the constant? And rely on a GCC >> extension? > > Indeed, I think an extra cast to Elf32_Word should keep the same type. > Wrt to GCC extension, this definition is already gated through _GNU_SOURCE > and afaik only used internally on glibc (I couldn't find any other project > that actually uses it), so I think it should be fine to rely on it. If it's an internal definition, should we move it into elf/include.h instead (with a NEWS entry)? Thanks, Florian
On 02/06/25 07:48, Florian Weimer wrote: > * Adhemerval Zanella Netto: > >> On 20/05/25 09:48, Florian Weimer wrote: >>> * Adhemerval Zanella: >>> >>>> From: Richard Henderson <rth@twiddle.net> >>>> >>>> When building with --enable-ubsan, the relocation code triggers: >>>> >>>> UBSAN: Undefined behaviour in get-dynamic-info.h:56:30 left shift of 1879047925 by 1 cannot be represented in type 'int' >>>> >>>> Originally from >>>> https://sourceware.org/pipermail/libc-alpha/2015-August/063015.html. >>>> --- >>>> elf/elf.h | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/elf/elf.h b/elf/elf.h >>>> index 1e1a59c14d..d48cf47b9a 100644 >>>> --- a/elf/elf.h >>>> +++ b/elf/elf.h >>>> @@ -995,7 +995,7 @@ typedef struct >>>> range. Be compatible. */ >>>> #define DT_AUXILIARY 0x7ffffffd /* Shared object to load before self */ >>>> #define DT_FILTER 0x7fffffff /* Shared object to get values from */ >>>> -#define DT_EXTRATAGIDX(tag) ((Elf32_Word)-((Elf32_Sword) (tag) <<1>>1)-1) >>>> +#define DT_EXTRATAGIDX(tag) (-((Elf32_Sword)((Elf32_Word)(tag) * 2) / 2 + 1)) >>>> #define DT_EXTRANUM 3 >>>> >>>> /* Values of `d_un.d_val' in the DT_FLAGS entry. */ >>> >>> Doesn't this change the type of the constant? And rely on a GCC >>> extension? >> >> Indeed, I think an extra cast to Elf32_Word should keep the same type. >> Wrt to GCC extension, this definition is already gated through _GNU_SOURCE >> and afaik only used internally on glibc (I couldn't find any other project >> that actually uses it), so I think it should be fine to rely on it. > > If it's an internal definition, should we move it into elf/include.h > instead (with a NEWS entry)? I am not sure since the search I did for its usage might not be that wide. I don't have a strong opinion about that.
diff --git a/elf/elf.h b/elf/elf.h index 1e1a59c14d..d48cf47b9a 100644 --- a/elf/elf.h +++ b/elf/elf.h @@ -995,7 +995,7 @@ typedef struct range. Be compatible. */ #define DT_AUXILIARY 0x7ffffffd /* Shared object to load before self */ #define DT_FILTER 0x7fffffff /* Shared object to get values from */ -#define DT_EXTRATAGIDX(tag) ((Elf32_Word)-((Elf32_Sword) (tag) <<1>>1)-1) +#define DT_EXTRATAGIDX(tag) (-((Elf32_Sword)((Elf32_Word)(tag) * 2) / 2 + 1)) #define DT_EXTRANUM 3 /* Values of `d_un.d_val' in the DT_FLAGS entry. */
From: Richard Henderson <rth@twiddle.net> When building with --enable-ubsan, the relocation code triggers: UBSAN: Undefined behaviour in get-dynamic-info.h:56:30 left shift of 1879047925 by 1 cannot be represented in type 'int' Originally from https://sourceware.org/pipermail/libc-alpha/2015-August/063015.html. --- elf/elf.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)