| Message ID | 20210615162313.26081-1-mark-pk.tsai@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] recordmcount: Correct st_shndx handling | expand |
On Wed, Jun 16, 2021 at 12:23:13AM +0800, Mark-PK Tsai wrote: > From: Peter Zijlstra <peterz@infradead.org> > > One should only use st_shndx when >SHN_UNDEF and <SHN_LORESERVE. When > SHN_XINDEX, then use .symtab_shndx. Otherwise use 0. > > This handles the case: st_shndx >= SHN_LORESERVE && st_shndx != SHN_XINDEX. > > Reported-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Tested-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com> > [handle endianness of sym->st_shndx] > Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com> > --- > scripts/recordmcount.h | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h > index f9b19524da11..ef9c3425f86b 100644 > --- a/scripts/recordmcount.h > +++ b/scripts/recordmcount.h > @@ -194,13 +194,18 @@ static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab, > unsigned long offset; > int index; > > + if (w2(sym->st_shndx) > SHN_UNDEF && > + w2(sym->st_shndx) < SHN_LORESERVE) > return w2(sym->st_shndx); > > + if (w2(sym->st_shndx) == SHN_XINDEX) { > + offset = (unsigned long)sym - (unsigned long)symtab; > + index = offset / sizeof(*sym); > > + return w(symtab_shndx[index]); > + } > + > + return 0; > } Thanks. However that leads to atrocious codegen because w2 is an indirect function, something like the below seems much better. 1d00: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi 1d05: c0 eb 04 shr $0x4,%bl 1d08: ff 15 7a 54 00 00 callq *0x547a(%rip) # 7188 <w2> 1d0e: 85 c0 test %eax,%eax 1d10: 74 16 je 1d28 <main+0xba8> 1d12: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi 1d17: ff 15 6b 54 00 00 callq *0x546b(%rip) # 7188 <w2> 1d1d: 3d ff fe 00 00 cmp $0xfeff,%eax 1d22: 0f 86 00 03 00 00 jbe 2028 <main+0xea8> 1d28: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi 1d2d: ff 15 55 54 00 00 callq *0x5455(%rip) # 7188 <w2> vs 1d0c: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi 1d11: ff 15 71 54 00 00 callq *0x5471(%rip) # 7188 <w2> --- diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h index f9b19524da11..b3e9d0563c03 100644 --- a/scripts/recordmcount.h +++ b/scripts/recordmcount.h @@ -192,15 +192,23 @@ static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab, Elf32_Word const *symtab_shndx) { unsigned long offset; + unsigned short shndx; int index; - if (sym->st_shndx != SHN_XINDEX) - return w2(sym->st_shndx); + shndx = w2(sym->st_shndx); - offset = (unsigned long)sym - (unsigned long)symtab; - index = offset / sizeof(*sym); + if (shndx > SHN_UNDEF && + shndx < SHN_LORESERVE) + return shndx; - return w(symtab_shndx[index]); + if (shndx == SHN_XINDEX) { + offset = (unsigned long)sym - (unsigned long)symtab; + index = offset / sizeof(*sym); + + return w(symtab_shndx[index]); + } + + return 0; } static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)
> On Wed, Jun 16, 2021 at 12:23:13AM +0800, Mark-PK Tsai wrote: > > From: Peter Zijlstra <peterz@infradead.org> > > > > One should only use st_shndx when >SHN_UNDEF and <SHN_LORESERVE. When > > SHN_XINDEX, then use .symtab_shndx. Otherwise use 0. > > > > This handles the case: st_shndx >= SHN_LORESERVE && st_shndx != SHN_XINDEX. > > > > Reported-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > Tested-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com> > > [handle endianness of sym->st_shndx] > > Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com> > > --- > > scripts/recordmcount.h | 13 +++++++++---- > > 1 file changed, 9 insertions(+), 4 deletions(-) > > > > diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h > > index f9b19524da11..ef9c3425f86b 100644 > > --- a/scripts/recordmcount.h > > +++ b/scripts/recordmcount.h > > @@ -194,13 +194,18 @@ static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab, > > unsigned long offset; > > int index; > > > > + if (w2(sym->st_shndx) > SHN_UNDEF && > > + w2(sym->st_shndx) < SHN_LORESERVE) > > return w2(sym->st_shndx); > > > > + if (w2(sym->st_shndx) == SHN_XINDEX) { > > + offset = (unsigned long)sym - (unsigned long)symtab; > > + index = offset / sizeof(*sym); > > > > + return w(symtab_shndx[index]); > > + } > > + > > + return 0; > > } > > Thanks. However that leads to atrocious codegen because w2 is an > indirect function, something like the below seems much better. Oh, I didn't notice that. I'll update in v4. Thanks! > > 1d00: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi > 1d05: c0 eb 04 shr $0x4,%bl > 1d08: ff 15 7a 54 00 00 callq *0x547a(%rip) # 7188 <w2> > 1d0e: 85 c0 test %eax,%eax > 1d10: 74 16 je 1d28 <main+0xba8> > 1d12: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi > 1d17: ff 15 6b 54 00 00 callq *0x546b(%rip) # 7188 <w2> > 1d1d: 3d ff fe 00 00 cmp $0xfeff,%eax > 1d22: 0f 86 00 03 00 00 jbe 2028 <main+0xea8> > 1d28: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi > 1d2d: ff 15 55 54 00 00 callq *0x5455(%rip) # 7188 <w2> > > vs > > 1d0c: 41 0f b7 7f 0e movzwl 0xe(%r15),%edi > 1d11: ff 15 71 54 00 00 callq *0x5471(%rip) # 7188 <w2> > > --- > diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h > index f9b19524da11..b3e9d0563c03 100644 > --- a/scripts/recordmcount.h > +++ b/scripts/recordmcount.h > @@ -192,15 +192,23 @@ static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab, > Elf32_Word const *symtab_shndx) > { > unsigned long offset; > + unsigned short shndx; > int index; > > - if (sym->st_shndx != SHN_XINDEX) > - return w2(sym->st_shndx); > + shndx = w2(sym->st_shndx); > > - offset = (unsigned long)sym - (unsigned long)symtab; > - index = offset / sizeof(*sym); > + if (shndx > SHN_UNDEF && > + shndx < SHN_LORESERVE) > + return shndx; > > - return w(symtab_shndx[index]); > + if (shndx == SHN_XINDEX) { > + offset = (unsigned long)sym - (unsigned long)symtab; > + index = offset / sizeof(*sym); > + > + return w(symtab_shndx[index]); > + } > + > + return 0; > } > > static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)
diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h index f9b19524da11..ef9c3425f86b 100644 --- a/scripts/recordmcount.h +++ b/scripts/recordmcount.h @@ -194,13 +194,18 @@ static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab, unsigned long offset; int index; - if (sym->st_shndx != SHN_XINDEX) + if (w2(sym->st_shndx) > SHN_UNDEF && + w2(sym->st_shndx) < SHN_LORESERVE) return w2(sym->st_shndx); - offset = (unsigned long)sym - (unsigned long)symtab; - index = offset / sizeof(*sym); + if (w2(sym->st_shndx) == SHN_XINDEX) { + offset = (unsigned long)sym - (unsigned long)symtab; + index = offset / sizeof(*sym); - return w(symtab_shndx[index]); + return w(symtab_shndx[index]); + } + + return 0; } static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)