[PATCH v3] recordmcount: Correct st_shndx handling

From: Mark-PK Tsai
Date: Tue Jun 15 2021 - 12:23:24 EST


From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

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@xxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx>
[handle endianness of sym->st_shndx]
Signed-off-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx>
---
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 (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)
--
2.18.0