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| author | Fangrui Song <maskray@google.com> | 2022-06-15 11:29:55 -0700 |
|---|---|---|
| committer | Fangrui Song <maskray@google.com> | 2022-06-15 11:29:55 -0700 |
| commit | de38b2a343e6d64b95c50004943d6107a9e380d0 (patch) | |
| tree | 7024de16def267741d9bcf6ff5f29d27dcdceeba /sysdeps/i386/dl-machine.h | |
| parent | ff439c47173565fbff4f0f78d07b0f14e4a7db05 (diff) | |
| download | glibc-de38b2a343e6d64b95c50004943d6107a9e380d0.zip glibc-de38b2a343e6d64b95c50004943d6107a9e380d0.tar.gz glibc-de38b2a343e6d64b95c50004943d6107a9e380d0.tar.bz2 | |
elf: Remove ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA
If an executable has copy relocations for extern protected data, that
can only work if the library containing the definition is built with
assumptions (a) the compiler emits GOT-generating relocations (b) the
linker produces R_*_GLOB_DAT instead of R_*_RELATIVE. Otherwise the
library uses its own definition directly and the executable accesses a
stale copy. Note: the GOT relocations defeat the purpose of protected
visibility as an optimization, but allow rtld to make the executable and
library use the same copy when copy relocations are present, but it
turns out this never worked perfectly.
ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA has strange semantics when both
a.so and b.so define protected var and the executable copy relocates
var: b.so accesses its own copy even with GLOB_DAT. The behavior change
is from commit 62da1e3b00b51383ffa7efc89d8addda0502e107 (x86) and then
copied to nios2 (ae5eae7cfc9c4a8297ff82ec6b794faca1976ecc) and arc
(0e7d930c4c11de896fe807f67fa1eb756c9c1e05).
Without ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA, b.so accesses the copy
relocated data like a.so.
There is now a warning for copy relocation on protected symbol since
commit 7374c02b683b7110b853a32496a619410364d70b. It's extremely
unlikely anyone relies on the ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA
behavior, so let's remove it: this removes a check in the symbol lookup
code.
Diffstat (limited to 'sysdeps/i386/dl-machine.h')
| -rw-r--r-- | sysdeps/i386/dl-machine.h | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h index 8779983..a8ee594 100644 --- a/sysdeps/i386/dl-machine.h +++ b/sysdeps/i386/dl-machine.h @@ -194,8 +194,7 @@ _dl_start_user:\n\ || (type) == R_386_TLS_DTPOFF32 || (type) == R_386_TLS_TPOFF32 \ || (type) == R_386_TLS_TPOFF || (type) == R_386_TLS_DESC) \ * ELF_RTYPE_CLASS_PLT) \ - | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY) \ - | (((type) == R_386_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA)) + | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY)) /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */ #define ELF_MACHINE_JMP_SLOT R_386_JMP_SLOT |