From a257f201dd557aa82c7efb7528277afe675c0468 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Tue, 7 Jan 2025 08:34:13 +0100 Subject: [PATCH] Revert "x86_64: Remove unused padding from tcbhead_t" This reverts commit 30d3fd7f4f4bc8f767d73ad4e4b005c1bd234310. The padding is required by Chromium's MaybeUpdateGlibcTidCache in sandbox/linux/services/namespace_sandbox.cc. Reviewed-by: Adhemerval Zanella --- sysdeps/x86_64/nptl/tls.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h index a9c348e696..551d342d52 100644 --- a/sysdeps/x86_64/nptl/tls.h +++ b/sysdeps/x86_64/nptl/tls.h @@ -62,16 +62,28 @@ typedef struct void *__private_ss; /* The marker for the current shadow stack. */ unsigned long long int ssp_base; + /* Must be kept even if it is no longer used by glibc since programs, + like AddressSanitizer, depend on the size of tcbhead_t. */ + __128bits __glibc_unused2[8][4] __attribute__ ((aligned (32))); + + void *__padding[8]; } tcbhead_t; # ifdef __ILP32__ /* morestack.S in libgcc uses offset 0x40 to access __private_ss, */ _Static_assert (offsetof (tcbhead_t, __private_ss) == 0x40, "offset of __private_ss != 0x40"); +/* NB: ssp_base used to be "long int __glibc_reserved2", which was + changed from 32 bits to 64 bits. Make sure that the offset of the + next field, __glibc_unused2, is unchanged. */ +_Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x60, + "offset of __glibc_unused2 != 0x60"); # else /* morestack.S in libgcc uses offset 0x70 to access __private_ss, */ _Static_assert (offsetof (tcbhead_t, __private_ss) == 0x70, "offset of __private_ss != 0x70"); +_Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80, + "offset of __glibc_unused2 != 0x80"); # endif #else /* __ASSEMBLER__ */