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authorH.J. Lu <hjl.tools@gmail.com>2020-02-10 07:58:45 -0800
committerH.J. Lu <hjl.tools@gmail.com>2020-02-10 07:59:10 -0800
commitbf6465d0461234ccd45ae34d5e2375a0bee0081d (patch)
tree71a56036daba549bcf0290f3780a4b27a1304c37 /gcc/fortran/array.c
parent1cad5e89a9e1b4ffa47bc6e3551643b342f6cfe8 (diff)
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i386: Properly pop restore token in signal frame
Linux CET kernel places a restore token on shadow stack for signal handler to enhance security. The restore token is 8 byte and aligned to 8 bytes. It is usually transparent to user programs since kernel will pop the restore token when signal handler returns. But when an exception is thrown from a signal handler, now we need to pop the restore token from shadow stack. For x86-64, we just need to treat the signal frame as normal frame. For i386, we need to search for the restore token to check if the original shadow stack is 8 byte aligned. If the original shadow stack is 8 byte aligned, we just need to pop 2 slots, one restore token, from shadow stack. Otherwise, we need to pop 3 slots, one restore token + 4 byte padding, from shadow stack. This patch also includes 2 tests, one has a restore token with 4 byte padding and one without. Tested on Linux/x86-64 CET machine with and without -m32. libgcc/ PR libgcc/85334 * config/i386/shadow-stack-unwind.h (_Unwind_Frames_Increment): New. gcc/testsuite/ PR libgcc/85334 * g++.target/i386/pr85334-1.C: New test. * g++.target/i386/pr85334-2.C: Likewise.
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