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author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2020-03-05 13:38:24 -0300 |
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committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2020-03-06 13:17:20 -0300 |
commit | b33e946fbb1659d2c5937c4dd756a7c49a132dff (patch) | |
tree | c13bbb769c86e0ec9b2646c7fd14e6464073e55e /sysdeps/wordsize-64 | |
parent | d2b2acefa60a0559b0104394be1279eae72c9bb3 (diff) | |
download | glibc-b33e946fbb1659d2c5937c4dd756a7c49a132dff.tar.gz glibc-b33e946fbb1659d2c5937c4dd756a7c49a132dff.tar.xz glibc-b33e946fbb1659d2c5937c4dd756a7c49a132dff.zip |
sparc: Move sigreturn stub to assembly
It seems that some gcc versions might generates a stack frame for the sigreturn stub requires on sparc signal handling. For instance: $ cat test.c #define _GNU_SOURCE #include <sys/syscall.h> __attribute__ ((__optimize__ ("-fno-stack-protector"))) void __sigreturn_stub (void) { __asm__ ("mov %0, %%g1\n\t" "ta 0x10\n\t" : /* no outputs */ : "i" (SYS_rt_sigreturn)); } $ gcc -v [...] gcc version 9.2.1 20200224 (Debian 9.2.1-30) $ gcc -O2 -m64 test.c -S -o - [...] __sigreturn_stub: save %sp, -176, %sp #APP ! 9 "t.c" 1 mov 101, %g1 ta 0x10 ! 0 "" 2 #NO_APP .size __sigreturn_stub, .-__sigreturn_stub As indicated by kernel developers [1], the sigreturn stub can not change the register window or the stack pointer since the kernel has setup the restore frame at a precise location relative to the stack pointer when the stub is invoked. I tried to play with some compiler flags and even with _Noreturn and __builtin_unreachable after the asm does not help (and Sparc does not support naked functions). To avoid similar issues, as the stack-protector support also have stumbled, this patch moves the implementation of the sigreturn stubs to assembly. Checked on sparcv9-linux-gnu and sparc64-linux-gnu with gcc 9.2.1 and gcc 7.5.0. [1] https://lkml.org/lkml/2016/5/27/465
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