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author | Rich Felker <dalias@aerifal.cx> | 2016-11-12 19:43:37 -0500 |
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committer | Rich Felker <dalias@aerifal.cx> | 2016-11-12 19:54:43 -0500 |
commit | 54991729fd1e3d3a0cb71884d758d86afe6da9e0 (patch) | |
tree | 220f219af4477a552995f66de3d26a71e603c26b /src | |
parent | 15094943050eb9a564f409323070e50b40f78816 (diff) | |
download | musl-54991729fd1e3d3a0cb71884d758d86afe6da9e0.tar.gz musl-54991729fd1e3d3a0cb71884d758d86afe6da9e0.tar.xz musl-54991729fd1e3d3a0cb71884d758d86afe6da9e0.zip |
work around gdb issues recognizing sigreturn trampoline on x86_64
gdb can only backtrace/unwind across signal handlers if it recognizes the sa_restorer trampoline. for x86_64, gdb first attempts to determine the symbol name for the function in which the program counter resides and match it against "__restore_rt". if no name can be found (e.g. in the case of a stripped binary), the exact instruction sequence is matched instead. when matching the function name, however, gdb's unwind code wrongly considers the interval [sym,sym+size] rather than [sym,sym+size). thus, if __restore_rt begins immediately after another function, gdb wrongly identifies pc as lying within the previous adjacent function. this patch adds a nop before __restore_rt to preclude that possibility. it also removes the symbol name __restore and replaces it with a macro since the stability of whether gdb identifies the function as __restore_rt or __restore is not clear. for the no-symbols case, the instruction sequence is changed to use %rax rather than %eax to match what gdb expects. based on patch by Szabolcs Nagy, with extended description and corresponding x32 changes added.
Diffstat (limited to 'src')
-rw-r--r-- | src/signal/x32/restore.s | 7 | ||||
-rw-r--r-- | src/signal/x86_64/restore.s | 7 |
2 files changed, 6 insertions, 8 deletions
diff --git a/src/signal/x32/restore.s b/src/signal/x32/restore.s index 27cd3cef..2f06e787 100644 --- a/src/signal/x32/restore.s +++ b/src/signal/x32/restore.s @@ -1,8 +1,7 @@ + nop .global __restore_rt -.global __restore .type __restore_rt,@function -.type __restore,@function __restore_rt: -__restore: - movl $0x40000201, %eax /* SYS_rt_sigreturn */ + mov $0x40000201, %rax /* SYS_rt_sigreturn */ syscall +.size __restore_rt,.-__restore_rt diff --git a/src/signal/x86_64/restore.s b/src/signal/x86_64/restore.s index 682af2dd..b5c6e37f 100644 --- a/src/signal/x86_64/restore.s +++ b/src/signal/x86_64/restore.s @@ -1,8 +1,7 @@ + nop .global __restore_rt -.global __restore .type __restore_rt,@function -.type __restore,@function __restore_rt: -__restore: - movl $15, %eax + mov $15, %rax syscall +.size __restore_rt,.-__restore_rt |