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56 lines
2.1 KiB
Diff
56 lines
2.1 KiB
Diff
From: Rich Felker <dalias@aerifal.cx>
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Date: Tue, 29 Sep 2015 02:44:05 +0000
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Subject: [PATCH] eliminate protected-visibility data in libc.so with vis.h
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preinclude
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some newer binutils versions print scary warnings about protected data
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because most gcc versions fail to produce the right address
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references/relocations for such data that might be subject to copy
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relocations. originally vis.h explicitly assigned default visibility
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to all public data symbols to avoid this issue, but commit
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b8dda24fe1caa901a99580f7a52defb95aedb67c removed this treatment for
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stdin/out/err to work around a gcc 3.x bug, and since they don't
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actually need it (because taking their addresses is not valid C).
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instead, a check for the gcc 3.x bug is added to the configure check
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for vis.h preinclude support; this feature will simply be disabled
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when using a buggy version of gcc.
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---
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--- a/configure
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+++ b/configure
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@@ -476,10 +476,18 @@ if test "x$visibility" = xauto ; then
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# - the -include option
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# - the attributes/pragmas used in vis.h
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# - linking code that takes the address of protected symbols
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+# - gcc 3.x bug that wrongly claims declarations mismatch
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printf "checking whether global visibility preinclude works... "
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-echo 'int (*fp)(void);' > "$tmpc"
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-echo 'int foo(void) { }' >> "$tmpc"
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-echo 'int bar(void) { fp = foo; return foo(); }' >> "$tmpc"
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+cat > "$tmpc" <<EOF
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+__attribute__((__visibility__("default")))
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+extern struct a *const x;
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+typedef struct a b;
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+extern b *const x;
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+b *const x;
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+int (*fp)(void);
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+int foo(void) { }
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+int bar(void) { fp = foo; return foo(); }
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+EOF
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if $CC $CFLAGS_C99FSE $CPPFLAGS $CFLAGS \
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-DSHARED -fPIC -I./src/internal -include vis.h \
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-nostdlib -shared -Wl,-Bsymbolic-functions \
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--- a/src/internal/vis.h
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+++ b/src/internal/vis.h
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@@ -12,6 +12,9 @@
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* exported data symbols. */
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__attribute__((__visibility__("default")))
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+extern struct _IO_FILE *const stdin, *const stdout, *const stderr;
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+
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+__attribute__((__visibility__("default")))
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extern int optind, opterr, optopt, optreset, __optreset, getdate_err, h_errno, daylight, __daylight, signgam, __signgam;
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__attribute__((__visibility__("default")))
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