09a87ae971
Testing confirmed what I suspected: x32 lseek uses kernel-sized (i.e. wide) long for offset parameter. * file.c: Delete sys_lseek32. * linux/syscall.h: Likewise. * linux/x32/syscallent1.h: Likewise. * test/x32_lseek.c: New file. Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
39 lines
1.1 KiB
C
39 lines
1.1 KiB
C
// Test program which explores whether lseek syscall (not llseek!)
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// on x32 uses 64-bit offset argument.
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// IOW: does _kernel_ truncate it on entry?
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// The answer appears to be "no, full 64-bit offset is used".
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// strace must show it correctly too - tricky if strace itself is x32 one!
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//
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// Build: x86_64-gcc -static -Wall -ox32_lseek x32_lseek.c
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// Run: $ strace ./x32_lseek 2>&1 | grep lseek | grep 1250999896321
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// lseek(0, 1250999896321, SEEK_SET) = 1250999896321
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#define _GNU_SOURCE
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#include <sys/types.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <sys/syscall.h>
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// Ensure we are compiling to 64 bits
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struct bug { int t[sizeof(long) > 4 ? 1 : -1]; };
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int main(int argc, char **argv)
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{
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long ofs = 0x12345678901;
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errno = 0;
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close(0);
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if (open("/etc/passwd", O_RDONLY))
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return 1;
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long r = syscall(
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(long) (__NR_lseek | 0x40000000), // make x32 call
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(long) (0),
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(long) (ofs),
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(long) (SEEK_SET)
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);
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printf("pos:%ld(0x%lx) errno:%m\n", r, r);
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if (!errno)
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printf((r == ofs) ? "64-bit offset used\n" : "Kernel truncated offset\n");
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return 0;
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}
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