Andy
following e6577a7ce9 ("x86, vdso: Move the vvar area before the
vdso text") gcc 4.3.4 tells me
.../arch/x86/vdso/vdso2c.c: In function ‘main’:
.../arch/x86/vdso/vdso2c.h:118: warning: assuming signed overflow does not
occur when assuming that (X + c) < X is
always false
.../arch/x86/vdso/vdso2c.h:118: warning: assuming signed overflow does not
occur when assuming that (X + c) < X is
always false
apparently because it unrolls the containing loop and finds i ==
sym_vvar_start on the first iteration. I think there was a hidden
dependency before your change on required_syms[] first two
entries matching up with special_pages[]. If that's correct, all
syms[i] within said loop would seem to need replacing by
syms[special_pages[i]] (similarly for required_syms[i] afaict, see
below draft patch), which also is in line with the loop iterating
over the array elements of special_pages[].
Question then of course is - are there any further hidden
dependencies that already got or may eventually get broken?
Jan
--- a/arch/x86/vdso/vdso2c.h
+++ b/arch/x86/vdso/vdso2c.h
@@ -109,18 +109,18 @@ static void BITSFUNC(go)(void *raw_addr,
/* Validate mapping addresses. */
for (i = 0; i < sizeof(special_pages) / sizeof(special_pages[0]); i++) {
- if (!syms[i])
+ if (!syms[special_pages[i]])
continue; /* The mapping isn't used; ignore it. */
- if (syms[i] % 4096)
+ if (syms[special_pages[i]] % 4096)
fail("%s must be a multiple of 4096\n",
- required_syms[i].name);
- if (syms[sym_vvar_start] > syms[i] + 4096)
+ required_syms[special_pages[i]].name);
+ if (syms[sym_vvar_start] > syms[special_pages[i]] + 4096)
fail("%s underruns begin_vvar\n",
- required_syms[i].name);
- if (syms[i] + 4096 > 0)
+ required_syms[special_pages[i]].name);
+ if (syms[special_pages[i]] + 4096 > 0)
fail("%s is on the wrong side of the vdso text\n",
- required_syms[i].name);
+ required_syms[special_pages[i]].name);
}
if (syms[sym_vvar_start] % 4096)
fail("vvar_begin must be a multiple of 4096\n");
--
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