This forces the entire per_cpu range to be reported as absolute without losing their linker symbol types, when the per_cpu area is 0-based. Without this, the variables are incorrectly shown as relocated under kASLR on x86_64.
Several kallsyms output in different boot states for comparison of various symbols: $ egrep ' (gdt_|_(stext|_per_cpu_))' /root/kallsyms.nokaslr 0000000000000000 D __per_cpu_start 0000000000004000 D gdt_page 0000000000014280 D __per_cpu_end ffffffff810001c8 T _stext ffffffff81ee53c0 D __per_cpu_offset $ egrep ' (gdt_|_(stext|_per_cpu_))' /root/kallsyms.kaslr1 000000001f200000 D __per_cpu_start 000000001f204000 D gdt_page 000000001f214280 D __per_cpu_end ffffffffa02001c8 T _stext ffffffffa10e53c0 D __per_cpu_offset $ egrep ' (gdt_|_(stext|_per_cpu_))' /root/kallsyms.kaslr2 000000000d400000 D __per_cpu_start 000000000d404000 D gdt_page 000000000d414280 D __per_cpu_end ffffffff8e4001c8 T _stext ffffffff8f2e53c0 D __per_cpu_offset $ egrep ' (gdt_|_(stext|_per_cpu_))' /root/kallsyms.kaslr-fixed 0000000000000000 D __per_cpu_start 0000000000004000 D gdt_page 0000000000014280 D __per_cpu_end ffffffffadc001c8 T _stext ffffffffaeae53c0 D __per_cpu_offset Signed-off-by: Kees Cook <[email protected]> --- v2: - only force absolute when per_cpu starts at 0. --- scripts/kallsyms.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c index 08f30ac5b07d..d3f93b8eb277 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -34,6 +34,7 @@ struct sym_entry { unsigned int len; unsigned int start_pos; unsigned char *sym; + int force_absolute; }; struct addr_range { @@ -51,6 +52,14 @@ static struct addr_range text_ranges[] = { #define text_range_text (&text_ranges[0]) #define text_range_inittext (&text_ranges[1]) +/* + * Variables in these ranges, when the start is 0 based, will be forced to + * be handled as absolute addresses. + */ +static struct addr_range abs_ranges[] = { + { "__per_cpu_start", "__per_cpu_end", -1ULL, 0 }, +}; + static struct sym_entry *table; static unsigned int table_size, table_cnt; static int all_symbols = 0; @@ -165,6 +174,10 @@ static int read_symbol(FILE *in, struct sym_entry *s) } strcpy((char *)s->sym + 1, str); s->sym[0] = stype; + s->force_absolute = 0; + + /* Check if we've found special absolute symbol range. */ + check_symbol_range(sym, s->addr, abs_ranges, ARRAY_SIZE(abs_ranges)); return 0; } @@ -211,6 +224,11 @@ static int symbol_valid(struct sym_entry *s) if (s->addr < kernel_start_addr) return 0; + /* Force zero-based range special symbols into being absolute. */ + i = symbol_in_range(s, abs_ranges, ARRAY_SIZE(abs_ranges)); + if (i >= 0 && abs_ranges[i].start == 0) + s->force_absolute = 1; + /* skip prefix char */ if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char) offset++; @@ -307,7 +325,7 @@ static int expand_symbol(unsigned char *data, int len, char *result) static int symbol_absolute(struct sym_entry *s) { - return toupper(s->sym[0]) == 'A'; + return s->force_absolute || toupper(s->sym[0]) == 'A'; } static void write_src(void) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
