Re: Problems with commit 'kallsyms: add support for relative offsets in kallsyms address table' (in mmotm)

From: Guenter Roeck
Date: Sun Jan 24 2016 - 13:02:33 EST

On 01/24/2016 09:20 AM, Ard Biesheuvel wrote:
[ ... ]
OK, there's an additional issue in my latest version: the
kallsyms_relative_base value itself is not relocated.

If you have more time to burn on this, could you try the following on
top? (If not, that is also fine, I will look into it myself on Monday)

diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 5ab13394dfd9..0f43f0751d47 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -137,8 +137,10 @@ static int read_symbol(FILE *in, struct sym_entry *s)

/* Ignore most absolute/undefined (?) symbols. */
- if (strcmp(sym, "_text") == 0)
+ if (strcmp(sym, "_text") == 0) {
_text = s->addr;
+ stype = 'T';
+ }
else if (check_symbol_range(sym, s->addr, text_ranges,
ARRAY_SIZE(text_ranges)) == 0)
/* nothing to do */;
@@ -406,7 +408,7 @@ static void write_src(void)

if (base_relative) {
- printf("\tPTR\t%#llx\n", relative_base);
+ printf("\tPTR\t_text - %#llx\n", _text - relative_base);

Does not help.

For x86? Or none of them?

I tested sparc32 and x86_64/nosmp. Doesn't help for any of them.
sparc32 has the following absolute symbols.

f035a420 A _etext
f03d9000 A _sdata
f03de8c4 A jiffies
f03f8860 A _edata
f03fc000 A __init_begin
f041bdc8 A __init_text_end
f0423000 A __bss_start
f0423000 A __init_end
f044457d A __bss_stop
f044457d A _end

This results in:

kallsyms failure: absolute symbol value 0xf035a420 out of range in relative mode

This is with binutils 2.22. I didn't test with binutils 2.25 for sparc, or re-test mips.

Looks like I'll need to add more test cases with binutils 2.22 vs. 2.25 for various
architectures, as well as more SMP vs. !SMP builds.