linux-kernel - [PATCH] recordmcount: avoid using ABS symbol as reference

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Date:   Mon, 7 Jun 2021 10:38:39 +0800
From:   Mark-PK Tsai <mark-pk.tsai@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
CC:     <rostedt@...dmis.org>, Mark-PK Tsai <mark-pk.tsai@...iatek.com>,
        "Sami Tolvanen" <samitolvanen@...gle.com>,
        Matt Helsley <mhelsley@...are.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <yj.chiang@...iatek.com>
Subject: [PATCH] recordmcount: avoid using ABS symbol as reference

Avoid using ABS symbol, which won't be relocate, as reference.

On arm64 platform, if there's shndx equals SHN_ABS(0xfff1).

Section Headers:
[Nr]    Name                         Type      Address          Off      Size   ES  Flg Lk     Inf    Al
[65521] .text.n_tty_receive_buf      PROGBITS  0000000000000000 3cdab520 000054 00  AX  0      0      4
[65522] .rela.text.n_tty_receive_buf RELA      0000000000000000 3cdab578 000030 18  I   152076 65521  8

find_secsym_ndx, which use r_info in rela section to find the reference
symbol, may take ABS symbol as base.

Symbol table '.symtab' contains 453285 entries:
   Num:    Value          Size Type    Bind   Vis       Ndx Name
     6: 0000000000000002     0 NOTYPE  LOCAL  DEFAULT   ABS section_count

Which cause an invalid address in __mcount_loc.

Signed-off-by: Mark-PK Tsai <mark-pk.tsai@...iatek.com>
---
 scripts/recordmcount.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
index f9b19524da11..9b69167fb7ff 100644
--- a/scripts/recordmcount.h
+++ b/scripts/recordmcount.h
@@ -526,6 +526,10 @@ static int find_secsym_ndx(unsigned const txtndx,
 	for (symp = sym0, t = nsym; t; --t, ++symp) {
 		unsigned int const st_bind = ELF_ST_BIND(symp->st_info);
 
+		/* avoid absolute symbols */
+		if (symp->st_shndx == SHN_ABS)
+			continue;
+
 		if (txtndx == get_symindex(symp, symtab, symtab_shndx)
 			/* avoid STB_WEAK */
 		    && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {
-- 
2.18.0