lkml.org 
[lkml]   [2020]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] recordmcount: only record relocation of type R_AARCH64_CALL26 on arm64.
Date
From: Gregory Herrero <gregory.herrero@oracle.com>

Currently, if a section has a relocation to '_mcount' symbol, a new
__mcount_loc entry will be added whatever the relocation type is.
This is problematic when a relocation to '_mcount' is in the middle of a
section and is not a call for ftrace use.

Such relocation could be generated with below code for example:
bool is_mcount(unsigned long addr)
{
return (target == (unsigned long) &_mcount);
}

With this snippet of code, ftrace will try to patch the mcount location
generated by this code on module load and fail with:

Call trace:
ftrace_bug+0xa0/0x28c
ftrace_process_locs+0x2f4/0x430
ftrace_module_init+0x30/0x38
load_module+0x14f0/0x1e78
__do_sys_finit_module+0x100/0x11c
__arm64_sys_finit_module+0x28/0x34
el0_svc_common+0x88/0x194
el0_svc_handler+0x38/0x8c
el0_svc+0x8/0xc
---[ end trace d828d06b36ad9d59 ]---
ftrace failed to modify
[<ffffa2dbf3a3a41c>] 0xffffa2dbf3a3a41c
actual: 66:a9:3c:90
Initializing ftrace call sites
ftrace record flags: 2000000
(0)
expected tramp: ffffa2dc6cf66724

So Limit the relocation type to R_AARCH64_CALL26 as in perl version of
recordmcount.

Fixes: ed60453fa8f8 ("ARM: 6511/1: ftrace: add ARM support for C version of recordmcount")
Signed-off-by: Gregory Herrero <gregory.herrero@oracle.com>
---
scripts/recordmcount.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index 7225107a9aaf..e59022b3f125 100644
--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -434,6 +434,11 @@ static int arm_is_fake_mcount(Elf32_Rel const *rp)
return 1;
}

+static int arm64_is_fake_mcount(Elf64_Rel const *rp)
+{
+ return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26;
+}
+
/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
* http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
* We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
@@ -547,6 +552,7 @@ static int do_file(char const *const fname)
make_nop = make_nop_arm64;
rel_type_nop = R_AARCH64_NONE;
ideal_nop = ideal_nop4_arm64;
+ is_fake_mcount64 = arm64_is_fake_mcount;
break;
case EM_IA_64: reltype = R_IA64_IMM64; break;
case EM_MIPS: /* reltype: e_class */ break;
--
2.27.0
\
 
 \ /
  Last update: 2020-07-17 16:36    [W:0.091 / U:0.076 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site