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ARM: 8950/1: ftrace/recordmcount: filter relocation types 

Scenario 1, ARMv7
=================

If code in arch/arm/kernel/ftrace.c would operate on mcount() pointer
the following may be generated:

00000230 <prealloc_fixed_plts>:
 230:   b5f8            push    {r3, r4, r5, r6, r7, lr}
 232:   b500            push    {lr}
 234:   f7ff fffe       bl      0 <__gnu_mcount_nc>
                        234: R_ARM_THM_CALL     __gnu_mcount_nc
 238:   f240 0600       movw    r6, #0
                        238: R_ARM_THM_MOVW_ABS_NC      __gnu_mcount_nc
 23c:   f8d0 1180       ldr.w   r1, [r0, #384]  ; 0x180

FTRACE currently is not able to deal with it:

WARNING: CPU: 0 PID: 0 at .../kernel/trace/ftrace.c:1979 ftrace_bug+0x1ad/0x230()
...
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.116-... #1
...
[<c0314e3d>] (unwind_backtrace) from [<c03115e9>] (show_stack+0x11/0x14)
[<c03115e9>] (show_stack) from [<c051a7f1>] (dump_stack+0x81/0xa8)
[<c051a7f1>] (dump_stack) from [<c0321c5d>] (warn_slowpath_common+0x69/0x90)
[<c0321c5d>] (warn_slowpath_common) from [<c0321cf3>] (warn_slowpath_null+0x17/0x1c)
[<c0321cf3>] (warn_slowpath_null) from [<c038ee9d>] (ftrace_bug+0x1ad/0x230)
[<c038ee9d>] (ftrace_bug) from [<c038f1f9>] (ftrace_process_locs+0x27d/0x444)
[<c038f1f9>] (ftrace_process_locs) from [<c08915bd>] (ftrace_init+0x91/0xe8)
[<c08915bd>] (ftrace_init) from [<c0885a67>] (start_kernel+0x34b/0x358)
[<c0885a67>] (start_kernel) from [<00308095>] (0x308095)
---[ end trace cb88537fdc8fa200 ]---
ftrace failed to modify [<c031266c>] prealloc_fixed_plts+0x8/0x60
 actual: 44:f2:e1:36
ftrace record flags: 0
 (0)   expected tramp: c03143e9

Scenario 2, ARMv4T
==================

ftrace: allocating 14435 entries in 43 pages
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:2029 ftrace_bug+0x204/0x310
CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.5 #1
Hardware name: Cirrus Logic EDB9302 Evaluation Board
[<c0010a24>] (unwind_backtrace) from [<c000ecb0>] (show_stack+0x20/0x2c)
[<c000ecb0>] (show_stack) from [<c03c72e8>] (dump_stack+0x20/0x30)
[<c03c72e8>] (dump_stack) from [<c0021c18>] (__warn+0xdc/0x104)
[<c0021c18>] (__warn) from [<c0021d7c>] (warn_slowpath_null+0x4c/0x5c)
[<c0021d7c>] (warn_slowpath_null) from [<c0095360>] (ftrace_bug+0x204/0x310)
[<c0095360>] (ftrace_bug) from [<c04dabac>] (ftrace_init+0x3b4/0x4d4)
[<c04dabac>] (ftrace_init) from [<c04cef4c>] (start_kernel+0x20c/0x410)
[<c04cef4c>] (start_kernel) from [<00000000>] (  (null))
---[ end trace 0506a2f5dae6b341 ]---
ftrace failed to modify
[<c000c350>] perf_trace_sys_exit+0x5c/0xe8
 actual:   1e:ff:2f:e1
Initializing ftrace call sites
ftrace record flags: 0
 (0)
 expected tramp: c000fb24

The analysis for this problem has been already performed previously,
refer to the link below.

Fix the above problems by allowing only selected reloc types in
__mcount_loc. The list itself comes from the legacy recordmcount.pl
script.

Link: https://lore.kernel.org/lkml/56961010.6000806@pengutronix.de/
Cc: stable@vger.kernel.org
Fixes: ed60453fa8 ("ARM: 6511/1: ftrace: add ARM support for C version of recordmcount")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Alex Sverdlin 2020-01-08 15:57:47 +01:00 committed by Russell King
parent e42617b825
commit 927d780ee3
1 changed files with 17 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
scripts/recordmcount.c
View File

@ -38,6 +38,10 @@
#define R_AARCH64_ABS64 257
#endif
#define R_ARM_PC24 1
#define R_ARM_THM_CALL 10
#define R_ARM_CALL 28
static int fd_map; /* File descriptor for file being modified. */
static int mmap_failed; /* Boolean flag. */
static char gpfx; /* prefix for global symbol name (sometimes '_') */
@ -418,6 +422,18 @@ static char const *already_has_rel_mcount = "success"; /* our work here is done!
#define RECORD_MCOUNT_64
#include "recordmcount.h"
static int arm_is_fake_mcount(Elf32_Rel const *rp)
{
switch (ELF32_R_TYPE(w(rp->r_info))) {
case R_ARM_THM_CALL:
case R_ARM_CALL:
case R_ARM_PC24:
return 0;
}
return 1;
}
/* 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]
@ -523,6 +539,7 @@ static int do_file(char const *const fname)
altmcount = "__gnu_mcount_nc";
make_nop = make_nop_arm;
rel_type_nop = R_ARM_NONE;
is_fake_mcount32 = arm_is_fake_mcount;
gpfx = 0;
break;
case EM_AARCH64: