From 927d780ee371d7e121cea4fc7812f6ef2cea461c Mon Sep 17 00:00:00 2001 From: Alex Sverdlin Date: Wed, 8 Jan 2020 15:57:47 +0100 Subject: [PATCH] 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 : 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 ... [] (unwind_backtrace) from [] (show_stack+0x11/0x14) [] (show_stack) from [] (dump_stack+0x81/0xa8) [] (dump_stack) from [] (warn_slowpath_common+0x69/0x90) [] (warn_slowpath_common) from [] (warn_slowpath_null+0x17/0x1c) [] (warn_slowpath_null) from [] (ftrace_bug+0x1ad/0x230) [] (ftrace_bug) from [] (ftrace_process_locs+0x27d/0x444) [] (ftrace_process_locs) from [] (ftrace_init+0x91/0xe8) [] (ftrace_init) from [] (start_kernel+0x34b/0x358) [] (start_kernel) from [<00308095>] (0x308095) ---[ end trace cb88537fdc8fa200 ]--- ftrace failed to modify [] 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 [] (unwind_backtrace) from [] (show_stack+0x20/0x2c) [] (show_stack) from [] (dump_stack+0x20/0x30) [] (dump_stack) from [] (__warn+0xdc/0x104) [] (__warn) from [] (warn_slowpath_null+0x4c/0x5c) [] (warn_slowpath_null) from [] (ftrace_bug+0x204/0x310) [] (ftrace_bug) from [] (ftrace_init+0x3b4/0x4d4) [] (ftrace_init) from [] (start_kernel+0x20c/0x410) [] (start_kernel) from [<00000000>] ( (null)) ---[ end trace 0506a2f5dae6b341 ]--- ftrace failed to modify [] 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: ed60453fa8f8 ("ARM: 6511/1: ftrace: add ARM support for C version of recordmcount") Signed-off-by: Alexander Sverdlin Acked-by: Steven Rostedt (VMware) Signed-off-by: Russell King --- scripts/recordmcount.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c index 612268eabef4..7225107a9aaf 100644 --- a/scripts/recordmcount.c +++ b/scripts/recordmcount.c @@ -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: