Re: [tip: core/kprobes] arm/ftrace: Use __patch_text()

Dmitry Osipenko
2020-01-22T21:26:55Z

04.12.2019 11:33, tip-bot2 for Peter Zijlstra пишет:
> The following commit has been merged into the core/kprobes branch of tip:
>
> Commit-ID: 5a735583b764750726621b0396d03e4782911b77
> Gitweb: https://git.kernel.org/tip/5a735583b764750726621b0396d03e4782911b77
> Author: Peter Zijlstra <peterz@infradead.org>
> AuthorDate: Tue, 15 Oct 2019 21:07:35 +02:00
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitterDate: Wed, 27 Nov 2019 07:44:25 +01:00
>
> arm/ftrace: Use __patch_text()
>
> Instead of flipping text protection, use the patch_text infrastructure
> that uses a fixmap alias where required.
>
> This removes the last user of set_all_modules_text_*().
>
> Tested-by: Will Deacon <will@kernel.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Brian Gerst <brgerst@gmail.com>
> Cc: Denys Vlasenko <dvlasenk@redhat.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: ard.biesheuvel@linaro.org
> Cc: james.morse@arm.com
> Cc: rabin@rab.in
> Link: https://lkml.kernel.org/r/20191113092636.GG4131@hirez.programming.kicks-ass.net
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> ---
> arch/arm/kernel/Makefile | 4 ++--
> arch/arm/kernel/ftrace.c | 10 ++--------
> 2 files changed, 4 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
> index 8cad594..a885172 100644
> --- a/arch/arm/kernel/Makefile
> +++ b/arch/arm/kernel/Makefile
> @@ -49,8 +49,8 @@ obj-$(CONFIG_HAVE_ARM_SCU) += smp_scu.o
> obj-$(CONFIG_HAVE_ARM_TWD) += smp_twd.o
> obj-$(CONFIG_ARM_ARCH_TIMER) += arch_timer.o
> obj-$(CONFIG_FUNCTION_TRACER) += entry-ftrace.o
> -obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o insn.o
> -obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o insn.o
> +obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o insn.o patch.o
> +obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o insn.o patch.o
> obj-$(CONFIG_JUMP_LABEL) += jump_label.o insn.o patch.o
> obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
> # Main staffs in KPROBES are in arch/arm/probes/ .
> diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
> index bda949f..2a5ff69 100644
> --- a/arch/arm/kernel/ftrace.c
> +++ b/arch/arm/kernel/ftrace.c
> @@ -22,6 +22,7 @@
> #include <asm/ftrace.h>
> #include <asm/insn.h>
> #include <asm/set_memory.h>
> +#include <asm/patch.h>
>
> #ifdef CONFIG_THUMB2_KERNEL
> #define NOP 0xf85deb04 /* pop.w {lr} */
> @@ -35,9 +36,7 @@ static int __ftrace_modify_code(void *data)
> {
> int *command = data;
>
> - set_kernel_text_rw();
> ftrace_modify_all_code(*command);
> - set_kernel_text_ro();
>
> return 0;
> }
> @@ -59,13 +58,11 @@ static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
>
> int ftrace_arch_code_modify_prepare(void)
> {
> - set_all_modules_text_rw();
> return 0;
> }
>
> int ftrace_arch_code_modify_post_process(void)
> {
> - set_all_modules_text_ro();
> /* Make sure any TLB misses during machine stop are cleared. */
> flush_tlb_all();
> return 0;
> @@ -97,10 +94,7 @@ static int ftrace_modify_code(unsigned long pc, unsigned long old,
> return -EINVAL;
> }
>
> - if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
> - return -EPERM;
> -
> - flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
> + __patch_text((void *)pc, new);
>
> return 0;
> }
>

Hello,

NVIDIA Tegra20/30 are not booting with CONFIG_FTRACE=y, but even with
CONFIG_FTRACE=n things are not working well.

Reverting this patch and "module: Remove set_all_modules_text_*()" (to
fix compilation) helps.

[ 13.363523] 8<--- cut here ---
[ 13.366887] Unable to handle kernel paging request at virtual address
3e24fca3
[ 13.370342] pgd = f9397380
[ 13.373625] [3e24fca3] *pgd=00000000
[ 13.377274] Internal error: Oops: 5 [#1] SMP THUMB2
[ 13.381086] Modules linked in:
[ 13.384372] CPU: 1 PID: 209 Comm: systemd-journal Not tainted
5.5.0-rc7-next-20200122-00177-g9b7833ca2e7a #983
[ 13.387929] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
[ 13.391500] PC is at __seccomp_filter+0x86/0x370
[ 13.395103] LR is at __seccomp_filter+0x77/0x370
[ 13.398584] pc : [<c0194d56>] lr : [<c0194d47>] psr: 600e0033
[ 13.402211] sp : ee6f3ee0 ip : ee6f3f20 fp : ee6f2000
[ 13.405769] r10: ffff0000 r9 : 7fff0000 r8 : ee6f3f20
[ 13.409844] r7 : 7fff0000 r6 : ee6b7280 r5 : 00000014 r4 : 7fff0000
[ 13.413776] r3 : 3e24fc7f r2 : 00000000 r1 : 3e24fca7 r0 : ee6f3f20
[ 13.417382] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA Thumb
Segment none
[ 13.420991] Control: 50c5387d Table: 2e76404a DAC: 00000051
[ 13.424667] Process systemd-journal (pid: 209, stack limit = 0x90194d37)
[ 13.428331] Stack: (0xee6f3ee0 to 0xee6f4000)
[ 13.432082] 3ee0: 00000008 00000000 c0fa23a8 c0c65958 00000008
000000c5 00000006 00000000
[ 13.435959] 3f00: 00000004 00000002 00000000 00000000 00000014
b6f5d4d0 edc96ee8 ee600908
[ 13.439786] 3f20: 00000006 40000028 b6e3cd56 00000000 00000014
00000000 00000002 00000000
[ 13.444285] 3f40: 00000000 00000000 00000000 00000000 00000014
00000000 b6f5d4d0 00000000
[ 13.448432] 3f60: 00000000 9445a58a 00000000 00000014 ffffe000
00000000 00000006 c01011e4
[ 13.452202] 3f80: ee6f2000 00000080 00000000 c01080d5 00000014
b6f5d4d0 00000000 00000006
[ 13.456025] 3fa0: c01011e4 c0101195 00000014 b6f5d4d0 00000014
00000002 00000000 00000000
[ 13.459872] 3fc0: 00000014 b6f5d4d0 00000000 00000006 b6f5d4e0
befa5610 00000002 00000000
[ 13.463736] 3fe0: 00000006 befa5518 b6eb6c7d b6e3cd56 800e0030
00000014 00000000 00000000
[ 13.467570] [<c0194d56>] (__seccomp_filter) from [<c01080d5>]
(syscall_trace_enter+0x45/0xac)
[ 13.471520] [<c01080d5>] (syscall_trace_enter) from [<c0101195>]
(__sys_trace+0x9/0x34)
[ 13.475592] Exception stack(0xee6f3fa8 to 0xee6f3ff0)
[ 13.480012] 3fa0: 00000014 b6f5d4d0 00000014
00000002 00000000 00000000
[ 13.484127] 3fc0: 00000014 b6f5d4d0 00000000 00000006 b6f5d4e0
befa5610 00000002 00000000
[ 13.488248] 3fe0: 00000006 befa5518 b6eb6c7d b6e3cd56
[ 13.492318] Code: 68f3 4640 f103 0128 (6a5b) 4798
[ 13.496597] ---[ end trace 2190b04c04a417a2 ]---
[ 13.520493] note: systemd-journal[209] exited with preempt_count 1
[ 13.532782] systemd[1]: systemd-journald.service: Service has no
hold-off time (RestartSec=0), scheduling restart.
[ 13.538055] systemd[1]: systemd-journald.service: Scheduled restart
job, restart counter is at 1.
[ 13.544960] systemd[1]: Stopped Journal Service.
[ 13.555123] systemd[1]: Condition check resulted in Journal Audit
Socket being skipped.
[ 13.566066] systemd[1]: Starting Journal Service...
[ 13.786668] systemd[1]: Started Journal Service.

[ 22.013861] BUG: Bad rss-counter state mm:26c62bde type:MM_ANONPAGES
val:170

This "Bad rss-counter" seems to be a new problem and unrelated to the
offending patch, I don't recall seeing it in next-20200117 and earlier.