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Mark Rutland 59d2dc7710 arm64: ftrace: add missing BTIs 
commit 35b6b28e69 upstream.

When branch target identifiers are in use, code reachable via an
indirect branch requires a BTI landing pad at the branch target site.

When building FTRACE_WITH_REGS atop patchable-function-entry, we miss
BTIs at the start start of the `ftrace_caller` and `ftrace_regs_caller`
trampolines, and when these are called from a module via a PLT (which
will use a `BR X16`), we will encounter a BTI failure, e.g.

| # insmod lkdtm.ko
| lkdtm: No crash points registered, enable through debugfs
| # echo function_graph > /sys/kernel/debug/tracing/current_tracer
| # cat /sys/kernel/debug/provoke-crash/DIRECT
| Unhandled 64-bit el1h sync exception on CPU0, ESR 0x34000001 -- BTI
| CPU: 0 PID: 174 Comm: cat Not tainted 5.16.0-rc2-dirty #3
| Hardware name: linux,dummy-virt (DT)
| pstate: 60400405 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=jc)
| pc : ftrace_caller+0x0/0x3c
| lr : lkdtm_debugfs_open+0xc/0x20 [lkdtm]
| sp : ffff800012e43b00
| x29: ffff800012e43b00 x28: 0000000000000000 x27: ffff800012e43c88
| x26: 0000000000000000 x25: 0000000000000000 x24: ffff0000c171f200
| x23: ffff0000c27b1e00 x22: ffff0000c2265240 x21: ffff0000c23c8c30
| x20: ffff8000090ba380 x19: 0000000000000000 x18: 0000000000000000
| x17: 0000000000000000 x16: ffff80001002bb4c x15: 0000000000000000
| x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000900ff0
| x11: ffff0000c4166310 x10: ffff800012e43b00 x9 : ffff8000104f2384
| x8 : 0000000000000001 x7 : 0000000000000000 x6 : 000000000000003f
| x5 : 0000000000000040 x4 : ffff800012e43af0 x3 : 0000000000000001
| x2 : ffff8000090b0000 x1 : ffff0000c171f200 x0 : ffff0000c23c8c30
| Kernel panic - not syncing: Unhandled exception
| CPU: 0 PID: 174 Comm: cat Not tainted 5.16.0-rc2-dirty #3
| Hardware name: linux,dummy-virt (DT)
| Call trace:
|  dump_backtrace+0x0/0x1a4
|  show_stack+0x24/0x30
|  dump_stack_lvl+0x68/0x84
|  dump_stack+0x1c/0x38
|  panic+0x168/0x360
|  arm64_exit_nmi.isra.0+0x0/0x80
|  el1h_64_sync_handler+0x68/0xd4
|  el1h_64_sync+0x78/0x7c
|  ftrace_caller+0x0/0x3c
|  do_dentry_open+0x134/0x3b0
|  vfs_open+0x38/0x44
|  path_openat+0x89c/0xe40
|  do_filp_open+0x8c/0x13c
|  do_sys_openat2+0xbc/0x174
|  __arm64_sys_openat+0x6c/0xbc
|  invoke_syscall+0x50/0x120
|  el0_svc_common.constprop.0+0xdc/0x100
|  do_el0_svc+0x84/0xa0
|  el0_svc+0x28/0x80
|  el0t_64_sync_handler+0xa8/0x130
|  el0t_64_sync+0x1a0/0x1a4
| SMP: stopping secondary CPUs
| Kernel Offset: disabled
| CPU features: 0x0,00000f42,da660c5f
| Memory Limit: none
| ---[ end Kernel panic - not syncing: Unhandled exception ]---

Fix this by adding the required `BTI C`, as we only require these to be
reachable via BL for direct calls or BR X16/X17 for PLTs. For now, these
are open-coded in the function prologue, matching the style of the
`__hwasan_tag_mismatch` trampoline.

In future we may wish to consider adding a new SYM_CODE_START_*()
variant which has an implicit BTI.

When ftrace is built atop mcount, the trampolines are marked with
SYM_FUNC_START(), and so get an implicit BTI. We may need to change
these over to SYM_CODE_START() in future for RELIABLE_STACKTRACE, in
case we need to apply special care aroud the return address being
rewritten.

Fixes: 97fed779f2 ("arm64: bti: Provide Kconfig for kernel mode BTI")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20211129135709.2274019-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-12-08 09:03:24 +01:00
arch arm64: ftrace: add missing BTIs 2021-12-08 09:03:24 +01:00
block block: Check ADMIN before NICE for IOPRIO_CLASS_RT 2021-11-26 10:39:19 +01:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:50:29 +02:00
crypto crypto: pcrypt - Delay write to padata->info 2021-11-18 14:04:12 +01:00
Documentation netfilter: ipvs: Fix reuse connection if RS weight is 0 2021-12-01 09:19:02 +01:00
drivers net: qlogic: qlcnic: Fix a NULL pointer dereference in qlcnic_83xx_add_rings() 2021-12-08 09:03:23 +01:00
fs fget: check that the fd still exists after getting a ref to it 2021-12-08 09:03:21 +01:00
include siphash: use _unaligned version by default 2021-12-08 09:03:23 +01:00
init bootconfig: init: Fix memblock leak in xbc_make_cmdline() 2021-11-21 13:46:35 +01:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:19:10 +01:00
kernel tracing/histograms: String compares should not care about signed values 2021-12-08 09:03:22 +01:00
lib siphash: use _unaligned version by default 2021-12-08 09:03:23 +01:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm hugetlbfs: flush TLBs correctly after huge_pmd_unshare 2021-11-26 10:39:21 +01:00
net net: mpls: Fix notifications when deleting a device 2021-12-08 09:03:23 +01:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-18 14:04:11 +01:00
scripts scripts/lld-version.sh: Rewrite based on upstream ld-version.sh 2021-11-21 13:46:37 +01:00
security selinux: fix NULL-pointer dereference when hashtab allocation fails 2021-11-26 10:39:21 +01:00
sound ALSA: intel-dsp-config: add quirk for JSL devices based on ES8336 codec 2021-12-01 09:19:04 +01:00
tools wireguard: device: reset peer src endpoint when netns exits 2021-12-08 09:03:22 +01:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: Disallow user memslot with size that exceeds "unsigned long" 2021-12-08 09:03:21 +01:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS f2fs: move ioctl interface definitions to separated file 2021-05-19 10:13:00 +02:00
Makefile Linux 5.10.83 2021-12-01 09:19:10 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.