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Mark Rutland bc28fde909 arm64: ftrace: consistently handle PLTs. 
[ Upstream commit a6253579977e4c6f7818eeb05bf2bc65678a7187 ]

Sometimes it is necessary to use a PLT entry to call an ftrace
trampoline. This is handled by ftrace_make_call() and ftrace_make_nop(),
with each having *almost* identical logic, but this is not handled by
ftrace_modify_call() since its introduction in commit:

  3b23e4991f ("arm64: implement ftrace with regs")

Due to this, if we ever were to call ftrace_modify_call() for a callsite
which requires a PLT entry for a trampoline, then either:

a) If the old addr requires a trampoline, ftrace_modify_call() will use
   an out-of-range address to generate the 'old' branch instruction.
   This will result in warnings from aarch64_insn_gen_branch_imm() and
   ftrace_modify_code(), and no instructions will be modified. As
   ftrace_modify_call() will return an error, this will result in
   subsequent internal ftrace errors.

b) If the old addr does not require a trampoline, but the new addr does,
   ftrace_modify_call() will use an out-of-range address to generate the
   'new' branch instruction. This will result in warnings from
   aarch64_insn_gen_branch_imm(), and ftrace_modify_code() will replace
   the 'old' branch with a BRK. This will result in a kernel panic when
   this BRK is later executed.

Practically speaking, case (a) is vastly more likely than case (b), and
typically this will result in internal ftrace errors that don't
necessarily affect the rest of the system. This can be demonstrated with
an out-of-tree test module which triggers ftrace_modify_call(), e.g.

| # insmod test_ftrace.ko
| test_ftrace: Function test_function raw=0xffffb3749399201c, callsite=0xffffb37493992024
| branch_imm_common: offset out of range
| branch_imm_common: offset out of range
| ------------[ ftrace bug ]------------
| ftrace failed to modify
| [<ffffb37493992024>] test_function+0x8/0x38 [test_ftrace]
|  actual:   1d:00:00:94
| Updating ftrace call site to call a different ftrace function
| ftrace record flags: e0000002
|  (2) R
|  expected tramp: ffffb374ae42ed54
| ------------[ cut here ]------------
| WARNING: CPU: 0 PID: 165 at kernel/trace/ftrace.c:2085 ftrace_bug+0x280/0x2b0
| Modules linked in: test_ftrace(+)
| CPU: 0 PID: 165 Comm: insmod Not tainted 5.19.0-rc2-00002-g4d9ead8b45ce #13
| Hardware name: linux,dummy-virt (DT)
| pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
| pc : ftrace_bug+0x280/0x2b0
| lr : ftrace_bug+0x280/0x2b0
| sp : ffff80000839ba00
| x29: ffff80000839ba00 x28: 0000000000000000 x27: ffff80000839bcf0
| x26: ffffb37493994180 x25: ffffb374b0991c28 x24: ffffb374b0d70000
| x23: 00000000ffffffea x22: ffffb374afcc33b0 x21: ffffb374b08f9cc8
| x20: ffff572b8462c000 x19: ffffb374b08f9000 x18: ffffffffffffffff
| x17: 6c6c6163202c6331 x16: ffffb374ae5ad110 x15: ffffb374b0d51ee4
| x14: 0000000000000000 x13: 3435646532346561 x12: 3437336266666666
| x11: 203a706d61727420 x10: 6465746365707865 x9 : ffffb374ae5149e8
| x8 : 336266666666203a x7 : 706d617274206465 x6 : 00000000fffff167
| x5 : ffff572bffbc4a08 x4 : 00000000fffff167 x3 : 0000000000000000
| x2 : 0000000000000000 x1 : ffff572b84461e00 x0 : 0000000000000022
| Call trace:
|  ftrace_bug+0x280/0x2b0
|  ftrace_replace_code+0x98/0xa0
|  ftrace_modify_all_code+0xe0/0x144
|  arch_ftrace_update_code+0x14/0x20
|  ftrace_startup+0xf8/0x1b0
|  register_ftrace_function+0x38/0x90
|  test_ftrace_init+0xd0/0x1000 [test_ftrace]
|  do_one_initcall+0x50/0x2b0
|  do_init_module+0x50/0x1f0
|  load_module+0x17c8/0x1d64
|  __do_sys_finit_module+0xa8/0x100
|  __arm64_sys_finit_module+0x2c/0x3c
|  invoke_syscall+0x50/0x120
|  el0_svc_common.constprop.0+0xdc/0x100
|  do_el0_svc+0x3c/0xd0
|  el0_svc+0x34/0xb0
|  el0t_64_sync_handler+0xbc/0x140
|  el0t_64_sync+0x18c/0x190
| ---[ end trace 0000000000000000 ]---

We can solve this by consistently determining whether to use a PLT entry
for an address.

Note that since (the earlier) commit:

  f1a54ae9af ("arm64: module/ftrace: intialize PLT at load time")

... we can consistently determine the PLT address that a given callsite
will use, and therefore ftrace_make_nop() does not need to skip
validation when a PLT is in use.

This patch factors the existing logic out of ftrace_make_call() and
ftrace_make_nop() into a common ftrace_find_callable_addr() helper
function, which is used by ftrace_make_call(), ftrace_make_nop(), and
ftrace_modify_call(). In ftrace_make_nop() the patching is consistently
validated by ftrace_modify_code() as we can always determine what the
old instruction should have been.

Fixes: 3b23e4991f ("arm64: implement ftrace with regs")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Will Deacon <will@kernel.org>
Tested-by: "Ivan T. Ivanov" <iivanov@suse.de>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220614080944.1349146-3-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2022-06-22 14:13:17 +02:00
Documentation x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data 2022-06-16 13:27:59 +02:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
arch arm64: ftrace: consistently handle PLTs. 2022-06-22 14:13:17 +02:00
block block: fix bio_clone_blkg_association() to associate with proper blkcg_gq 2022-06-09 10:21:31 +02:00
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: cryptd - Protect per-CPU resource by disabling BH. 2022-06-09 10:21:17 +02:00
drivers net: bgmac: Fix an erroneous kfree() in bgmac_remove() 2022-06-22 14:13:17 +02:00
fs pNFS: Avoid a live lock condition in pnfs_update_layout() 2022-06-22 14:13:16 +02:00
include x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data 2022-06-16 13:27:59 +02:00
init Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug 2022-06-09 10:21:25 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-09 10:21:17 +02:00
kernel dma-debug: make things less spammy under memory pressure 2022-06-22 14:13:13 +02:00
lib nodemask: Fix return values to be unsigned 2022-06-14 18:32:45 +02:00
mm hugetlb: fix huge_pmd_unshare address update 2022-06-09 10:21:27 +02:00
net net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg 2022-06-22 14:13:17 +02:00
samples samples/bpf, xdpsock: Fix race when running for fix duration of time 2022-04-08 14:40:21 +02:00
scripts scripts/gdb: change kernel config dumping method 2022-06-14 18:32:45 +02:00
security ima: remove the IMA_TEMPLATE Kconfig option 2022-06-09 10:21:25 +02:00
sound ALSA: hda/realtek - Add HW8326 support 2022-06-22 14:13:15 +02:00
tools KVM: x86/speculation: Disable Fill buffer clear within guests 2022-06-16 13:27:59 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:25:48 +01:00
virt KVM: Prevent module exit until all VMs are freed 2022-04-08 14:40:38 +02:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
…
.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 MAINTAINERS: add git tree for random.c 2022-05-30 09:33:24 +02:00
Makefile Linux 5.10.123 2022-06-16 13:28:00 +02:00
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.