Software stepping checks for the correct handler by iterating over a list
of dynamically registered handlers and calling all of them until one
handles the exception.
This is the only generic way to handle software stepping handlers in arm64
as the exception does not provide an immediate that could be checked,
contrary to software breakpoints.
However, the registration mechanism is not exported and has only
two current users : the KGDB stepping handler, and the uprobe single step
handler.
Given that one comes from user mode and the other from kernel mode, call
the appropriate one by checking the source EL of the exception.
Add a stand-in that returns DBG_HOOK_ERROR when the configuration
options are not enabled.
Remove `arch_init_uprobes()` as it is not useful anymore and is
specific to arm64.
Unify the naming of the handler to XXX_single_step_handler(), making it
clear they are related.
Signed-off-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Tested-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Reviewed-by: Will Deacon <will@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20250707114109.35672-5-ada.coupriediaz@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Software breakpoints pass an immediate value in ESR ("comment") that can
be used to call a specialized handler (KGDB, KASAN...).
We do so in two different ways :
- During early boot, `early_brk64` statically checks against known
immediates and calls the corresponding handler,
- During init, handlers are dynamically registered into a list. When
called, the generic software breakpoint handler will iterate over
the list to find the appropriate handler.
The dynamic registration does not provide any benefit here as it is not
exported and all its uses are within the arm64 tree. It also depends on an
RCU list, whose safe access currently relies on the non-preemptible state
of `do_debug_exception`.
Replace the list iteration logic in `call_break_hooks` to call
the breakpoint handlers statically if they are enabled, like in
`early_brk64`.
Expose the handlers in their respective headers to be reachable from
`arch/arm64/kernel/debug-monitors.c` at link time.
Unify the naming of the software breakpoint handlers to XXX_brk_handler(),
making it clear they are related and to differentiate from the
hardware breakpoints.
Signed-off-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Tested-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Reviewed-by: Will Deacon <will@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20250707114109.35672-4-ada.coupriediaz@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
The arm64 uprobes code is broken for big-endian kernels as it doesn't
convert the in-memory instruction encoding (which is always
little-endian) into the kernel's native endianness before analyzing and
simulating instructions. This may result in a few distinct problems:
* The kernel may may erroneously reject probing an instruction which can
safely be probed.
* The kernel may erroneously erroneously permit stepping an
instruction out-of-line when that instruction cannot be stepped
out-of-line safely.
* The kernel may erroneously simulate instruction incorrectly dur to
interpretting the byte-swapped encoding.
The endianness mismatch isn't caught by the compiler or sparse because:
* The arch_uprobe::{insn,ixol} fields are encoded as arrays of u8, so
the compiler and sparse have no idea these contain a little-endian
32-bit value. The core uprobes code populates these with a memcpy()
which similarly does not handle endianness.
* While the uprobe_opcode_t type is an alias for __le32, both
arch_uprobe_analyze_insn() and arch_uprobe_skip_sstep() cast from u8[]
to the similarly-named probe_opcode_t, which is an alias for u32.
Hence there is no endianness conversion warning.
Fix this by changing the arch_uprobe::{insn,ixol} fields to __le32 and
adding the appropriate __le32_to_cpu() conversions prior to consuming
the instruction encoding. The core uprobes copies these fields as opaque
ranges of bytes, and so is unaffected by this change.
At the same time, remove MAX_UINSN_BYTES and consistently use
AARCH64_INSN_SIZE for clarity.
Tested with the following:
| #include <stdio.h>
| #include <stdbool.h>
|
| #define noinline __attribute__((noinline))
|
| static noinline void *adrp_self(void)
| {
| void *addr;
|
| asm volatile(
| " adrp %x0, adrp_self\n"
| " add %x0, %x0, :lo12:adrp_self\n"
| : "=r" (addr));
| }
|
|
| int main(int argc, char *argv)
| {
| void *ptr = adrp_self();
| bool equal = (ptr == adrp_self);
|
| printf("adrp_self => %p\n"
| "adrp_self() => %p\n"
| "%s\n",
| adrp_self, ptr, equal ? "EQUAL" : "NOT EQUAL");
|
| return 0;
| }
.... where the adrp_self() function was compiled to:
| 00000000004007e0 <adrp_self>:
| 4007e0: 90000000 adrp x0, 400000 <__ehdr_start>
| 4007e4: 911f8000 add x0, x0, #0x7e0
| 4007e8: d65f03c0 ret
Before this patch, the ADRP is not recognized, and is assumed to be
steppable, resulting in corruption of the result:
| # ./adrp-self
| adrp_self => 0x4007e0
| adrp_self() => 0x4007e0
| EQUAL
| # echo 'p /root/adrp-self:0x007e0' > /sys/kernel/tracing/uprobe_events
| # echo 1 > /sys/kernel/tracing/events/uprobes/enable
| # ./adrp-self
| adrp_self => 0x4007e0
| adrp_self() => 0xffffffffff7e0
| NOT EQUAL
After this patch, the ADRP is correctly recognized and simulated:
| # ./adrp-self
| adrp_self => 0x4007e0
| adrp_self() => 0x4007e0
| EQUAL
| #
| # echo 'p /root/adrp-self:0x007e0' > /sys/kernel/tracing/uprobe_events
| # echo 1 > /sys/kernel/tracing/events/uprobes/enable
| # ./adrp-self
| adrp_self => 0x4007e0
| adrp_self() => 0x4007e0
| EQUAL
Fixes: 9842ceae9f ("arm64: Add uprobe support")
Cc: stable@vger.kernel.org
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20241008155851.801546-4-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
After we fixed the uprobe inst endian in aarch_be, the sparse check report
the following warning info:
sparse warnings: (new ones prefixed by >>)
>> kernel/events/uprobes.c:223:25: sparse: sparse: restricted __le32 degrades to integer
>> kernel/events/uprobes.c:574:56: sparse: sparse: incorrect type in argument 4 (different base types)
@@ expected unsigned int [addressable] [usertype] opcode @@ got restricted __le32 [usertype] @@
kernel/events/uprobes.c:574:56: sparse: expected unsigned int [addressable] [usertype] opcode
kernel/events/uprobes.c:574:56: sparse: got restricted __le32 [usertype]
>> kernel/events/uprobes.c:1483:32: sparse: sparse: incorrect type in initializer (different base types)
@@ expected unsigned int [usertype] insn @@ got restricted __le32 [usertype] @@
kernel/events/uprobes.c:1483:32: sparse: expected unsigned int [usertype] insn
kernel/events/uprobes.c:1483:32: sparse: got restricted __le32 [usertype]
use the __le32 to u32 for uprobe_opcode_t, to keep the same.
Fixes: 60f07e22a7 ("arm64:uprobe fix the uprobe SWBP_INSN in big-endian")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: junhua huang <huang.junhua@zte.com.cn>
Link: https://lore.kernel.org/r/202212280954121197626@zte.com.cn
Signed-off-by: Will Deacon <will@kernel.org>
Based on 2 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 4122 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This patch adds support for uprobe on ARM64 architecture.
Unit tests for following have been done so far and they have been found
working
1. Step-able instructions, like sub, ldr, add etc.
2. Simulation-able like ret, cbnz, cbz etc.
3. uretprobe
4. Reject-able instructions like sev, wfe etc.
5. trapped and abort xol path
6. probe at unaligned user address.
7. longjump test cases
Currently it does not support aarch32 instruction probing.
Signed-off-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
