kernel/arch/mips/include/asm/ptrace.h, branch linux-rolling-stable

MIPS: Fix MAX_REG_OFFSET

2025-05-18T06:26:07Z

[ Upstream commit c44572e0cc13c9afff83fd333135a0aa9b27ba26 ] Fix MAX_REG_OFFSET to point to the last register in 'pt_regs' and not to the marker itself, which could allow regs_get_register() to return an invalid offset. Fixes: 40e084a506eb ("MIPS: Add uprobes support.") Suggested-by: Maciej W. Rozycki Signed-off-by: Thorsten Blum Signed-off-by: Thomas Bogendoerfer Signed-off-by: Sasha Levin

MIPS: Export syscall stack arguments properly for remote use

2025-02-13T11:41:18Z

We have several places across the kernel where we want to access another task's syscall arguments, such as ptrace(2), seccomp(2), etc., by making a call to syscall_get_arguments(). This works for register arguments right away by accessing the task's `regs' member of `struct pt_regs', however for stack arguments seen with 32-bit/o32 kernels things are more complicated. Technically they ought to be obtained from the user stack with calls to an access_remote_vm(), but we have an easier way available already. So as to be able to access syscall stack arguments as regular function arguments following the MIPS calling convention we copy them over from the user stack to the kernel stack in arch/mips/kernel/scall32-o32.S, in handle_sys(), to the current stack frame's outgoing argument space at the top of the stack, which is where the handler called expects to see its incoming arguments. This area is also pointed at by the `pt_regs' pointer obtained by task_pt_regs(). Make the o32 stack argument space a proper member of `struct pt_regs' then, by renaming the existing member from `pad0' to `args' and using generated offsets to access the space. No functional change though. With the change in place the o32 kernel stack frame layout at the entry to a syscall handler invoked by handle_sys() is therefore as follows: $sp + 68 -> | ... | <- pt_regs.regs[9] +---------------------+ $sp + 64 -> | $t0 | <- pt_regs.regs[8] +---------------------+ $sp + 60 -> | $a3/argument #4 | <- pt_regs.regs[7] +---------------------+ $sp + 56 -> | $a2/argument #3 | <- pt_regs.regs[6] +---------------------+ $sp + 52 -> | $a1/argument #2 | <- pt_regs.regs[5] +---------------------+ $sp + 48 -> | $a0/argument #1 | <- pt_regs.regs[4] +---------------------+ $sp + 44 -> | $v1 | <- pt_regs.regs[3] +---------------------+ $sp + 40 -> | $v0 | <- pt_regs.regs[2] +---------------------+ $sp + 36 -> | $at | <- pt_regs.regs[1] +---------------------+ $sp + 32 -> | $zero | <- pt_regs.regs[0] +---------------------+ $sp + 28 -> | stack argument #8 | <- pt_regs.args[7] +---------------------+ $sp + 24 -> | stack argument #7 | <- pt_regs.args[6] +---------------------+ $sp + 20 -> | stack argument #6 | <- pt_regs.args[5] +---------------------+ $sp + 16 -> | stack argument #5 | <- pt_regs.args[4] +---------------------+ $sp + 12 -> | psABI space for $a3 | <- pt_regs.args[3] +---------------------+ $sp + 8 -> | psABI space for $a2 | <- pt_regs.args[2] +---------------------+ $sp + 4 -> | psABI space for $a1 | <- pt_regs.args[1] +---------------------+ $sp + 0 -> | psABI space for $a0 | <- pt_regs.args[0] +---------------------+ holding user data received and with the first 4 frame slots reserved by the psABI for the compiler to spill the incoming arguments from $a0-$a3 registers (which it sometimes does according to its needs) and the next 4 frame slots designated by the psABI for any stack function arguments that follow. This data is also available for other tasks to peek/poke at as reqired and where permitted. Signed-off-by: Maciej W. Rozycki Signed-off-by: Thomas Bogendoerfer

MIPS: scall: Save thread_info.syscall unconditionally on entry

2024-04-09T14:52:21Z

thread_info.syscall is used by syscall_get_nr to supply syscall nr over a thread stack frame. Previously, thread_info.syscall is only saved at syscall_trace_enter when syscall tracing is enabled. However rest of the kernel code do expect syscall_get_nr to be available without syscall tracing. The previous design breaks collect_syscall. Move saving process to syscall entry to fix it. Reported-by: Xi Ruoyao Link: https://github.com/util-linux/util-linux/issues/2867 Signed-off-by: Jiaxun Yang Signed-off-by: Thomas Bogendoerfer

MIPS: Clear Cause.BD in instruction_pointer_set

2024-02-12T22:04:40Z

Clear Cause.BD after we use instruction_pointer_set to override EPC. This can prevent exception_epc check against instruction code at new return address. It won't be considered as "in delay slot" after epc being overridden anyway. Signed-off-by: Jiaxun Yang Signed-off-by: Thomas Bogendoerfer

ptrace: Introduce exception_ip arch hook

2024-02-12T22:04:34Z

On architectures with delay slot, architecture level instruction pointer (or program counter) in pt_regs may differ from where exception was triggered. Introduce exception_ip hook to invoke architecture code and determine actual instruction pointer to the exception. Link: https://lore.kernel.org/lkml/00d1b813-c55f-4365-8d81-d70258e10b16@app.fastmail.com/ Signed-off-by: Jiaxun Yang Signed-off-by: Thomas Bogendoerfer

Revert "MIPS: Add basic support for ptrace single step"

2021-02-18T10:57:44Z

This reverts commit 7c86ff9925cbc83e8a21f164a8fdc2767e03531e. There are too many special cases for MIPS not covered by this patch. In the end it might be better to implement single stepping in userland than emulating it in the kernel. Signed-off-by: Thomas Bogendoerfer

MIPS: Add basic support for ptrace single step

2021-02-13T08:49:19Z

In the current code, arch_has_single_step() is not defined on MIPS, that means MIPS does not support instruction single-step for user mode. Delve is a debugger for the Go programming language, the ptrace syscall PtraceSingleStep() failed [1] on MIPS and then the single step function can not work well, we can see that PtraceSingleStep() definition returns ptrace(PTRACE_SINGLESTEP) [2]. So it is necessary to support ptrace single step on MIPS. At the beginning, we try to use the Debug Single Step exception on the Loongson 3A4000 platform, but it has no effect when set CP0_DEBUG SSt bit, this is because CP0_DEBUG NoSSt bit is 1 which indicates no single-step feature available [3], so this way which is dependent on the hardware is almost impossible. With further research, we find out there exists a common way used with break instruction in arch/alpha/kernel/ptrace.c, it is workable. For the above analysis, define arch_has_single_step(), add the common function user_enable_single_step() and user_disable_single_step(), set flag TIF_SINGLESTEP for child process, use break instruction to set breakpoint. We can use the following testcase to test it: tools/testing/selftests/breakpoints/step_after_suspend_test.c $ make -C tools/testing/selftests TARGETS=breakpoints $ cd tools/testing/selftests/breakpoints Without this patch: $ ./step_after_suspend_test -n TAP version 13 1..4 # ptrace(PTRACE_SINGLESTEP) not supported on this architecture: Input/output error ok 1 # SKIP CPU 0 # ptrace(PTRACE_SINGLESTEP) not supported on this architecture: Input/output error ok 2 # SKIP CPU 1 # ptrace(PTRACE_SINGLESTEP) not supported on this architecture: Input/output error ok 3 # SKIP CPU 2 # ptrace(PTRACE_SINGLESTEP) not supported on this architecture: Input/output error ok 4 # SKIP CPU 3 # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:4 error:0 With this patch: $ ./step_after_suspend_test -n TAP version 13 1..4 ok 1 CPU 0 ok 2 CPU 1 ok 3 CPU 2 ok 4 CPU 3 # Totals: pass:4 fail:0 xfail:0 xpass:0 skip:0 error:0 [1] https://github.com/go-delve/delve/blob/master/pkg/proc/native/threads_linux.go#L50 [2] https://github.com/go-delve/delve/blob/master/vendor/golang.org/x/sys/unix/syscall_linux.go#L1573 [3] http://www.t-es-t.hu/download/mips/md00047f.pdf Reported-by: Guoqi Chen Signed-off-by: Xingxing Su Signed-off-by: Tiezhu Yang Reported-by: kernel test robot Signed-off-by: Thomas Bogendoerfer

MIPS: fix kernel_stack_pointer()

2021-02-03T10:32:52Z

MIPS always save kernel stack pointer in regs[29] Signed-off-by: Huang Pei Signed-off-by: Thomas Bogendoerfer

asm-generic: remove ptrace.h

2019-07-01T15:51:40Z

No one is using this header anymore. Signed-off-by: Christoph Hellwig Acked-by: Arnd Bergmann Acked-by: Oleg Nesterov Acked-by: Paul Burton Signed-off-by: Arnd Bergmann

MIPS: ptrace: Fix regs_return_value for kernel context

2016-10-12T12:34:45Z

Currently regs_return_value always negates reg[2] if it determines the syscall has failed, but when called in kernel context this check is invalid and may result in returning a wrong value. This fixes errors reported by CONFIG_KPROBES_SANITY_TEST Fixes: d7e7528bcd45 ("Audit: push audit success and retcode into arch ptrace.h") Signed-off-by: Marcin Nowakowski Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org # 3.3+ Patchwork: https://patchwork.linux-mips.org/patch/14381/ Signed-off-by: Ralf Baechle