Re: [PATCH v4 5/8] powerpc: add exit_flags field in pt_regs

On 7/22/26 12:31 PM, Dmitry V. Levin wrote:

On Fri, Jan 23, 2026 at 01:09:13PM +0530, Mukesh Kumar Chaurasiya wrote:

quoted

From: Mukesh Kumar Chaurasiya <redacted>

Add a new field `exit_flags` in the pt_regs structure. This field will hold
the flags set during interrupt or syscall execution that are required during
exit to user mode.

Apparently, this change breaks PTRACE_GETREGS as the latter has no means
to communicate the size of struct pt_regs being written to userspace.

We added the exit_flag at the end of the struct so that other element
offsets will not be affected with this change.

As result, the kernel with this patch will write to userpsace 32 more
bytes than before, and unless the userspace is re-compiled with the latest
ptrace.h, 32 bytes of userspace memory after struct pt_regs will be
overwritten.

We are looking at other options and thanks for reporting this
Maddy

This issue was detected by strace test suite, specifically, the test that
checks whether the actual number of bytes written by
ptrace(PTRACE_GETREGS) matches sizeof(struct pt_regs), and that test failed
with runtime version v7.1 and headers version v7.2-rc1.

quoted

diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h
index 01e630149d48..a393b7f2760a 100644
--- a/arch/powerpc/include/uapi/asm/ptrace.h
+++ b/arch/powerpc/include/uapi/asm/ptrace.h

@@ -55,6 +55,8 @@ struct pt_regs
  	unsigned long dar;		/* Fault registers */
  	unsigned long dsisr;		/* on 4xx/Book-E used for ESR */
  	unsigned long result;		/* Result of a system call */
+	unsigned long exit_flags;	/* System call exit flags */
+	unsigned long __pt_regs_pad[3];	/* Maintain 16 byte interrupt stack alignment */
  };
  
  #endif /* __ASSEMBLER__ */