Re: [PATCH v4 5/8] powerpc: add exit_flags field in pt_regs
From: Dmitry V. Levin <hidden>
Date: 2026-07-23 11:10:23
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On Thu, Jul 23, 2026 at 03:02:38PM +0530, Mukesh Kumar Chaurasiya wrote:
On Wed, Jul 22, 2026 at 10:01:55AM +0300, Dmitry V. Levin wrote:quoted
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. 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. 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.[...] Hey, Can you try this fix? This should fix the ABI breakage.
[...]
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h index a393b7f2760a..01e630149d48 100644 --- a/arch/powerpc/include/uapi/asm/ptrace.h +++ b/arch/powerpc/include/uapi/asm/ptrace.h@@ -55,8 +55,6 @@ 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__ */@@ -116,12 +114,10 @@ struct pt_regs #define PT_DAR 41 #define PT_DSISR 42 #define PT_RESULT 43 -#define PT_EXIT_FLAGS 44 -#define PT_PAD 47 /* 3 times */ -#define PT_DSCR 48 -#define PT_REGS_COUNT 48 +#define PT_DSCR 44 +#define PT_REGS_COUNT 44 -#define PT_FPR0 (PT_REGS_COUNT + 4) /* each FP reg occupies 2 slots in this space */ +#define PT_FPR0 48 /* each FP reg occupies 2 slots in this space */ #ifndef __powerpc64__@@ -133,7 +129,7 @@ struct pt_regs #define PT_FPSCR (PT_FPR0 + 32) /* each FP reg occupies 1 slot in 64-bit space */ -#define PT_VR0 (PT_FPSCR + 2) /* <82> each Vector reg occupies 2 slots in 64-bit */ +#define PT_VR0 82 /* each Vector reg occupies 2 slots in 64-bit */ #define PT_VSCR (PT_VR0 + 32*2 + 1) #define PT_VRSAVE (PT_VR0 + 33*2)@@ -141,7 +137,7 @@ struct pt_regs /* * Only store first 32 VSRs here. The second 32 VSRs in VR0-31 */ -#define PT_VSR0 (PT_VRSAVE + 2) /* each VSR reg occupies 2 slots in 64-bit */ +#define PT_VSR0 150 /* each VSR reg occupies 2 slots in 64-bit */ #define PT_VSR31 (PT_VSR0 + 2*31) #endif /* __powerpc64__ */
As this patch essentially reverts the uapi header to its v7.1 state, the uapi part of the patch is definitely fine. -- ldv