On Tue, Dec 16, 2025 at 10:52:42AM +0100, Christophe Leroy (CS GROUP) wrote: > > > Le 14/12/2025 à 14:02, Mukesh Kumar Chaurasiya a écrit : > > From: Mukesh Kumar Chaurasiya <[email protected]> > > > > 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. > > > > Specifically, the `TIF_RESTOREALL` flag, stored in this field, helps the > > exit routine determine if any NVGPRs were modified and need to be restored > > before returning to userspace. > > In the current implementation we did our best to keep this information in a > local var for performance reasons. Have you assessed the performance impact > of going through the stack for that ? > I needed this information out of the stack calls so kept it here. After enabling the code as a whole i didn't see much of an impact. > > > > This addition ensures a clean and architecture-specific mechanism to track > > per-syscall or per-interrupt state transitions related to register restore. > > > > Changes: > > - Add `exit_flags` and `__pt_regs_pad` to maintain 16-byte stack alignment > > - Update asm-offsets.c and ptrace.c for offset and validation > > - Update PT_* constants in uapi header to reflect the new layout > > > > Signed-off-by: Mukesh Kumar Chaurasiya <[email protected]> > > --- > > arch/powerpc/include/asm/ptrace.h | 3 +++ > > arch/powerpc/include/uapi/asm/ptrace.h | 14 +++++++++----- > > arch/powerpc/kernel/asm-offsets.c | 1 + > > arch/powerpc/kernel/ptrace/ptrace.c | 1 + > > 4 files changed, 14 insertions(+), 5 deletions(-) > > > > diff --git a/arch/powerpc/include/asm/ptrace.h > > b/arch/powerpc/include/asm/ptrace.h > > index 94aa1de2b06e..3af8a5898fe3 100644 > > --- a/arch/powerpc/include/asm/ptrace.h > > +++ b/arch/powerpc/include/asm/ptrace.h > > @@ -53,6 +53,9 @@ struct pt_regs > > unsigned long esr; > > }; > > unsigned long result; > > + unsigned long exit_flags; > > + /* Maintain 16 byte interrupt stack alignment */ > > On powerpc/32, one 'long' is 4 bytes not 8. > Oh ohk. Will fix this in next revision. > > + unsigned long __pt_regs_pad[1]; > > }; > > }; > > #if defined(CONFIG_PPC64) || defined(CONFIG_PPC_KUAP) > > diff --git a/arch/powerpc/include/uapi/asm/ptrace.h > > b/arch/powerpc/include/uapi/asm/ptrace.h > > index 01e630149d48..de56b216c9c5 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[1]; /* Maintain 16 byte interrupt stack > > alignment */ > > On powerpc/32, one 'long' is 4 bytes not 8. > Will fix this too. > > }; > > #endif /* __ASSEMBLER__ */ > > @@ -114,10 +116,12 @@ struct pt_regs > > #define PT_DAR 41 > > #define PT_DSISR 42 > > #define PT_RESULT 43 > > -#define PT_DSCR 44 > > -#define PT_REGS_COUNT 44 > > +#define PT_EXIT_FLAGS 44 > > +#define PT_PAD 45 > > +#define PT_DSCR 46 > > +#define PT_REGS_COUNT 46 > > -#define PT_FPR0 48 /* each FP reg occupies 2 slots in this space */ > > +#define PT_FPR0 (PT_REGS_COUNT + 4) /* each FP reg occupies 2 slots > > in this space */ > > #ifndef __powerpc64__ > > @@ -129,7 +133,7 @@ struct pt_regs > > #define PT_FPSCR (PT_FPR0 + 32) /* each FP reg occupies 1 slot in > > 64-bit space */ > > -#define PT_VR0 82 /* each Vector reg occupies 2 slots in 64-bit */ > > +#define PT_VR0 (PT_FPSCR + 2) /* <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) > > @@ -137,7 +141,7 @@ struct pt_regs > > /* > > * Only store first 32 VSRs here. The second 32 VSRs in VR0-31 > > */ > > -#define PT_VSR0 150 /* each VSR reg occupies 2 slots in 64-bit */ > > +#define PT_VSR0 (PT_VRSAVE + 2) /* each VSR reg occupies 2 slots in > > 64-bit */ > > #define PT_VSR31 (PT_VSR0 + 2*31) > > #endif /* __powerpc64__ */ > > diff --git a/arch/powerpc/kernel/asm-offsets.c > > b/arch/powerpc/kernel/asm-offsets.c > > index a4bc80b30410..c0bb09f1db78 100644 > > --- a/arch/powerpc/kernel/asm-offsets.c > > +++ b/arch/powerpc/kernel/asm-offsets.c > > @@ -292,6 +292,7 @@ int main(void) > > STACK_PT_REGS_OFFSET(_ESR, esr); > > STACK_PT_REGS_OFFSET(ORIG_GPR3, orig_gpr3); > > STACK_PT_REGS_OFFSET(RESULT, result); > > + STACK_PT_REGS_OFFSET(EXIT_FLAGS, exit_flags); > > Where is that used ? > It's not used anywhere as of now but kept it there as a convention. Should this be removed?
Regards, Mukesh > > STACK_PT_REGS_OFFSET(_TRAP, trap); > > #ifdef CONFIG_PPC64 > > STACK_PT_REGS_OFFSET(SOFTE, softe); > > diff --git a/arch/powerpc/kernel/ptrace/ptrace.c > > b/arch/powerpc/kernel/ptrace/ptrace.c > > index c6997df63287..2134b6d155ff 100644 > > --- a/arch/powerpc/kernel/ptrace/ptrace.c > > +++ b/arch/powerpc/kernel/ptrace/ptrace.c > > @@ -432,6 +432,7 @@ void __init pt_regs_check(void) > > CHECK_REG(PT_DAR, dar); > > CHECK_REG(PT_DSISR, dsisr); > > CHECK_REG(PT_RESULT, result); > > + CHECK_REG(PT_EXIT_FLAGS, exit_flags); > > #undef CHECK_REG > > BUILD_BUG_ON(PT_REGS_COUNT != sizeof(struct user_pt_regs) / > > sizeof(unsigned long)); >
