Le 19/09/2022 à 16:01, Nicholas Piggin a écrit : > Using a 16-bit constant for this marker allows it to be loaded with > a single 'li' instruction. On 64-bit this avoids a TOC entry and a > TOC load that depends on the r2 value that has just been loaded from > the PACA. > > XXX: this probably should be 64-bit change and use 2 instruction > sequence that 32-bit uses, to avoid false positives.
Yes would probably be safer ? It is only one instruction more, would likely be unnoticeable. Why value 0xffffba51 ? Why not 0xffffdead like PPC64 ? Christophe > > Signed-off-by: Nicholas Piggin <npig...@gmail.com> > --- > arch/powerpc/include/asm/ptrace.h | 6 +++--- > arch/powerpc/kernel/entry_32.S | 9 ++++----- > arch/powerpc/kernel/exceptions-64e.S | 8 +------- > arch/powerpc/kernel/exceptions-64s.S | 2 +- > arch/powerpc/kernel/head_32.h | 3 +-- > arch/powerpc/kernel/head_64.S | 7 ------- > arch/powerpc/kernel/head_booke.h | 3 +-- > arch/powerpc/kernel/interrupt_64.S | 6 +++--- > 8 files changed, 14 insertions(+), 30 deletions(-) > > diff --git a/arch/powerpc/include/asm/ptrace.h > b/arch/powerpc/include/asm/ptrace.h > index a03403695cd4..f47066f7878e 100644 > --- a/arch/powerpc/include/asm/ptrace.h > +++ b/arch/powerpc/include/asm/ptrace.h > @@ -115,10 +115,10 @@ struct pt_regs > > #define STACK_FRAME_OVERHEAD 112 /* size of minimum stack frame > */ > #define STACK_FRAME_LR_SAVE 2 /* Location of LR in stack frame */ > -#define STACK_FRAME_REGS_MARKER ASM_CONST(0x7265677368657265) > +#define STACK_FRAME_REGS_MARKER ASM_CONST(0xffffffffffffdead) > #define STACK_INT_FRAME_SIZE (sizeof(struct pt_regs) + \ > STACK_FRAME_OVERHEAD + KERNEL_REDZONE_SIZE) > -#define STACK_FRAME_MARKER 12 > +#define STACK_FRAME_MARKER 1 /* Reuse CR+reserved word */ > > #ifdef CONFIG_PPC64_ELF_ABI_V2 > #define STACK_FRAME_MIN_SIZE 32 > @@ -136,7 +136,7 @@ struct pt_regs > #define KERNEL_REDZONE_SIZE 0 > #define STACK_FRAME_OVERHEAD 16 /* size of minimum stack frame > */ > #define STACK_FRAME_LR_SAVE 1 /* Location of LR in stack frame */ > -#define STACK_FRAME_REGS_MARKER ASM_CONST(0x72656773) > +#define STACK_FRAME_REGS_MARKER ASM_CONST(0xffffba51) > #define STACK_INT_FRAME_SIZE (sizeof(struct pt_regs) + > STACK_FRAME_OVERHEAD) > #define STACK_FRAME_MARKER 2 > #define STACK_FRAME_MIN_SIZE STACK_FRAME_OVERHEAD > diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S > index 1d599df6f169..c221e764cefd 100644 > --- a/arch/powerpc/kernel/entry_32.S > +++ b/arch/powerpc/kernel/entry_32.S > @@ -108,9 +108,8 @@ transfer_to_syscall: > #ifdef CONFIG_BOOKE_OR_40x > rlwinm r9,r9,0,14,12 /* clear MSR_WE (necessary?) */ > #endif > - lis r12,STACK_FRAME_REGS_MARKER@ha /* exception frame marker */ > + li r12,STACK_FRAME_REGS_MARKER /* exception frame marker */ > SAVE_GPR(2, r1) > - addi r12,r12,STACK_FRAME_REGS_MARKER@l > stw r9,_MSR(r1) > li r2, INTERRUPT_SYSCALL > stw r12,8(r1) > @@ -265,7 +264,7 @@ fast_exception_return: > mtcr r10 > lwz r10,_LINK(r11) > mtlr r10 > - /* Clear the exception_marker on the stack to avoid confusing > stacktrace */ > + /* Clear the STACK_FRAME_REGS_MARKER on the stack to avoid confusing > stacktrace */ > li r10, 0 > stw r10, 8(r11) > REST_GPR(10, r11) > @@ -322,7 +321,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS) > li r0,0 > > /* > - * Leaving a stale exception_marker on the stack can confuse > + * Leaving a stale STACK_FRAME_REGS_MARKER on the stack can confuse > * the reliable stack unwinder later on. Clear it. > */ > stw r0,8(r1) > @@ -374,7 +373,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS) > mtspr SPRN_XER,r5 > > /* > - * Leaving a stale exception_marker on the stack can confuse > + * Leaving a stale STACK_FRAME_REGS_MARKER on the stack can confuse > * the reliable stack unwinder later on. Clear it. > */ > stw r0,8(r1) > diff --git a/arch/powerpc/kernel/exceptions-64e.S > b/arch/powerpc/kernel/exceptions-64e.S > index 67dc4e3179a0..08b7d6bd4da6 100644 > --- a/arch/powerpc/kernel/exceptions-64e.S > +++ b/arch/powerpc/kernel/exceptions-64e.S > @@ -389,7 +389,7 @@ exc_##n##_common: > \ > ld r9,excf+EX_R1(r13); /* load orig r1 back from PACA */ \ > lwz r10,excf+EX_CR(r13); /* load orig CR back from PACA */ \ > lbz r11,PACAIRQSOFTMASK(r13); /* get current IRQ softe */ \ > - ld r12,exception_marker@toc(r2); \ > + li r12,STACK_FRAME_REGS_MARKER; \ > li r0,0; \ > std r3,GPR10(r1); /* save r10 to stackframe */ \ > std r4,GPR11(r1); /* save r11 to stackframe */ \ > @@ -470,12 +470,6 @@ exc_##n##_bad_stack: > \ > bl hdlr; \ > b interrupt_return > > -/* This value is used to mark exception frames on the stack. */ > - .section ".toc","aw" > -exception_marker: > - .tc ID_EXC_MARKER[TC],STACK_FRAME_REGS_MARKER > - > - > /* > * And here we have the exception vectors ! > */ > diff --git a/arch/powerpc/kernel/exceptions-64s.S > b/arch/powerpc/kernel/exceptions-64s.S > index 3d0dc133a9ae..5c110e5e5819 100644 > --- a/arch/powerpc/kernel/exceptions-64s.S > +++ b/arch/powerpc/kernel/exceptions-64s.S > @@ -589,7 +589,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR) > li r9,IVEC > std r9,_TRAP(r1) /* set trap number */ > li r10,0 > - ld r11,exception_marker@toc(r2) > + li r11,STACK_FRAME_REGS_MARKER > std r10,RESULT(r1) /* clear regs->result */ > std r11,STACK_FRAME_OVERHEAD-16(r1) /* mark the frame */ > .endm > diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h > index c3286260a7d1..5cf80f29d839 100644 > --- a/arch/powerpc/kernel/head_32.h > +++ b/arch/powerpc/kernel/head_32.h > @@ -110,8 +110,7 @@ _ASM_NOKPROBE_SYMBOL(\name\()_virt) > > .macro COMMON_EXCEPTION_PROLOG_END trapno > stw r0,GPR0(r1) > - lis r10,STACK_FRAME_REGS_MARKER@ha /* exception frame marker */ > - addi r10,r10,STACK_FRAME_REGS_MARKER@l > + li r10,STACK_FRAME_REGS_MARKER /* exception frame marker */ > stw r10,8(r1) > li r10, \trapno > stw r10,_TRAP(r1) > diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S > index cf2c08902c05..cac3e1b58360 100644 > --- a/arch/powerpc/kernel/head_64.S > +++ b/arch/powerpc/kernel/head_64.S > @@ -192,13 +192,6 @@ __secondary_hold: > #endif > CLOSE_FIXED_SECTION(first_256B) > > -/* This value is used to mark exception frames on the stack. */ > - .section ".toc","aw" > -/* This value is used to mark exception frames on the stack. */ > -exception_marker: > - .tc ID_EXC_MARKER[TC],STACK_FRAME_REGS_MARKER > - .previous > - > /* > * On server, we include the exception vectors code here as it > * relies on absolute addressing which is only possible within > diff --git a/arch/powerpc/kernel/head_booke.h > b/arch/powerpc/kernel/head_booke.h > index bb6d5d0fc4ac..fe36237197c2 100644 > --- a/arch/powerpc/kernel/head_booke.h > +++ b/arch/powerpc/kernel/head_booke.h > @@ -82,8 +82,7 @@ END_BTB_FLUSH_SECTION > > .macro COMMON_EXCEPTION_PROLOG_END trapno > stw r0,GPR0(r1) > - lis r10, STACK_FRAME_REGS_MARKER@ha /* exception frame marker */ > - addi r10, r10, STACK_FRAME_REGS_MARKER@l > + li r10, STACK_FRAME_REGS_MARKER /* exception frame marker */ > stw r10, 8(r1) > li r10, \trapno > stw r10,_TRAP(r1) > diff --git a/arch/powerpc/kernel/interrupt_64.S > b/arch/powerpc/kernel/interrupt_64.S > index ce25b28cf418..14c409fd4c38 100644 > --- a/arch/powerpc/kernel/interrupt_64.S > +++ b/arch/powerpc/kernel/interrupt_64.S > @@ -92,7 +92,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name) > std r11,_TRAP(r1) > std r12,_CCR(r1) > addi r10,r1,STACK_FRAME_OVERHEAD > - ld r11,exception_marker@toc(r2) > + li r11,STACK_FRAME_REGS_MARKER > std r11,-16(r10) /* "regshere" marker */ > > BEGIN_FTR_SECTION > @@ -276,7 +276,7 @@ END_BTB_FLUSH_SECTION > std r11,_TRAP(r1) > std r12,_CCR(r1) > addi r10,r1,STACK_FRAME_OVERHEAD > - ld r11,exception_marker@toc(r2) > + li r11,STACK_FRAME_REGS_MARKER > std r11,-16(r10) /* "regshere" marker */ > > #ifdef CONFIG_PPC_BOOK3S > @@ -619,7 +619,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS) > mtspr SPRN_XER,r5 > > /* > - * Leaving a stale exception_marker on the stack can confuse > + * Leaving a stale STACK_FRAME_REGS_MARKER on the stack can confuse > * the reliable stack unwinder later on. Clear it. > */ > std r0,STACK_FRAME_OVERHEAD-16(r1)