Re: [RFC PATCH 1/7] powerpc: use 16-bit immediate for STACK_FRAME_REGS_MARKER
Le 23/09/2022 à 09:32, Michael Ellerman a écrit : > Christophe Leroy writes: >> 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. > > Yeah "regshere" has definitely saved me some time over the years > starting at memory dumps. > > I'd settle for 0x + "regs". That's not a sign-extended 32 bits value
Re: [RFC PATCH 1/7] powerpc: use 16-bit immediate for STACK_FRAME_REGS_MARKER
Christophe Leroy writes: > 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. Yeah "regshere" has definitely saved me some time over the years starting at memory dumps. I'd settle for 0x + "regs". cheers
Re: [RFC PATCH 1/7] powerpc: use 16-bit immediate for STACK_FRAME_REGS_MARKER
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 0xba51 ? Why not 0xdead like PPC64 ? Christophe > > Signed-off-by: Nicholas Piggin > --- > 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_OVERHEAD112 /* 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(0xdead) > #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_SIZE32 > @@ -136,7 +136,7 @@ struct pt_regs > #define KERNEL_REDZONE_SIZE 0 > #define STACK_FRAME_OVERHEAD16 /* 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(0xba51) > #define STACK_INT_FRAME_SIZE(sizeof(struct pt_regs) + > STACK_FRAME_OVERHEAD) > #define STACK_FRAME_MARKER 2 > #define STACK_FRAME_MIN_SIZESTACK_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) > - addir12,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: > mtcrr10 > lwz r10,_LINK(r11) > mtlrr10 > - /* 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
[RFC PATCH 1/7] powerpc: use 16-bit immediate for STACK_FRAME_REGS_MARKER
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. Signed-off-by: Nicholas Piggin --- 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_SAVE2 /* Location of LR in stack frame */ -#define STACK_FRAME_REGS_MARKERASM_CONST(0x7265677368657265) +#define STACK_FRAME_REGS_MARKERASM_CONST(0xdead) #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_SIZE0 #define STACK_FRAME_OVERHEAD 16 /* size of minimum stack frame */ #define STACK_FRAME_LR_SAVE1 /* Location of LR in stack frame */ -#define STACK_FRAME_REGS_MARKERASM_CONST(0x72656773) +#define STACK_FRAME_REGS_MARKERASM_CONST(0xba51) #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) - addir12,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: mtcrr10 lwz r10,_LINK(r11) mtlrr10 - /* 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;
