| Message ID | 20220923032512.535725-2-npiggin@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | powerpc/64: avoid GOT addressing, don't put data in TOC | expand |
Le 23/09/2022 à 05:25, Nicholas Piggin a écrit : > Using a 32-bit constant for this marker allows it to be loaded with > two ALU instructions, like 32-bit. This avoids a TOC entry and a > TOC load that depends on the r2 value that has just been loaded from > the PACA. > > This changes the value for 32-bit as well, so both have the same > value in the low 4 bytes and 64-bit has 0xffffffff in the top bytes. > > Signed-off-by: Nicholas Piggin <npiggin@gmail.com> > --- > arch/powerpc/include/asm/ptrace.h | 5 +++-- > arch/powerpc/kernel/entry_32.S | 6 +++--- > arch/powerpc/kernel/exceptions-64e.S | 8 +------- > arch/powerpc/kernel/exceptions-64s.S | 2 +- > arch/powerpc/kernel/head_64.S | 7 ------- > arch/powerpc/kernel/interrupt_64.S | 6 +++--- > 6 files changed, 11 insertions(+), 23 deletions(-) > > diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h > index a03403695cd4..49d720bb888b 100644 > --- a/arch/powerpc/include/asm/ptrace.h > +++ b/arch/powerpc/include/asm/ptrace.h > @@ -99,6 +99,9 @@ struct pt_regs > > #define STACK_FRAME_WITH_PT_REGS (STACK_FRAME_OVERHEAD + sizeof(struct pt_regs)) > > +/* 0xffffffff8d9a988d on 64-bit */ > +#define STACK_FRAME_REGS_MARKER ASM_CONST(-0x72656773) /* 0x8d9a988d */ > + 0x72656773 is "REGS" in ASCII (Big Endian) and you can spot it immediatly in a memory dump. 0x7265677368657265 is "REGSHERE". 0x8d9a988d is not printable. Don't know if it can be a problem. Christophe
On Fri Sep 23, 2022 at 3:34 PM AEST, Christophe Leroy wrote: > > > Le 23/09/2022 à 05:25, Nicholas Piggin a écrit : > > Using a 32-bit constant for this marker allows it to be loaded with > > two ALU instructions, like 32-bit. This avoids a TOC entry and a > > TOC load that depends on the r2 value that has just been loaded from > > the PACA. > > > > This changes the value for 32-bit as well, so both have the same > > value in the low 4 bytes and 64-bit has 0xffffffff in the top bytes. > > > > Signed-off-by: Nicholas Piggin <npiggin@gmail.com> > > --- > > arch/powerpc/include/asm/ptrace.h | 5 +++-- > > arch/powerpc/kernel/entry_32.S | 6 +++--- > > arch/powerpc/kernel/exceptions-64e.S | 8 +------- > > arch/powerpc/kernel/exceptions-64s.S | 2 +- > > arch/powerpc/kernel/head_64.S | 7 ------- > > arch/powerpc/kernel/interrupt_64.S | 6 +++--- > > 6 files changed, 11 insertions(+), 23 deletions(-) > > > > diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h > > index a03403695cd4..49d720bb888b 100644 > > --- a/arch/powerpc/include/asm/ptrace.h > > +++ b/arch/powerpc/include/asm/ptrace.h > > @@ -99,6 +99,9 @@ struct pt_regs > > > > #define STACK_FRAME_WITH_PT_REGS (STACK_FRAME_OVERHEAD + sizeof(struct pt_regs)) > > > > +/* 0xffffffff8d9a988d on 64-bit */ > > +#define STACK_FRAME_REGS_MARKER ASM_CONST(-0x72656773) /* 0x8d9a988d */ > > + > > 0x72656773 is "REGS" in ASCII (Big Endian) and you can spot it > immediatly in a memory dump. > 0x7265677368657265 is "REGSHERE". > > 0x8d9a988d is not printable. > > Don't know if it can be a problem. Oh. I guess it doesn't really matter if it has zeroes or f in the top 4 bytes so I should keep it "REGS" then. I was thinking about later moving it into the reserved word next to the CR word on 64-bit so we would only have 4 bytes for it anyway. Thanks, Nick
diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h index a03403695cd4..49d720bb888b 100644 --- a/arch/powerpc/include/asm/ptrace.h +++ b/arch/powerpc/include/asm/ptrace.h @@ -99,6 +99,9 @@ struct pt_regs #define STACK_FRAME_WITH_PT_REGS (STACK_FRAME_OVERHEAD + sizeof(struct pt_regs)) +/* 0xffffffff8d9a988d on 64-bit */ +#define STACK_FRAME_REGS_MARKER ASM_CONST(-0x72656773) /* 0x8d9a988d */ + #ifdef __powerpc64__ /* @@ -115,7 +118,6 @@ 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_INT_FRAME_SIZE (sizeof(struct pt_regs) + \ STACK_FRAME_OVERHEAD + KERNEL_REDZONE_SIZE) #define STACK_FRAME_MARKER 12 @@ -136,7 +138,6 @@ 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_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..c2516f982cfa 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -265,7 +265,7 @@ fast_exception_return: mtcr r10 lwz r10,_LINK(r11) mtlr r10 - /* Clear the exception_marker on the stack to avoid confusing stacktrace */ + /* Clear the exception marker on the stack to avoid confusing stacktrace */ li r10, 0 stw r10, 8(r11) REST_GPR(10, r11) @@ -322,7 +322,7 @@ 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 exception marker on the stack can confuse * the reliable stack unwinder later on. Clear it. */ stw r0,8(r1) @@ -374,7 +374,7 @@ 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 exception 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..08a3139079b7 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); \ + LOAD_REG_IMMEDIATE(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..9d375ea58add 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) + LOAD_REG_IMMEDIATE(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_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/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S index ce25b28cf418..ee2d2d410c5a 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) + LOAD_REG_IMMEDIATE(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) + LOAD_REG_IMMEDIATE(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)
Using a 32-bit constant for this marker allows it to be loaded with two ALU instructions, like 32-bit. This avoids a TOC entry and a TOC load that depends on the r2 value that has just been loaded from the PACA. This changes the value for 32-bit as well, so both have the same value in the low 4 bytes and 64-bit has 0xffffffff in the top bytes. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/include/asm/ptrace.h | 5 +++-- arch/powerpc/kernel/entry_32.S | 6 +++--- arch/powerpc/kernel/exceptions-64e.S | 8 +------- arch/powerpc/kernel/exceptions-64s.S | 2 +- arch/powerpc/kernel/head_64.S | 7 ------- arch/powerpc/kernel/interrupt_64.S | 6 +++--- 6 files changed, 11 insertions(+), 23 deletions(-)