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Message-ID: <db3b71f3-2554-69b0-6ef9-a70e31d034b6@csgroup.eu>
Date: Tue, 20 Apr 2021 15:37:06 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Michael Ellerman <mpe@...erman.id.au>,
Paul Mackerras <paulus@...ba.org>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v1 2/2] powerpc: Enable OPTPROBES on PPC32
Le 20/04/2021 à 08:51, Naveen N. Rao a écrit :
> Christophe Leroy wrote:
>> For that, create a 32 bits version of patch_imm64_load_insns()
>> and create a patch_imm_load_insns() which calls
>> patch_imm32_load_insns() on PPC32 and patch_imm64_load_insns()
>> on PPC64.
>>
>> Adapt optprobes_head.S for PPC32. Use PPC_LL/PPC_STL macros instead
>> of raw ld/std, opt out things linked to paca and use stmw/lmw to
>> save/restore registers.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
>> ---
>> arch/powerpc/Kconfig | 2 +-
>> arch/powerpc/kernel/optprobes.c | 24 +++++++++++++--
>> arch/powerpc/kernel/optprobes_head.S | 46 +++++++++++++++++++---------
>> 3 files changed, 53 insertions(+), 19 deletions(-)
>
> Thanks for adding support for ppc32. It is good to see that it works without too many changes.
>
>>
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index c1344c05226c..49b538e54efb 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -227,7 +227,7 @@ config PPC
>> select HAVE_MOD_ARCH_SPECIFIC
>> select HAVE_NMI if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
>> select HAVE_HARDLOCKUP_DETECTOR_ARCH if PPC64 && PPC_BOOK3S && SMP
>> - select HAVE_OPTPROBES if PPC64
>> + select HAVE_OPTPROBES
>> select HAVE_PERF_EVENTS
>> select HAVE_PERF_EVENTS_NMI if PPC64
>> select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI &&
>> !HAVE_HARDLOCKUP_DETECTOR_ARCH
>> diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
>> index 58fdb9f66e0f..cdf87086fa33 100644
>> --- a/arch/powerpc/kernel/optprobes.c
>> +++ b/arch/powerpc/kernel/optprobes.c
>> @@ -141,11 +141,21 @@ void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
>> }
>> }
>>
>> +static void patch_imm32_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
>> +{
>> + patch_instruction((struct ppc_inst *)addr,
>> + ppc_inst(PPC_RAW_LIS(reg, IMM_H(val))));
>> + addr++;
>> +
>> + patch_instruction((struct ppc_inst *)addr,
>> + ppc_inst(PPC_RAW_ORI(reg, reg, IMM_L(val))));
>> +}
>> +
>> /*
>> * Generate instructions to load provided immediate 64-bit value
>> * to register 'reg' and patch these instructions at 'addr'.
>> */
>> -static void patch_imm64_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
>> +static void patch_imm64_load_insns(unsigned long long val, int reg, kprobe_opcode_t *addr)
>
> Do you really need this?
Without it I get:
from arch/powerpc/kernel/optprobes.c:8:
arch/powerpc/kernel/optprobes.c: In function 'patch_imm64_load_insns':
arch/powerpc/kernel/optprobes.c:163:14: error: right shift count >= width of type
[-Werror=shift-count-overflow]
163 | ((val >> 48) & 0xffff)));
| ^~
./arch/powerpc/include/asm/inst.h:69:48: note: in definition of macro 'ppc_inst'
69 | #define ppc_inst(x) ((struct ppc_inst){ .val = x })
| ^
arch/powerpc/kernel/optprobes.c:169:31: error: right shift count >= width of type
[-Werror=shift-count-overflow]
169 | ___PPC_RS(reg) | ((val >> 32) & 0xffff)));
| ^~
./arch/powerpc/include/asm/inst.h:69:48: note: in definition of macro 'ppc_inst'
69 | #define ppc_inst(x) ((struct ppc_inst){ .val = x })
| ^
>
>> {
>> /* lis reg,(op)@highest */
>> patch_instruction((struct ppc_inst *)addr,
>> @@ -177,6 +187,14 @@ static void patch_imm64_load_insns(unsigned long val, int reg, kprobe_opcode_t *
>> ___PPC_RS(reg) | (val & 0xffff)));
>> }
>>
>> +static void patch_imm_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
>> +{
>> + if (IS_ENABLED(CONFIG_PPC64))
>> + patch_imm64_load_insns(val, reg, addr);
>> + else
>> + patch_imm32_load_insns(val, reg, addr);
>> +}
>> +
>> int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>> {
>> struct ppc_inst branch_op_callback, branch_emulate_step, temp;
>> @@ -230,7 +248,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>> * Fixup the template with instructions to:
>> * 1. load the address of the actual probepoint
>> */
>> - patch_imm64_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX);
>> + patch_imm_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX);
>>
>> /*
>> * 2. branch to optimized_callback() and emulate_step()
>> @@ -264,7 +282,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>> * 3. load instruction to be emulated into relevant register, and
>> */
>> temp = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
>> - patch_imm64_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX);
>> + patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX);
>>
>> /*
>> * 4. branch back from trampoline
>> diff --git a/arch/powerpc/kernel/optprobes_head.S b/arch/powerpc/kernel/optprobes_head.S
>> index ff8ba4d3824d..49f31e554573 100644
>> --- a/arch/powerpc/kernel/optprobes_head.S
>> +++ b/arch/powerpc/kernel/optprobes_head.S
>> @@ -30,39 +30,47 @@ optinsn_slot:
>> .global optprobe_template_entry
>> optprobe_template_entry:
>> /* Create an in-memory pt_regs */
>> - stdu r1,-INT_FRAME_SIZE(r1)
>> + PPC_STLU r1,-INT_FRAME_SIZE(r1)
>> SAVE_GPR(0,r1)
>> /* Save the previous SP into stack */
>> addi r0,r1,INT_FRAME_SIZE
>> - std r0,GPR1(r1)
>> + PPC_STL r0,GPR1(r1)
>> +#ifdef CONFIG_PPC64
>> SAVE_10GPRS(2,r1)
>> SAVE_10GPRS(12,r1)
>> SAVE_10GPRS(22,r1)
>> +#else
>> + stmw r2, GPR2(r1)
>> +#endif
>> /* Save SPRS */
>> mfmsr r5
>> - std r5,_MSR(r1)
>> + PPC_STL r5,_MSR(r1)
>> li r5,0x700
>> - std r5,_TRAP(r1)
>> + PPC_STL r5,_TRAP(r1)
>> li r5,0
>> - std r5,ORIG_GPR3(r1)
>> - std r5,RESULT(r1)
>> + PPC_STL r5,ORIG_GPR3(r1)
>> + PPC_STL r5,RESULT(r1)
>> mfctr r5
>> - std r5,_CTR(r1)
>> + PPC_STL r5,_CTR(r1)
>> mflr r5
>> - std r5,_LINK(r1)
>> + PPC_STL r5,_LINK(r1)
>> mfspr r5,SPRN_XER
>> - std r5,_XER(r1)
>> + PPC_STL r5,_XER(r1)
>> mfcr r5
>> - std r5,_CCR(r1)
>> + PPC_STL r5,_CCR(r1)
>> +#ifdef CONFIG_PPC64
>> lbz r5,PACAIRQSOFTMASK(r13)
>> std r5,SOFTE(r1)
>> +#endif
>>
>> /*
>> * We may get here from a module, so load the kernel TOC in r2.
>> * The original TOC gets restored when pt_regs is restored
>> * further below.
>> */
>> +#ifdef CONFIG_PPC64
>> ld r2,PACATOC(r13)
>> +#endif
>
> Are the ISA and ABI documents for ppc32 available publicly?
ABI: https://wiki.raptorcs.com/w/images/0/03/Power-Arch-32-bit-ABI-supp-1.0-Unified.pdf
ISA: https://www.nxp.com/files-static/product/doc/MPCFPE32B.pdf
> I would have thought that the TOC issues
> apply to ppc32 as well, but want to understand why this isn't a problem there.
r2 is the pointer to 'current' on PPC32.
No TOC.
>
>>
>> .global optprobe_template_op_address
>> optprobe_template_op_address:
>> @@ -72,9 +80,11 @@ optprobe_template_op_address:
>> */
>> nop
>> nop
>> +#ifdef CONFIG_PPC64
>> nop
>> nop
>> nop
>> +#endif
>> /* 2. pt_regs pointer in r4 */
>> addi r4,r1,STACK_FRAME_OVERHEAD
>>
>> @@ -94,9 +104,11 @@ optprobe_template_insn:
>> /* 2, Pass instruction to be emulated in r4 */
>> nop
>> nop
>> +#ifdef CONFIG_PPC64
>> nop
>> nop
>> nop
>> +#endif
>
> It would be nice to put these behind a macro so as to avoid these #ifdef blocks here, as well as
> with the register save/restore sequence.
>
Will see what I can do
Christophe
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