Subject: Re: [PATCH v3 08/13] riscv: extend execmem_params for generated code allocations

From: Mike Rapoport <[email-masked]>
Date: Sat, 23 Sep 2023 19:23:40 +0300

On Fri, Sep 22, 2023 at 12:37:07PM +0200, Alexandre Ghiti wrote:
> Hi Mike,
> 
> On 18/09/2023 09:29, Mike Rapoport wrote:
> > From: "Mike Rapoport (IBM)" <[email-masked]>
> > 
> > The memory allocations for kprobes and BPF on RISC-V are not placed in
> > the modules area and these custom allocations are implemented with
> > overrides of alloc_insn_page() and  bpf_jit_alloc_exec().
> > 
> > Slightly reorder execmem_params initialization to support both 32 and 64
> > bit variants, define EXECMEM_KPROBES and EXECMEM_BPF ranges in
> > riscv::execmem_params and drop overrides of alloc_insn_page() and
> > bpf_jit_alloc_exec().
> > 
> > Signed-off-by: Mike Rapoport (IBM) <[email-masked]>
> > ---
> >   arch/riscv/kernel/module.c         | 21 ++++++++++++++++++++-
> >   arch/riscv/kernel/probes/kprobes.c | 10 ----------
> >   arch/riscv/net/bpf_jit_core.c      | 13 -------------
> >   3 files changed, 20 insertions(+), 24 deletions(-)
> > 
> > diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> > index 343a0edfb6dd..31505ecb5c72 100644
> > --- a/arch/riscv/kernel/module.c
> > +++ b/arch/riscv/kernel/module.c
> > @@ -436,20 +436,39 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> >   	return 0;
> >   }
> > -#if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
> > +#ifdef CONFIG_MMU
> >   static struct execmem_params execmem_params __ro_after_init = {
> >   	.ranges = {
> >   		[EXECMEM_DEFAULT] = {
> >   			.pgprot = PAGE_KERNEL,
> >   			.alignment = 1,
> >   		},
> > +		[EXECMEM_KPROBES] = {
> > +			.pgprot = PAGE_KERNEL_READ_EXEC,
> > +			.alignment = 1,
> > +		},
> > +		[EXECMEM_BPF] = {
> > +			.pgprot = PAGE_KERNEL,
> > +			.alignment = 1,
> 
> 
> Not entirely sure it is the same alignment (sorry did not go through the
> entire series), but if it is, the alignment above ^ is not the same that is
> requested by our current bpf_jit_alloc_exec() implementation which is
> PAGE_SIZE.
 
This literally translates vmalloc() in alloc_insn_page() to a set of
parameters, so "1" comes from there. And using alignment of 1 with
vmalloc() implicitly sets it to PAGE_SIZE.

> > +		},
> >   	},
> >   };
> >   struct execmem_params __init *execmem_arch_params(void)
> >   {
> > +#ifdef CONFIG_64BIT
> >   	execmem_params.ranges[EXECMEM_DEFAULT].start = MODULES_VADDR;
> >   	execmem_params.ranges[EXECMEM_DEFAULT].end = MODULES_END;
> > +#else
> > +	execmem_params.ranges[EXECMEM_DEFAULT].start = VMALLOC_START;
> > +	execmem_params.ranges[EXECMEM_DEFAULT].end = VMALLOC_END;
> > +#endif
> > +
> > +	execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_START;
> > +	execmem_params.ranges[EXECMEM_KPROBES].end = VMALLOC_END;
> > +
> > +	execmem_params.ranges[EXECMEM_BPF].start = BPF_JIT_REGION_START;
> > +	execmem_params.ranges[EXECMEM_BPF].end = BPF_JIT_REGION_END;
> >   	return &execmem_params;
> >   }
> > diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
> > index 2f08c14a933d..e64f2f3064eb 100644
> > --- a/arch/riscv/kernel/probes/kprobes.c
> > +++ b/arch/riscv/kernel/probes/kprobes.c
> > @@ -104,16 +104,6 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
> >   	return 0;
> >   }
> > -#ifdef CONFIG_MMU
> > -void *alloc_insn_page(void)
> > -{
> > -	return  __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
> > -				     GFP_KERNEL, PAGE_KERNEL_READ_EXEC,
> > -				     VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
> > -				     __builtin_return_address(0));
> > -}
> > -#endif
> > -
> >   /* install breakpoint in text */
> >   void __kprobes arch_arm_kprobe(struct kprobe *p)
> >   {
> > diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
> > index 7b70ccb7fec3..c8a758f0882b 100644
> > --- a/arch/riscv/net/bpf_jit_core.c
> > +++ b/arch/riscv/net/bpf_jit_core.c
> > @@ -218,19 +218,6 @@ u64 bpf_jit_alloc_exec_limit(void)
> >   	return BPF_JIT_REGION_SIZE;
> >   }
> > -void *bpf_jit_alloc_exec(unsigned long size)
> > -{
> > -	return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START,
> > -				    BPF_JIT_REGION_END, GFP_KERNEL,
> > -				    PAGE_KERNEL, 0, NUMA_NO_NODE,
> > -				    __builtin_return_address(0));
> > -}
> > -
> > -void bpf_jit_free_exec(void *addr)
> > -{
> > -	return vfree(addr);
> > -}
> > -
> >   void *bpf_arch_text_copy(void *dst, void *src, size_t len)
> >   {
> >   	int ret;
> 
> 
> Otherwise, you can add:
> 
> Reviewed-by: Alexandre Ghiti <[email-masked]>
> 
> Thanks,
> 
> Alex
> 
> 

-- 
Sincerely yours,
Mike.