Messages in this thread | | | Subject | Re: [PATCH v2] riscv: Map the kernel with correct permissions the first time | From | Alex Ghiti <> | Date | Fri, 28 May 2021 10:24:43 +0200 |
| |
Hi Christoph,
Le 27/05/2021 à 08:35, Christoph Hellwig a écrit : > On Wed, May 26, 2021 at 03:41:10PM +0200, Alexandre Ghiti wrote: >> #ifdef CONFIG_64BIT >> +#define is_kernel_mapping(x) ((x) >= kernel_virt_addr && (x) < (kernel_virt_addr + load_sz)) >> +#define is_linear_mapping(x) ((x) >= PAGE_OFFSET && (x) < kernel_virt_addr) >> + > > Overly long lines. Independ of that complex macros are generally much > more readable if they are written more function-like, that is the name > and paramtes are kept on a line of their own: > > #define is_kernel_mapping(x) \ > ((x) >= kernel_virt_addr && (x) < (kernel_virt_addr + load_sz)) > > But what is the reason to not make them type-safe inline functions > anyway?
No reason. I will then make those macros inline functions and send another patchset to make the below macro an inline function too.
> >> #define __va_to_pa_nodebug(x) ({ \ >> unsigned long _x = x; \ >> - (_x < kernel_virt_addr) ? \ >> + is_linear_mapping(_x) ? \ >> linear_mapping_va_to_pa(_x) : kernel_mapping_va_to_pa(_x); \ >> }) > > ... especially for something complex like this. > >> +static inline bool is_va_kernel_lm_alias_text(uintptr_t va) >> +{ >> + return (va >= (uintptr_t)lm_alias(_start) && va < (uintptr_t)lm_alias(__init_text_begin)); > > Overly long line as well. And useless braces.
Ok.
> >> +static inline bool is_va_kernel_init_text(uintptr_t va) >> +{ >> + return (va >= (uintptr_t)__init_text_begin && va < (uintptr_t)__init_data_begin); >> +} > > Same here.
checkpatch does not complain about those lines which are under 100 characters, what's the point in breaking them on multiple lines?
> >> +#ifdef CONFIG_STRICT_KERNEL_RWX >> +static __init pgprot_t pgprot_from_va(uintptr_t va) >> +{ >> +#ifdef CONFIG_64BIT >> + if (is_va_kernel_text(va) || is_va_kernel_init_text(va)) >> + return PAGE_KERNEL_READ_EXEC; >> + >> + /* >> + * We must mark only text as read-only as init text will get freed later >> + * and rodata section is marked readonly in mark_rodata_ro. >> + */ >> + if (is_va_kernel_lm_alias_text(va)) >> + return PAGE_KERNEL_READ; >> + >> + return PAGE_KERNEL; >> +#else >> + if (is_va_kernel_text(va)) >> + return PAGE_KERNEL_READ_EXEC; >> + >> + if (is_va_kernel_init_text(va)) >> + return PAGE_KERNEL_EXEC; >> + >> + return PAGE_KERNEL; >> +#endif /* CONFIG_64BIT */ >> +} > > If the entire function is different for config symbols please just > split it into two separate functions. But to make the difference more > clear IS_ENABLED might fit better here: > > static __init pgprot_t pgprot_from_va(uintptr_t va) > { > if (is_va_kernel_text(va)) > return PAGE_KERNEL_READ_EXEC; > if (is_va_kernel_init_text(va)) > return IS_ENABLED(CONFIG_64BIT) ? > PAGE_KERNEL_READ_EXEC : PAGE_KERNEL_EXEC; > if (IS_ENABLED(CONFIG_64BIT) && is_va_kernel_lm_alias_text(va)) > return PAGE_KERNEL_READ; > return PAGE_KERNEL; > } > > Preferable with comments explaining the 32-bit vs 64-bit difference.
Ok this is more compact, I'll do that with the comment.
> >> +void mark_rodata_ro(void) >> +{ >> + unsigned long rodata_start = (unsigned long)__start_rodata; >> + unsigned long data_start = (unsigned long)_data; >> + unsigned long __maybe_unused lm_rodata_start = (unsigned long)lm_alias(__start_rodata); >> + unsigned long __maybe_unused lm_data_start = (unsigned long)lm_alias(_data); >> + >> + set_memory_ro(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT); >> +#ifdef CONFIG_64BIT >> + set_memory_ro(lm_rodata_start, (lm_data_start - lm_rodata_start) >> PAGE_SHIFT); >> +#endif > > Lots of unreadable overly lone lines. Why not add a helper and do > something like: > > static void set_kernel_memory_ro(char *startp, char *endp) > { > unsigned long start = (unsigned long)startp; > unsigned long end = (unsigned long)endp; > > set_memory_ro(start, (start - end) >> PAGE_SHIFT); > } > > set_kernel_memory_ro(_start_rodata, _data); > if (IS_ENABLED(CONFIG_64BIT)) > set_kernel_memory_ro(lm_alias(__start_rodata), lm_alias(_data)); > >
Ok, that's better indeed. I will do something like that instead, to avoid multiple versions of this helper:
int set_kernel_memory(char *startp, char *endp,
int (*set_memory)(unsigned long start, int num_pages))
>> +static __init pgprot_t pgprot_from_va(uintptr_t va) >> +{ >> +#ifdef CONFIG_64BIT >> + if (is_kernel_mapping(va)) >> + return PAGE_KERNEL_EXEC; >> + >> + if (is_linear_mapping(va)) >> + return PAGE_KERNEL; >> + >> + return PAGE_KERNEL; >> +#else >> + return PAGE_KERNEL_EXEC; >> +#endif /* CONFIG_64BIT */ >> +} >> +#endif /* CONFIG_STRICT_KERNEL_RWX */ >> + > > Same comment as for the other version. This could become: > > static __init pgprot_t pgprot_from_va(uintptr_t va) > { > if (IS_ENABLED(CONFIG_64BIT) && !is_kernel_mapping(va)) > return PAGE_KERNEL; > return PAGE_KERNEL_EXEC; > }
Ok I'll do that.
> >> -static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size) >> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size, bool early) > > Overly long line. > >> for (va = kernel_virt_addr; va < end_va; va += map_size) >> create_pgd_mapping(pgdir, va, >> load_pa + (va - kernel_virt_addr), >> - map_size, PAGE_KERNEL_EXEC); >> + map_size, early ? PAGE_KERNEL_EXEC : pgprot_from_va(va)); > > Same here. But why not pass in a "pgprot_t ram_pgprot" instead of the > bool, which would be self-documenting.
This function is used to map the kernel mapping, the pgprot_t is then different in create_kernel_page_table depending on the virtual address so I can't pass a single pgprot_t for that or I would need a dummy pgprot_t to test anyway.
Thank you for your review,
Alex
> > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv >
| |