Messages in this thread Patch in this message | | | Date | Fri, 14 Aug 2020 14:38:16 -0400 | From | Steven Rostedt <> | Subject | Re: [RFC PATCH] vsprintf: Add %pv extension replacement for print_vma_addr |
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On Fri, 14 Aug 2020 10:53:03 -0700 Joe Perches <joe@perches.com> wrote:
> There is a print_vma_addr function used several places > that requires KERN_CONT use. > > Add a %pv mechanism to avoid the need for KERN_CONT. > > An example conversion is arch/x86/kernel/signal.c > > from: > if (show_unhandled_signals && printk_ratelimit()) { > printk("%s" > "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx", > task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG, > me->comm, me->pid, where, frame, > regs->ip, regs->sp, regs->orig_ax); > print_vma_addr(KERN_CONT " in ", regs->ip); > pr_cont("\n"); > to: > printk("%s" > "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx in %pv\n", > task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG, > me->comm, me->pid, where, frame, > regs->ip, regs->sp, regs->orig_ax, (void *)regs->ip); > --- > lib/vsprintf.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 52 insertions(+) > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index c155769559ab..654402c43f8d 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -995,6 +995,12 @@ static const struct printf_spec default_dec_spec = { > .precision = -1, > }; > > +static const struct printf_spec default_hex_spec = { > + .base = 16, > + .precision = -1, > + .flags = SMALL, > +}; > + > static const struct printf_spec default_dec02_spec = { > .base = 10, > .field_width = 2, > @@ -2089,6 +2095,50 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode, > return widen_string(buf, buf - buf_start, end, spec); > } > > +static noinline_for_stack > +char *vma_addr(char *buf, char *end, void *ip, > + struct printf_spec spec, const char *fmt) > +{ > +#ifdef CONFIG_MMU > + struct mm_struct *mm = current->mm; > + struct vm_area_struct *vma; > + > + /* > + * we might be running from an atomic context so we cannot sleep > + */ > + if (!mmap_read_trylock(mm)) > + return buf; > + > + vma = find_vma(mm, (unsigned long)ip); > + if (vma && vma->vm_file) { > + char *p; > + struct file *f = vma->vm_file; > + char *page = (char *)__get_free_page(GFP_NOWAIT); > + > + if (page) { > + p = file_path(f, page, PAGE_SIZE); > + if (IS_ERR(p)) > + p = "?"; > + buf = string(buf, end, kbasename(p), default_str_spec); > + buf = string_nocheck(buf, end, "[", default_str_spec); > + buf = pointer_string(buf, end, > + (void *)vma->vm_start, > + default_hex_spec); > + buf = string_nocheck(buf, end, "+", default_str_spec); > + buf = pointer_string(buf, end, > + (void *)(vma->vm_end - vma->vm_start), > + default_hex_spec); > + buf = string_nocheck(buf, end, "]", default_str_spec); > + free_page((unsigned long)page); > + } > + } > + mmap_read_unlock(mm); > +#else > + buf = string_nocheck(buf, end, "CONFIG_MMU=n", default_str_spec); > +#endif
I'm fine with all his, but I feel more comfortable if this patch created a single copy of the code. Perhaps add:
diff --git a/mm/memory.c b/mm/memory.c index 87ec87cdc1ff..795a4db4d83d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4771,32 +4771,7 @@ EXPORT_SYMBOL_GPL(access_process_vm); */ void print_vma_addr(char *prefix, unsigned long ip) { - struct mm_struct *mm = current->mm; - struct vm_area_struct *vma; - - /* - * we might be running from an atomic context so we cannot sleep - */ - if (!mmap_read_trylock(mm)) - return; - - vma = find_vma(mm, ip); - if (vma && vma->vm_file) { - struct file *f = vma->vm_file; - char *buf = (char *)__get_free_page(GFP_NOWAIT); - if (buf) { - char *p; - - p = file_path(f, buf, PAGE_SIZE); - if (IS_ERR(p)) - p = "?"; - printk("%s%s[%lx+%lx]", prefix, kbasename(p), - vma->vm_start, - vma->vm_end - vma->vm_start); - free_page((unsigned long)buf); - } - } - mmap_read_unlock(mm); + printk("%s%pv", prefix, ip); } #if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
And of course this would need for documentation.
-- Steve
> + return buf; > +} > + > /* > * Show a '%p' thing. A kernel extension is that the '%p' is followed > * by an extra set of alphanumeric characters that are extended format > @@ -2254,6 +2304,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, > return uuid_string(buf, end, ptr, spec, fmt); > case 'V': > return va_format(buf, end, ptr, spec, fmt); > + case 'v': > + return vma_addr(buf, end, ptr, spec, fmt); > case 'K': > return restricted_pointer(buf, end, ptr, spec); > case 'N': >
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