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Message-ID: <CA+V-a8tLhbLs7V_vbrzfFcFbqfCiWZAEDrxftzn_Udsa=hb6ng@mail.gmail.com>
Date: Mon, 4 Dec 2023 20:30:55 +0000
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Charlie Jenkins <charlie@...osinc.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>, Ron Economos <re@...z.net>,
Samuel Holland <samuel.holland@...ive.com>,
Andreas Schwab <schwab@...ux-m68k.org>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] riscv: Safely remove entries from relocation list
On Mon, Nov 27, 2023 at 10:08 PM Charlie Jenkins <charlie@...osinc.com> wrote:
>
> Use the safe versions of list and hlist iteration to safely remove
> entries from the module relocation lists. To allow mutliple threads to
> load modules concurrently, move relocation list pointers onto the stack
> rather than using global variables.
>
> Fixes: 8fd6c5142395 ("riscv: Add remaining module relocations")
> Reported-by: Ron Economos <re@...z.net>
> Closes: https://lore.kernel.org/linux-riscv/444de86a-7e7c-4de7-5d1d-c1c40eefa4ba@w6rz.net
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> ---
> arch/riscv/kernel/module.c | 110 +++++++++++++++++++++++++++++++++------------
> 1 file changed, 82 insertions(+), 28 deletions(-)
>
This fixes issues seen on RZ/Five SMARC EVK.
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com> #On
RZ/Five SMARC EVK
Cheers,
Prabhakar
> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> index 56a8c78e9e21..53593fe58cd8 100644
> --- a/arch/riscv/kernel/module.c
> +++ b/arch/riscv/kernel/module.c
> @@ -40,15 +40,6 @@ struct relocation_handlers {
> long buffer);
> };
>
> -unsigned int initialize_relocation_hashtable(unsigned int num_relocations);
> -void process_accumulated_relocations(struct module *me);
> -int add_relocation_to_accumulate(struct module *me, int type, void *location,
> - unsigned int hashtable_bits, Elf_Addr v);
> -
> -struct hlist_head *relocation_hashtable;
> -
> -struct list_head used_buckets_list;
> -
> /*
> * The auipc+jalr instruction pair can reach any PC-relative offset
> * in the range [-2^31 - 2^11, 2^31 - 2^11)
> @@ -604,7 +595,10 @@ static const struct relocation_handlers reloc_handlers[] = {
> /* 192-255 nonstandard ABI extensions */
> };
>
> -void process_accumulated_relocations(struct module *me)
> +static void
> +process_accumulated_relocations(struct module *me,
> + struct hlist_head **relocation_hashtable,
> + struct list_head *used_buckets_list)
> {
> /*
> * Only ADD/SUB/SET/ULEB128 should end up here.
> @@ -624,18 +618,25 @@ void process_accumulated_relocations(struct module *me)
> * - Each relocation entry for a location address
> */
> struct used_bucket *bucket_iter;
> + struct used_bucket *bucket_iter_tmp;
> struct relocation_head *rel_head_iter;
> + struct hlist_node *rel_head_iter_tmp;
> struct relocation_entry *rel_entry_iter;
> + struct relocation_entry *rel_entry_iter_tmp;
> int curr_type;
> void *location;
> long buffer;
>
> - list_for_each_entry(bucket_iter, &used_buckets_list, head) {
> - hlist_for_each_entry(rel_head_iter, bucket_iter->bucket, node) {
> + list_for_each_entry_safe(bucket_iter, bucket_iter_tmp,
> + used_buckets_list, head) {
> + hlist_for_each_entry_safe(rel_head_iter, rel_head_iter_tmp,
> + bucket_iter->bucket, node) {
> buffer = 0;
> location = rel_head_iter->location;
> - list_for_each_entry(rel_entry_iter,
> - rel_head_iter->rel_entry, head) {
> + list_for_each_entry_safe(rel_entry_iter,
> + rel_entry_iter_tmp,
> + rel_head_iter->rel_entry,
> + head) {
> curr_type = rel_entry_iter->type;
> reloc_handlers[curr_type].reloc_handler(
> me, &buffer, rel_entry_iter->value);
> @@ -648,11 +649,14 @@ void process_accumulated_relocations(struct module *me)
> kfree(bucket_iter);
> }
>
> - kfree(relocation_hashtable);
> + kfree(*relocation_hashtable);
> }
>
> -int add_relocation_to_accumulate(struct module *me, int type, void *location,
> - unsigned int hashtable_bits, Elf_Addr v)
> +static int add_relocation_to_accumulate(struct module *me, int type,
> + void *location,
> + unsigned int hashtable_bits, Elf_Addr v,
> + struct hlist_head *relocation_hashtable,
> + struct list_head *used_buckets_list)
> {
> struct relocation_entry *entry;
> struct relocation_head *rel_head;
> @@ -661,6 +665,10 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
> unsigned long hash;
>
> entry = kmalloc(sizeof(*entry), GFP_KERNEL);
> +
> + if (!entry)
> + return -ENOMEM;
> +
> INIT_LIST_HEAD(&entry->head);
> entry->type = type;
> entry->value = v;
> @@ -669,7 +677,10 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
>
> current_head = &relocation_hashtable[hash];
>
> - /* Find matching location (if any) */
> + /*
> + * Search for the relocation_head for the relocations that happen at the
> + * provided location
> + */
> bool found = false;
> struct relocation_head *rel_head_iter;
>
> @@ -681,19 +692,45 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
> }
> }
>
> + /*
> + * If there has not yet been any relocations at the provided location,
> + * create a relocation_head for that location and populate it with this
> + * relocation_entry.
> + */
> if (!found) {
> rel_head = kmalloc(sizeof(*rel_head), GFP_KERNEL);
> +
> + if (!rel_head) {
> + kfree(entry);
> + return -ENOMEM;
> + }
> +
> rel_head->rel_entry =
> kmalloc(sizeof(struct list_head), GFP_KERNEL);
> +
> + if (!rel_head->rel_entry) {
> + kfree(entry);
> + kfree(rel_head);
> + return -ENOMEM;
> + }
> +
> INIT_LIST_HEAD(rel_head->rel_entry);
> rel_head->location = location;
> INIT_HLIST_NODE(&rel_head->node);
> if (!current_head->first) {
> bucket =
> kmalloc(sizeof(struct used_bucket), GFP_KERNEL);
> +
> + if (!bucket) {
> + kfree(entry);
> + kfree(rel_head);
> + kfree(rel_head->rel_entry);
> + return -ENOMEM;
> + }
> +
> INIT_LIST_HEAD(&bucket->head);
> bucket->bucket = current_head;
> - list_add(&bucket->head, &used_buckets_list);
> + list_add(&bucket->head, used_buckets_list);
> }
> hlist_add_head(&rel_head->node, current_head);
> }
> @@ -704,7 +741,9 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
> return 0;
> }
>
> -unsigned int initialize_relocation_hashtable(unsigned int num_relocations)
> +static unsigned int
> +initialize_relocation_hashtable(unsigned int num_relocations,
> + struct hlist_head **relocation_hashtable)
> {
> /* Can safely assume that bits is not greater than sizeof(long) */
> unsigned long hashtable_size = roundup_pow_of_two(num_relocations);
> @@ -720,12 +759,13 @@ unsigned int initialize_relocation_hashtable(unsigned int num_relocations)
>
> hashtable_size <<= should_double_size;
>
> - relocation_hashtable = kmalloc_array(hashtable_size,
> - sizeof(*relocation_hashtable),
> - GFP_KERNEL);
> - __hash_init(relocation_hashtable, hashtable_size);
> + *relocation_hashtable = kmalloc_array(hashtable_size,
> + sizeof(*relocation_hashtable),
> + GFP_KERNEL);
> + if (!*relocation_hashtable)
> + return -ENOMEM;
>
> - INIT_LIST_HEAD(&used_buckets_list);
> + __hash_init(*relocation_hashtable, hashtable_size);
>
> return hashtable_bits;
> }
> @@ -742,7 +782,17 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> Elf_Addr v;
> int res;
> unsigned int num_relocations = sechdrs[relsec].sh_size / sizeof(*rel);
> - unsigned int hashtable_bits = initialize_relocation_hashtable(num_relocations);
> + struct hlist_head *relocation_hashtable;
> + struct list_head used_buckets_list;
> + unsigned int hashtable_bits;
> +
> + hashtable_bits = initialize_relocation_hashtable(num_relocations,
> + &relocation_hashtable);
> +
> + if (hashtable_bits < 0)
> + return hashtable_bits;
> +
> + INIT_LIST_HEAD(&used_buckets_list);
>
> pr_debug("Applying relocate section %u to %u\n", relsec,
> sechdrs[relsec].sh_info);
> @@ -823,14 +873,18 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> }
>
> if (reloc_handlers[type].accumulate_handler)
> - res = add_relocation_to_accumulate(me, type, location, hashtable_bits, v);
> + res = add_relocation_to_accumulate(me, type, location,
> + hashtable_bits, v,
> + relocation_hashtable,
> + &used_buckets_list);
> else
> res = handler(me, location, v);
> if (res)
> return res;
> }
>
> - process_accumulated_relocations(me);
> + process_accumulated_relocations(me, &relocation_hashtable,
> + &used_buckets_list);
>
> return 0;
> }
>
> --
> 2.42.0
>
>
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> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
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