[PATCH v3 2/3] efi: Allow use of malloc() for the EFI pool
Sughosh Ganu
sughosh.ganu at linaro.org
Mon Sep 9 09:44:10 CEST 2024
On Fri, 6 Sept 2024 at 18:31, Simon Glass <sjg at chromium.org> wrote:
>
> Hi Sughosh,
>
> On Fri, 6 Sept 2024 at 00:23, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
> >
> > On Mon, 2 Sept 2024 at 03:53, Simon Glass <sjg at chromium.org> wrote:
> > >
> > > This API call is intended for allocating small amounts of memory,
> > > similar to malloc(). The current implementation rounds up to whole pages
> > > which can waste large amounts of memory. It also implements its own
> > > malloc()-style header on each block.
> > >
> > > For certain allocations (those of type EFI_BOOT_SERVICES_DATA) we can
> > > use U-Boot's built-in malloc() instead, at least until the app starts.
> > > This avoids poluting the memory space with blocks of data which may
> > > interfere with boot scripts, etc.
> > >
> > > Once the app has started, there is no advantage to using malloc(), since
> > > it doesn't matter what memory is used: everything is under control of
> > > the EFI subsystem. Also, using malloc() after the app starts might
> > > result in running of memory, since U-Boot's malloc() space is typically
> > > quite small.
> > >
> > > In fact, malloc() is already used for most EFI-related allocations, so
> > > the impact of this change is fairly small.
> > >
> > > One side effect is that this seems to be showing up some bugs in the
> > > EFI code, since the malloc() pool becomes corrupted with some tests.
> > > This has likely crept in due to the very large gaps between allocations
> > > (around 4KB), which provides a lot of leeway when the allocation size is
> > > too small. Work around this by increasing the size for now, until these
> > > (presumed) bugs are located.
> > >
> > > Signed-off-by: Simon Glass <sjg at chromium.org>
> > > ---
> > >
> > > (no changes since v1)
> > >
> > > common/dlmalloc.c | 7 +++
> > > include/efi_loader.h | 18 ++++++
> > > include/malloc.h | 7 +++
> > > lib/efi_loader/efi_bootbin.c | 2 +
> > > lib/efi_loader/efi_memory.c | 110 ++++++++++++++++++++++++++---------
> > > 5 files changed, 117 insertions(+), 27 deletions(-)
> > >
> > > diff --git a/common/dlmalloc.c b/common/dlmalloc.c
> > > index 1ac7ce3f43c..48e9f3515f7 100644
> > > --- a/common/dlmalloc.c
> > > +++ b/common/dlmalloc.c
> > > @@ -613,6 +613,13 @@ void mem_malloc_init(ulong start, ulong size)
> > > #endif
> > > }
> > >
> > > +bool malloc_check_in_range(void *ptr)
> > > +{
> > > + ulong val = (ulong)ptr;
> > > +
> > > + return val >= mem_malloc_start && val < mem_malloc_end;
> > > +}
> > > +
> > > /* field-extraction macros */
> > >
> > > #define first(b) ((b)->fd)
> > > diff --git a/include/efi_loader.h b/include/efi_loader.h
> > > index 38971d01442..d07bc06bad4 100644
> > > --- a/include/efi_loader.h
> > > +++ b/include/efi_loader.h
> > > @@ -805,6 +805,24 @@ int efi_disk_probe(void *ctx, struct event *event);
> > > int efi_disk_remove(void *ctx, struct event *event);
> > > /* Called by board init to initialize the EFI memory map */
> > > int efi_memory_init(void);
> > > +
> > > +/**
> > > + * enum efi_alloc_flags - controls EFI memory allocation
> > > + *
> > > + * @EFIAF_USE_MALLOC: Use malloc() pool for pool allocations of type
> > > + * EFI_BOOT_SERVICES_DATA, otherwise use page allocation
> > > + */
> > > +enum efi_alloc_flags {
> > > + EFIAF_USE_MALLOC = BIT(0),
> > > +};
> > > +
> > > +/**
> > > + * efi_set_alloc() - Set behaviour of EFI memory allocation
> > > + *
> > > + * @flags: new value for allocation flags (see enum efi_alloc_flags)
> > > + */
> > > +void efi_set_alloc(int flags);
> > > +
> > > /* Adds new or overrides configuration table entry to the system table */
> > > efi_status_t efi_install_configuration_table(const efi_guid_t *guid, void *table);
> > > /* Sets up a loaded image */
> > > diff --git a/include/malloc.h b/include/malloc.h
> > > index 07d3e90a855..a64f117e2f2 100644
> > > --- a/include/malloc.h
> > > +++ b/include/malloc.h
> > > @@ -983,6 +983,13 @@ extern ulong mem_malloc_brk;
> > >
> > > void mem_malloc_init(ulong start, ulong size);
> > >
> > > +/**
> > > + * malloc_check_in_range() - Check if a pointer is within the malloc() region
> > > + *
> > > + * Return: true if within malloc() region
> > > + */
> > > +bool malloc_check_in_range(void *ptr);
> > > +
> > > #ifdef __cplusplus
> > > }; /* end of extern "C" */
> > > #endif
> > > diff --git a/lib/efi_loader/efi_bootbin.c b/lib/efi_loader/efi_bootbin.c
> > > index a87006b3c0e..5bb0fdcf75d 100644
> > > --- a/lib/efi_loader/efi_bootbin.c
> > > +++ b/lib/efi_loader/efi_bootbin.c
> > > @@ -201,6 +201,8 @@ efi_status_t efi_binary_run(void *image, size_t size, void *fdt)
> > > {
> > > efi_status_t ret;
> > >
> > > + efi_set_alloc(0);
> > > +
> >
> > Here we are setting the flags to use the efi_allocate_pages() route to
> > allocate memory, when booting into an EFI app. Do we need to set it
> > back to EFIAF_USE_MALLOC if the app exits and control lands back in
> > U-Boot? I am not sure that is being handled.
>
> I don't believe so. Once we have booted into the app, U-Boot loses
> control of its memory layout, in the sense that the
> efi_allocate_pages() has likely been called and placed things all over
> the place in the memory. People should expect this.
I am referring to a scenario where the app exits and control returns
back to U-Boot, which I believe is a valid scenario. In such a case,
should control not switch back to the malloc based allocations.
Otherwise we do not have consistent behaviour with the allocations --
any subsequent calls to efi_allocate_pool on return from an EFI app
would continue using the other (efi_allocate_pages() based) path.
This is of course with the assumption that the EFI maintainers are
fine with using this hybrid approach on the allocations.
-sughosh
>
> We can potentially deal with this if we find a specific problem, but I
> can't think of one at the moment.
>
> >
> > -sughosh
> >
> > > /* Initialize EFI drivers */
> > > ret = efi_init_obj_list();
> > > if (ret != EFI_SUCCESS) {
> > > diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
> > > index 50cb2f3898b..206d10f207a 100644
> > > --- a/lib/efi_loader/efi_memory.c
> > > +++ b/lib/efi_loader/efi_memory.c
> > > @@ -24,6 +24,14 @@ DECLARE_GLOBAL_DATA_PTR;
> > > /* Magic number identifying memory allocated from pool */
> > > #define EFI_ALLOC_POOL_MAGIC 0x1fe67ddf6491caa2
> > >
> > > +/* Flags controlling EFI memory-allocation - see enum efi_alloc_flags */
> > > +static int alloc_flags;
> > > +
> > > +void efi_set_alloc(int flags)
> > > +{
> > > + alloc_flags = flags;
> > > +}
> > > +
> > > efi_uintn_t efi_memory_map_key;
> > >
> > > struct efi_mem_list {
> > > @@ -57,8 +65,12 @@ void *efi_bounce_buffer;
> > > * The checksum calculated in function checksum() is used in FreePool() to avoid
> > > * freeing memory not allocated by AllocatePool() and duplicate freeing.
> > > *
> > > - * EFI requires 8 byte alignment for pool allocations, so we can
> > > - * prepend each allocation with these header fields.
> > > + * EFI requires 8-byte alignment for pool allocations, so we can prepend each
> > > + * allocation with these header fields.
> > > + *
> > > + * Note that before the EFI app is booted, EFI_BOOT_SERVICES_DATA allocations
> > > + * are served using malloc(), bypassing this struct. This helps to avoid memory
> > > + * fragmentation, since efi_allocate_pages() uses any pages it likes.
> > > */
> > > struct efi_pool_allocation {
> > > u64 num_pages;
> > > @@ -631,18 +643,19 @@ void *efi_alloc_aligned_pages(u64 len, int memory_type, size_t align)
> > > /**
> > > * efi_allocate_pool - allocate memory from pool
> > > *
> > > + * This uses malloc() for EFI_BOOT_SERVICES_DATA allocations if EFIAF_USE_MALLOC
> > > + * is enabled
> > > + *
> > > * @pool_type: type of the pool from which memory is to be allocated
> > > * @size: number of bytes to be allocated
> > > * @buffer: allocated memory
> > > * Return: status code
> > > */
> > > -efi_status_t efi_allocate_pool(enum efi_memory_type pool_type, efi_uintn_t size, void **buffer)
> > > +efi_status_t efi_allocate_pool(enum efi_memory_type pool_type, efi_uintn_t size,
> > > + void **buffer)
> > > {
> > > efi_status_t r;
> > > u64 addr;
> > > - struct efi_pool_allocation *alloc;
> > > - u64 num_pages = efi_size_in_pages(size +
> > > - sizeof(struct efi_pool_allocation));
> > >
> > > if (!buffer)
> > > return EFI_INVALID_PARAMETER;
> > > @@ -652,13 +665,43 @@ efi_status_t efi_allocate_pool(enum efi_memory_type pool_type, efi_uintn_t size,
> > > return EFI_SUCCESS;
> > > }
> > >
> > > - r = efi_allocate_pages(EFI_ALLOCATE_ANY_PAGES, pool_type, num_pages,
> > > - &addr);
> > > - if (r == EFI_SUCCESS) {
> > > - alloc = (struct efi_pool_allocation *)(uintptr_t)addr;
> > > - alloc->num_pages = num_pages;
> > > - alloc->checksum = checksum(alloc);
> > > - *buffer = alloc->data;
> > > + if ((alloc_flags & EFIAF_USE_MALLOC) &&
> > > + pool_type == EFI_BOOT_SERVICES_DATA) {
> > > + void *ptr;
> > > +
> > > + /*
> > > + * Some tests crash on qemu_arm etc. if the correct size is
> > > + * allocated.
> > > + * Adding 0x10 seems to fix test_efi_selftest_device_tree
> > > + * Increasing it to 0x20 seems to fix test_efi_selftest_base
> > > + * except * for riscv64 (in CI only). But 0x100 fixes CI too.
> > > + *
> > > + * This workaround can be dropped once these problems are
> > > + * resolved
> > > + */
> > > + ptr = memalign(8, size + 0x100);
> > > + if (!ptr)
> > > + return EFI_OUT_OF_RESOURCES;
> > > +
> > > + *buffer = ptr;
> > > + r = EFI_SUCCESS;
> > > + log_debug("EFI pool: malloc(%zx) = %p\n", size, ptr);
> > > + } else {
> > > + u64 num_pages = efi_size_in_pages(size +
> > > + sizeof(struct efi_pool_allocation));
> > > +
> > > + r = efi_allocate_pages(EFI_ALLOCATE_ANY_PAGES, pool_type,
> > > + num_pages, &addr);
> > > + if (r == EFI_SUCCESS) {
> > > + struct efi_pool_allocation *alloc;
> > > +
> > > + alloc = (struct efi_pool_allocation *)(uintptr_t)addr;
> > > + alloc->num_pages = num_pages;
> > > + alloc->checksum = checksum(alloc);
> > > + *buffer = alloc->data;
> > > + log_debug("EFI pool: pages alloc(%zx) type %d = %p\n",
> > > + size, pool_type, *buffer);
> > > + }
> > > }
> > >
> > > return r;
> > > @@ -686,27 +729,37 @@ void *efi_alloc(size_t size)
> > > efi_status_t efi_free_pool(void *buffer)
> > > {
> > > efi_status_t ret;
> > > - struct efi_pool_allocation *alloc;
> > >
> > > if (!buffer)
> > > return EFI_INVALID_PARAMETER;
> > >
> > > - ret = efi_check_allocated((uintptr_t)buffer, true);
> > > - if (ret != EFI_SUCCESS)
> > > - return ret;
> > > + if (malloc_check_in_range(buffer)) {
> > > + log_debug("EFI pool: free(%p)\n", buffer);
> > > + free(buffer);
> > > + ret = EFI_SUCCESS;
> > > + } else {
> > > + struct efi_pool_allocation *alloc;
> > >
> > > - alloc = container_of(buffer, struct efi_pool_allocation, data);
> > > + ret = efi_check_allocated((uintptr_t)buffer, true);
> > > + if (ret != EFI_SUCCESS)
> > > + return ret;
> > >
> > > - /* Check that this memory was allocated by efi_allocate_pool() */
> > > - if (((uintptr_t)alloc & EFI_PAGE_MASK) ||
> > > - alloc->checksum != checksum(alloc)) {
> > > - printf("%s: illegal free 0x%p\n", __func__, buffer);
> > > - return EFI_INVALID_PARAMETER;
> > > - }
> > > - /* Avoid double free */
> > > - alloc->checksum = 0;
> > > + alloc = container_of(buffer, struct efi_pool_allocation, data);
> > >
> > > - ret = efi_free_pages((uintptr_t)alloc, alloc->num_pages);
> > > + /*
> > > + * Check that this memory was allocated by efi_allocate_pool()
> > > + */
> > > + if (((uintptr_t)alloc & EFI_PAGE_MASK) ||
> > > + alloc->checksum != checksum(alloc)) {
> > > + printf("%s: illegal free 0x%p\n", __func__, buffer);
> > > + return EFI_INVALID_PARAMETER;
> > > + }
> > > + /* Avoid double free */
> > > + alloc->checksum = 0;
> > > +
> > > + ret = efi_free_pages((uintptr_t)alloc, alloc->num_pages);
> > > + log_debug("EFI pool: pages free(%p)\n", buffer);
> > > + }
> > >
> > > return ret;
> > > }
> > > @@ -926,6 +979,9 @@ static void add_u_boot_and_runtime(void)
> > >
> > > int efi_memory_init(void)
> > > {
> > > + /* use malloc() pool where possible */
> > > + efi_set_alloc(EFIAF_USE_MALLOC);
> > > +
> > > efi_add_known_memory();
> > >
> > > add_u_boot_and_runtime();
> > > --
> > > 2.34.1
> > >
>
> Regards,
> Simon
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