From 0133b19ced41a10134973c374adb3429323b20e4 Mon Sep 17 00:00:00 2001 From: Tushar Sugandhi Date: Mon, 3 Jan 2022 14:08:56 -0800 Subject: [PATCH 1/3] kexec_file: Add mechanism to update kexec segments kexec_update_segment allows a given segment in kexec_image to have its contents updated. This is useful if the current kernel wants to send information to the next kernel that is up-to-date at the time of reboot. Co-developed-by: Thiago Jung Bauermann Signed-off-by: Thiago Jung Bauermann Signed-off-by: Tushar Sugandhi --- include/linux/kexec.h | 2 + kernel/kexec_core.c | 102 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 104 insertions(+) diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 0c994ae37729..d14c9be7faa3 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -182,6 +182,8 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name, void *buf, unsigned int size, bool get_value); void *kexec_purgatory_get_symbol_addr(struct kimage *image, const char *name); +int kexec_update_segment(const char *buffer, unsigned long bufsz, + unsigned long load_addr, unsigned long memsz); /* Architectures may override the below functions */ int arch_kexec_kernel_image_probe(struct kimage *image, void *buf, diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 5a5d192a89ac..af8ea7bf0251 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -779,6 +779,108 @@ static struct page *kimage_alloc_page(struct kimage *image, return page; } +/** + * kexec_update_segment - update the contents of a kimage segment + * @buffer: New contents of the segment. + * @bufsz: @buffer size. + * @load_addr: Segment's physical address in the next kernel. + * @memsz: Segment size. + * + * This function assumes kexec_mutex is held. + * + * Return: 0 on success, negative errno on error. + */ +int kexec_update_segment(const char *buffer, unsigned long bufsz, + unsigned long load_addr, unsigned long memsz) +{ + int i; + unsigned long entry; + unsigned long *ptr = NULL; + void *dest = NULL; + + if (kexec_image == NULL) { + pr_err("Can't update segment: no kexec image loaded.\n"); + return -EINVAL; + } + + /* + * kexec_add_buffer rounds up segment sizes to PAGE_SIZE, so + * we have to do it here as well. + */ + memsz = ALIGN(memsz, PAGE_SIZE); + + for (i = 0; i < kexec_image->nr_segments; i++) + /* We only support updating whole segments. */ + if (load_addr == kexec_image->segment[i].mem && + memsz == kexec_image->segment[i].memsz) { + /* + * TusharSu: Not doing the checksum test for the time being. + * if (kexec_image->segment[i].do_checksum) { + * pr_err("Trying to update non-modifiable segment.\n"); + * return -EINVAL; + * } + */ + break; + } + + if (i == kexec_image->nr_segments) { + pr_err("Couldn't find segment to update: 0x%lx, size 0x%lx\n", + load_addr, memsz); + return -EINVAL; + } + + for (entry = kexec_image->head; !(entry & IND_DONE) && memsz; + entry = *ptr++) { + void *addr = (void *) (entry & PAGE_MASK); + + switch (entry & IND_FLAGS) { + case IND_DESTINATION: + dest = addr; + break; + case IND_INDIRECTION: + ptr = __va(addr); + break; + case IND_SOURCE: + /* Shouldn't happen, but verify just to be safe. */ + if (dest == NULL) { + pr_err("Invalid kexec entries list."); + return -EINVAL; + } + + if (dest == (void *) load_addr) { + struct page *page; + char *ptr; + size_t uchunk, mchunk; + + page = kmap_to_page(addr); + + ptr = kmap_atomic(page); + ptr += load_addr & ~PAGE_MASK; + mchunk = min_t(size_t, memsz, + PAGE_SIZE - (load_addr & ~PAGE_MASK)); + uchunk = min(bufsz, mchunk); + memcpy(ptr, buffer, uchunk); + + kunmap_atomic(ptr); + + bufsz -= uchunk; + load_addr += mchunk; + buffer += mchunk; + memsz -= mchunk; + } + dest += PAGE_SIZE; + } + + /* Shouldn't happen, but verify just to be safe. */ + if (ptr == NULL) { + pr_err("Invalid kexec entries list."); + return -EINVAL; + } + } + + return 0; +} + static int kimage_load_normal_segment(struct kimage *image, struct kexec_segment *segment) { -- 2.25.1