[RESEND PATCH v5 04/11] ppc64/kexec_file: avoid stomping memory used by special regions

Hari Bathini
2020-07-26T19:38:26Z

crashkernel region could have an overlap with special memory regions
like opal, rtas, tce-table & such. These regions are referred to as
exclude memory ranges. Setup this ranges during image probe in order
to avoid them while finding the buffer for different kdump segments.
Override arch_kexec_locate_mem_hole() to locate a memory hole taking
these ranges into account.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---

v4 -> v5:
* Unchanged. Added Reviewed-by tag from Thiago.

v3 -> v4:
* Dropped KDUMP_BUF_MIN & KDUMP_BUF_MAX macros and fixed off-by-one error
in arch_locate_mem_hole() helper routines.

v2 -> v3:
* If there are no exclude ranges, the right thing to do is fallbacking
back to default kexec_locate_mem_hole() implementation instead of
returning 0. Fixed that.

v1 -> v2:
* Did arch_kexec_locate_mem_hole() override to handle special regions.
* Ensured holes in the memory are accounted for while locating mem hole.
* Updated add_rtas_mem_range() & add_opal_mem_range() callsites based on
the new prototype for these functions.

arch/powerpc/include/asm/kexec.h | 7 +
arch/powerpc/kexec/elf_64.c | 8 +
arch/powerpc/kexec/file_load_64.c | 337 +++++++++++++++++++++++++++++++++++++
3 files changed, 348 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index ac8fd4839171..835dc92e091c 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -100,14 +100,16 @@ void relocate_new_kernel(unsigned long indirection_page, unsigned long reboot_co
#ifdef CONFIG_KEXEC_FILE
extern const struct kexec_file_ops kexec_elf64_ops;

-#ifdef CONFIG_IMA_KEXEC
#define ARCH_HAS_KIMAGE_ARCH

struct kimage_arch {
+ struct crash_mem *exclude_ranges;
+
+#ifdef CONFIG_IMA_KEXEC
phys_addr_t ima_buffer_addr;
size_t ima_buffer_size;
-};
#endif
+};

int setup_purgatory(struct kimage *image, const void *slave_code,
const void *fdt, unsigned long kernel_load_addr,
@@ -125,6 +127,7 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt,
unsigned long initrd_load_addr,
unsigned long initrd_len, const char *cmdline);
#endif /* CONFIG_PPC64 */
+
#endif /* CONFIG_KEXEC_FILE */

#else /* !CONFIG_KEXEC_CORE */
diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index 23ad04ccaf8e..64c15a5a280b 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -46,6 +46,14 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
if (ret)
goto out;

+ if (image->type == KEXEC_TYPE_CRASH) {
+ /* min & max buffer values for kdump case */
+ kbuf.buf_min = pbuf.buf_min = crashk_res.start;
+ kbuf.buf_max = pbuf.buf_max =
+ ((crashk_res.end < ppc64_rma_size) ?
+ crashk_res.end : (ppc64_rma_size - 1));
+ }
+
ret = kexec_elf_load(image, &ehdr, &elf_info, &kbuf, &kernel_load_addr);
if (ret)
goto out;
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index 41fe8b6c72d6..2df6f4273ddd 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -17,12 +17,262 @@
#include <linux/kexec.h>
#include <linux/of_fdt.h>
#include <linux/libfdt.h>
+#include <linux/memblock.h>
+#include <asm/kexec_ranges.h>

const struct kexec_file_ops * const kexec_file_loaders[] = {
&kexec_elf64_ops,
NULL
};

+/**
+ * get_exclude_memory_ranges - Get exclude memory ranges. This list includes
+ * regions like opal/rtas, tce-table, initrd,
+ * kernel, htab which should be avoided while
+ * setting up kexec load segments.
+ * @mem_ranges: Range list to add the memory ranges to.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int get_exclude_memory_ranges(struct crash_mem **mem_ranges)
+{
+ int ret;
+
+ ret = add_tce_mem_ranges(mem_ranges);
+ if (ret)
+ goto out;
+
+ ret = add_initrd_mem_range(mem_ranges);
+ if (ret)
+ goto out;
+
+ ret = add_htab_mem_range(mem_ranges);
+ if (ret)
+ goto out;
+
+ ret = add_kernel_mem_range(mem_ranges);
+ if (ret)
+ goto out;
+
+ ret = add_rtas_mem_range(mem_ranges);
+ if (ret)
+ goto out;
+
+ ret = add_opal_mem_range(mem_ranges);
+ if (ret)
+ goto out;
+
+ ret = add_reserved_ranges(mem_ranges);
+ if (ret)
+ goto out;
+
+ /* exclude memory ranges should be sorted for easy lookup */
+ sort_memory_ranges(*mem_ranges, true);
+out:
+ if (ret)
+ pr_err("Failed to setup exclude memory ranges\n");
+ return ret;
+}
+
+/**
+ * __locate_mem_hole_top_down - Looks top down for a large enough memory hole
+ * in the memory regions between buf_min & buf_max
+ * for the buffer. If found, sets kbuf->mem.
+ * @kbuf: Buffer contents and memory parameters.
+ * @buf_min: Minimum address for the buffer.
+ * @buf_max: Maximum address for the buffer.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int __locate_mem_hole_top_down(struct kexec_buf *kbuf,
+ u64 buf_min, u64 buf_max)
+{
+ int ret = -EADDRNOTAVAIL;
+ phys_addr_t start, end;
+ u64 i;
+
+ for_each_mem_range_rev(i, &memblock.memory, NULL, NUMA_NO_NODE,
+ MEMBLOCK_NONE, &start, &end, NULL) {
+ /*
+ * memblock uses [start, end) convention while it is
+ * [start, end] here. Fix the off-by-one to have the
+ * same convention.
+ */
+ end -= 1;
+
+ if (start > buf_max)
+ continue;
+
+ /* Memory hole not found */
+ if (end < buf_min)
+ break;
+
+ /* Adjust memory region based on the given range */
+ if (start < buf_min)
+ start = buf_min;
+ if (end > buf_max)
+ end = buf_max;
+
+ start = ALIGN(start, kbuf->buf_align);
+ if (start < end && (end - start + 1) >= kbuf->memsz) {
+ /* Suitable memory range found. Set kbuf->mem */
+ kbuf->mem = ALIGN_DOWN(end - kbuf->memsz + 1,
+ kbuf->buf_align);
+ ret = 0;
+ break;
+ }
+ }
+
+ return ret;
+}
+
+/**
+ * locate_mem_hole_top_down_ppc64 - Skip special memory regions to find a
+ * suitable buffer with top down approach.
+ * @kbuf: Buffer contents and memory parameters.
+ * @buf_min: Minimum address for the buffer.
+ * @buf_max: Maximum address for the buffer.
+ * @emem: Exclude memory ranges.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int locate_mem_hole_top_down_ppc64(struct kexec_buf *kbuf,
+ u64 buf_min, u64 buf_max,
+ const struct crash_mem *emem)
+{
+ int i, ret = 0, err = -EADDRNOTAVAIL;
+ u64 start, end, tmin, tmax;
+
+ tmax = buf_max;
+ for (i = (emem->nr_ranges - 1); i >= 0; i--) {
+ start = emem->ranges[i].start;
+ end = emem->ranges[i].end;
+
+ if (start > tmax)
+ continue;
+
+ if (end < tmax) {
+ tmin = (end < buf_min ? buf_min : end + 1);
+ ret = __locate_mem_hole_top_down(kbuf, tmin, tmax);
+ if (!ret)
+ return 0;
+ }
+
+ tmax = start - 1;
+
+ if (tmax < buf_min) {
+ ret = err;
+ break;
+ }
+ ret = 0;
+ }
+
+ if (!ret) {
+ tmin = buf_min;
+ ret = __locate_mem_hole_top_down(kbuf, tmin, tmax);
+ }
+ return ret;
+}
+
+/**
+ * __locate_mem_hole_bottom_up - Looks bottom up for a large enough memory hole
+ * in the memory regions between buf_min & buf_max
+ * for the buffer. If found, sets kbuf->mem.
+ * @kbuf: Buffer contents and memory parameters.
+ * @buf_min: Minimum address for the buffer.
+ * @buf_max: Maximum address for the buffer.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int __locate_mem_hole_bottom_up(struct kexec_buf *kbuf,
+ u64 buf_min, u64 buf_max)
+{
+ int ret = -EADDRNOTAVAIL;
+ phys_addr_t start, end;
+ u64 i;
+
+ for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
+ MEMBLOCK_NONE, &start, &end, NULL) {
+ /*
+ * memblock uses [start, end) convention while it is
+ * [start, end] here. Fix the off-by-one to have the
+ * same convention.
+ */
+ end -= 1;
+
+ if (end < buf_min)
+ continue;
+
+ /* Memory hole not found */
+ if (start > buf_max)
+ break;
+
+ /* Adjust memory region based on the given range */
+ if (start < buf_min)
+ start = buf_min;
+ if (end > buf_max)
+ end = buf_max;
+
+ start = ALIGN(start, kbuf->buf_align);
+ if (start < end && (end - start + 1) >= kbuf->memsz) {
+ /* Suitable memory range found. Set kbuf->mem */
+ kbuf->mem = start;
+ ret = 0;
+ break;
+ }
+ }
+
+ return ret;
+}
+
+/**
+ * locate_mem_hole_bottom_up_ppc64 - Skip special memory regions to find a
+ * suitable buffer with bottom up approach.
+ * @kbuf: Buffer contents and memory parameters.
+ * @buf_min: Minimum address for the buffer.
+ * @buf_max: Maximum address for the buffer.
+ * @emem: Exclude memory ranges.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int locate_mem_hole_bottom_up_ppc64(struct kexec_buf *kbuf,
+ u64 buf_min, u64 buf_max,
+ const struct crash_mem *emem)
+{
+ int i, ret = 0, err = -EADDRNOTAVAIL;
+ u64 start, end, tmin, tmax;
+
+ tmin = buf_min;
+ for (i = 0; i < emem->nr_ranges; i++) {
+ start = emem->ranges[i].start;
+ end = emem->ranges[i].end;
+
+ if (end < tmin)
+ continue;
+
+ if (start > tmin) {
+ tmax = (start > buf_max ? buf_max : start - 1);
+ ret = __locate_mem_hole_bottom_up(kbuf, tmin, tmax);
+ if (!ret)
+ return 0;
+ }
+
+ tmin = end + 1;
+
+ if (tmin > buf_max) {
+ ret = err;
+ break;
+ }
+ ret = 0;
+ }
+
+ if (!ret) {
+ tmax = buf_max;
+ ret = __locate_mem_hole_bottom_up(kbuf, tmin, tmax);
+ }
+ return ret;
+}
+
/**
* setup_purgatory_ppc64 - initialize PPC64 specific purgatory's global
* variables and call setup_purgatory() to initialize
@@ -67,6 +317,67 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt,
return setup_new_fdt(image, fdt, initrd_load_addr, initrd_len, cmdline);
}

+/**
+ * arch_kexec_locate_mem_hole - Skip special memory regions like rtas, opal,
+ * tce-table, reserved-ranges & such (exclude
+ * memory ranges) as they can't be used for kexec
+ * segment buffer. Sets kbuf->mem when a suitable
+ * memory hole is found.
+ * @kbuf: Buffer contents and memory parameters.
+ *
+ * Assumes minimum of PAGE_SIZE alignment for kbuf->memsz & kbuf->buf_align.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+int arch_kexec_locate_mem_hole(struct kexec_buf *kbuf)
+{
+ struct crash_mem **emem;
+ u64 buf_min, buf_max;
+ int ret;
+
+ /*
+ * Use the generic kexec_locate_mem_hole for regular
+ * kexec_file_load syscall
+ */
+ if (kbuf->image->type != KEXEC_TYPE_CRASH)
+ return kexec_locate_mem_hole(kbuf);
+
+ /* Look up the exclude ranges list while locating the memory hole */
+ emem = &(kbuf->image->arch.exclude_ranges);
+ if (!(*emem) || ((*emem)->nr_ranges == 0)) {
+ pr_warn("No exclude range list. Using the default locate mem hole method\n");
+ return kexec_locate_mem_hole(kbuf);
+ }
+
+ /* Segments for kdump kernel should be within crashkernel region */
+ buf_min = (kbuf->buf_min < crashk_res.start ?
+ crashk_res.start : kbuf->buf_min);
+ buf_max = (kbuf->buf_max > crashk_res.end ?
+ crashk_res.end : kbuf->buf_max);
+
+ if (buf_min > buf_max) {
+ pr_err("Invalid buffer min and/or max values\n");
+ return -EINVAL;
+ }
+
+ if (kbuf->top_down)
+ ret = locate_mem_hole_top_down_ppc64(kbuf, buf_min, buf_max,
+ *emem);
+ else
+ ret = locate_mem_hole_bottom_up_ppc64(kbuf, buf_min, buf_max,
+ *emem);
+
+ /* Add the buffer allocated to the exclude list for the next lookup */
+ if (!ret) {
+ add_mem_range(emem, kbuf->mem, kbuf->memsz);
+ sort_memory_ranges(*emem, true);
+ } else {
+ pr_err("Failed to locate memory buffer of size %lu\n",
+ kbuf->memsz);
+ }
+ return ret;
+}
+
/**
* arch_kexec_kernel_image_probe - Does additional handling needed to setup
* kexec segments.
@@ -79,9 +390,31 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt,
int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
unsigned long buf_len)
{
- /* We don't support crash kernels yet. */
- if (image->type == KEXEC_TYPE_CRASH)
+ if (image->type == KEXEC_TYPE_CRASH) {
+ int ret;
+
+ /* Get exclude memory ranges needed for setting up kdump segments */
+ ret = get_exclude_memory_ranges(&(image->arch.exclude_ranges));
+ if (ret)
+ pr_err("Failed to setup exclude memory ranges for buffer lookup\n");
+ /* Return this until all changes for panic kernel are in */
return -EOPNOTSUPP;
+ }

return kexec_image_probe_default(image, buf, buf_len);
}
+
+/**
+ * arch_kimage_file_post_load_cleanup - Frees up all the allocations done
+ * while loading the image.
+ * @image: kexec image being loaded.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+int arch_kimage_file_post_load_cleanup(struct kimage *image)
+{
+ kfree(image->arch.exclude_ranges);
+ image->arch.exclude_ranges = NULL;
+
+ return kexec_image_post_load_cleanup_default(image);
+}