***Background: People reported that KASLR may randomly choose some positions which are located in movable memory regions. This will break memory hotplug feature and make the movable memory chosen by KASLR can't be removed.
***Solutions: Get the information of memory hot-remove, then KASLR will know the right regions. Information about memory hot-remove is in ACPI tables, which will be parsed after start_kernel(), so that KASLR can't get the information. Somebody suggest to add a kernel parameter to specify the immovable memory so that limit KASLR in these regions. Then I make a PATCHSET. After several versions, Ingo gave a suggestion: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1634024.html Follow Ingo's suggestion, imitate the ACPI code to parse the ACPI tables, so that the kaslr can get necessary memory information in ACPI tables. I think ACPI code is an independent part, so imitate the codes and functions to 'compressed/' directory, so that kaslr won't influence the initialization of ACPI. PATCH 1/6 Copy kstrtoull() to boot/string.c PATCH 2/6 Add get_acpi_rsdp() to parse RSDP in cmdline from KEXEC PATCH 3/6 Add efi_get_rsdp_addr() to find RSDP from EFI table when booting from EFI. PATCH 4/6 Add bios_get_rsdp_addr() to search RSDP in memory when EFI table not found. PATCH 5/6 Compute SRAT from RSDP and walk SRAT to store the immovable memory regions. PATCH 6/6 Calculate the intersection between memory regions from e820/efi memory table and immovable memory regions. Limit KASLR to choosing these regions for randomization. v1->v2: - Simplify some code. Follow Baoquan He's suggestion: - Reuse the head file of acpi code. v2->v3: - Test in more conditions, so remove the 'RFC' tag. - Change some comments. v3->v4: Follow Thomas Gleixner's suggestion: - Put the whole efi related function into #define CONFIG_EFI and return false in the other stub. v4->v5: Follow Dou Liyang's suggestion: - Add more comments about some functions based on kernel code. - Change some typo in comments. - Clean useless variable. - Add check for the boundary of array. - Add check for 'movable_node' parameter v5->v6: Follow Baoquan He's suggestion: - Change some log. - Add the check for acpi_rsdp - Change some code logical to make code clear v6->v7: Follow Rafael's suggestion: - Add more comments and patch log. Follow test robot's suggestion: - Add "static" tag for function v7-v8: Follow Kees Cook's suggestion: - Use mem_overlaps() to check memory region. - Use #ifdef in the definition of function. v8-v9: Follow Boris' suggestion: - Change code style. - Splite PATCH 1/3 to more path. - Introduce some new function - Use existing function to rework some code Follow Masayoshi's suggetion: - Make code more readable v9->v10: Follow Baoquan's suggestion: - Change some log - Merge last two patch together. v10->v11: Follow Boris' suggestion: - Link kstrtoull() instead of copying it. - Drop the useless wrapped function. v11->v12: Follow Boris' suggestion: - Change patch log and code comments. - Add 'CONFIG_EARLY_PARSE_RSDP' to make code easy to read - Put strtoull() to misc.c Follow Masa's suggestion: - Remove the detection for 'movable_node' - Change the code logical about cmdline_find_option() v12->v13: Follow Boris' suggestion: - Copy kstrtoull() to boot/string.c Follow Masa's suggestion: - Change some code logical Follow Baoquan's suggestion: - Add tag to disable export symbol Any comments will be welcome. Chao Fan (6): x86/boot: Introduce kstrtoull() to boot directory instead of simple_strtoull() x86/boot: Introduce get_acpi_rsdp() to parse RSDP in cmdline from KEXEC x86/boot: Introduce efi_get_rsdp_addr() to find RSDP from EFI table x86/boot: Introduce bios_get_rsdp_addr() to search RSDP in memory x86/boot: Parse SRAT from RSDP and store immovable memory x86/boot/KASLR: Limit KASLR to extracting kernel in immovable memory arch/x86/Kconfig | 10 + arch/x86/boot/compressed/Makefile | 2 + arch/x86/boot/compressed/acpi.c | 322 ++++++++++++++++++++++++++++++ arch/x86/boot/compressed/kaslr.c | 79 ++++++-- arch/x86/boot/compressed/misc.h | 21 ++ arch/x86/boot/string.c | 137 +++++++++++++ arch/x86/boot/string.h | 2 + 7 files changed, 558 insertions(+), 15 deletions(-) create mode 100644 arch/x86/boot/compressed/acpi.c -- 2.19.2
