From: Fangyu Yu <[email protected]> Crash kexec uses riscv_kexec_norelocate as a trampoline to jump into the crashkernel. Add a small helper to build dedicated 4KB page tables that map the trampoline page as executable.
Two mappings are installed: - VA(__kexec_tramp_text_start) -> PA(__kexec_tramp_text_start) - PA(__kexec_tramp_text_start) -> PA(__kexec_tramp_text_start) This allows the trampoline to run regardless of whether it is entered via its linked virtual address or its physical address. Signed-off-by: Fangyu Yu <[email protected]> --- arch/riscv/kernel/machine_kexec.c | 67 +++++++++++++++++++++++++++++++ 1 file changed, 67 insertions(+) diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c index 2306ce3e5f22..9b4b495e7c15 100644 --- a/arch/riscv/kernel/machine_kexec.c +++ b/arch/riscv/kernel/machine_kexec.c @@ -18,6 +18,65 @@ #include <linux/interrupt.h> #include <linux/irq.h> +static pgd_t kexec_tramp_pgd[PTRS_PER_PGD] __aligned(PAGE_SIZE); +static p4d_t kexec_tramp_p4d[PTRS_PER_P4D] __aligned(PAGE_SIZE); +static pud_t kexec_tramp_pud[PTRS_PER_PUD] __aligned(PAGE_SIZE); +static pmd_t kexec_tramp_pmd[PTRS_PER_PMD] __aligned(PAGE_SIZE); +static pte_t kexec_tramp_pte[PTRS_PER_PTE] __aligned(PAGE_SIZE); +static p4d_t kexec_tramp_p4d2[PTRS_PER_P4D] __aligned(PAGE_SIZE); +static pud_t kexec_tramp_pud2[PTRS_PER_PUD] __aligned(PAGE_SIZE); +static pmd_t kexec_tramp_pmd2[PTRS_PER_PMD] __aligned(PAGE_SIZE); +static pte_t kexec_tramp_pte2[PTRS_PER_PTE] __aligned(PAGE_SIZE); + +static void map_tramp_page(p4d_t *p4ds, pud_t *puds, pmd_t *pmds, pte_t *ptes, + unsigned long va, unsigned long pa) +{ + pgd_t *pgd = (pgd_t *)kexec_tramp_pgd + pgd_index(va); + pmd_t *pmd; + + if (pgtable_l5_enabled) { + p4d_t *p4d; + + set_pgd(pgd, pfn_pgd(PFN_DOWN(__pa_symbol(p4ds)), PAGE_TABLE)); + p4d = (p4d_t *)p4ds + p4d_index(va); + if (pgtable_l4_enabled) + set_p4d(p4d, pfn_p4d(PFN_DOWN(__pa_symbol(puds)), + PAGE_TABLE)); + else + set_p4d(p4d, pfn_p4d(PFN_DOWN(__pa_symbol(pmds)), + PAGE_TABLE)); + } else { + set_pgd(pgd, pfn_pgd(PFN_DOWN(__pa_symbol(puds)), PAGE_TABLE)); + } + + if (pgtable_l4_enabled) { + pud_t *pud = (pud_t *)puds + pud_index(va); + + set_pud(pud, pfn_pud(PFN_DOWN(__pa_symbol(pmds)), PAGE_TABLE)); + pmd = (pmd_t *)pmds + pmd_index(va); + } else { + pmd = (pmd_t *)puds + pmd_index(va); + } + set_pmd(pmd, pfn_pmd(PFN_DOWN(__pa_symbol(ptes)), PAGE_TABLE)); + + set_pte((pte_t *)ptes + pte_index(va), + pfn_pte(PFN_DOWN(pa), PAGE_KERNEL_EXEC)); +} + +static void riscv_kexec_build_tramp(unsigned long va, unsigned long pa) +{ + /* VA -> PA: map the trampoline page via its kernel VA. */ + map_tramp_page(kexec_tramp_p4d, kexec_tramp_pud, + kexec_tramp_pmd, kexec_tramp_pte, va, pa); + + /* + * PA -> PA: identity-map the same page so the second-pass code + * can keep executing after the kernel VA mapping is dropped. + */ + map_tramp_page(kexec_tramp_p4d2, kexec_tramp_pud2, + kexec_tramp_pmd2, kexec_tramp_pte2, pa, pa); +} + /* * machine_kexec_prepare - Initialize kexec * @@ -73,6 +132,14 @@ machine_kexec_prepare(struct kimage *image) /* Mark the control page executable */ set_memory_x((unsigned long) control_code_buffer, 1); + } else { + /* + * Crash kexec uses riscv_kexec_norelocate as a trampoline. + * Pre-build the trampoline page tables here so the panic + * path only has to switch satp and jump. + */ + riscv_kexec_build_tramp((unsigned long)__kexec_tramp_text_start, + __pa_symbol(__kexec_tramp_text_start)); } return 0; -- 2.50.1
