[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [RFC PATCH 19/28] x86/boot/64: Avoid intentional absolute symbol references in .head.text
From: Ard Biesheuvel <ardb@xxxxxxxxxx> The code in .head.text executes from a 1:1 mapping and cannot generally refer to global variables using their kernel virtual addresses. However, there are some occurrences of such references that are valid: the kernel virtual addresses of _text and _end are needed to populate the page tables correctly, and some other section markers are used in a similar way. To avoid the need for making exceptions to the rule that .head.text must not contain any absolute symbol references, derive these addresses from the RIP-relative 1:1 mapped physical addresses, which can be safely determined using RIP_REL_REF(). Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> --- arch/x86/kernel/head64.c | 30 ++++++++++++-------- 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index de33ac34773c..49e8ba1c0d34 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -91,9 +91,11 @@ static inline bool check_la57_support(void) return true; } -static unsigned long __head sme_postprocess_startup(struct boot_params *bp, pmdval_t *pmd) +static unsigned long __head sme_postprocess_startup(struct boot_params *bp, + pmdval_t *pmd, + unsigned long p2v_offset) { - unsigned long vaddr, vaddr_end; + unsigned long paddr, paddr_end; int i; /* Encrypt the kernel and related (if SME is active) */ @@ -106,10 +108,10 @@ static unsigned long __head sme_postprocess_startup(struct boot_params *bp, pmdv * attribute. */ if (sme_get_me_mask()) { - vaddr = (unsigned long)__start_bss_decrypted; - vaddr_end = (unsigned long)__end_bss_decrypted; + paddr = (unsigned long)&RIP_REL_REF(__start_bss_decrypted); + paddr_end = (unsigned long)&RIP_REL_REF(__end_bss_decrypted); - for (; vaddr < vaddr_end; vaddr += PMD_SIZE) { + for (; paddr < paddr_end; paddr += PMD_SIZE) { /* * On SNP, transition the page to shared in the RMP table so that * it is consistent with the page table attribute change. @@ -118,11 +120,11 @@ static unsigned long __head sme_postprocess_startup(struct boot_params *bp, pmdv * mapping (kernel .text). PVALIDATE, by way of * early_snp_set_memory_shared(), requires a valid virtual * address but the kernel is currently running off of the identity - * mapping so use __pa() to get a *currently* valid virtual address. + * mapping so use the PA to get a *currently* valid virtual address. */ - early_snp_set_memory_shared(__pa(vaddr), __pa(vaddr), PTRS_PER_PMD); + early_snp_set_memory_shared(paddr, paddr, PTRS_PER_PMD); - i = pmd_index(vaddr); + i = pmd_index(paddr - p2v_offset); pmd[i] -= sme_get_me_mask(); } } @@ -146,6 +148,7 @@ unsigned long __head __startup_64(unsigned long p2v_offset, { pmd_t (*early_pgts)[PTRS_PER_PMD] = RIP_REL_REF(early_dynamic_pgts); unsigned long physaddr = (unsigned long)&RIP_REL_REF(_text); + unsigned long va_text, va_end; unsigned long pgtable_flags; unsigned long load_delta; pgdval_t *pgd; @@ -172,6 +175,9 @@ unsigned long __head __startup_64(unsigned long p2v_offset, if (load_delta & ~PMD_MASK) for (;;); + va_text = physaddr - p2v_offset; + va_end = (unsigned long)&RIP_REL_REF(_end) - p2v_offset; + /* Include the SME encryption mask in the fixup value */ load_delta += sme_get_me_mask(); @@ -232,7 +238,7 @@ unsigned long __head __startup_64(unsigned long p2v_offset, pmd_entry += sme_get_me_mask(); pmd_entry += physaddr; - for (i = 0; i < DIV_ROUND_UP(_end - _text, PMD_SIZE); i++) { + for (i = 0; i < DIV_ROUND_UP(va_end - va_text, PMD_SIZE); i++) { int idx = i + (physaddr >> PMD_SHIFT); pmd[idx % PTRS_PER_PMD] = pmd_entry + i * PMD_SIZE; @@ -257,11 +263,11 @@ unsigned long __head __startup_64(unsigned long p2v_offset, pmd = &RIP_REL_REF(level2_kernel_pgt)->pmd; /* invalidate pages before the kernel image */ - for (i = 0; i < pmd_index((unsigned long)_text); i++) + for (i = 0; i < pmd_index(va_text); i++) pmd[i] &= ~_PAGE_PRESENT; /* fixup pages that are part of the kernel image */ - for (; i <= pmd_index((unsigned long)_end); i++) + for (; i <= pmd_index(va_end); i++) if (pmd[i] & _PAGE_PRESENT) pmd[i] += load_delta; @@ -269,7 +275,7 @@ unsigned long __head __startup_64(unsigned long p2v_offset, for (; i < PTRS_PER_PMD; i++) pmd[i] &= ~_PAGE_PRESENT; - return sme_postprocess_startup(bp, pmd); + return sme_postprocess_startup(bp, pmd, p2v_offset); } /* Wipe all early page tables except for the kernel symbol map */ -- 2.46.0.792.g87dc391469-goog
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |