From patchwork Mon Jan 31 04:14:07 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Kardashevskiy X-Patchwork-Id: 1586528 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org (client-ip=112.213.38.117; helo=lists.ozlabs.org; envelope-from=linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org; receiver=) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4JnF7x4DxTz9sFr for ; Mon, 31 Jan 2022 15:14:37 +1100 (AEDT) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4JnF7v2dQFz3bbT for ; Mon, 31 Jan 2022 15:14:35 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.ru (client-ip=107.174.27.60; helo=ozlabs.ru; envelope-from=aik@ozlabs.ru; receiver=) Received: from ozlabs.ru (unknown [107.174.27.60]) by lists.ozlabs.org (Postfix) with ESMTP id 4JnF7g2lMcz2xrj for ; Mon, 31 Jan 2022 15:14:21 +1100 (AEDT) Received: from fstn1-p1.ozlabs.ibm.com. (localhost [IPv6:::1]) by ozlabs.ru (Postfix) with ESMTP id A1A9280AC4; Sun, 30 Jan 2022 23:14:12 -0500 (EST) From: Alexey Kardashevskiy To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH kernel] powerpc/64: Add UADDR64 relocation support Date: Mon, 31 Jan 2022 15:14:07 +1100 Message-Id: <20220131041407.435244-1-aik@ozlabs.ru> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , Alan Modra , Nicholas Piggin , Paul Mackerras Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" When ld detects unaligned relocations, it emits R_PPC64_UADDR64 relocations instead of R_PPC64_RELATIVE. Currently R_PPC64_UADDR64 are detected by arch/powerpc/tools/relocs_check.sh and expected not to work. Below is a simple chunk to trigger this behaviour: \#pragma GCC push_options \#pragma GCC optimize ("O0") struct entry { const char *file; int line; } __attribute__((packed)); static const struct entry e1 = { .file = __FILE__, .line = __LINE__ }; static const struct entry e2 = { .file = __FILE__, .line = __LINE__ }; ... prom_printf("e1=%s %lx %lx\n", e1.file, (unsigned long) e1.file, mfmsr()); prom_printf("e2=%s %lx\n", e2.file, (unsigned long) e2.file); \#pragma GCC pop_options This adds support for UADDR64 for 64bit. This reuses __dynamic_symtab from the 32bit which supports more relocation types already. This adds a workaround for the number of relocations as the DT_RELACOUNT ELF Dynamic Array Tag does not include relocations other than R_PPC64_RELATIVE. This instead iterates over the entire .rela.dyn section. Signed-off-by: Alexey Kardashevskiy --- Tested via qemu gdb stub (the kernel is loaded at 0x400000). Disasm: c000000001a804d0 : c000000001a804d0: b0 04 a8 01 .long 0x1a804b0 c000000001a804d0: R_PPC64_RELATIVE *ABS*-0x3ffffffffe57fb50 c000000001a804d4: 00 00 00 c0 lfs f0,0(0) c000000001a804d8: fa 08 00 00 .long 0x8fa c000000001a804dc : ... c000000001a804dc: R_PPC64_UADDR64 .rodata+0x4b0 Before relocation: >>> p *(unsigned long *) 0x1e804d0 $1 = 0xc000000001a804b0 >>> p *(unsigned long *) 0x1e804dc $2 = 0x0 After: >>> p *(unsigned long *) 0x1e804d0 $1 = 0x1e804b0 >>> p *(unsigned long *) 0x1e804dc $2 = 0x1e804b0 --- arch/powerpc/kernel/reloc_64.S | 47 +++++++++++++++++++++++++----- arch/powerpc/kernel/vmlinux.lds.S | 3 +- arch/powerpc/tools/relocs_check.sh | 6 ---- 3 files changed, 41 insertions(+), 15 deletions(-) diff --git a/arch/powerpc/kernel/reloc_64.S b/arch/powerpc/kernel/reloc_64.S index 02d4719bf43a..a91175723d9d 100644 --- a/arch/powerpc/kernel/reloc_64.S +++ b/arch/powerpc/kernel/reloc_64.S @@ -10,6 +10,7 @@ RELA = 7 RELACOUNT = 0x6ffffff9 R_PPC64_RELATIVE = 22 +R_PPC64_UADDR64 = 43 /* * r3 = desired final address of kernel @@ -25,6 +26,8 @@ _GLOBAL(relocate) add r9,r9,r12 /* r9 has runtime addr of .rela.dyn section */ ld r10,(p_st - 0b)(r12) add r10,r10,r12 /* r10 has runtime addr of _stext */ + ld r13,(p_sym - 0b)(r12) + add r13,r13,r12 /* r13 has runtime addr of .dynsym */ /* * Scan the dynamic section for the RELA and RELACOUNT entries. @@ -46,8 +49,8 @@ _GLOBAL(relocate) b 1b 4: cmpdi r7,0 /* check we have both RELA and RELACOUNT */ cmpdi cr1,r8,0 - beq 6f - beq cr1,6f + beq 9f + beq cr1,9f /* * Work out linktime address of _stext and hence the @@ -60,25 +63,55 @@ _GLOBAL(relocate) subf r10,r7,r10 subf r3,r10,r3 /* final_offset */ + /* + * FIXME + * Here r8 is a number of relocations in .rela.dyn. + * When ld issues UADDR64 relocations, they end up at the end + * of the .rela.dyn section. However RELACOUNT does not include + * them so the loop below is going to finish after the last + * R_PPC64_RELATIVE as they normally go first. + * Work out the size of .rela.dyn at compile time. + */ + ld r8,(p_rela_end - 0b)(r12) + ld r18,(p_rela - 0b)(r12) + sub r8,r8,r18 + li r18,24 /* 24 == sizeof(elf64_rela) */ + divd r8,r8,r18 + /* * Run through the list of relocations and process the - * R_PPC64_RELATIVE ones. + * R_PPC64_RELATIVE and R_PPC64_UADDR64 ones. */ mtctr r8 -5: ld r0,8(9) /* ELF64_R_TYPE(reloc->r_info) */ +5: lwa r0,8(r9) /* ELF64_R_TYPE(reloc->r_info) */ cmpdi r0,R_PPC64_RELATIVE bne 6f ld r6,0(r9) /* reloc->r_offset */ ld r0,16(r9) /* reloc->r_addend */ - add r0,r0,r3 + b 7f + +6: cmpdi r0,R_PPC64_UADDR64 + bne 8f + ld r6,0(r9) + ld r0,16(r9) + lwa r14,12(r9) /* ELF64_R_SYM(reloc->r_info) */ + mulli r14,r14,24 /* 24 == sizeof(elf64_sym) */ + add r14,r14,r13 /* elf64_sym[ELF64_R_SYM] */ + ld r14,8(r14) + add r0,r0,r14 + +7: add r0,r0,r3 stdx r0,r7,r6 - addi r9,r9,24 + +8: addi r9,r9,24 bdnz 5b -6: blr +9: blr .balign 8 p_dyn: .8byte __dynamic_start - 0b p_rela: .8byte __rela_dyn_start - 0b +p_rela_end: .8byte __rela_dyn_end - 0b +p_sym: .8byte __dynamic_symtab - 0b p_st: .8byte _stext - 0b diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index 2bcca818136a..e9d9bda3ffaf 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -281,9 +281,7 @@ SECTIONS . = ALIGN(8); .dynsym : AT(ADDR(.dynsym) - LOAD_OFFSET) { -#ifdef CONFIG_PPC32 __dynamic_symtab = .; -#endif *(.dynsym) } .dynstr : AT(ADDR(.dynstr) - LOAD_OFFSET) { *(.dynstr) } @@ -299,6 +297,7 @@ SECTIONS { __rela_dyn_start = .; *(.rela*) + __rela_dyn_end = .; } #endif /* .exit.data is discarded at runtime, not link time, diff --git a/arch/powerpc/tools/relocs_check.sh b/arch/powerpc/tools/relocs_check.sh index 014e00e74d2b..956b9e236a60 100755 --- a/arch/powerpc/tools/relocs_check.sh +++ b/arch/powerpc/tools/relocs_check.sh @@ -54,9 +54,3 @@ fi num_bad=$(echo "$bad_relocs" | wc -l) echo "WARNING: $num_bad bad relocations" echo "$bad_relocs" - -# If we see this type of relocation it's an idication that -# we /may/ be using an old version of binutils. -if echo "$bad_relocs" | grep -q -F -w R_PPC64_UADDR64; then - echo "WARNING: You need at least binutils >= 2.19 to build a CONFIG_RELOCATABLE kernel" -fi