From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave.Martin@arm.com (Dave Martin) Date: Wed, 24 Jul 2013 18:52:21 +0100 Subject: [PATCH 3/4] ARM: module: correctly relocate instructions in BE8 In-Reply-To: <1374510833-25716-4-git-send-email-ben.dooks@codethink.co.uk> References: <1374510833-25716-1-git-send-email-ben.dooks@codethink.co.uk> <1374510833-25716-4-git-send-email-ben.dooks@codethink.co.uk> Message-ID: <20130724175221.GD4610@localhost.localdomain> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Jul 22, 2013 at 05:33:52PM +0100, Ben Dooks wrote: > When in BE8 mode, our instructions are not in the same ordering as the > data, so use to take this into account. > > Note, also requires modules to be built --be8 > > Signed-off-by: Ben Dooks > --- > arch/arm/kernel/module.c | 57 +++++++++++++++++++++++++++------------------- > 1 file changed, 34 insertions(+), 23 deletions(-) > > diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c > index 1e9be5d..7e13787 100644 > --- a/arch/arm/kernel/module.c > +++ b/arch/arm/kernel/module.c > @@ -24,6 +24,7 @@ > #include > #include > #include > +#include > > #ifdef CONFIG_XIP_KERNEL > /* > @@ -60,6 +61,7 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, > Elf32_Sym *sym; > const char *symname; > s32 offset; > + u32 tmp; > #ifdef CONFIG_THUMB2_KERNEL > u32 upper, lower, sign, j1, j2; > #endif > @@ -95,7 +97,8 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, > case R_ARM_PC24: > case R_ARM_CALL: > case R_ARM_JUMP24: > - offset = (*(u32 *)loc & 0x00ffffff) << 2; > + offset = __mem_to_opcode_arm(*(u32 *)loc); > + offset = (offset & 0x00ffffff) << 2; > if (offset & 0x02000000) > offset -= 0x04000000; > > @@ -111,9 +114,10 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, > } > > offset >>= 2; > + offset &= 0x00ffffff; > > - *(u32 *)loc &= 0xff000000; > - *(u32 *)loc |= offset & 0x00ffffff; > + *(u32 *)loc &= __opcode_to_mem_arm(0xff000000); > + *(u32 *)loc |= __opcode_to_mem_arm(offset); Here it's assumed that __opcode_to_mem_arm(x | y) == __opcode_to_mem_arm(x) | __opcode_to_mem_arm(x) (and related rules) Since the macros really do just shuffle bits, that does work, but it may be a bit cleaner to build on the instruction in canonical representation and use __opcode_to_mem_arm() just once to avoid such subtleties. Then we can simply treat instructions in memory as opaque data, which all flows into the code through __mem_to_opcode*() and back out through __opcode_to_mem*(). (analogous to ntohs() ... do something useful ... htons() etc.) So: tmp = __mem_to_opcode_arm(*(u32 *)loc); tmp = (tmp & 0xff000000) | offset; *(u32 *)loc = __opcode_to_mem_arm(tmp); I think that's cleaner, but it's open to debate. GCC might generate slightly inferior code, depending on how clever it is ... but this isn't a fast path. The same style could be applied to all the relocations here. It could help to avoid confusion about which byte order a particular vairable or literal uses -- i.e., ARM ARM order is used for everything except the contents of memory. I have to abort this review now ... I'll try to look at the rest tomorrow. Cheers ---Dave > break; > > case R_ARM_V4BX: > @@ -121,8 +125,8 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, > * other bits to re-code instruction as > * MOV PC,Rm. > */ > - *(u32 *)loc &= 0xf000000f; > - *(u32 *)loc |= 0x01a0f000; > + *(u32 *)loc &= __opcode_to_mem_arm(0xf000000f); > + *(u32 *)loc |= __opcode_to_mem_arm(0x01a0f000); > break; > > case R_ARM_PREL31: > @@ -132,7 +136,7 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, > > case R_ARM_MOVW_ABS_NC: > case R_ARM_MOVT_ABS: > - offset = *(u32 *)loc; > + offset = tmp = __mem_to_opcode_arm(*(u32 *)loc); > offset = ((offset & 0xf0000) >> 4) | (offset & 0xfff); > offset = (offset ^ 0x8000) - 0x8000; > > @@ -140,16 +144,18 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, > if (ELF32_R_TYPE(rel->r_info) == R_ARM_MOVT_ABS) > offset >>= 16; > > - *(u32 *)loc &= 0xfff0f000; > - *(u32 *)loc |= ((offset & 0xf000) << 4) | > - (offset & 0x0fff); > + tmp &= 0xfff0f000; > + tmp |= ((offset & 0xf000) << 4) | > + (offset & 0x0fff); > + > + *(u32 *)loc = __opcode_to_mem_arm(tmp); > break; > > #ifdef CONFIG_THUMB2_KERNEL > case R_ARM_THM_CALL: > case R_ARM_THM_JUMP24: > - upper = *(u16 *)loc; > - lower = *(u16 *)(loc + 2); > + upper = __mem_to_opcode_thumb16(*(u16 *)loc); > + lower = __mem_to_opcode_thumb16(*(u16 *)(loc + 2)); > > /* > * 25 bit signed address range (Thumb-2 BL and B.W > @@ -198,17 +204,20 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, > sign = (offset >> 24) & 1; > j1 = sign ^ (~(offset >> 23) & 1); > j2 = sign ^ (~(offset >> 22) & 1); > - *(u16 *)loc = (u16)((upper & 0xf800) | (sign << 10) | > + upper = (u16)((upper & 0xf800) | (sign << 10) | > ((offset >> 12) & 0x03ff)); > - *(u16 *)(loc + 2) = (u16)((lower & 0xd000) | > - (j1 << 13) | (j2 << 11) | > - ((offset >> 1) & 0x07ff)); > + lower = (u16)((lower & 0xd000) | > + (j1 << 13) | (j2 << 11) | > + ((offset >> 1) & 0x07ff)); > + > + *(u16 *)loc = __opcode_to_mem_thumb16(upper); > + *(u16 *)(loc + 2) = __opcode_to_mem_thumb16(lower); > break; > > case R_ARM_THM_MOVW_ABS_NC: > case R_ARM_THM_MOVT_ABS: > - upper = *(u16 *)loc; > - lower = *(u16 *)(loc + 2); > + upper = __mem_to_opcode_thumb16(*(u16 *)loc); > + lower = __mem_to_opcode_thumb16(*(u16 *)(loc + 2)); > > /* > * MOVT/MOVW instructions encoding in Thumb-2: > @@ -229,12 +238,14 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, > if (ELF32_R_TYPE(rel->r_info) == R_ARM_THM_MOVT_ABS) > offset >>= 16; > > - *(u16 *)loc = (u16)((upper & 0xfbf0) | > - ((offset & 0xf000) >> 12) | > - ((offset & 0x0800) >> 1)); > - *(u16 *)(loc + 2) = (u16)((lower & 0x8f00) | > - ((offset & 0x0700) << 4) | > - (offset & 0x00ff)); > + upper = (u16)((upper & 0xfbf0) | > + ((offset & 0xf000) >> 12) | > + ((offset & 0x0800) >> 1)); > + lower = (u16)((lower & 0x8f00) | > + ((offset & 0x0700) << 4) | > + (offset & 0x00ff)); > + *(u16 *)loc = __opcode_to_mem_thumb16(upper); > + *(u16 *)(loc + 2) = __opcode_to_mem_thumb16(lower); > break; > #endif > > -- > 1.7.10.4 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel