From 9b1a735de64cc975c31a1642ec55e082ddbdfeaf Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Tue, 24 Jun 2008 11:33:02 +1000 Subject: [PATCH] powerpc: Add logic to patch alternative feature sections This commit adds the logic to patch alternative sections. This is fairly straightforward, except for branches. Relative branches that jump from inside the else section to outside of it need to be translated as they're moved, otherwise they will jump to the wrong location. Signed-off-by: Michael Ellerman Signed-off-by: Paul Mackerras --- arch/powerpc/lib/feature-fixups.c | 79 +++++++++++++++++++++++++------ 1 file changed, 65 insertions(+), 14 deletions(-) diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c index 973d547ef0..174c1eba9a 100644 --- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c @@ -26,24 +26,66 @@ struct fixup_entry { long alt_end_off; }; -static void patch_feature_section(unsigned long value, struct fixup_entry *fcur) +static unsigned int *calc_addr(struct fixup_entry *fcur, long offset) { - unsigned int *pstart, *pend, *p; + /* + * We store the offset to the code as a negative offset from + * the start of the alt_entry, to support the VDSO. This + * routine converts that back into an actual address. + */ + return (unsigned int *)((unsigned long)fcur + offset); +} + +static int patch_alt_instruction(unsigned int *src, unsigned int *dest, + unsigned int *alt_start, unsigned int *alt_end) +{ + unsigned int instr; + + instr = *src; + + if (instr_is_relative_branch(*src)) { + unsigned int *target = (unsigned int *)branch_target(src); + + /* Branch within the section doesn't need translating */ + if (target < alt_start || target >= alt_end) { + instr = translate_branch(dest, src); + if (!instr) + return 1; + } + } + + patch_instruction(dest, instr); + + return 0; +} + +static int patch_feature_section(unsigned long value, struct fixup_entry *fcur) +{ + unsigned int *start, *end, *alt_start, *alt_end, *src, *dest; + + start = calc_addr(fcur, fcur->start_off); + end = calc_addr(fcur, fcur->end_off); + alt_start = calc_addr(fcur, fcur->alt_start_off); + alt_end = calc_addr(fcur, fcur->alt_end_off); + + if ((alt_end - alt_start) > (end - start)) + return 1; if ((value & fcur->mask) == fcur->value) - return; + return 0; - pstart = ((unsigned int *)fcur) + (fcur->start_off / 4); - pend = ((unsigned int *)fcur) + (fcur->end_off / 4); + src = alt_start; + dest = start; - for (p = pstart; p < pend; p++) { - *p = PPC_NOP_INSTR; - asm volatile ("dcbst 0, %0" : : "r" (p)); + for (; src < alt_end; src++, dest++) { + if (patch_alt_instruction(src, dest, alt_start, alt_end)) + return 1; } - asm volatile ("sync" : : : "memory"); - for (p = pstart; p < pend; p++) - asm volatile ("icbi 0,%0" : : "r" (p)); - asm volatile ("sync; isync" : : : "memory"); + + for (; dest < end; dest++) + patch_instruction(dest, PPC_NOP_INSTR); + + return 0; } void do_feature_fixups(unsigned long value, void *fixup_start, void *fixup_end) @@ -53,6 +95,15 @@ void do_feature_fixups(unsigned long value, void *fixup_start, void *fixup_end) fcur = fixup_start; fend = fixup_end; - for (; fcur < fend; fcur++) - patch_feature_section(value, fcur); + for (; fcur < fend; fcur++) { + if (patch_feature_section(value, fcur)) { + __WARN(); + printk("Unable to patch feature section at %p - %p" \ + " with %p - %p\n", + calc_addr(fcur, fcur->start_off), + calc_addr(fcur, fcur->end_off), + calc_addr(fcur, fcur->alt_start_off), + calc_addr(fcur, fcur->alt_end_off)); + } + } } -- 2.39.5