diff options
Diffstat (limited to 'src/cmd/ld/lib.c')
| -rw-r--r-- | src/cmd/ld/lib.c | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/src/cmd/ld/lib.c b/src/cmd/ld/lib.c index c144d4295..e645502b3 100644 --- a/src/cmd/ld/lib.c +++ b/src/cmd/ld/lib.c @@ -31,6 +31,8 @@ #include "l.h" #include "lib.h" +#include "../../pkg/runtime/stack.h" + #include <ar.h> int iconv(Fmt*); @@ -1084,3 +1086,208 @@ be64(uchar *b) Endian be = { be16, be32, be64 }; Endian le = { le16, le32, le64 }; + +typedef struct Chain Chain; +struct Chain +{ + Sym *sym; + Chain *up; + int limit; // limit on entry to sym +}; + +static int stkcheck(Chain*, int); +static void stkprint(Chain*, int); +static void stkbroke(Chain*, int); +static Sym *morestack; +static Sym *newstack; + +enum +{ + HasLinkRegister = (thechar == '5'), + CallSize = (!HasLinkRegister)*PtrSize, // bytes of stack required for a call +}; + +void +dostkcheck(void) +{ + Chain ch; + Sym *s; + + morestack = lookup("runtime.morestack", 0); + newstack = lookup("runtime.newstack", 0); + + // First the nosplits on their own. + for(s = textp; s != nil; s = s->next) { + if(s->text == nil || s->text->link == nil || (s->text->textflag & NOSPLIT) == 0) + continue; + cursym = s; + ch.up = nil; + ch.sym = s; + ch.limit = StackLimit - CallSize; + stkcheck(&ch, 0); + s->stkcheck = 1; + } + + // Check calling contexts. + // Some nosplits get called a little further down, + // like newproc and deferproc. We could hard-code + // that knowledge but it's more robust to look at + // the actual call sites. + for(s = textp; s != nil; s = s->next) { + if(s->text == nil || s->text->link == nil || (s->text->textflag & NOSPLIT) != 0) + continue; + cursym = s; + ch.up = nil; + ch.sym = s; + ch.limit = StackLimit - CallSize; + stkcheck(&ch, 0); + } +} + +static int +stkcheck(Chain *up, int depth) +{ + Chain ch, ch1; + Prog *p; + Sym *s; + int limit, prolog; + + limit = up->limit; + s = up->sym; + p = s->text; + + // Small optimization: don't repeat work at top. + if(s->stkcheck && limit == StackLimit-CallSize) + return 0; + + if(depth > 100) { + diag("nosplit stack check too deep"); + stkbroke(up, 0); + return -1; + } + + if(p == nil || p->link == nil) { + // external function. + // should never be called directly. + // only diagnose the direct caller. + if(depth == 1) + diag("call to external function %s", s->name); + return -1; + } + + if(limit < 0) { + stkbroke(up, limit); + return -1; + } + + // morestack looks like it calls functions, + // but it switches the stack pointer first. + if(s == morestack) + return 0; + + ch.up = up; + prolog = (s->text->textflag & NOSPLIT) == 0; + for(p = s->text; p != P; p = p->link) { + limit -= p->spadj; + if(prolog && p->spadj != 0) { + // The first stack adjustment in a function with a + // split-checking prologue marks the end of the + // prologue. Assuming the split check is correct, + // after the adjustment there should still be at least + // StackLimit bytes available below the stack pointer. + // If this is not the top call in the chain, no need + // to duplicate effort, so just stop. + if(depth > 0) + return 0; + prolog = 0; + limit = StackLimit; + } + if(limit < 0) { + stkbroke(up, limit); + return -1; + } + if(iscall(p)) { + limit -= CallSize; + ch.limit = limit; + if(p->to.type == D_BRANCH) { + // Direct call. + ch.sym = p->to.sym; + if(stkcheck(&ch, depth+1) < 0) + return -1; + } else { + // Indirect call. Assume it is a splitting function, + // so we have to make sure it can call morestack. + limit -= CallSize; + ch.sym = nil; + ch1.limit = limit; + ch1.up = &ch; + ch1.sym = morestack; + if(stkcheck(&ch1, depth+2) < 0) + return -1; + limit += CallSize; + } + limit += CallSize; + } + + } + return 0; +} + +static void +stkbroke(Chain *ch, int limit) +{ + diag("nosplit stack overflow"); + stkprint(ch, limit); +} + +static void +stkprint(Chain *ch, int limit) +{ + char *name; + + if(ch->sym) + name = ch->sym->name; + else + name = "function pointer"; + + if(ch->up == nil) { + // top of chain. ch->sym != nil. + if(ch->sym->text->textflag & NOSPLIT) + print("\t%d\tassumed on entry to %s\n", ch->limit, name); + else + print("\t%d\tguaranteed after split check in %s\n", ch->limit, name); + } else { + stkprint(ch->up, ch->limit + (!HasLinkRegister)*PtrSize); + if(!HasLinkRegister) + print("\t%d\ton entry to %s\n", ch->limit, name); + } + if(ch->limit != limit) + print("\t%d\tafter %s uses %d\n", limit, name, ch->limit - limit); +} + +int +headtype(char *name) +{ + int i; + + for(i=0; headers[i].name; i++) + if(strcmp(name, headers[i].name) == 0) { + headstring = headers[i].name; + return headers[i].val; + } + fprint(2, "unknown header type -H %s\n", name); + errorexit(); + return -1; // not reached +} + +void +undef(void) +{ + int i; + Sym *s; + + for(i=0; i<NHASH; i++) + for(s = hash[i]; s != S; s = s->hash) + if(s->type == SXREF) + diag("%s(%d): not defined", s->name, s->version); +} |