| Message ID | 20240223083245.80175-1-philmd@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC] target/ppc/mmu: Silent maybe-uninitialized error in ppc_hash64_xlate() | expand |
On 23/02/2024 09.32, Philippe Mathieu-Daudé wrote: > Initialize apshift to avoid a maybe-uninitialized error: > > C compiler for the host machine: cc -m64 -mbig-endian (gcc 13.2.0 "cc (Debian 13.2.0-10) 13.2.0") > C linker for the host machine: cc -m64 -mbig-endian ld.bfd 2.41.90.20240115 > Host machine cpu family: ppc64 > Host machine cpu: ppc64 > ... > target/ppc/mmu-hash64.c: In function 'ppc_hash64_xlate': > target/ppc/mmu-hash64.c:1154:15: error: 'apshift' may be used uninitialized [-Werror=maybe-uninitialized] > 1154 | *raddrp = deposit64(pte.pte1 & HPTE64_R_RPN, 0, apshift, eaddr); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > target/ppc/mmu-hash64.c:947:14: note: 'apshift' was declared here > 947 | unsigned apshift; > | ^~~~~~~ > > The call chain is: > > ppc_hash64_xlate -> ppc_hash64_htab_lookup -> ppc_hash64_pteg_search > > ppc_hash64_pteg_search() either sets *pshift or returns -1, > > ppc_hash64_htab_lookup() returns if ppc_hash64_pteg_search() > returned -1: > > 1068: ptex = ppc_hash64_htab_lookup(cpu, slb, eaddr, &pte, &apshift); > 1069: if (ptex == -1) { > 1070: if (!guest_visible) { > 1071: return false; > 1072: } > ... > 1087: return false; > > So IIUC this "uninitialized use" can not happens. > > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> > --- > I had this in an old branch (2 months old) I just rebased, > and don't get why nobody else got this error yet. That's weird, indeed. Did you maybe compile without optimizations when you hit the error? Thomas
diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c index d645c0bb94..cd1e0c13c8 100644 --- a/target/ppc/mmu-hash64.c +++ b/target/ppc/mmu-hash64.c @@ -944,7 +944,7 @@ bool ppc_hash64_xlate(PowerPCCPU *cpu, vaddr eaddr, MMUAccessType access_type, CPUPPCState *env = &cpu->env; ppc_slb_t vrma_slbe; ppc_slb_t *slb; - unsigned apshift; + unsigned apshift = 0; hwaddr ptex; ppc_hash_pte64_t pte; int exec_prot, pp_prot, amr_prot, prot;
Initialize apshift to avoid a maybe-uninitialized error: C compiler for the host machine: cc -m64 -mbig-endian (gcc 13.2.0 "cc (Debian 13.2.0-10) 13.2.0") C linker for the host machine: cc -m64 -mbig-endian ld.bfd 2.41.90.20240115 Host machine cpu family: ppc64 Host machine cpu: ppc64 ... target/ppc/mmu-hash64.c: In function 'ppc_hash64_xlate': target/ppc/mmu-hash64.c:1154:15: error: 'apshift' may be used uninitialized [-Werror=maybe-uninitialized] 1154 | *raddrp = deposit64(pte.pte1 & HPTE64_R_RPN, 0, apshift, eaddr); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ target/ppc/mmu-hash64.c:947:14: note: 'apshift' was declared here 947 | unsigned apshift; | ^~~~~~~ The call chain is: ppc_hash64_xlate -> ppc_hash64_htab_lookup -> ppc_hash64_pteg_search ppc_hash64_pteg_search() either sets *pshift or returns -1, ppc_hash64_htab_lookup() returns if ppc_hash64_pteg_search() returned -1: 1068: ptex = ppc_hash64_htab_lookup(cpu, slb, eaddr, &pte, &apshift); 1069: if (ptex == -1) { 1070: if (!guest_visible) { 1071: return false; 1072: } ... 1087: return false; So IIUC this "uninitialized use" can not happens. Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> --- I had this in an old branch (2 months old) I just rebased, and don't get why nobody else got this error yet. --- target/ppc/mmu-hash64.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)