Re: [PATCH v2 01/13] livepatch: Fix build failure on 32 bits processors

[Miroslav Benes]

On Mon, 20 Dec 2021, Christophe Leroy wrote:

> Trying to build livepatch on powerpc/32 results in:
> 
>   kernel/livepatch/core.c: In function 'klp_resolve_symbols':
>   kernel/livepatch/core.c:221:23: warning: cast to pointer from integer 
> of different size [-Wint-to-pointer-cast]
> 221 | sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + 
> ELF_R_SYM(relas[i].r_info);
> |   ^
>   kernel/livepatch/core.c:221:21: error: assignment to 'Elf32_Sym *' {aka 
> 'struct elf32_sym *'} from incompatible pointer type 'Elf64_Sym *' {aka 
> 'struct elf64_sym *'} [-Werror=incompatible-pointer-types]
> 221 | sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + 
> ELF_R_SYM(relas[i].r_info);
> | ^
>   kernel/livepatch/core.c: In function 'klp_apply_section_relocs':
>   kernel/livepatch/core.c:312:35: error: passing argument 1 of 
> 'klp_resolve_symbols' from incompatible pointer type 
> [-Werror=incompatible-pointer-types]
> 312 | ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, 
> sec_objname);
> |   ^~~
> |   |
> |   Elf32_Shdr * {aka struct 
> elf32_shdr *}
>   kernel/livepatch/core.c:193:44: note: expected 'Elf64_Shdr *' {aka 
> 'struct elf64_shdr *'} but argument is of type 'Elf32_Shdr *' {aka 'struct 
> elf32_shdr *'}
> 193 | static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char 
> *strtab,
> |^~~
> 
> Fix it by using the right types instead of forcing 64 bits types.
> 
> Fixes: 7c8e2bdd5f0d ("livepatch: Apply vmlinux-specific KLP relocations 
> early")
> Signed-off-by: Christophe Leroy 
> Acked-by: Petr Mladek 

Acked-by: Miroslav Benes 

M

[PATCH v2 01/13] livepatch: Fix build failure on 32 bits processors

[Christophe Leroy]

Trying to build livepatch on powerpc/32 results in:

kernel/livepatch/core.c: In function 'klp_resolve_symbols':
kernel/livepatch/core.c:221:23: warning: cast to pointer from integer 
of different size [-Wint-to-pointer-cast]
  221 | sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + 
ELF_R_SYM(relas[i].r_info);
  |   ^
kernel/livepatch/core.c:221:21: error: assignment to 'Elf32_Sym *' {aka 
'struct elf32_sym *'} from incompatible pointer type 'Elf64_Sym *' {aka 'struct 
elf64_sym *'} [-Werror=incompatible-pointer-types]
  221 | sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + 
ELF_R_SYM(relas[i].r_info);
  | ^
kernel/livepatch/core.c: In function 'klp_apply_section_relocs':
kernel/livepatch/core.c:312:35: error: passing argument 1 of 
'klp_resolve_symbols' from incompatible pointer type 
[-Werror=incompatible-pointer-types]
  312 | ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, 
sec_objname);
  |   ^~~
  |   |
  |   Elf32_Shdr * {aka struct 
elf32_shdr *}
kernel/livepatch/core.c:193:44: note: expected 'Elf64_Shdr *' {aka 
'struct elf64_shdr *'} but argument is of type 'Elf32_Shdr *' {aka 'struct 
elf32_shdr *'}
  193 | static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char 
*strtab,
  |^~~

Fix it by using the right types instead of forcing 64 bits types.

Fixes: 7c8e2bdd5f0d ("livepatch: Apply vmlinux-specific KLP relocations early")
Signed-off-by: Christophe Leroy 
Acked-by: Petr Mladek 
---
 kernel/livepatch/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 335d988bd811..c0789383807b 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -190,7 +190,7 @@ static int klp_find_object_symbol(const char *objname, 
const char *name,
return -EINVAL;
 }
 
-static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,
+static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
   unsigned int symndx, Elf_Shdr *relasec,
   const char *sec_objname)
 {
@@ -218,7 +218,7 @@ static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const 
char *strtab,
relas = (Elf_Rela *) relasec->sh_addr;
/* For each rela in this klp relocation section */
for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
-   sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + 
ELF_R_SYM(relas[i].r_info);
+   sym = (Elf_Sym *)sechdrs[symndx].sh_addr + 
ELF_R_SYM(relas[i].r_info);
if (sym->st_shndx != SHN_LIVEPATCH) {
pr_err("symbol %s is not marked as a livepatch 
symbol\n",
   strtab + sym->st_name);
-- 
2.33.1