From: Ricardo Ribalda ribalda@chromium.org
commit 8652d44f466ad5772e7d1756e9457046189b0dfc upstream.
Patch series "kexec: Fix kexec_file_load for llvm16 with PGO", v7.
When upreving llvm I realised that kexec stopped working on my test platform.
The reason seems to be that due to PGO there are multiple .text sections on the purgatory, and kexec does not supports that.
This patch (of 4):
Clang16 links the purgatory text in two sections when PGO is in use:
[ 1] .text PROGBITS 0000000000000000 00000040 00000000000011a1 0000000000000000 AX 0 0 16 [ 2] .rela.text RELA 0000000000000000 00003498 0000000000000648 0000000000000018 I 24 1 8 ... [17] .text.hot. PROGBITS 0000000000000000 00003220 000000000000020b 0000000000000000 AX 0 0 1 [18] .rela.text.hot. RELA 0000000000000000 00004428 0000000000000078 0000000000000018 I 24 17 8
And both of them have their range [sh_addr ... sh_addr+sh_size] on the area pointed by `e_entry`.
This causes that image->start is calculated twice, once for .text and another time for .text.hot. The second calculation leaves image->start in a random location.
Because of this, the system crashes immediately after:
kexec_core: Starting new kernel
Link: https://lkml.kernel.org/r/20230321-kexec_clang16-v7-0-b05c520b7296@chromium.... Link: https://lkml.kernel.org/r/20230321-kexec_clang16-v7-1-b05c520b7296@chromium.... Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_puragory") Signed-off-by: Ricardo Ribalda ribalda@chromium.org Reviewed-by: Ross Zwisler zwisler@google.com Reviewed-by: Steven Rostedt (Google) rostedt@goodmis.org Reviewed-by: Philipp Rudo prudo@redhat.com Cc: Albert Ou aou@eecs.berkeley.edu Cc: Baoquan He bhe@redhat.com Cc: Borislav Petkov (AMD) bp@alien8.de Cc: Christophe Leroy christophe.leroy@csgroup.eu Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Dave Young dyoung@redhat.com Cc: Eric W. Biederman ebiederm@xmission.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ingo Molnar mingo@redhat.com Cc: Michael Ellerman mpe@ellerman.id.au Cc: Nathan Chancellor nathan@kernel.org Cc: Nicholas Piggin npiggin@gmail.com Cc: Nick Desaulniers ndesaulniers@google.com Cc: Palmer Dabbelt palmer@dabbelt.com Cc: Palmer Dabbelt palmer@rivosinc.com Cc: Paul Walmsley paul.walmsley@sifive.com Cc: Simon Horman horms@kernel.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Tom Rix trix@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/kexec_file.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
--- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -910,10 +910,22 @@ static int kexec_purgatory_setup_sechdrs }
offset = ALIGN(offset, align); + + /* + * Check if the segment contains the entry point, if so, + * calculate the value of image->start based on it. + * If the compiler has produced more than one .text section + * (Eg: .text.hot), they are generally after the main .text + * section, and they shall not be used to calculate + * image->start. So do not re-calculate image->start if it + * is not set to the initial value, and warn the user so they + * have a chance to fix their purgatory's linker script. + */ if (sechdrs[i].sh_flags & SHF_EXECINSTR && pi->ehdr->e_entry >= sechdrs[i].sh_addr && pi->ehdr->e_entry < (sechdrs[i].sh_addr - + sechdrs[i].sh_size)) { + + sechdrs[i].sh_size) && + !WARN_ON(kbuf->image->start != pi->ehdr->e_entry)) { kbuf->image->start -= sechdrs[i].sh_addr; kbuf->image->start += kbuf->mem + offset; }